To help me narrow down the size.... What's the range of KWs I should be looking at? Please don't tell me to start adding up the wattage of every light bulb I will be using; compensate for the coefficient of expansion, and arrive at my own conclusions. I'm just trying to get a general idea. You know ...ballpark. ;D
Thanks.
Chazwood.
4 to 15 kw. HTH
HTH? So My estimations of around 10kw would handle just about anything. (outside of that hot tub and full laundromat my wife was talking about.)
Chaz,
A significant part of your decision rests with using propane or not. I you use propane for cooking then I think 6-8 kw is more than adequate With a little power management, you can have 3 1 ton air conditioners and electric hot water.
Mineis all electric and can reach 10 KW load withheat and cooking . Jerry
Hi Chazwood,
I'm also all electric and I have a 12.5 kw. Most likely, more then I need but, I have powered a fellow busnuts coach
when his genset crapped out last fall. I also powered my house last fall during a power outage.
Ask yourself, What will your needs be?
Anything worth doing, is always worth Overdoing.... ;D
Good Luck
Nick-
I have a household type water heater and refriderator and use electric heaters on 10k.
I think a 7k or 8k would be fine.
Probably the key here is use management. Be sure to include an ammeter in the system so that you will know where you are in terms of capacity usage (multiply amps time volts to get a "measure" of usage)
I have a 10 KW and wish I had a 12.5 at times. I wired my 10KW for 240V because of our dryer (general consensus is that you should not wire anything less than a 12KW for 240V). That means I have to work at balancing the loads on each leg (using two ammeters).
When the dryer is on, I have to limit air conditioning etc.(that is when I wish I had 12.5KW). With the dryer off, I can run most anything (three roof airs, microwave, house fridge, etc.). I have each AC labeled as to which leg it is on, and can play with the load balancing. The microwave is a hog, so if I am going to use it for more than just a simple warm-up, I will turn off an AC on that leg.
Most folks do not have their generator wired for 240V and that makes life a bunch easier.
Folks will warn you not to go too big, as a lightly loaded generator is supposedly hard on the generator engine. I don't think that is as much of a problem with modern diesel engines. Having said that, when I just want to "exercise" the generator, I will turn on heavy loads (like the useless heat strips in the ACs) to make the generator work hard. I am on the road quite a bit so I don't have to exercise the generator very often (mostly when I get ready to change the oil).
Jim
7.5 or so will suit most
Depends on if you have over the road A/C or not. Since the vast majority of us do take out the over the road A/C, the rule of thumb is if you have two tons (like two roof tops) of cooling 8-10kw. If you have three (like I do) 10-12kw. If you have four 15-20kw. If you're all electric, then you should be on the high side. My only propane run appliances is the furnace (35,000btu Atwood) and a 3 burner stove (also Atwood) and with 3 roof tops have plenty of power with the 10kw Powertech. If you use a 12kw, then you'll have 50amps per leg for a total of 100amps at 120vac. This means then your 50 amp land line will be the same power capability as the 12kw generator. Good Luck, TomC
Quote from: chazwood on March 09, 2008, 07:04:03 AM
What's the range of KWs I should be looking at? Please don't tell me to start adding up the wattage of every light bulb I will be using; compensate for the coefficient of expansion, and arrive at my own conclusions.
Umm, you know, you really can not answer this question at all without first doing the very work that you say you don't want to do.
Stan's answer, in that case, was dead on -- 4 to 15 kW. How can you possibly expect anything more precise than that?
Here are all the things I'd need to know to even begin to tell you which end of that scale to start from:
How many cubic feet of coach?
How much insulation?
Single- or double-pane windows?
Diesel, propane, or electric heat?
Diesel, propane, or electric water heater?
Propane or electric stove?
Propane or electric oven?
120-volt, 12/24-volt, or propane refrigerator?
Size of refrigerator?
How many days in a row will you boondock (away from power hookups)?
Washer and/or dryer on board? Dishwasher?
Any 240-volt loads?
How big is your battery bank? How about the coach alternator?
Any solar panels?
Number and type of air conditioners?
Inverter? How big, and load-supporting or not?
And, yes, even how many light bulbs, and what type (incandescent, fluorescent, or LED)?
When we got our bus, it had a 17kW(!) genny on board, and that was
just enough for the way the conversion had been designed (no ventilation at all, four basement airs, 240-volt cooktop, inefficient battery charger, 100% incandescent "indirect" lighting, yada, yada.). We still have the darn thing -- it was one of the very few items we were able to salvage from the original conversion.
We redesigned the bus to be super-efficient, so we could boondock for two weeks at a stretch. If I were to replace my generator today, I would replace it with a 6kW. Just about a third the size of what's on there now.
It is my personal (and widely disputed) opinion that if you need more than 8kW, you've made a design error someplace else (unless, with deference to my good friend Jim, you have a washer-dryer aboard that you want to run off-grid, in which case, you'll need much more -- the dryer alone can use 6-7kW). But that's just me -- you're own cost/benefit point might lie elsewhere, and putting in a larger generator and, for example, a smaller battery bank or perhaps no inverter might make more sense for a coach that is used only a few weekends a year, or is consistently operated in hot or humid areas where 24/7 air conditioning is a requirement.
FWIW.
-Sean
http://OurOdyssey.BlogSpot.com
To build on Sean's comments, it does not make much sense to run something like a dryer off grid. However, we are sometimes forced to do that when we are not hooked to a 50A pole (30A, obviously, does not provide the 240V). We try to save our washing for the somewhat infrequent 50A pole, but sometimes I start to stink :D
One other consideration is the fuel consumed. I am not sure that there is "official" consumption numbers, but I have heard that a fairly loaded 10KW uses about a half gallon per hour. My consumption would suggest that is about right. That can really add up. Indeed, we have had to fill the aux tank twice on this trip (about 50% on the pole) and each time was well over $100. At the FMCA show in Pomona they charged $160 for 20A power. That sounds like a heck of a lot, but we used over $100 in fuel, so their charge is not as outrageous as it sounds.
