Solar powering shop A/C system - looking for controls and direction

[K-fab]

My largest cost in my shop is the A/C system. Being that I'm generally in it during daylight I'm thinking that if I can remove the highest energy eater and convert it to solar I can drop my electrical bill quite dramatically (probably pay for the system in less than a year).

Present idea is to power the two A/C systems (both 220V on 30A circuits - no, I've not climbed up on the roof and actually looked at wattage requirements of each unit, that's my next step to size accordingly) via solar as long as there's sufficient output from the PV panels. I'm in central AZ so lack of sun isn't much of an issue often.

The basics are pretty straight forward and I have a pretty good understanding of what I need to set this up but here's the caveat - I'd like this setup to switch back to public utility powered when the PV setup can't keep up (which should only be when the sun's not providing enough light to the PVs).

Does something like the Growatt or EG4 have the ability to switch load control? I want this to be stand alone and NOT feed back into the grid therefore the units would be set up on their own separate circuits and I was originally thinking a manual selector switch but is there a switch out there that can be programmed to do this? - is that something that either the Growatt or EG4 can do?

I know, newbie question. Hopefully someone can chime in (without telling me to search - I have, probably not to everyone's satisfaction). We all start at the beginning and I'm standing here at the door to that world.

Thanks in advance.

 

[sunshine_eggo]

Almost any inverter/charger you buy will have that feature in one form or another. The issue with Growatt or EG4 are finding units that can handle the surge associated with most compressors. You'll either need units that have inverter compressors (18 SEER and higher typically) where there is no surge, or you'll need to install something like a microair easystart to drop the surge current down to manageable levels.

Down here in Mesa, I'm considering getting the EG4 2 ton PV powered minisplit that does all of it on its own... powers with PV and supplements with AC if needed.

My thought is to just install it and let it run ONLY when PV is sufficient while keeping my house A/C off during peak periods. I'd install the unit in the great room to provide a large volume of comfortable space. I figure I'll pay for it in 3-4 years of savings.

 

[GSXR1000]

1 you will need soft starts on each AC compressor
2 yes eg4 and growatt will do transfer switch
3 you will need a battery to start the units and deal with moving clouds.

 

[K-fab]

Thanks, excellent info.
I wondered about start up spikes.
Speaking with a friend who's pretty deep into solar power (and got me wandering down this road) he mentioned the same thing.

I take it the battery pack would act like a starting capacitor that you find on larger electric motors? - Supplies the "oomph" to get stuff running then the solar runs it once the peak load has disappeared.

 

[K-fab]

Down here in Mesa, I'm considering getting the EG4 2 ton PV powered minisplit that does all of it on its own... powers with PV and supplements with AC if needed.

Of course I just replaced all three heads and the compressor of my shop a/c system (fondly called Medusa) in June and now I find all the new, trick solar setups. I could have done a full solar setup for less than the cost of Medusa. Oh well... Such is life at times. I was at San Tan Solar a couple of days ago and took a long look at their mini-split on the showroom floor. Made a few caveman noises as did my buddy who's tossed me down this road.

As stated in my first post, I need to get up on the roof and see what the requirements of each system is and then work from there.

It does sound like I'll end up with a battery in the system, as I kind of expected.

My biggest "non-want" is for it to feed back into the utilities so I was concerned with switching but it looks like both the EG4 and Growatt are completely programmable as to what goes where. I'm just trying to separate and feed the A/C w/o interfering with anything else in the shop.

 

[sunshine_eggo]

I take it the battery pack would act like a starting capacitor that you find on larger electric motors? - Supplies the "oomph" to get stuff running then the solar runs it once the peak load has disappeared.

Not at all. While a bigger battery might help reduce voltage drop due to high current draw, it plays no direct role in surge. That's 1000% a function of the inverter. Most EG4 and Growatts have a 0W surge capability for the purposes of starting an A/C compressor.

Of course I just replaced all three heads and the compressor of my shop a/c system (fondly called Medusa) in June and now I find all the new, trick solar setups. I could have done a full solar setup for less than the cost of Medusa. Oh well... Such is life at times. I was at San Tan Solar a couple of days ago and took a long look at their mini-split on the showroom floor. Made a few caveman noises as did my buddy who's tossed me down this road.

LOL... I work only about a mile from Santan... looks like I need to take a lunch break there.

As stated in my first post, I need to get up on the roof and see what the requirements of each system is and then work from there.

This is absolutely critical. Until you have an idea of what's actually required, most of this conversation is moot.

It does sound like I'll end up with a battery in the system, as I kind of expected.

If this is the case, your payback period is going to lengthen substantially.

My biggest "non-want" is for it to feed back into the utilities so I was concerned with switching but it looks like both the EG4 and Growatt are completely programmable as to what goes where. I'm just trying to separate and feed the A/C w/o interfering with anything else in the shop.

With grid as a backup option to an off-grid capable inverter, this isn't an issue.

