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Author Topic: FYI - Real-life A/C on inverter power consumption numbers  (Read 2437 times)
Lin
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« Reply #30 on: June 25, 2014, 08:46:19 AM »

Interesting looking solar mounting system.  It's good to know that you are getting a decent charge even in the shade.  One of the reasons that I decided not to do solar on the roof was that most times we want to be in the shade and I was told it would not work. 
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« Reply #31 on: June 25, 2014, 10:12:38 AM »

<snip>
Don't know if this is what you wanted, Bruce, but I hope it's helpful. My original plan was to buy an 8 or 10 KW generator head and put it on one of the Isuzu/Thermoking diesels I have on hand. I was planning to put that where the original air handler was. With our solar panels and the fact that we decided we can live without two or more large AC units, the big generator would be silly. We could get by with 2000 watts of Honda or Yamaha for backup, but since we already have a good 4500 watt Kohler out of our old motorhome, I have spruced it up and am currently working on getting it installed above the engine. Run what ya brung, as they say.
<snip>
Jim in NC

That's a nice setup.  If you don't mind me saying, by my way of thinking, if you do start considering a diesel generator in the future, a used APU seems like it might fit your bill.   At about 24" wide, they put out about 4kw (some vac, some vdc only).  Small by comparison to most generators, but enough to charge batteries, and if it's hooked up, you get one of those A/C's that you've decided to forego along with it (using none of that 4kw of electrical generation).  Heat too.   Probably only affordable by those who are willing to buy used and tinker, but you did mention mounting generator heads onto different engines so I guess you're game for projects.

I get excited seeing solar on people's rigs.  Aside from a boat, I can't see a better use of it.  I mean, RV's and marine are by nature...off grid right from the start, whereas houses are designed to be on grid yet usually are the first to get PV's.

Thanks for the pic's!
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« Reply #32 on: June 25, 2014, 12:48:17 PM »

One of the reasons that I decided not to do solar on the roof was that most times we want to be in the shade and I was told it would not work.  


Lin, of course your situation will be different than mine, and of course those panels have to have SOME sunshine to work with. We base on a spot with lots of shade because it puts us close to sewer and water. This time of year we probably get around 5 hours of sun. About the same in winter because the leaves are off.

With that said, I AM amazed at this system's performance. It's a joy to watch battery voltage come up on cloudy days. AND, at night I point the cart mounted panels toward a nearby street light. We get some gain that way. Part of it is high capacity panels. 1020 watts is much more than would fit in that space even a few years ago. Mostly, though, I thank the MPPT controller.

Audiomaker, tell me more about APU. I don't know what that is, but I'm not afraid of a project. You should see my yard. On second thought, maybe it's best you don't.

Mobile houses and solar power are a natural fit. I confess, though, that I never considered taking a bus off grid until I first read Rob Gray's build thread in 2010. He made it seem so obvious.  www.graynomad.com

Our build thread is here: http://www.nomadicista.com/viewtopic.php?f=4&t=2541

Best to all,

Jim in NC
« Last Edit: June 25, 2014, 07:09:57 PM by Lostranger » Logged

Jim Huskins
Marion, NC
1999 Gillig H2000LF
Yes Virginia,
You CAN convert a low floor.
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« Reply #33 on: June 25, 2014, 03:48:56 PM »

<snip>
Audiomaker, tell me more about APU. I don't know what that is, but I'm not afraid of a project. You should see my yard. On second thought, maybe it's best you don't.

Too late, but I'll make it short.  An "APU" or "Auxiliary Power Unit" is a small (usually 2cyl) self contained diesel unit designed to power the things that OTR truckers used to keep their engines running to power.   In other words, it is supposed to power everything the engine does except moving the truck.  They usually have a high capacity alternator, an A/C compressor, and a heat exchanger.
Outboard of the main unit is the remote A/C blower unit that they install in their sleepers.   The heat exchanger is routed either through the trucks engine where the driver uses the factory heating core and fans to heat the sleeper, or sometimes a heater exchanger can be installed elsewhere in the sleeper.  The advantage to doing the engine circuit heat is that the engine is warm when they wake up and want to get going.
In some cases, the electric or cooling is also routed to a refer trailer...etc.