On this lengthy trip (approaching 2 1/2 months), we have been off grid quite a bit. In Quartzsite we were off grid for about 10 days and used about 30 gallons (have separate tank for Aqua-Hot and generator). We did not run the air conditioners, but did have to run the heater in the evenings and early mornings, plus hot water. The generator was used to recharge the batteries (we run the generator when we know we will have big loads, so we try to kill two birds with one stone). We have 3 large solar panels (not too efficient this time of year), but that only provide about 1/2 of our needs. We have 8 golf cart batteries and quite a bit of power usage. The house type fridge uses more than I would like. We also have quite a bit of electronic things going as well. I am very careful not to let the batteries drop below 50% as measured by a Bogart Tri-metric sate of charge meter.
The reason I bring all of this up, is that it DOES make a huge difference what you are running. Secondly, it does cost more to run a bigger generator than you need. I can't give you good numbers on fuel vs KW delivered vs KW capacity, but it just stands to reason that running a big generator at less than 50% capacity, wastes fuel. Having said that, newer diesel engines are probably less affected by partial vs full load conditions.
Sorry about the rambling, but I think there is a point or two worth considering in this post ??? :o
Jim
I'm getting by nicely with a 5500w Onan on LP fuel. To top it off, I'm usually above 5000' msl, and currently at 6880' msl., where I suffer about a 20% loss of output capacity, but can still run my two roof airs or both electric toekicks.
It still leaves me plenty for the microwave, HDTV's, and battery charging.
It works well for me, but may not for you.
Jay
87 SaftLiner
I have had RV's in the past with 4KW generators. For the most part, that was enough. There were times however when more power would have been nice. I now have a 7.5 kw which is quite adequate for my needs. I do use propane for heat, stove and frig though.
All good stuff, I'm listening, I'm listening, but could you get out your slide rules and burn through this? (You guys are better than wiki ;) ) I got a DMc-9 with the over the road heat and air intact. Every nook and cranny foamed with the closed cell foam.(20r at 2inches) Kept the og windows (I'm a sucker for those double hung, dark tinted green) planning on a lp cook top and on demand water heater. Momma wants a washer and dryer but I might just try to put down my foot....(probably draw back a bloody stump). I love heat pumps because we stay down south and need air more than heat so I'm hoping a heat pump in the bay. Besides that (without the dryer) all I need is a few lights and some microwavage,and of course all the fans. (my kids can't sleep without a fan 3 inches from their nose.) What do you all think? We stay down in the hot humid southeast. This is why a bank of batteries and an inverter isn't making too much sense to me, because.....well, because ......(y'all tell me if I'm missing something) maybe it's necessary in milder climes where no conditioning of the air is necessary for long periods, but not here.... we run the air in December sometimes.
That being said....get this. Here I am, foaming all the holes in the dad-gum frame, for heavens sake, and I notice for the first time that the whole front of the bus is open to the wind like a blown-out boxer. What is up with that? The whole front bumper gapes open to the wind and weather like a toothless hag and I'm foaming pin holes in the frame? I'm speechless. You can't really insulate the area because of all the stuff down there close to the floor ceiling....you can't insulate under the steps which are solid stainless steel; can we say cold? (maybe that's what the layer of dirt was for.) It seem to my little pea brain that I got a great insulation job, but what good is that, if I always leave the front door open? Oh well, never mind, I digress....I'm more interested in the genset for now. ;D
Hi Chazwood,
Your a funny guy! ;D ;D
Well, your on the right path and thats good. Genset, LP, Heat Pumps, OTR Air & Heat, and you did leave out the inverter and batt bank....?? Why?
What will you do while traveling to your destination and your kids want to watch TV, play video's, keep the beverages cold, and lighting?
Thats one thing that you will most surely add later after expierencing the above.....
Good Luck
Nick-
Chazwood- if you're near Florida, I'd check out Powertech out of Leesburg. They have some nice fully enclosed gensets that when installed in the baggage compartments, are near silent running. I would suggest the 10-12kw size, with 12kw my choice for the prementioned 100 amp service with both the genset and land line. Good Luck, TomC
Will yo have 2 or 3 airs, and when you run them how cold do you like it? Running 3 airs, you should think about the 10k to 12k diesel.
Whe I bo9ught mine, the footprint of the 12k was very similar to the smaller ones.
By going up to 15k or 20 k, it would have made my space requirments much larger, and by goig smaller, all I would have saved is $ and fuel consumtion.
So partly the answer is what kind of deal you find out there when you start looking. All this theory and planning can go out the window in a hurry when you find something that you think can work for you.
Quote from: H3Jim on March 09, 2008, 09:54:20 PM
... Running 3 airs, you should think about the 10k to 12k diesel. ...
Wow, Jim -- how much draw are your airs pulling?
Our 13,500 BTU/hr units pull around 1600 watts each, running full blast. That would make 4.8kW to comfortably run three of them full-tilt. Start-up, of course, is much higher, but (1) they generally do not all start together, (2) the stand-by rating of the generator (which is higher than the "continuous" ratings we've been discussing) should easily accommodate the start-up of any single unit and (3) that's what the load-support feature of the inverter is for, if you go that route (and this, of course, is one of the key benefits of a load-supporting inverter -- it lets you, among other things, get by with a smaller generator).
We actually have more like 55,000 BTU/hr total (~4.5 tons), although we seldom run all of it at once (the fourth unit is downstairs, in the cockpit), which still only comes out to around 6.5 kW.
BTW, FWIW, our 17kW genset burns over a gallon an hour at about half load. I figure if we had a modern 7.5, which would be the most we could really ever use at once, it would burn about half that for the same loads. And, if I were generator-shopping, I'd probably go down to a 6.0 or 6.5, because I certainly don't feel the need to run the battery charger full-tilt at the same time I'm running, say, all four airs.
We kept the old fuel-guzzling monster because, even at today's diesel prices, it would take a lot of hours at half a gallon extra per each to get up to what a decent generator costs. Besides, this way we have a buddy plug, and can power another rig or two, or maybe an entire third-world country. ;D
-Sean
http://OurOdyssey.BlogSpot.com
Hi Sean,
You have to remember one thing about RV airs, the amp ratings on the plate are determined at 80 deg. outside ambiant.
I have seen my "14amp" rated 15,000btu airs pull 22 amps on a 98 deg. day.. not uncommon!
