I've added another inverter (Victron in Parallel) which allowed me to run my 2 Coleman mach 3's no problem. We decided to head east to Wisconsin for a day trip, as a small shakedown with all our new improvements. We had both ACs running for a few hours before we left and in the heat and sun got the inside down to 75 or so, it felt great inside.
Before you read this next bit, keep in mind I have the valve up by the driver turned off for heat and another in the engine bay that supplies water to the heater core (is there a second? I can't find it, I imagine it's a loop)
So we head out, I'm commenting to the Mrs about how nice this is, ride is quiet, nothing is squeaking or rattling ( one of the things I hate about most RVs) and then I start to notice every once and a while this feeling of warm humid air. I can't quite figure out where it's coming from, could be the door, but then we settle on it coming from around where the old ramp was. I've since framed over it, but there was a gap in between the drivers floor level and the passenger where that framing was, I put my hand down there felt the heat. By the time we reached our destination it was 80 inside, no bear in mind we left around 6:30pm and didn't arrive until 8:30 or so, the sun was low and curtains drawn / most of this heat I'm convinced was from the engine one way or another.
To start I took off my covering over the old ramp area and filled it with fiberglass insulation and also put some under the next level down (with the air lines, etc) I believe this was an air return for the OTR HVAC system, so it makes some sense that heat could seep up, hopefully this stops it. My door seals might not be in the best shape, last year I tried to put some aftermarket weather stripping on it and it wouldn't close properly, so I took it off.
What are some other areas to look for? And is there a second shutoff for the heater core? Or could hot air be circulating all the way back from the engine up front and up through that bay even if it was off?
What don't I know that I don't know boys? (and gals if you're out there)
Yep, hot air rushing at the front of the bus will find its way in. Two A/C's on a hot summer day is not enough, you need three or more depending on your insulation and sealing levels. I know Eagles best, but I have driven many MC9's. Open the outside panel opposite the driver floor area, there you will see the hose connections to the heat valve on the inside. Make sure that the hot coolant is not getting there. The front dash area could have corrosion of the bulkhead and floor panels that has left holes for the hot air to come in, and there are fresh air vents that might have leaks, or be wide open even though you think they are closed. I have driven Eagles across Texas on super hot days with three 13,500 btu A/C's going full blast - same result as yours. The big entertainer coaches usually have five A/C's on top, and their doors are sealed well. The stars don't like to sweat. ;D
Ah well, I didn't want to go the route of 3+ roof ACs because then I'd almsot certainly have to run a big generator while driving and I've been wanting to avoid that for a number of reasons.
I'll pull that outside cover and maybe even the one inside in the bay to check for heat coming in. I'll probably have to take it out again... uh just the worst :-) Right now I love taking it out, we'll see how I feel about it after our trip to the Black Hills and then Texas later this summer.
Can you close a door to the bedroom and run two a/c's to cool the smaller area? My recent trip I talked about on the other thread, we got to 80 degrees and I was confused b/c I've never gotten that warm. I told her to close the door and it helped a little. I was thinking oh great, another problem. Then after awhile, I ask her, did you put it on low cool or high cool? She said Low. I bit my lip and told her to pls put it on high cool.
You know, I don't recall what it was set at, maybe they were on low. I insulated the snot out of the back to protect against heat and noise, not to say it's not part of the problem.
Right now I have one ducted AC and it runs the length of the bus, it's nice in the evening to just run one up front and still get cool air in our bedroom. The other is normal and spits out air from the unit only. I'm planning to convert the both to ducted to hopefully pressurize the system more to really get the air moving.
Quote from: neoneddy on June 18, 2018, 10:12:42 AM
Ah well, I didn't want to go the route of 3+ roof ACs because then I'd almsot certainly have to run a big generator while driving and I've been wanting to avoid that for a number of reasons.