They were more of a luxury in the past, but as more states pass anti-idle laws, they are now on most OTR trucks.
The disadvantage of an APU vs a regular generator is that they don't generally have enough wattage in comparison, but the advantage is that they have mechanical A/C and heat built in which is normally the biggest draw on a generator/inverter system, so one can get away with a lower amount of electric since you're mostly just charging batteries.... especially if you can supplement it with solar (which the truckers don't).
The units are pretty small...about 2' wide, 25" high, and maybe 30" or so deep.
Because they've been around for awhile now, they get pulled from scrapped trucks, or as part of the service program on fleets.
You can find them on ebay and such... often pretty rough looking, but if you get one that runs and has a rebuildable diesel in it, you can probably put a rebuild on the "later" list.

I have friends who drive truck, and they love the things.  I hear all about how they keep the sleeper warm...or cool...etc.
"Warm and cool" are what my generator/inverter system struggles with.    A/C and electric heat are the big energy hogs, so it's smart how they get around that with the APU setup where those two items are mechanical.

Although I suppose most people don't use electric heat, most can, and I kinda laugh and wince at the same time when my 7k generator is pushing my 1500 watt heater.   A tiny bit of heat from the heater, and massive heat from the wasted generator's radiator to do it.
The APU uses that engine heat, and that's smart in my book.   At least its smart enough to explain why cars don't come with electric heaters and electric a/c's...which is what the RV crowd seems to end up with.

Smiley

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« Reply #34 on: June 25, 2014, 03:53:15 PM »

the "graynomad.com" link is dead - gets you a "For Sale for $2,095.00" notice.
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« Reply #35 on: June 25, 2014, 04:33:07 PM »

Interestingly this thread has now begun to discuss alternatives to typical RV/conversion A/C needs.   Further to my previous question why mini-splits aren't more popular,  I'il be using one simply because I cannot run a typical roof-wart for long off my solar panels, but a mini-split drawing only a fraction of the power is well within my panels' capacity.   I have eight Sharp 255W panels, giving me 2,040 theoretical watts, and they will feed two Morningstar TS-MPPT-60 controllers to charge two separate battery banks, each bank being eventually four golfcart or L-16 batteries.   (Sort of Jim times two.)   With that much power I can easily run a mini-split or a 5,000 BTU window A/C, but probably not both together.

I've made a walkway that runs along the 26 feet of space between my two roof hatches, and from this walkway will be hinged the panels, or more specifically the panels' support frames (each panel will sit in its own support frame made from 6063 angle).   Each panel can sit down against the roof at about 20 degrees down (the ideal angle for SoCal summers!), or at horizontal, or at 20 or 30 or 40 or 50 degrees up (for winter sun), with all their cables and combiner boxes protected under the walkway.   There will be absolutely zero shade on any panels at any time from anything on the bus.   As long as I can park in an east/west direction I should get good insolation, and even if I can't I should still get lots of usable power, likewise on cloudy or dull days.   One other incidental benefit is that almost my entire roof is shaded this way, hugely reducing the sun's heatload onto it, and somewhat reducing interior temperatures.

I want A/C, but without needing to ever run a generator for it.   I think my setup will work well for me  -  whether it's useful for other folk is up to them, but as they say "Do it your way"!

John   
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« Reply #36 on: June 25, 2014, 05:12:39 PM »

Interestingly this thread has now begun to discuss alternatives to typical RV/conversion A/C needs.   <snip>
John   

Well, for some the season is already here.  For others (like myself) it's coming soon.

I'd love to see or watch your solar install progress.  I have a similar plan as I have room for 10 of the 250 watt panels.

I don't know if the thread has really gone off topic... I mean you could call it "how many ways can someone power an air conditioner?".
The OP can power his it seems from his engine's alternator and that's pretty cool (ack!).

The solar equation is pretty intriguing too for those who have enough real estate to even consider it.   The idea that the hotter it gets outside, the cooler it could be inside (for free) is a fun challenge.
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« Reply #37 on: June 25, 2014, 06:05:34 PM »

the "graynomad.com" link is dead - gets you a "For Sale for $2,095.00" notice.