Nick-
As fas as fuel consumption, PowerTech website list the 8 KW (3 cylinder Kubota) at .32 @ 1/2 load and .64 @ full load. The 8 KW numbers are consistent with our fuel use.
They list the 10 KW (4 cylinder Kubata) at .64 @ 1/2 load and 1.0 @ full load. Jack
Chaz,
If you are going to use a stackable or separate washer-dryer (vs a combo unit) then why not go for a gas dryer? A lot easier than running the gen or searching for a 220 pole.
When I had my bus, it had a dual basement air and electric hot water and a 6kw generator. I had a relay wired into the water heater which would turn off one AC when the WH came on.
Len
Quote from: Nick Badame Refrig. Co. on March 09, 2008, 06:37:33 PM
Hi Chazwood,
Your a funny guy! ;D ;D
Well, your on the right path and thats good. Genset, LP, Heat Pumps, OTR Air & Heat, and you did leave out the inverter and batt bank....?? Why?
What will you do while traveling to your destination and your kids want to watch TV, play video's, keep the beverages cold, and lighting?
Thats one thing that you will most surely add later after expierencing the above.....
Good Luck
Nick-
So that's what the inverter and battery bank is for. This may sound strange but even though I've been keeping my eyes peeled (and putting out far too subtle hints) I haven't been able to figure out what the inverter and battery bank is for, because, I just thought I would run all those things off the bus generator/alternator while I blasted down the road. Guess not huh? I mean, It had enough reading lights to rival Shea stadium, I just thought we would use all that power for my 72 inch plasma wide screen (24v?) TV.
Incidentally, early in this post I asked if anyone had the new Onan HQD all in one system and someone responded that onan will only put those systems in new units......not right. My local onan dealer just called and said he could get me the whole package for a measly $16,000. ($5000 more than I paid for the bus :o) If I put something that nice in my old "Basset Bingo Bus" it would probably revolt and blow a gasket.
Quote from: chazwood on March 10, 2008, 05:57:29 AM
So that's what the inverter and battery bank is for. This may sound strange but even though I've been keeping my eyes peeled (and putting out far too subtle hints) I haven't been able to figure out what the inverter and battery bank is for, because, I just thought I would run all those things off the bus generator while I blasted down the road. Guess not huh? I mean, It had enough reading lights to rival Shea stadium, I just thought we would use all that power for my 72 inch plasma wide screen (24v?) TV.
If you have OTR heat and air, I don't understand why you would run the generator and NOT use the power that's available from that big alternator on the engine (while driving).
David
Quote from: DavidInWilmNC on March 10, 2008, 06:39:25 AM
Quote from: chazwood on March 10, 2008, 05:57:29 AM
So that's what the inverter and battery bank is for. This may sound strange but even though I've been keeping my eyes peeled (and putting out far too subtle hints) I haven't been able to figure out what the inverter and battery bank is for, because, I just thought I would run all those things off the bus generator while I blasted down the road. Guess not huh? I mean, It had enough reading lights to rival Shea stadium, I just thought we would use all that power for my 72 inch plasma wide screen (24v?) TV.
If you have OTR heat and air, I don't understand why you would run the generator and NOT use the power that's available from that big alternator on the engine (while driving).
David
well? so, I CAN use the alternator to run the tv and stuff while on the road? If I could do that would I still need a battery bank?
Chazwood, yes you can use the bus alternator to power your inverter so you can have 120 volts while driving. As soon as you shut the bus engine off, without a house battery bank you will either
1. shut off all 120 volt things
2. run down your start batteries
3. start your generator and never shut it off.
Its probably good to have at least a small house battery set for things like lights when nothing else is running. I made it a religion to never run stuff off my start batteries. Overkill, but its nice to be able to start when you need to. The starts are not meant to be run down much they don't handle the deep cycle stuff well and will have a much shorter life if you use them very much for house stuff.
Sean, well I made the decision to buy that generator within a week or two after buying the bus when I was hot to get started. I really didn't know how everything was going to end up. I was partly relying on the advice of others. I had never even thought about solar then either. Its true, I'd don't think I've ever really used the generator to full capacity. But, its done, and it is handy to always have more than enough power available. I don't think I sacrificed any square footage, as the smaller capacity units seemed to have a similar footprint. The only downside is that its a little less efficient.
Quote from: Nick Badame Refrig. Co. on March 09, 2008, 06:37:33 PM
What will you do while traveling to your destination and your kids want to watch TV, play video's, keep the beverages cold, and lighting?
I have a small inverter, 500W to run lights when I do not have the genset running. I run the genset all the time and when driving. I spent about 5k on a 8kw Powertech genset. It will run both A/C's no problem. If I wanted to run an inverter to power the A/C's while running down the road, I would likely need a SW4024 or equivalent, which can run 2,500 - 3,000. So , why am I spending 2500 bucks to not run my genset I spent 5k on? I've never understood the reasoning that you get the inverter to not have to run the genset. Both are going to use fuel, and the genset is likely to be more efficient. Real gensets like the Powertech, and others, are designed to be run all the time. If you were using a cheap generator, then I might agree you would only want to run it for a couple hours at a time.
If you do plan on a big inverter to power the A/C's, then it is true that most bus alternators will power it. However, that is usually only at higher RPM's, so you will need a decent sized battery bank to handle the times when you are at idle. The genset doesn't care one bit.
Chris, I use my inverter while parked, boondocking. Its powered by a 600 amp hour (@24 volts) house battery set. The answer is total quiet, not to mention flexibility - I can always have power and I don't have to spend 3/4 gallon an hour to do it. Mostly I don't run it at all, so I am saving lots of fuel. Its one of the things that sold me on the solar - its totally quiet and vibration free. Not taking away anything from my Wrico generator with remote radiator and quiet box- its is very quiet for a 12k generator. Just not nearly as quiet as not running at all.
Quote from: Nick Badame Refrig. Co. on March 10, 2008, 03:23:36 AM
You have to remember one thing about RV airs, the amp ratings on the plate are determined at 80 deg. outside ambiant.
Nick,
My figures are measured actual, not nameplate (which is actually higher).
