M380 Solar - An All-Electric Conversion

[DW SD]

Kev and Van-
How many amps does an AC unit draw on average?

Thanks,

Doug

[NoGas]

I’ll be doing a two year update to this thread shortly (a few tweeks but it’s all still working great! ). Is water under the bridge, but just noticed Mike’s post above and wanted to answer:

Originally Posted by rtpn60

BUT, most over the road transit buses are 24v systems. They also have 24v starters, etc... So in our buses you'd have to deal with 24 to 12 volt converters and that's not a good direction, especially for large current items like starters

Had I not already owned an almost new 12v inverter/charger, I would definitely have gone with a 24v Magnum instead. Mikes converter point would’ve been easily solved with a simple wiring addition. My coach has two 12v -31 AGM engine/chassis batts. Going with 12v parallel to the chassis/engine and 24v series from the charger to that battery pair (it’s rarely used to charge the engine batts) would’ve solved the problem. Same principle for the coach batts, though the number of 6v L16’s mightve been changed to either 4 or 8 (something divisible by 12). Instead, I would likely have stayed with six batts and used an inexpensive DC-DC converter for the small number of 12v DC low load items in my coach. The advantage of less voltage “sag” (technical term ), when under heavy load with a 24v vs 12v inverter supplying 120v AC is significant.

Doug - Between 10 and 13 worst case when compressor is running. With just the fan in between it’s much lower, of course. There is a momentary spike to more than 20 on initial compressor start. However that settles down almost immediately and the micro air easily compensates, preventing an inverter fault. At this point had I to do it again, I probably would’ve just stayed with a soft capacitor upfront. That’s because I so seldom use my generator and providing BOTH ac units when traveling provides a good opportunity to do so. When bonondocking, I do occasionally run the front AC unit off the inverter mid-day, when solar is at its most productive.

[badandy]

Originally Posted by DW SD

Kev and Van-
How many amps does an AC unit draw on average?

Thanks,

Doug

They are 10-15 amps running. My new Atwoods are about 10-12a depending on temps. My old clunker original Dometics would take 15-18a, but one died and the others weren't far behind.

I installed a Microair on the middle Atwood and I've been running it pretty much nonstop without issues. I need to put my meter on it to see what the peak came down to, but you can even hear the difference when it's starting up.

[DW SD]

Thank you, Amigos!
I was noodling on the idea of a soft start on my front AC unit and running it for an hour or two in the heat of the day from battery and inverter.

I'd have to see how well the solar compensates. Seems like @ 13A, that translates to 100 amps DC. I'm guessing solar could make up 40 to 50 amps of that.

Then again... it probably just makes sense to run the generator for an hour or two if need be. That only costs $2 in diesel if it burns 1/2 gallon / hour.

Back to your regularly scheduled programming.. Van's kick a$$ upgrade channel.

Best,
Doug

[NoGas]

Originally Posted by DW SD

...I was noodling on the idea of a soft start on my front AC unit and running it for an hour or two in the heat of the day from battery and inverter...

Before trying AC off batts/solar, go back and read Micro-Air’s post (#28 on Page 3, this thread). It’s the initial compressor locked rotor startup spike not the running amp draw that creates a problem for the inverter. That huge fraction of a second startup slam typically “red light” faults a 3,000 watt inverter. Not a good way to ensure it’s longevity. M-A’s product solves that issue completely. Naturally, they recommend their product over a soft start cap. The PT100’s charger output by itself can’t quite keep up with one A/C’s draw. However, I can confirm it works if one rewires the rear AC CB panel such that the front A/C feeds off the inverter and they limit their other AC draws. Again when it’s HOT, I usually run the geny and both A/C’s.

Someday, I’d like to see and be dazzled by Andy’s coach .

[DW SD]

Hi Van,
When I wrote soft start, I meant something like Micro-Air (not capacitor - only) solution.

In this case, I think I can better spend my $ on Diesel when I need AC here and there.

Doug

[nbedinger]

Originally Posted by rtpn60

Aaron, Not sure I understand your statement.
<snip>
The only time I've run my generator in the last 2 years was to power up the 3 AC units in Arizona while travelling during the day in the summer heat... because I could.

Michael

������

The temps and humidity here on the edge of The Dismal Swamp are truly oppressive—so hot and humid I am soaked with sweat sitting here. The house has central AC but I’m in the SP with just ceiling fan on. I know a couple of weeks is what’s needed for my body to adjust, then I will be cool to do a little work outdoors or sit comfortably inside without AC. The body gets in tune with the climate if you give it time. But I’m looking forward to AZ winter, it’s the COLD that I can’tt abide!

[rtpn60]

Good update guys!

I am tempted to play with the idea of running a front AC unit off solar/alternator/inverter while travelling. But I'm still on a 2000w pure sine wave, live in AZ where one AC just isn't going to cut it. So IF I were to play with this setup it would be with a 24v 3000w inverter but then again, stuck with one AC in Arizona.... On top of all that I've upgraded all 3 AC units to 15,000 BTU units so just doesn't seem to be a logical solution for this old bus.

[badandy]

Originally Posted by rtpn60

Good update guys!

I am tempted to play with the idea of running a front AC unit off solar/alternator/inverter while travelling. But I'm still on a 2000w pure sine wave, live in AZ where one AC just isn't going to cut it. So IF I were to play with this setup it would be with a 24v 3000w inverter but then again, stuck with one AC in Arizona.... On top of all that I've upgraded all 3 AC units to 15,000 BTU units so just doesn't seem to be a logical solution for this old bus.

You might be surprised - did you measure the running current of the new A/C's? If it's under 15 amps, which I bet it is, you could probably run two of them on that 3000w 24v inverter if you put Microairs in them.