inverters

bevans6 · February 19, 2011, 06:58:27 AM

I use an inverter to run my rooftop AC on the road. I looked at installing a water cooled, quiet, diesel generator and my cost was going to be at least $5K for the way that I would do it. I needed an inverter setup anyway, I sure wanted to be able to make coffee or run the microwave while travelling if I wanted to, and for $2K I installed a 3KW PSW inverter with fully automatic switching, etc, that runs my roof AC just fine, and has can run any other load I might install as well. I can't come up with a scenario that saves me the $3K I didn't have to spend on a generator that I could run while on the road. I carry a Yamaha 3Kw gas generator that I can run while parked for those times that I need to run the AC without a plugin, and I can run everything in the bus aside from the AC for a couple of days on the batteries. Yes, I had to buy the Yamaha, it cost $1200 plus a trade-in, and I needed it anyway for emergency power and power at the race track.

That's why I don't run a generator on the road. Plus the noise, vibration, maintenance, etc. Not to say that those that do run a generator are wrong, just that running an inverter does make an awful lot of sense too.

Brian

belfert · February 19, 2011, 08:36:03 AM

Isn't there also an issue of losing engine performance when powering A/C from the alternator? Those of us with the smaller engines need all the power we can get.

I do have an inverter, but only 3,000 watts. It could potentially run two A/C units, but not anything else. (I can run both A/Cs from my 30 amp outlet at home.) I don't use my A/C on the road enough to justify a larger inverter. I just start the generator.

bevans6 · February 19, 2011, 08:45:33 AM

2,000 watts to run a rooftop is 2.7 horsepower without losses. Call it 4 or 5 hp. Impossible to notice, I would expect. Less than the horsepower needed to carry the generator, I would wager

Brian

Sean · February 19, 2011, 11:02:46 AM

Quote from: belfert on February 19, 2011, 08:36:03 AM
Isn't there also an issue of losing engine performance when powering A/C from the alternator? Those of us with the smaller engines need all the power we can get.

Only a touch, as Brian wrote. My 50DN uses about 10hp when it is cranking out well over 200 amps (nearly 6kW), and we barely notice it.

When we are climbing a long or steep grade, I will sometimes turn off the house inter-tie, returning the alternator to just running the paltry chassis loads. That probably saves me 8hp at the time when I need it the most. The inverter continues to run everything from the house batteries. When we hit the top of the grade, I turn the inter-tie back on -- all the power generated on the downhill side is free, and we get to save a couple degrees on the retarder as well.

-Sean
http://OurOdyssey.BlogSpot.com

tony · February 19, 2011, 11:17:47 AM

ok so what i am reading is 6 of one a half dozen of the other so do i even need an inverter i have a 8k des generator i have a gas refrig would i be better off just using 12 volt lights so if i want to get up at night to see thanks tony

Barn Owl · February 19, 2011, 12:52:19 PM

Tony,

You are finding that it is difficult to get a simple answer for such a simple question. If I had the money I would have one of everything and not have to worry about it. My bus came with 12v lighting and I like turning a switch and it works. I have added a few 120v lights thinking I would use them while plugged in and am finding I don't. The bus has a converter that is on when plugged up so I don't use much battery power parked. With that being said I have never run my batteries out when dry camping. My generator mostly runs the A/Cs and microwave. I have a 400w inverter that runs a TV and DVD player. Depending on how you use your bus mostly determines what you need. You can always add more when money permits. I like the 12v lighting and it is a simple and inexpensive solution to a basic need. I would install one if I was doing a bus conversion from a shell.

HTH

bevans6 · February 19, 2011, 01:13:50 PM

The problem is that it's a simple question with a lot of right answers! If you already have a generator that you could run on the road. then it's free and it's only your fuel cost. Then I would buy a small, 1,000 - 1500 watt pure sine inverter. That's so you have reserve to run a fridge if you decide to, and run everything else too. I would use 12v or 24v DC lights regardless, that's more efficient that running 120 volt lights through the inverter. You have to learn what your choices are, ask around for ideas, and then decide what makes the most sense for you!

Ain't buses grand! All the things to choose from!

Brian

happycamperbrat · February 20, 2011, 01:27:22 PM

Another option that I am considering, is to have 12 volt cigarette lighters at various places inside the coach. Most stores sell cheap little inverters for charging cell phones and other things on the road. Im thinking about possibly getting a bunch of those little inverters for a bunch of cigarette lighters to run AC current stuff. If one goes out it would be no big deal to replace it and you have redundancy. Maybe do this with a big expensive inverter to run an air conditioner...