-Sean
http://OurOdyssey.BlogSpot.com
Quote from: H3Jim on March 10, 2008, 08:31:38 AM
... I don't think I sacrificed any square footage, as the smaller capacity units seemed to have a similar footprint. The only downside is that its a little less efficient.
That's what we decided, too. It was clear we would not save any money by downsizing -- in fact, it would cost us several thousand to get a smaller unit, even considering whatever we could get for our old one on the open market. So I started to look at how much space and/or weight we could save by downsizing it, and the answer was pretty close to zero, so we just kept it. We spend a bit more on fuel for it, but, as I said, it will be a long time before we catch up to what it would have cost to replace it with a smaller one.
-Sean
http://OurOdyssey.BlogSpot.com
Would it be reasonable to think I could run one AC and the refrigerator off the batteries and the engine while going down the road?
I am trying to figure if I will need to run the 14 kw gen set while going down the road.
I plan on having at least 4 deep scycle battries and maybe 2 others set aside to start the engine.
Does that sound possible?
I still have not gotten my bus home but am trying to think ahead.
Quote from: Chris 85 RTS on March 10, 2008, 09:59:53 AM
... I've never understood the reasoning that you get the inverter to not have to run the genset.
As Jim said, the inverter running from batteries is quiet. If you stay at national parks, as we do frequently, you will find that generator operating hours are restricted, in some cases quite severely.
We just wrapped up a stay at Furnace Creek in Death Valley, where generators are only allowed for four hours each day (two in the morning, and two in the afternoon). We couldn't even brew a pot of coffee in the morning without the inverter, nor use the microwave to make dinner, etc. Texas Springs campground, across the road, does not permit generators at all.
The story is the same throughout the national park system, as well as many other federal and state campgrounds. We also end up spending nights on the street in residential neighborhoods, and nothing will attract a midnight knock on the door from the local constabulary like running the generator after the neighbors have retired for the evening.
We've even spent several nights indoors (we spend more time in the shop than I'd like to admit), where the generator is completely out of the question. So, it all depends on how you use your coach, but I wouldn't trade my battery/inverter combination for anything. In fact, I wish I had room for (1) more batteries and (2) more solar panels.
Quote
... Both are going to use fuel, and the genset is likely to be more efficient.
That's just plain incorrect. A 6.5kW generator will use typically about .6 gallons per hour at full load. By contrast, the Delco 50DN alternator, generating the same 6.5kW, will use roughly .1-.2 gallon per hour with the engine running at road speed. "Stealing" a dozen horsepower from a ~450BHP engine working in it's power band is more efficient that using a smaller engine to do the same work. Think of it this way -- what would make a more efficient generator: One 100hp engine, or two 50hp engines? The larger the engine, the more work per unit fuel you will get out of it (generally speaking).
All of that assumes that you are driving at normal RPM on a flat, straight road. The efficiency equation actually improves when you throw hills into the mix. That's because power being generated by the alternator is completely free on the down side. Where does this amazing free energy come from? It is the energy that otherwise would have been expended as waste heat in the brakes (or retarder, if so equipped). Think of it as poor man's regenerative braking.
All of that being said, there is, of course, no way that the efficiency improvements of using the engine alternator over a generator will ever pay for a $2,000 inverter, at least not in the time most of us will own and use our buses. So you need to justify the inverter for other reasons. But once you've done that, then the cost/benefit equation for using the alternator vs. the generator is an easy one.
-Sean
http://OurOdyssey.BlogSpot.com
Quote from: Bob Gil on March 10, 2008, 11:23:59 AM
Would it be reasonable to think I could run one AC and the refrigerator off the batteries and the engine while going down the road?
Bob,
That all depends on how big your engine alternator is. You don't say in your post (or your profile) what kind of bus or engine you have, so it's hard to even guess here.
The alternator that was supplied as OEM equipment on the 2-stroke Detroits in many large 24-volt coaches is a 270-amp Delco 50DN. The huge output was needed to run massive blowers for the passenger air conditioning system. These alternators can put out nearly 7,300 watts when running at rated speed under full load, and are rated for 6.5kW continuous duty. That was generally achieved by using oil cooling and direct gear drive.
Let us know what alternator you've got, and we can give you some guidance.
-Sean
http://OurOdyssey.BlogSpot.com
Another point in favor of an inverter in addition to a generator is the refrigerator. Unless one uses an LP absorption 'fridge, the generator will always be running just to keep the food cold - at truck stops (or wherever one buys diesel), in the winter when there's no need for the A/C's, etc. Inverters can be expensive, obviously. I didn't spend $2-3K on a true sine wave inverter. I spent about $300 on a Vanner 3600 watt inverter/charger on eBay. Buying used is always an option. I've run small and medium sized refrigerators off inexpensive MSW inverters for years with no problems. I've never had a problem with anything I've run off of my MSW inverters. The biggest is only 1000 watts, so I obviously haven't tried to run an A/C from it, but I wouldn't hesitate to do this with my big inverter. I don't look at an inverter as a substitute for a generator all the time, just some of the time.
David
To give you an idea about running A/C's off your battery bank..
I did an expierement when i had a 840 amp hour Flooded lead acid batt. bank set up for 12v. [1000amp hr now]
My 3000w Xantrex RS3000 has an english language monitor panel that displays all parameters, amps, volts, in and out, battery charge state,
volts and amps, and incomming volts and amps of both legs of 50 amp. So this was a no brainer to do..Starting at 13.6 volts,
I ran 1 15,000 btu HP in A/C mode on a 90 deg. day with no incomming charge or landline/genset hooked up. The low voltage alarm
tripped at 10.6 volts and total run time was 44 min's
Not much...huh
FYI
Nick-
another option on the refrigerator is to get one of the ones that run on 12 or 24 dc, then you don't need an inverter or a generator to run it. The downside there is that they are pricy.
My turn,
We use a 13.5kw kubota 3cyl. w/turbo, the turbo was a prototype from Dick Wright and it does seem to keep me closer to .75/gal. per hour.
We also have 6 AGM Batteries wired 24v for our house bank.
We love the inverter for its loadsharing ability, which is probably the best thing you could ever do for power management issues.
We plant trees for a living and at times we can be off-grid for a week or two. If you don't want to hear your genset run constantly you should IMO have a pretty good sustainable system.