I apologize. try www.robgray.com
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Jim Huskins
Marion, NC
1999 Gillig H2000LF
Yes Virginia,
You CAN convert a low floor.
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« Reply #38 on: June 25, 2014, 06:18:14 PM »

An "APU" or "Auxiliary Power Unit" is a small (usually 2cyl) self contained diesel unit designed to power the things that OTR truckers used to keep their engines running to power.... They usually have a high capacity alternator, an A/C compressor, and a heat exchanger....   

Well powder my butt with flour and call me a biscuit! What rock have I been under while this little development rocked the trucking world? I'm too much in shock to say whether I'm happy or sad to have made the APU connection, but I do know that I gotta have one. Would tie up many loose or semi fixed ends in my conversion.

So happens that we need to build a small walk-in cooler for the organic produce business....

Thanks, Audiomaker, or curses! Depends on how much of an investment this turns out to be.

Jim in NC
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Jim Huskins
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« Reply #39 on: June 25, 2014, 06:38:15 PM »

Well powder my butt with flour and call me a biscuit! What rock have I been under while this little development rocked the trucking world? I'm too much in shock to say whether I'm happy or sad to have made the APU connection, but I do know that I gotta have one. Would tie up many loose or semi fixed ends in my conversion.

So happens that we need to build a small walk-in cooler for the organic produce business....

Thanks, Audiomaker, or curses! Depends on how much of an investment this turns out to be.

Jim in NC

Well the bright side might be that they usually sell to truckers...who don't need projects.  They just need to get back on the road.
To that end, "project" APU's can be had for under a grand.... I've seen them as low as $500.  I suppose that's about the same game as a generator. Better off to get one with at least the cabin A/C unit still attached as I wouldn't want to piece that together.
Those are eBay #'s.  Junkyards and such you might do better (and not have to ship).

Anyway, just something to research in your spare time and see if it might fit.

All the Best
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« Reply #40 on: June 25, 2014, 09:04:07 PM »

"While in theory, you could have a huge battery bank (that's spelled "$$$$$$$$$$") but you'd only be measuring in minutes, not like overnight."

I have bus AC for going down the road and I run the generator when stopped overnight if it is really hot. However I can and do run one roof air for 8-10 hours overnight off batteries on a regular basis. I have 8 4D batteries. I thought it was overkill until I realized the full capabilities of a big battery bank.

Davy
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« Reply #41 on: June 25, 2014, 10:34:35 PM »

  "While in theory, you could have a huge battery bank (that's spelled "$$$$$$$$$$") but you'd only be measuring in minutes, not like overnight."

I have bus AC for going down the road and I run the generator when stopped overnight if it is really hot. However I can and do run one roof air for 8-10 hours overnight off batteries on a regular basis. I have 8 4D batteries. I thought it was overkill until I realized the full capabilities of a big battery bank.   Davy

    A roof air?  What amps does it pull?  It's great that you have it worked out to do that - not too many people have been successful.  How many amp hours is your battery bank rated for?  How far down on "State of Charge" does an overnight pull it down?  Is 8 4D's the equivalent of 4 8D's?

Thanks for the info!  BH  NC   USA
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Bruce H; Wallace (near Wilmington) NC
1976 Daimler (British) Double-Decker Bus; 34' long
6-cyl, 4-stroke, Leyland O-680 engine

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« Reply #42 on: June 25, 2014, 11:32:14 PM »

  Hey Bruce. Good to hear from you.  ...

   And you!  Thanks for that info.  I was especially thinking about panels (I see you're just over 1000 watts) and the charge controller -- that Morningstar controller must be really making the most of every bit of power from the panels.  Good to hear about your battery bank.  Does 4 8D's give you a total of about 930 amp/hours, total (limited to about 460 to go from full to 50% State of Charge)? 

   I like your "manual" aiming device; it's clear that keeping panels at a right angle to the sun makes a bid difference.  Yes, lots of detail there and i thank you for that.