 

[manfre]

Have you considered adding another PV only A/C, instead of replacing your existing two? That would

My thought is to just install it and let it run ONLY when PV is sufficient while keeping my house A/C off during peak periods. I'd install the unit in the great room to provide a large volume of comfortable space. I figure I'll pay for it in 3-4 years of savings.

I know some one who has done similar. They have a couple of window U inverter A/Cs connected to an off-grid PV outlets. They're temp is set lower than the house A/C. The house A/C still runs, but less often and it this had a big impact on their electric bill.

Of course I just replaced all three heads and the compressor of my shop a/c system (fondly called Medusa) in June

I'm just trying to separate and feed the A/C w/o interfering with anything else in the shop

The simple approach is to do similar to the above with mini splits. Connect 1-2 mini splits to an off grid PV setup in addition to the existing Medusa system. The PV won't need to be as large or need batteries, it won't interfere with any of the existing electrical, and you don't lose the money recently spent on the Medusa system because it'll still be used (just less often).

 

[GSXR1000]

Thanks, excellent info.
I wondered about start up spikes.
Speaking with a friend who's pretty deep into solar power (and got me wandering down this road) he mentioned the same thing.

I take it the battery pack would act like a starting capacitor that you find on larger electric motors? - Supplies the "oomph" to get stuff running then the solar runs it once the peak load has disappeared.

sadly a starting capacitors don't store any energy on AC voltage.. what it does is phase shift the sin wave on the start windings allowing the anglers difference from the run windings to start the motor spinning..

 

[Johneb]

I would add the micro air easy starts to your existing system. Decreases starting amps so your inverter(s) can handle the startup load. Did this with our heat pump and dropped our total electric bill by 1/3rd. Haven’t done solar yet, but that is coming. I figure the easy start has already paid for itself.

 

[K-fab]

Okay, let's start with what Medusa requires to run.
Carrier Minisplit running three heads; one 1.5 ton and two .75 ton heads.
Attached pic is the info off of the compressor - https://www.appliancesconnection.com/carrier-38mgrq36d3.html

Looks like I need 25A at 220V - so 5.5 mW

btw - my reference to a starting capacitor was just that "it kinda works like this". I forget that I'm talking to a bunch of electron chasers. Sorry about that.

I'm still going to need a setup that can deal with starting surge, correct?

The Micro Air Easy Start sounds intriguing. Time for some Google-fu.

 

[sunshine_eggo]

"mini-split" implies no surge as does the very high SEER rating. Can you find a RLA and LRA ratings for the compressor?

 

[Johneb]

My mistake. I thought he had two rooftop a/c (non mini split) units. If they are mini splits the micro air most likley wouldnt work.(

 

[RV10flyer]

It is an inverter driven rotary compressor. Looks like RLA= 25A at 240VAC or 6000W. MCA or Min Circuit Ampacity= 35A.

 

[Johneb]

It sounds like your A/C is already as efficient as you can get. (Inverter driven)

 

[K-fab]

My mistake. I thought he had two rooftop a/c (non mini split) units. If they are mini splits the micro air most likley wouldnt work.

No worries there - it's actually applicable to our travel trailer.
If I can run our trailer off of my little Honda EU2200 (instead of the noisy pain in the butt built in Onan) using one of those that would be the hot ticket. I can run the trailer on it other than AC starting surge and then it gets really grumpy.

a few minutes later....
Ordered a Micro Air for our trailer. Am very interested to see how it does.

It is an inverter driven rotary compressor. Looks like RLA= 25A at 240VAC or 6000W. MCA or Min Circuit Ampacity= 35A.

Right on the label, Minimum Circuit Ampacity 25A

 

[sunshine_eggo]

No worries there - it's actually applicable to our travel trailer.
If I can run our trailer off of my little Honda EU2200 (instead of the noisy pain in the butt built in Onan) using one of those that would be the hot ticket. I can run the trailer on it other than AC starting surge and then it gets really grumpy.


Right on the label, Minimum Circuit Ampacity 25A

Minimum circuit ampacity is not LRA. LRA embodies any surge current and is typically 5X or more the minimum circuit ampacity.

Often inverter type compressors will list an LRA equal to the running amps confirming that there is no surge, and the compressor is inverter-type.

 

[K-fab]

I looked fo

Minimum circuit ampacity is not LRA. LRA embodies any surge current and is typically 5X or more the minimum circuit ampacity.

Often inverter type compressors will list an LRA equal to the running amps confirming that there is no surge, and the compressor is inverter-type.

Not seeing LRA on any of the tech specs in the link to the compressor given a few posts up.
Looked through (searched for LRA) the spec sheet PDF on Carrier's site and didn't get squat: https://static.appliancesconnection.com/attachments/D59132c316f738.pdf

 

[sunshine_eggo]

Page 10, spec sheet says, "Rotary Inverter" for the compressor motor and a 21A rated current. That's a no-surge compressor.