One time in Yellowstone Nat. Park we parked just down the road from a geyser that was scheduled to blow in the next hour or so. My kids laid in their bunks and watched out the window for the eruption, We ran the fridge, 1 A/C, and cruised the internet on a sat. connection. There were about 100 people waiting in the viewing area, And we did not offend anyone with the noise of a genset.
FWIW
Devin
Great thread. Always interesting to see how others have skinned the cat. I am holding off on sizing/shopping for the genset until I am much further along with the new bus. I'll know better what size to look for after choosing and installing the rest of the gear. Hoping that by then there is an inverted based genset designed for RV use.
Old bus has 5.5KW and we never need more but it is a very simple layout with one noisy rooftop AC. We are accustom to a little power management. At any rate, I am planning on a layout that will be livable on a 30Amp pole and in fat city on 50. With a Proheat doing the heat and hot water, that leaves the big loads of the ACs, the micowave, and battery charging. Have not picked the refer type yet but leaning toward AC or DC with enough solar to support it. A SW series or equal inverter with power supplementing should make living on 30/50Amps pole or genset doable. Since the rest of the system is designed for 50Amp I cannot see needing much more that 6.5KW from the genset.
If I had to buy a genset today it would be the Honda EU6500is converted to permanent installation by me. I hate noisy Gensets and even worse noisy AC. Why not start with a quiet unit right off? Now if someone designs an inverter based diesel genset around 6 or 7KW in the mean time, that would be great as long as it is quiet.
Don 4107
Don,
Don't forget about propane fridges! They are very efficient. Run one on your inverter while going down the road and fire it up once you reach a boondocking place. Same thing for hot water. I'm doing some of the same things mentioned above. 7.5 KW genset (gasoline, got a great deal on it) Xantrex 4024 Inverter to allow me to run several AC's while on the road, 50Amp Shore line, 12V lighting, propane furnace, stove and fridge (110 also). I'll also have a 110 hotwater heater with a heat exchanger. I'll have some solar panels to help charge the batteries. I won't have a big battery bank to start, but I'm not going to use much 110 except while driving. Good luck!
Quote from: Don4107 on March 10, 2008, 06:24:05 PM
Great thread. Always interesting to see how others have skinned the cat. I am holding off on sizing/shopping for the genset until I am much further along with the new bus. I'll know better what size to look for after choosing and installing the rest of the gear. Hoping that by then there is an inverted based genset designed for RV use.
Old bus has 5.5KW and we never need more but it is a very simple layout with one noisy rooftop AC. We are accustom to a little power management. At any rate, I am planning on a layout that will be livable on a 30Amp pole and in fat city on 50. With a Proheat doing the heat and hot water, that leaves the big loads of the ACs, the micowave, and battery charging. Have not picked the refer type yet but leaning toward AC or DC with enough solar to support it. A SW series or equal inverter with power supplementing should make living on 30/50Amps pole or genset doable. Since the rest of the system is designed for 50Amp I cannot see needing much more that 6.5KW from the genset.
If I had to buy a genset today it would be the Honda EU6500is converted to permanent installation by me. I hate noisy Gensets and even worse noisy AC. Why not start with a quiet unit right off? Now if someone designs an inverter based diesel genset around 6 or 7KW in the mean time, that would be great as long as it is quiet.
Don 4107
Hi Don,
I do know an OEM that will sell to you but, that will have to be in a PM.
http://www.cumminsonan.com/www/pdf/specsheets/a-1502.pdf
Nick-
Quote from: Nick Badame Refrig. Co. on March 10, 2008, 12:42:15 PM
To give you an idea about running A/C's off your battery bank..
... The low voltage alarm tripped at 10.6 volts and total run time was 44 min's
Not much...huh
Nick,
Just to give the flip side, we regularly run one A/C all night on the batteries alone. Generally, we don't do this unless the outside temp is pushing 90 or above.
The numbers: We have 920 amp-hours of batteries, or 22kWh at nominal 24 volts. Our A/C's are a tad smaller than yours: 13,500 BTU/hr each. As I said earlier, I measure them out at about 1600 watts when running. On a typical night, though, they do cycle on and off, so that's not really a continuous number.
Even if they don't cycle, 1600 watts times about eight hours is about 13kWh, or just over half our battery capacity. With AGM batteries, we regularly go down to 70% depletion. So one air conditioner overnight is very comfortably within the working capacity of the system.
Of course, one thing that let's us do this comfortably without, umm, losing any sleep, is the generator autostart feature of the inverter. Should our overnight loads draw the batteries down below the thresholds that we've set, for whatever reason, then the generator will come on automatically, thus avoiding either damaging the batteries or having the whole system shut down on LBCO.
Of course, YMMV, etc.
-Sean
http://OurOdyssey.BlogSpot.com
Don- Cummins/Onan is making a "hybrid" system that uses a small Diesel generator with inverter technology. Interesting theory on paper, but I'm always leary about Onan since they use their own electronics, and they always seem to go out at some time at an expensive amount of money. I just talked today to Wrico, and they are still using mechanical switching that is very reliable. Personally, a good simple generator (read Powertech or Wrico) with a load sharing inverter with auto start should do the trick. Good Luck, TomC
:o Finally got the profile to take.
Sean: I do not have an engine alternator at this time, I was trying to see what I should get.
My bus was the one with the engine compartment fire. It does not have the engine alternator that most have it is powered off of the belt on the blower.
I hope that I can one of the big ones i have for the Mack's to work on it.
By the way thanks to the group for menting Fleet Pride I found there is a new one about a mile from me. They have only been there 5 months. Their prices are great too.
I wish there weren't so many ways to skin a cat. >:( It'd sure make all the decisions a lot easier ;D
Quote from: Bob Gil on March 11, 2008, 12:37:23 AM
...
My bus was the one with the engine compartment fire. It does not have the engine alternator that most have it is powered off of the belt on the blower.
Do you know if your coach electrics (Starter, gauges, exterior lights, etc.) are 24 volt? If so, you will be, IMO, better off putting in a 24-volt house system than a 12-volt one.