    I have heard some not-nice things about the Detroit 40 series engines but you don't run generalities -- you run what's in your bus.  I was thinking that a Cummins ISC 8.3 would be nice, too, and yeah, the retarder sounds really sweet.  Not that I've really been thinking much about it.
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Bruce H; Wallace (near Wilmington) NC
1976 Daimler (British) Double-Decker Bus; 34' long
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« Reply #43 on: June 26, 2014, 03:44:07 AM »

Does 4 8D's give you a total of about 930 amp/hours, total (limited to about 460 to go from full to 50% State of Charge)? 

I like your "manual" aiming device; it's clear that keeping panels at a right angle to the sun makes a bid difference....

I was thinking that a Cummins ISC 8.3 would be nice....

The retarder sounds really sweet. Not that I've really been thinking much about it.

Bruce, my battery bank is rated 490 amp/hours at 24v. We refer to the Manual Solar Tracking Ensemble as the NASTY. I've already come to the conclusion that, should a repower become necessary, it's ISC for me.

You know, you're not really gonna be happy until you buy a wrecked Gillig and slip the engine and drive train under your Daimler. Who knows, in the process, you might even lower it enough to be able to paint the roof.
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Jim Huskins
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« Reply #44 on: June 26, 2014, 04:59:56 AM »

    A roof air?  What amps does it pull?  It's great that you have it worked out to do that - not too many people have been successful.  How many amp hours is your battery bank rated for?  How far down on "State of Charge" does an overnight pull it down?  Is 8 4D's the equivalent of 4 8D's?

Thanks for the info!  BH  NC   USA

My roof airs are 13.5 Duo Therm Penguin's by Dometic. I added them in 2009 and removed the original Cruise Air units.

The display in my coach shows about 3 amps with the fan on low and 10-12 more amps with the compressor running. I do not know exactly how accurate that is but it is consistent.

Honestly I do not know the amp hours on the batteries and I can not take credit for the set up. I am the 3rd owner but as far as I can tell this was the standard set up for a Vantare conversion of my vintage. The batteries were very weak and beyond their life span when I bought the bus in 2008. When I found out it had 8 batteries I was bound and determined to figure out how to put fewer batteries in when I replaced them. I was cautioned by several folks that I needed to understand my system better before I tinkered much with the engineering because ALL the electric runs through the inverters on a Vantare. There are no "inverter circuits" and "non inverter ciruits" in my bus. Everything runs through the inverters and everything has the potential to be ran on battery power in theory. I never get close to the amp threshold but the inverters will bring the generator online the amp pull reaches a certain set point.

I decided to replace all 8 batteries the first time and completely diagram all the battery and inverter wiring while I was at it so that I could better know the system and figure out how to reduce to 4 batteries the next time they need to be replaced hopefully 5-7 years down the road.

But, after living with the convenience of 8 new batteries and the freedom that gives me I will probably never downsize to 4. When my batteries were shot and I pulled into a Flying J or WalMart for the night while traveling, I had to turn on the generator within and hour if I wanted even the fridge to run. I had no flexibility at all. My options were either shore power or generator if I was stopped. I was fine with that because that is all I had ever known. I basically go from shore power to shore power every week in a new location. The only exception is travel days.

After I installed new AGM batteries I had a whole new realm of possibilities. Stopping for the night is absolutely no problem now. We run the fridge, a fan, all of our computers and chargers and do not have to worry about it. I did change about 30 halogen lights to LEDs to eliminate those amps. If it is a little warm then I turn one air on and run it as much as I need it although I do keep a close eye on the numbers. If it is warmer and we need more than one AC or my wife needs to cook then I do not hesitate to start the generator.

The conversion companies have invested a lot of time and money into engineering the electrical systems. They all do something a little different but they do it for specific reasons. If I was building something from scratch (I could not but I absolutely admire you guys that can) I would try to look at every system I could and take the good from each.

I do not have anything that tells me the percentage of charge but as long as my inverters are telling me the battery voltage is 25 or above I am satisfied. If it gets too low I have it set to auto start the generator but I watch it close and start it manually.

Davy
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