I'll pull that outside cover and maybe even the one inside in the bay to check for heat coming in. I'll probably have to take it out again... uh just the worst :-) Right now I love taking it out, we'll see how I feel about it after our trip to the Black Hills and then Texas later this summer.
I think you will feel very hot and sweaty about it. Try crossing the west at night, park in the shade (if possible) during the day, but then, do you have any generator now and are you dependent on being plugged in?
Not sure how the MCI is set up, but in the nose of the GM buses there is a vent which was intended to bring fresh air into the bus. Our 4106 had this vent covered with sheet metal, but our current one has a damper that can open or close it. Is there such a thing in the front of an MCI?
Also, the factory OEM probably had fresh air intake(s) somewhere. On the GM they're on the sides. If these exist and are still in place, they could be forcing outside air into the bus when at speed.
Does your manual show what the original airflow pattern was with the factory HVAC system? If it doesn't my first step would be to be certain that all the possible intake routes are thoroughly closed.
@doubleeagle yeah that was a thought, I prefer driving at night anyway.
We have a small generator and almost 2000 watt of solar to boondock with, but we'll be at campgrounda for alot of our blackhills adventure.
@richard - I'll check for venting, thanks.
I would much rather drive at night but I feel that my lights aren't that bright and I underestimated how much I like to see in the mirrors. I'm wondering if I can get brighter lights that are just plug and play. I think I can take my lights to Napa and see what can be replaced.
Sorry OP, I missed that you don't have AC units on the roof. I guess closing a portion off inside wouldn't do much.
@branderson , No I do have 2 units on the roof, but I have them ducted in the ceiling.
I have set of these https://www.amazon.com/Rectangle-Headlights-Freightinger-Chevrolet-Oldsmobile/dp/B077NZKSJ6/ref=sr_1_1?ie=UTF8&qid=1529349466&sr=8-1&keywords=led+peterbilt+headlight (https://www.amazon.com/Rectangle-Headlights-Freightinger-Chevrolet-Oldsmobile/dp/B077NZKSJ6/ref=sr_1_1?ie=UTF8&qid=1529349466&sr=8-1&keywords=led+peterbilt+headlight)
Normally only a small section of 1 set is on, when they switch to high beams it's like the sun. https://youtu.be/wOKKGaRRp_w?t=615 (https://youtu.be/wOKKGaRRp_w?t=615) Here is the video where I installed them.
I did some more looking and reading in the maintenance manual. http://busrvparts.com/PDF_Files_MCI_9_Maint_Manual/MC-9-Maint_Manual_Section_16.pdf (http://busrvparts.com/PDF_Files_MCI_9_Maint_Manual/MC-9-Maint_Manual_Section_16.pdf)
The Air intake is sealed up with some rubbery / gummy stuff, on purpose it seems, not by me.
My door vents are covered by a decorative vinyl piece, I 'll need to look behind there soon anyway. Then I noticed there is a bottom door exhaust, huh I'll need to close that up. Then reading further " Approximately 20% of the conditioner air is fresh outside air. This provides a healthy fresh atmosphere in the coach" That was true with 40 passengers and an AC system capable of making indoor ice, but not now. I'm so fighting a loosing battle here if it's 20% . I'll start closing everything off and see where that gets me.
That ducting could be absorbing a great deal of heat from roof and ceiling. Check duct outlet temp. I can't see how you will be cool in hot weather with only two a/c's that are ducted in a 40 ft coach. What btu outputs are they and where are they located?
They are bout 10ft in from each end.
I also have most of the roof covered in solar so it's a built in shade.
Last I checked the outlets blew about 20 degrees cooler than ambient inside. I measured with a thermal gun.
Sent from my iPhone using Tapatalk
I am not as familiar with the MC9, but I would imagine it is close to the C3. With that said, the C3 has vents in the front of the bus, just above the bumper. Tiny slots that route to a 3 or 4 inch tube that leads to the return ramp. That is where the 20% fresh air would have to comes from. I think there is a dampener just before the air enters the return ramp area on the C3. Maybe on the MC9 as well. You should be able to access it all from the spare tire area.