-Sean
http://OurOdyssey.BlogSpot.com
If you are talking to me I assume it is all 12 volt as it has two batteries and the ground on them go to the fram and the pos on each goes seprately to the starter and it starts very easly. I figure if it were 24 they would be wired together and it would not start very well the way it is wired now.
I hope I am correct.
Fellow up here had built the space for 16 golf cart batteries in the spare tire compartment of an MC9.
Last I saw it, many years ago, he had 8 installed, with the other 8 to come.
He hated generator noise, and could run the one roof air in the rear bedroom no problem overnight on the batteries.
The trick is, starting with the coach cool, then the AC will cycle?
Celebrate the differences!!!
happy coaching!
buswarrior
I have noticed some talk about remote radiators on the gensets. It would seem to me that if your unit was self-contained (all in one box) , you would need to open some kind of vents into your bay to allow proper air flow. (Get out the sawzaw? :o ) Before I bought my bus, I was looking at a mc-8, that was for sale locally, and noticed a bay door that looked like it had been shot full of holes at a rifle range. I thought ,what is the meaning of this?.... I opened the door and saw what looked like a car engine (genset...) bolted to the floor of the bay. I was shocked at the wanton destruction of the bus bay. Not only had they drilled 50 holes in the door but they also cut two giant three-sided cutouts in the floor and bent down the metal to make whopping air scoops for the genset. Is this necessary? I wouldn't want to trash my bay in this manner. How do we handle the necessary cooling air requirements in an enclosed bay?
My genset requires fresh air for the engine along with some air movement over the engine.
In addition, my genset radiator which I have mounted remotely, requires a fan that can more at least 2500 CFM of air through it. Sounds like maybe those people did not spend much time on design, and just did it, requiring mods later to keep it cool enough. It does sound like a butcher job, and there are other ways to do it.
Quote from: H3Jim on March 12, 2008, 08:01:11 AM
My genset requires fresh air for the engine along with some air movement over the engine.
In addition, my genset radiator which I have mounted remotely, requires a fan that can more at least 2500 CFM of air through it. Sounds like maybe those people did not spend much time on design, and just did it, requiring mods later to keep it cool enough. It does sound like a butcher job, and there are other ways to do it.
I'm all ears ;D
Where is your radiator? Does your fresh engine air (assuming you have remote radiator) require cutting open your bay? Give me some proven locations for this in a mc-9 with otr air and heat. Please?
Thanks.
Quote from: chazwood on March 12, 2008, 07:35:10 AM
I have noticed some talk about remote radiators on the gensets. It would seem to me that if your unit was self-contained (all in one box) , you would need to open some kind of vents into your bay to allow proper air flow. (Get out the sawzaw? :o ) Before I bought my bus, I was looking at a mc-8, that was for sale locally, and noticed a bay door that looked like it had been shot full of holes at a rifle range. I thought ,what is the meaning of this?.... I opened the door and saw what looked like a car engine (genset...) bolted to the floor of the bay. I was shocked at the wanton destruction of the bus bay. Not only had they drilled 50 holes in the door but they also cut two giant three-sided cutouts in the floor and bent down the metal to make whopping air scoops for the genset. Is this necessary? I wouldn't want to trash my bay in this manner. How do we handle the necessary cooling air requirements in an enclosed bay?
You have to get a lot of air into and out of both the radiator (remote or self contained) and the genset itself. With careful planning, you can have both the air supply(s) and returns in the bottom of the bay and spare the doors. You must be careful not to short circuit the supply so that you don't re-intake hot exhaust air and the exhaust must not be so powerful and directed straight down that it stirs up clouds of dust and dirt. Also, be sure that the tires don't throw water up into the intake. Both the supply and exhaust air should go through some baffles and turns for noise reduction. I would also remote the engine air intake so it is getting cooler air.
With a remote radiator, I would use a sail switch for an alarm or put it in the shut down circuit in case your blower fails.
FWIW,
Len
Since I have a transit with no real baggage compartments, I made my gen compartment in a hole that was next to the drivers seat. It mounts like a front engine, the compartment is even with the raised drivers seat. But the compartment is tight. With using a Powertech 10kw with 4 cylinder Kubota, it required I remote mount, the air cleaner, radiator, and muffler outside the box. I made the box with a 1/4" steel floor with 2" angle iron bolted to the perimeter. I mounted 3/4 plywood for the sides (Dick Wright at Wrico knows of a really dead plywood for noise suppression) and lined the walls and top with 1" foam lead insulation (really effective). The only real bummer is that the generator had to be mounted from the front side door inside, and the only access is through the trap door on top of the generator from inside next to the driver's seat (got to do weird stuff sometimes). I made my own remote blower out of a Grainger 9" squirrel cage blower that can take 150 degree air with single inlet. I mounted the radiator to the inlet side of the blower, and with a 1/2hp 2 spd enclosed fan cooled ball bearing motor, mounted it under the drivers seat with the radiator facing forward and the exhaust for the blower out the left side through a cut hole in the skirt. I use two speeds-high for during the day and low for quiet night time use. It works well. The only time it couldn't keep up is when I stopped for a break in 107 degree weather and had all three A/C's on. I imagine the pavement was up around 150 degrees it slowly heated up. Just turned off one of the A/C's and it was all right. But going down the road its' fine.
For ventilating the cabinet, I have a 8" bathroom axial flow blower that can get wet mounted in the front left corner with a small rectangular hole at the left front radius for fresh frontal air. This 8" is branched to 2-6" hoses that blows the fresh air directly onto alternator end of the radiator (the genset is mounted backwards as compared to a car engine). It then exits the rear of the gen cabinet through 2-6" hoses that are covered with screens to keep the little critters out. Has worked well for 600 hours (like 24,000mile worth-40mph is the conversion). It works so well, will probably use the same system again. Good Luck, TomC
I guess my point about inverters was not clear. It's not that I don't see their value or their potential need, it's that it seems to be a common thought that you have to have one. And that the reason to have one is to not run the genset because you need to not run the genset. I don't buy that logic, and not having a big inverter works fine for me under my usage profile. However, I will agree that if you are camping at places that limit generator usage, then you have no choice, but be prepared, it is going to be expensive, and those batteries do require periodic servicing and replacing. Just be sure you are aware of what you are getting into. I think that most people will agree that you need a genset and if you want a quiet/reliable/powerful one it is going to be costly. If you can get away with it, based on your usage profile, why spend alot more money on batteries and inverters to not run the genset you spent alot of money on.