Sean · February 20, 2011, 03:47:11 PM

Quote from: happycamperbrat on February 20, 2011, 01:27:22 PM
Another option that I am considering, is to have 12 volt cigarette lighters at various places inside the coach. Most stores sell cheap little inverters for charging cell phones and other things on the road. Im thinking about possibly getting a bunch of those little inverters for a bunch of cigarette lighters to run AC current stuff. If one goes out it would be no big deal to replace it and you have redundancy.

The problem with that approach is that it is much, much less efficient than one larger inverter. It's also a lot more expensive. Ten 300-watt inverters will cost more than twice what one 3,000-watt inverter will, and two 300-watt inverters running 300-watt loads will use 20% more power than those same two 300-watt loads connected to the single 3,000-watt inverter.

Lastly, remember that transmitting DC power over distance is way less efficient (and requires way more copper) than transmitting the same amount of AC power over the same distance. The additional losses in your DC lines and the lighter sockets will rob you of even more efficiency.

-Sean
http://OurOdyssey.BlogSpot.com

happycamperbrat · February 20, 2011, 05:39:58 PM

Quote from: Sean on February 20, 2011, 03:47:11 PM
The problem with that approach is that it is much, much less efficient than one larger inverter. It's also a lot more expensive. Ten 300-watt inverters will cost more than twice what one 3,000-watt inverter will, and two 300-watt inverters running 300-watt loads will use 20% more power than those same two 300-watt loads connected to the single 3,000-watt inverter.

Lastly, remember that transmitting DC power over distance is way less efficient (and requires way more copper) than transmitting the same amount of AC power over the same distance. The additional losses in your DC lines and the lighter sockets will rob you of even more efficiency.

-Sean

Well Poop that would kinda defeat most of the purpose.........

Nellie Wilson · February 20, 2011, 05:59:06 PM

I contribute NO technical advice to this post. It's just a comment I've wanted to make for some time. And that is: I wish I knew 1/4 of the stuff Sean knows.

Nellie

Sean · February 20, 2011, 06:35:42 PM

Quote from: Nellie Wilson on February 20, 2011, 05:59:06 PM
... just a comment I've wanted to make for some time. And that is: I wish I knew 1/4 of the stuff Sean knows.

And I wish I could have one tenth your musical talent. I love music, but I can't carry a tune in a bushel basket. I am often asked to sing tenor... ten or eleven miles away. (But I do it in the shower when no one else is home, and sometimes on the dance floor if I've had enough to drink, much to the dismay of those around me.)

Each of us has his or her own talents. Mine, apparently, is bloviating on the Internet about technical topics. Occasionally, I can even actually fix something. But the price I pay for having a head crammed full of engineering constants and technical gibberish is there is no room left for art, and I can't tell a treble clef from treble damages.

So I will make you a deal: I will relax with a friendly glass of some inexpensive claret while you entertain, and you can ask me all the inverter questions you'd like

-Sean
http://OurOdyssey.BlogSpot.com

babell2 · February 20, 2011, 09:49:11 PM

Quote from: Sean on February 20, 2011, 06:35:42 PM
I will relax with a friendly glass of some inexpensive claret while you entertain, and you can ask me all the inverter questions you'd like

Sean
I find my self as the "go-to guy" at work. If someone has a question on how, why, what, I seem to get the call. I would love to share a bottle of Pinot Noir, Pinot Grigio, or even a couple snifters of single malt and pick your brain on systems.

I am also in need of an inverter for my project but am having a hard time justifying a box that cost 2/3 of what my bus ran me.

Brassman · February 20, 2011, 09:58:31 PM

I'm thinking of two stacked inverters for 240 ac for all input configurations. Has anybody done this?

babell2 · February 20, 2011, 10:16:02 PM

Brassman
They make inverters that produce/use 240 volts
http://www.tripplite.com/en/products/product-series.cfm?txtSeriesID=818
or ones that sync and stack like you are thinking about.
http://cgi.ebay.com/STACKABLE-POWER-INVERTER-2500-5000-W-24V-DC-240V-AC-/290534680285?pt=LH_DefaultDomain_0&hash=item43a53766dd
I personally don't trust the Stack type inverters FWIW
Brice