Hopefully this helps.
IMHO, trying to seal off all the gaps will be a futile effort because when the bus is going down the road, there is a pressure differential (vacuum) on the interior of the bus. You would be ahead of the game to choose your point of air exchange so you can manage it.
SD
OP? b/c? means?
The original coach air is about the only thing that will over come the leaks and air loss on a bus ,I have 5 roof airs Penguins with a 20kw generator and wish I had the OEM air conditioning because of the generator time
I'm not giving up with out a fight :-) If there is one thing I'm good at, it's being stubborn.
OEM, there is fresh air into the dash, silver handle down at left knee (not ankle) controls a damper door inside dash. If it doesn't seal closed, nothing you do will cool underway. The intake is on the front above the bumper. Tape 'em shut for now.
It is nice for this to work, as you get nice, fresh warm ram air in the heating season, like your car.
The stock HVAC gets the fresh air via the two small grills face height, back of the front wheels. You may simply tape them over on the outside for a simple fix for now.
Fibreglass insulation is useless against air intrusion. You need to seal the air gaps, not filter them!
Happy coaching!
Buswarrior
Quote from: neoneddy on June 19, 2018, 09:02:57 AM
I'm not giving up with out a fight :-) If there is one thing I'm good at, it's being stubborn.
Good luck but it is a up hill battle trying to cool a 40ft bus with 26 or 30,000 btu of AC when driving,the AC in your automobile or pickup are 28 to 45,000 btu.Living in AZ 2 roof tops would get you nowhere on a spring day
OP? b/c? means?
Those abbreviations are annoying for sure. Sometimes I don't know what they mean and have to look them up. The posters using them are just lazy and wrongly assume that everybody knows what they mean. How long does it take to type a word full length ?
JC
Quote from: luvrbus on June 19, 2018, 08:53:11 AM
The original coach air is about the only thing that will over come the leaks and air loss on a bus ,I have 5 roof airs Penguins with a 20kw generator and wish I had the OEM air conditioning because of the generator time
This post makes me feel at least a little bit better about the last three weeks of struggles getting out OTR a/c working again. A series of small obstacles that have added up to cause big delays.
Back to the original topic... Isn't it odd that however much fresh air seems to rush in to heat the bus when the a/c is running, it never seems to be enough to keep it comfortable enough to shut the a/c off.
I agree about the side and front vents. Now that you know where they are I'd suggest sealing them best you can so that the fiberglass can go back to insulating, since it's not terribly good at sealing anything. Whatever you can do to stop the flow through these vents is going to go a long way to keeping you comfortable inside the bus. However, come fall when the weather turns colder and you want to remove condensation inside the windshield, you might find the need to let in some fresh air. I'm assuming that you've got a window that can be opened, but if not then you might want to find a way to get the damper working.
When I found the damper for our nose vent it was not working to block incoming air, but a 1" thick layer of foam and some weatherstripping on the sheet metal damper made it so that now it works pretty good.
About that pressure differential.... What causes it, is there a reason for it, and is there anything that can be done about it?
I've heard over and over again how it causes toilet odor to enter the living space. Surely we have the technology...
Jim
Good news, took the ol hound out for a quick spin up to Cambridge (30 miles) plenty of time to get everything hot that was going to. It got well into the 80s this afternoon and with the only real change being the insulation in the tunnel we held a nice 74 all the way there and back.
The wife said she felt some warmth from the door area still, I checked the driver's heat radiator, it was cold / not warm. Only thing we can figure is the door iself specifically the bottom area where the manual says it let's in some air in. I've got some rubber door seal stuff I'm going to try.
I know we haven't hit the west 90+ degree heat yet, but I'm hopeful with my cellular blinds and shades we can keep the sun at Bay and comfortable with 2 ACs.