As for the efficiency comment, I wish I had 450 hp to steal a couple dozen from! ???
Quote from: Chris 85 RTS on March 12, 2008, 09:19:38 AM
... be prepared, it is going to be expensive, and those batteries do require periodic servicing and replacing. ... If you can get away with it, based on your usage profile, why spend alot more money on batteries and inverters to not run the genset you spent alot of money on.
As I said, it does all depend on how you use your bus. But to respond to these last comments on the economics, let me just say that our inverter and battery bank have already paid for themselves.
We paid about $3,000 for our inverter and original battery bank, and I have since replaced the bank at a cost of about $2,400, for a total of $5,400. You need to deduct from that number at least something for whatever minimal house batteries and charger or converter you would need anyway to run whatever low voltage stuff you have, unless you have a straight 120-VAC coach (hard to do if you want things like roof vent fans and a decent water pump). So let's call it $5k even.
By contrast, my generator costs me about $4 per hour to run. (That's total costs, not just fuel. You need to figure oil and filter changes, valve jobs, top end rebuilds every so many hours, total lifetime and replacement costs, etc.). That number was probably closer to $3 when we hit the road (lower fuel prices), so call it $3.50 on average.
When we are parked long-term in temperate climates, we run the generator a total of about an hour per day. If we had no inverter at all, that number would increase to at least 2-3 hours per day. When we are parked in hot climates, where air conditioning is needed 24/7, we run the generator about half time. With no inverter, we'd have to run it full time. And lastly, when we drive every day or two, we usually don't have to run the generator at all, whereas with no inverter, we'd be back to the 2-3 hours per day.
Since I have not kept careful track of how many days we drive versus park, or how many days were hot versus temperate, it's hard to be precise. But clearly the inverter and batteries have reduced my generator run time by no less than half, and could be as much as 80%. Let's say it is about one third what it would be without the inverter.
Since hitting the road, we've put 1,100 hours on the generator. Without the inverter, then, I would have put around 3,300 hours on it. Those extra 2,200 hours would have cost me $7,700. So my $5k investment in inverter technology has already saved me $2,700 in three years, and those savings will only continue to increase over time. Bottom line: the inverter was "free," with a payback of less than three years.
The savings are actually much higher than that, because the inverter allows us to go places that we otherwise could not go without spending ~$30 per night for a campground.
The analysis comes out much differently, of course, if you only use your coach part time. But it is never cut and dried, slam-dunk -- you need to do the math. Only then can you answer your own question: "Why spend a lot more money on batteries and inverters to not run the genset you spent a lot of money on?"
-Sean
http://OurOdyssey.BlogSpot.com
While I will admit I have not done the research, and thus those numbers could be completely accurate, I really can't imagine that 2,200 hours of genset run time will cost 7,700 dollars. At full load my 8kW genset uses 0.5 gal/hour. Even at $4 a gal that is $4,400 in fuel cost, leaving $3,300 in maintence costs for 2,200 hours? That seems a bit high.
Also, if you spent $3k on inverter and batteries, and then spent another $2400 on replacment batteries, then either you got a great deal on the inverter or on the initial batteries. I am never so lucky to get deals like that, so I always base my costs on retail costs. When people talk about running 2 AC's on the road, the first thing that is always recommended is a SW4024, which is going to cost the average unlucky person at least $2500 plus $2400 in batteries for $4900 initial investment, and you have not driven an hour yet.
As for running off inverter while driving, there is a cost to that, it is not free. I agree that it will depend on your busses engine efficiency. In my case, I get about 8 mpg, and at 60 mph that is 7.5 gal/hour. If I am running my genset during that time, that would be a total of 8 gal/hr max. That's is a 6.6% increase. Now, let's guess that motoring down the road takes 200hp and running the inverter is going to take 10hp from the alternator, that is a 5% increase in load on the motor, not sure how that is going to affect mileage, but I am guessing alot of people would love to shave 5% load off their motor.
I think we've beaten this enough I suppose, and I agree that evenones usage is unique, and that it will work both ways. Just be sure you look at how you are going to use it, and where and when you want to spend your money. One size does not fit all.
Quote from: Chris 85 RTS on March 12, 2008, 02:21:21 PM
... At full load my 8kW genset uses 0.5 gal/hour. Even at $4 a gal that is $4,400 in fuel cost, leaving $3,300 in maintence costs for 2,200 hours? That seems a bit high.
As I said, these were my numbers, which, of course, will be different from anyone else's. My generator burns about 1.1 gph at about 50% load. That's high, I admit. If I were to buy a generator today for this coach, I would have bought one in the 6-7.5k range, where I would expect the consumption to be more like yours. However, when I did the math, it would have taken me ten years or more to pay back the cost of changing generators (the one we've got now, an older but massive 17kW unit, came with the bus).
The rest of the numbers break down to about $0.20 per hour for oil and filters, and roughly $0.50 per hour for rebuild/replacement costs (average of 20,000 hour life expectancy for a typical 1800rpm diesel generator, with $10,000 average rebuild/replace cost). So add about 70 cents per hour to the hourly fuel cost, in my case about $3.70 or so, so I am actually at about $4.40 per hour to run the generator right now. (BTW, we use this figure when deciding whether to pay for hookups -- if we'll need to run the genny for, say, four hours a day due to air conditioning needs or whatever, then suddenly a premium of $16 for electric hookups starts looking like a good deal.)
In your case, at half a gallon an hour, with today's fuel prices of ~$3.40 or so, you are looking at $2.40 per hour to run your generator. That's a real-world number, but, of course, it's average. Your generator could crap out long before 20k hours, or it could go for double that number without needing any major maintenance -- it's random (actually, a bell curve).
Quote
Also, if you spent $3k on inverter and batteries, and then spent another $2400 on replacment batteries, then either you got a great deal on the inverter or on the initial batteries.
