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Topic: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C (Read 5852 times) previous topic - next topic

Re: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C

Reply #20 –
Where do you find the "favorable" sun to give 60A out of 1140w panel array?

Re: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C

Reply #21 –
We get 50-60A on a daily basis pretty much anywhere with no clouds in the sky.  Closer to 50A during the late winter months in Maryland.  Closer to 60 during our trip to Missouri/Kansas/Texas.  See 55-58A in full sun in Covington, VA where we currently are.

Credit to John Palmer (Palmer Energy Systems - Mayo, FL).  I suggest searching the forum for John Palmer!

Re: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C

Reply #22 –
We've used the A/C on battery power 7 or 8 times, so time to report back on some items of note:
Refresher on our setup summary: 1170 AH batteries (585 AH usable), 1140W solar on roof, Magnum MS2812 Inverter, Micro Air Easy Start wired into original Duo Therm A/C.  Re-wired front A/C unit through the inverter breaker box to use A/C on battery power.

1) We're generally running the A/C for 45-60 minutes.

2) Display suggests this draws (net) in the 100-140 Amp range, depending on state of the sun.  It ends up using 100-150 AHs of battery power total.

3) The primary item of note is that the use of the A/C is not sufficient to kick the solar charge controller out of float charge mode and back into bulk charge mode.  As per the TriStar MPPT manual, the charging schedule for a given day is determined by the overnight low voltage from the previous night.  So apparently, once the TriStar sees 95%-100%, it pops into float charge mode, and remains there until the next day.  Perhaps one would be able to "reset" this, and restart the bulk charging by temporarily pulling the charge controller fuse for a few minutes - but then does one lose the controller's "learned" size of your battery?  Not sure, but I haven't tried this yet. For comparison's sake, I popped the generator and turned on the MS2812 charge feature, but it also functioned the same way.  Stayed in float charge mode, even after pulling the batteries down to 12.6V or so.  I found this strange.

4) I've seen higher compressor kick spikes than I was hoping - the magnum display suggests a split second kick to about 450 Amps.  So, a 5000+W spike. When factoring in the high draw inefficiency power loss this value includes (I believe), it is still within the surge specs of the MS2812, but not by a whole lot.  However, for the sake of scientific research, we've decided to continue using the A/C through the inverter.  If something goes wrong, we'll report back!

5) Using one A/C for an hour is not useful for dealing with mid-day 95 degree temps - that still requires a two units and a generator - but an hour of one A/C unit is very useful to speed up cooling down an 85 degree interior to a more comfortable 78 degree interior before bed when the exterior temps and the Kool-Matic wouldn't allow for an efficient process.  As such, we find ourselves using the A/C on battery power more as the sun is going down.  Didn't expect to be using it this way, but the float charge behavior in #3) above made this the most viable option.

6) With a conscious energy day and some sun, we generally hit the "full according to the display" charge by the following evening - although because of the long absorb charge requirement of our battery bank wiring / size, it may be an additional evening until the battery is truly full and will hold at 13+V at rest after the sun goes down.

7) Haven't noticed any adverse effects on the batteries.  Still showing the same charging patterns, full voltage, etc.  But they are brand new, and it's still early in the high power A/C draw process, so stay tuned!

Anything I'm missing, or any questions?

Re: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C

Reply #23 –
Two updates:

1) I've continued to see large compressor spikes - even higher than the 400+ Amps I've seen generally.  Given that I doubt the magnum display is "fast" enough to give an accurate reading of the spikes, I'll assume the highest reading I've seen in 15-20 iterations of the compressor turning on (750 Amps!!!) is the standard spike.  That is high enough to make me think the Micro Air is NOT performing as I'd hoped.  It is also high enough to be outside the specs of the Magnum Inverter.

2) As you may know the AUTO setting on the Duo Therm units automatically changes operation from High-to-Med-to-Low the closer the interior temperature gets to the desired thermostat temperature.  I must have been caught in a funky temperature transition today, and the A/C cycled between Med-and-High 3 or 4 times within a minute.  Then (I guess because of the repeated spikes) the Magnum inverter shut down with an "A/C fault."  First time that has happened.  Worth noting that it did not pop the built-in breaker on the inverter itself (which DW did pop once when she tried to turn on every kitchen appliance at the same time....).  In any case, moving forward, I will run the A/C using a constant fan speed (probably Low), and avoid using the AUTO setting.

I'm starting to think that, rather than try to modify the existing A/C unit to be within the specs of your system, it may be safer to buy a low energy A/C that is actually within the specs.  There is a solar company out there that sells a low-energy A/C unit to go along with the solar kits it sells - but my google-fu is lacking this morning and I'm having trouble locating it again.

Re: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C

Reply #24 –
Great information. Keep us posted as you learn more.

Are you able to run the ac long enough to cool down the coach? How long do you leave it running?

Re: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C

Reply #25 –
Might try some adjustsable time delay relay on the evaporator fan and condenser fan circuits 5 & 10 seconds might help. Invertor compressor lock rotor (inrush) amps are approximately only 10% more than full load amps. This is the future for RV a/c units. Can you build a 12,000 btuh unit that starts on 10 amps inrush and 900 watt operation? Yes with widely available components today.

Re: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C

Reply #26 –
Quote from: Blinded04 –
I'm starting to think that, rather than try to modify the existing A/C unit to be within the specs of your system, it may be safer to buy a low energy A/C that is actually within the specs.  There is a solar company out there that sells a low-energy A/C unit to go along with the solar kits it sells - but my google-fu is lacking this morning and I'm having trouble locating it again.

I think you are talking about this unit from Kingtec Solar but it operates on 48v DC power which is going to be a problem for you. 

I find it kind of embarassing at how behind the times the US RV market is regarding this.  Check out Dometic Australia's inverter air conditioner that probably will never make it to the US market.  Dometic EU seems to have lots of different options that also aren't available in the US.  All the improvements to the US market have been small alterations of the same design as we had 50 years ago.
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Re: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C

Reply #27 –
SEER numbers are bogus ratings that are manipulated by the manf, and ARI. They are established by one off prototypes. EER numbers are less manipulated. Friedreichs makes a 14 eer 115 vac unit
 

Re: Micro-air Easy Start Installation - Wiring Diagrams for Duo-Therm and Exmple A/C

Reply #28 –
Quote from: turbojack –
Are you able to run the ac long enough to cool down the coach? How long do you leave it running?

We usually run it for about an hour.  Not really helpful in 95 degree weather, but perfect for getting coach from, say, 86, to a more more reasonable 78-80 right before bed when the exterior temperatures wouldn't allow for the kool matic and a few open windows to accomplish the same.