@jim... now that is something I'll need to watch for. Don't want that stanky smell coming inside. Would PVC check valves on the vents help? Lets gasses out, but stop a vacuum condition sucking air in?
LOL a 90 degree day out here is spring or winter time temps people don't even turn a AC on for that temperature,get you taste of the 117 we had last week
Quote from: Jim Blackwood on June 25, 2018, 08:48:02 AM
About that pressure differential.... What causes it,
Fluid Dynamics is the cause. I don't think it is a simple enough subject to explain here, but I bet if you google it, you will find more than you would ever want to know about a bus moving through fluid.
As for the toilet smell, there is a gadget you can buy to attach to the vent pipe on the roof to pull a low vacuum on the tank as you drive down the road.... it too uses fluid dynamics.
SD
Quote from: lostagain on June 19, 2018, 11:47:57 AM
OP? b/c? means?
Those abbreviations are annoying for sure. Sometimes I don't know what they mean and have to look them up. The posters using them are just lazy and wrongly assume that everybody knows what they mean. How long does it take to type a word full length ?
JC
Original Poster and Because
LOL I don't have a problem with AC I know what it means,this why I don't do texting I never understand the abbreviations people use
The bus door lets air OUT.
The same as the toll window, air is sucked out, as there is a lower air pressure region just aft of the bus front, when it hurtles thru the air.
Bothj moving and sitting still... the coach door can ruin your hVAC efforts.
Happy coaching!
Buswarrior
The bus door lets air OUT.
The same as the toll window, air is sucked out, as there is a lower air pressure region just aft of the bus front, when it hurtles thru the air.
Bothj moving and sitting still... the coach door can ruin your hVAC efforts.
Happy coaching!
Buswarrior
Glass and the metal heat soaking kills the AC unless you have enough BTU to over come it or use plenty of closed cell spray foam on the top,floor and sides
Well, if it's letting air out / sucking it out, it means it's sucking back in some place else.
In all honestly, foaming and insulation is good, I've done plenty, not as good as others, but I feel I've got a good start with how I made my ceiling and the 4" in the walls. Not a ton on the floor, I'll be adding that from the underside to keep headroom.
I noticed the biggest change when I started adding the cellular blinds and trapping the heat behind them. The sun heats up my windows and frames past 120 degrees, thats a lot of BTUs to have to cool. I opted to keep many of my windows, in hind sight I'd remove 2 more (1 each side for 6 total removed) .
This was made abundantly clear as I was pulling out a few days ago with shorts on and felt the sun directly hit my leg and I instantly thought heat was coming in through the floor again. Nope just radiant heat.
Anyway, my next steps are to add the black vinyl back to the tops of the windshields and a few other areas that are covered by other items anyway.
JC
I am with you on the abbreviations. They say some of the people now days don't even know how to read because of them and writing in schools has changed. There are some schools that no longer teach cursive writing. :o ;)
Several years ago I looked up the specs of the OTR A/C, IIRC the original A/C is comparable to approximately 4-5 3bedroom residential house units. In other words the OTR unit is gigantic. I don?t think you could fit enough roof top units to even compete. Knowing that I still removed my OTR A/C as it was due for many maintenance items and cost/benefit was not worth it for me.
SD
I have 60,000 btu on my roof it does a good job in the AZ heat the draw back is I have to run the generator which is not bad but it cost $3.00 a hour to run the 20kw
Quote from: neoneddy on June 26, 2018, 07:31:39 AM
Well, if it's letting air out / sucking it out, it means it's sucking back in some place else.
In all honestly, foaming and insulation is good, I've done plenty, not as good as others, but I feel I've got a good start with how I made my ceiling and the 4" in the walls. Not a ton on the floor, I'll be adding that from the underside to keep headroom.
I noticed the biggest change when I started adding the cellular blinds and trapping the heat behind them. The sun heats up my windows and frames past 120 degrees, thats a lot of BTUs to have to cool. I opted to keep many of my windows, in hind sight I'd remove 2 more (1 each side for 6 total removed) .