I'll give you the actual figures. I paid $1,800 for my SW4024, brand new. You can certainly get them today for this price, I would not pay any more for one. And I got a great deal on batteries that I knew would not live long (cheap Xantrex crap that had been sitting on someone's shelf for who knows how long, even though "new"), but at less than a grand for ~840 amp-hours (at 24 volts), it was a deal I could not pass up. I got good use out of them, but there's a reason why I needed new batteries at only three years. Many, many more details on this on my blog archive.
That deal no longer existed, of course, when I went to replace them. I bought 920 amp-hours of Trojan AGMS for the $2,400 I mentioned. Again, full details on the blog.
Quote
I am never so lucky to get deals like that, so I always base my costs on retail costs. When people talk about running 2 AC's on the road, the first thing that is always recommended is a SW4024, which is going to cost the average unlucky person at least $2500 plus $2400 in batteries for $4900 initial investment, and you have not driven an hour yet.
As I said, I would not pay more than about $1,800 for a SW4024. The "retail" price reflects an enormous markup, and the business is very competitive. You may have to hunt around and/or bide your time (or accept a factory refurb, with 90-day warranty) to get this low a price, but $2,000 can be had easily.
Quote
As for running off inverter while driving, there is a cost to that, it is not free. I agree that it will depend on your busses engine efficiency. In my case, I get about 8 mpg, and at 60 mph that is 7.5 gal/hour. If I am running my genset during that time, that would be a total of 8 gal/hr max. That's is a 6.6% increase. Now, let's guess that motoring down the road takes 200hp and running the inverter is going to take 10hp from the alternator, that is a 5% increase in load on the motor, not sure how that is going to affect mileage, but I am guessing alot of people would love to shave 5% load off their motor.
I've discussed this extensively in other posts. It does, of course, depend on what engine you have and what kind of driving you do. The ~10hp that the alternator will rob on level ground or going up hill will cost you about .1-.2 gph. Even with your efficient 0.5gph genset, this is only 20-40% of that amount. Also, drawing this power from the alternator will not change your main engine maintenance intervals, so the oil and filter component goes away, and it will probably have a much smaller effect on engine life expectancy than for the dedicated power plant. All told, perhaps only a quarter of the cost per unit of energy than running the generator.
Remember also that all the power coming off the alternator is 100% free when going downgrade, so the numbers are actually better than this in "average" driving.
Quote
I think we've beaten this enough I suppose, and I agree that evenones usage is unique, and that it will work both ways. Just be sure you look at how you are going to use it, and where and when you want to spend your money. One size does not fit all.
Here, I could not agree with you more. I was just trying to answer, for
everyone's benefit, your comment about not understanding why people think they need inverters. It's because, for the vast majority of us, it makes both economic and lifestyle sense.
I hope, by sharing my direct experience here, that people will be able to take a look at their own numbers and work through this to arrive at a more informed decision.
-Sean
http://OurOdyssey.BlogSpot.com
I have to agree that one thing will not work for every body.
More so when some of did not build them our selves and they were not build the best way in the first place. I think that I have learned from this that there are things that i can do with what I inherited to make the best of it.
I figure if I can get an inverter to run the icebox while I am going down the road and maybe the TV I will be able to save on the genset some. and when it is hot i will need the genset. I will add some 12 DC outlets in it as it does not have any at this time, there are a lot of things i run off of DC.
I may not be able to afford a full set of batteries when I first get it going since I figure I will not be using it more than once every other month. I many just take the deep cycle batteries I have in the the suburban (I have 2) and the two I have in the pickup (I use them both and it keeps the batteries up pretty good.) along with the two in the buss. I know they may not all be balanced but using them this way 4 days every other month may be better investment than buying new ones to set.
I hope every body else has better funds for their bus toys. I am going to have to pay as I go and hope I can make it. The wife is wanting to get it ready for vacation in June to Allentown PA and VA but I don't thin I can rush it that fast. I think I want to do some short trips in it first, better to have problems worked out close to home. :)
Quote from: chazwood on March 12, 2008, 08:20:26 AM
I'm all ears ;D
Where is your radiator? Does your fresh engine air (assuming you have remote radiator) require cutting open your bay? Give me some proven locations for this in a mc-9 with otr air and heat. Please?
Thanks.
Here's how I ventilated my generator enclosure. The hot air is exhausted through the floor of the bay. I obviously still have a few things to do, but this seems to work well keeping the generator cool (enough).
David
David,
While that looks very professional..... I was hoping to avoid any serious mods to the bus metal. (not going to happen I suppose :()
Quote from: chazwood on March 12, 2008, 06:57:46 PM
While that looks very professional..... I was hoping to avoid any serious mods to the bus metal. (not going to happen I suppose :()
The nice thing is that all I have to do is to replace the aluminum strip I cut and you wouldn't be able to tell that anything was ever done to the door. You may be able to see where my bay door is damaged... I ran over a tree root. I have to replace the panel anyway, so none of these minor mods are really an issue to me!
David
I have my generator mounted in the front bay (driver side) with a remote radiator. The intake for the radiator is from the front bulkhead and the exhaust is out of the floor.
The intake for the generator box is from the middle bay via a squirrel cage fan and the exhaust is out the floor.
With this installation, I did not have to modify any exterior panels.
The arrangement for the remote radiator works very well.
There is enough air "leakage" in the bays that I get pretty good flow in the generator box. I have one of my sensors in the box and it stays at about 140* or less except on the hottest days when parked. The middle bay gets pretty warm in the middle of summer and the generator box has gotten as high as 160*. That is not bad, but I open the bay door a bit when we are parked on a hot day and that keeps the temperature at 140* most of the time.
I have some pictures of the remote radiator installation on my project pages listed in my signature.
For best generator performance the gen compartment should stay under 120 degrees. Good luck, TomC
We remoted our radiator to the rear of the former spare tire compartment. Since the radiator is the main heat source removing it from the generater compartment greatly reduced the amount of cooling necessary for the compartment. We added three 240 CFM bilge blowers to the generator compartment, with ducts added to get the hotter air at the top of the compartment. We monitor the air temp in the compartment with a thermistor located near the top of the compartment. The temps in our compartment usually run 10-15 degrees above the outside air temp. This a photo of the compartment air intake grilles and the exhaust fans. Jack