This was made abundantly clear as I was pulling out a few days ago with shorts on and felt the sun directly hit my leg and I instantly thought heat was coming in through the floor again. Nope just radiant heat.
Anyway, my next steps are to add the black vinyl back to the tops of the windshields and a few other areas that are covered by other items anyway.
Shoot the frames on the windows you will be shocked at the heat transfer between the frames and the bus body.I am researching for a bond breaker for my Peninsula windows the off the shelf roll putty isn't cutting it and why do they paint a window frame black ?
@luvurbus Oh I did, it's what I meant, those areas can slow cook some meats on a rotisserie. I figured there was no way to keep them cool while in motion, so I need to trap the heat they generate as best I can. Kind of like how home roof systems work.
Quote from: Branderson on June 26, 2018, 06:24:37 AM
Original Poster and Because
One needs a grand-daughter on speed dial for these items...
I have studied fluid dynamics and do understand that fairly well, plus have a good bit of practical experience with it. The toll window makes sense as does the door when the bus is in motion but is the low inside pressure just an incidental then, rather than something planned? If so it would seem like a pretty simple thing to pressurize the coach slightly. How many places would there be for the air to leak out? Does the door generally leak air enough that all your cold air gets sucked right out? Sounds like a need for better seals but I can see how that might be difficult. You have a huge low pressure area behind the bus too and the wheelwells are generally low pressure areas. High pressure in front and forwards of any obstruction in the airstream.
I actually made one of those vent venturis out of PVC pipe adapters for my old S&S a decade and a half ago. Extended it up into the airstream too. But keeping water in the bowl was more effective. I think something more along the lines of the overhead exhaust diffusers on the newer transits might be adapted and get better results, maybe with an opening in the front. It'd take some experimentation. I haven't seen the commercial vent venturis. Positive pressure in the cabin would be even better, and might be usable to do the job when stationary.
Jim
The cool air does not get sucked out of a leaky front door, rather, hot air blows in under pressure. Any rusted out areas in the front along with pipe and wire passages, and leaky vents also allow air in. In many coaches in passenger service, the cooler air tends to go along the floor and gravitate to the rear. In an MC9, for instance, the driver could be sweating, but the passengers in the rear are complaining that it is too cold. (In the winter, the driver is cooler while the passengers in the rear are toasty). There is also the factor of the glass area in the front that lets in a lot of solar heating adding to the need for extra cooling. It is no wonder that many coaches had additional separate A/C's up front for the driver, and all of the A/C systems have fresh air inlets to improve air quality. The only way to keep a coach cool in all situations is to have excess capacity like the systems that came with the coaches originally, or for conversions, have five roof airs, or a combination of basement airs, or split units.
I am not down in the valley right now but in Scottsdale,it's 115 there today and my phone has rang non stop people with AC problems and the generator quitting.It is hard to explain to people in that kind of heat the amp draw will exceed 4 amps over the RLA (rated load amps) (for JC ) on a unit then x 3 units with a 7500 or 8000 watts generator and the amps falling off because of the heat.
I tell them turn 1 off,one guy told me no way it would be to hot inside you could not make him understand so I told him to find a place along the river with shade and park till the sun goes down because I cannot help you it is what it is with your setup
Makes a lot of sense Walter.
OK, so here's just a thought. Since going down the road the air higher up should usually be a little cooler, how about a roof scoop in the rear that is configured to run through your A/C evaporator? Might not be the simplest thing to do but it's undoubtedly possible and with enough thought there might even be a simple way to manage it.
If that worked it should counter the pressure pushing air in at the front and reduce the flow from front to rear so it seems like it should help with that. Plus if it provided fresh air through the A/C when parked maybe it'd help with the bathroom vent too. Pure speculation on my part and you guys would know better than I do, but it seems like something worth a little thought.
Jim