Solar Powered Heat Pump - Unexpected Challenges. Throwing In The Towel...

[markpj23]

I'm enclosing a screen room and will add a mini-split for cooling (in AZ). Since we lose power a lot here I thought it might be worth it to buy one of the solar powered units either from EG4 or Airspool. The Airspool unit is now Energy Star rated so I figured that's the way to go.
Then the details snuck up on me.....

The questions / obstacles I have run into are:
Issue #1: These units require at least 80VDC to operate, and the 4-panel 'kit' offered by some resellers puts you in the 200 - 250VDC range (panels in series). That voltage then requires DC Arc Fault protection - and I've yet to find a UL listed AFCI rated for DC. Even the non-UL breakers that meet the spec are well over $400 on Amazon...

Issue #2: Since it's high voltage, the neutral current carrying connector (B-) must be bonded to the equipment grounding connector. If this does not happen within the heat pump itself (similar to the way inverters handle this) then I must proving a bonding lead somewhere. Within the roof top junction box perhaps? So I assume I can just connect the B- box in & box out leads to the EGC terminal block or must I use a wire nut?

Related to Issue #2: IF the heat pump DOES bond the B- to EGC internally, then that means that the suggested way to connect it to AC using a standard 120v 3-prong plug (for 12KBtu and smaller units) will NOT meet code. Unplugging the unit would break the B- to EGC bond. So I still need a hard wired service disconnect. (Awaiting a tech reply from Airspool - who has been very responsive BTW).

Issue #3: Since the high voltage DC must use a bonded B- conductor, the NEC requires that wire color to be either Grey or White. The cable sets offered in the kits are all red & black. So no using pre-made cables with MC4 connectors - I'll have to make my own. Crimpers, connectors, etc are now added to the list.....

Issue #4: Since it's high voltage DC, I cannot run the EGC inside the same conduit as the B+ / B- conductors? What about putting the EGC inside the same roof top junction box? Doesn't make too much sense to me.... two conduits exiting the same junction box?

Issue #5: I do NOT plan to run the DC leads inside the house. Rather, I plan to penetrate the roof at the overhang and just run the conduit down the exterior wall to the heat pump. So can I use PVC conduit or must it still be EMT? In this heat I'll probably wrestle with the EMT though....

Issue #6: Finding UL listed PV disconnects, ground-fault breakers and enclosures that won't break the bank....

These solar-powered mini-splits may not be quite as plug-n-play as the marketing folks would have me believe.....

 

[Mkgough]

I'm enclosing a screen room and will add a mini-split for cooling (in AZ). Since we lose power a lot here I thought it might be worth it to buy one of the solar powered units either from EG4 or Airspool. The Airspool unit is now Energy Star rated so I figured that's the way to go.
Then the details snuck up on me.....

The questions / obstacles I have run into are:
Issue #1: These units require at least 80VDC to operate, and the 4-panel 'kit' offered by some resellers puts you in the 200 - 250VDC range (panels in series). That voltage then requires DC Arc Fault protection - and I've yet to find a UL listed AFCI rated for DC. Even the non-UL breakers that meet the spec are well over $400 on Amazon...

Issue #2: Since it's high voltage, the neutral current carrying connector (B-) must be bonded to the equipment grounding connector. If this does not happen within the heat pump itself (similar to the way inverters handle this) then I must proving a bonding lead somewhere. Within the roof top junction box perhaps? So I assume I can just connect the B- box in & box out leads to the EGC terminal block or must I use a wire nut?

Related to Issue #2: IF the heat pump DOES bond the B- to EGC internally, then that means that the suggested way to connect it to AC using a standard 120v 3-prong plug (for 12KBtu and smaller units) will NOT meet code. Unplugging the unit would break the B- to EGC bond. So I still need a hard wired service disconnect. (Awaiting a tech reply from Airspool - who has been very responsive BTW).

Issue #3: Since the high voltage DC must use a bonded B- conductor, the NEC requires that wire color to be either Grey or White. The cable sets offered in the kits are all red & black. So no using pre-made cables with MC4 connectors - I'll have to make my own. Crimpers, connectors, etc are now added to the list.....

Issue #4: Since it's high voltage DC, I cannot run the EGC inside the same conduit as the B+ / B- conductors? What about putting the EGC inside the same roof top junction box? Doesn't make too much sense to me.... two conduits exiting the same junction box?

Issue #5: I do NOT plan to run the DC leads inside the house. Rather, I plan to penetrate the roof at the overhang and just run the conduit down the exterior wall to the heat pump. So can I use PVC conduit or must it still be EMT? In this heat I'll probably wrestle with the EMT though....

Issue #6: Finding UL listed PV disconnects, ground-fault breakers and enclosures that won't break the bank....

These solar-powered mini-splits may not be quite as plug-n-play as the marketing folks would have me believe.....

I have a 12k EG4 and the manual lies about how much min solar it needs. I have 4 ground mount 200w Rich Solar panels for 800watts of PV input. Now I also have an Eco-Worthy solar tracker with 1095watts that charges my Bluetti AC300. I can use the tracker if needed and will when I move as the Bluetti will go with me freeing up the tracker. The 1095w the tracker provides will provide all the PV the 12k would ever need being it is more efficient following the sun. The 12k needs 20a 120v grid… orrrrr I have an extension cord to my AC300 for grid and have the Disconnect box which I have pulled the connection, but can use it. So the 4 ground panels provide a fair amount of the daytime solar needs and the Bluetti the rest. It takes around 500w on a big cool and less when it is just maintaining the cool 300w ish, I expect similar numbers in the winter, we shall see. Very efficient units these EG4 power wise. The Airspool and EG4 are the same maker BTW. It was very easy to install. I do not have a solar disconnect, though I could add one since it is under the eave. Mine comes from the ground as my pipes are barely buried in 2” pvc. I could even put it on the track post come to think. Metal conduit is your best bet for roof mount and future inspections. You can use a utility box to put your PV disconnect in, so cheaper one needed and metal conduit around the eave into the utility box and then typical flex conduit to the mini-split.

 

[markpj23]

After many hours of researching, shopping for the best deals, and navigating the permit maze I've decided to throw in the towel. Going the solar mini-split route was roughly $1800 more expensive (meaning double the cost) than the conventional route, plus the added aggravation of the permitting process and the surprises that it promised to deliver. Payback period is decent, but these units don't draw much to begin with.
Seems to me to be more practical to just buy a decent sized solar generator, avoid the permit hassle, and be able to run more than just a mini-split during an outage. Prime Day saved me $400 on a Mr Cool DIY unit that's also a 22 SEER rated unit. Not the latest & greatest perhaps, but easily doable with less hassle.
Yes, the cost per watt has come down but all the assorted pieces parts have done the opposite. If there was a permit-ready kit being sold I might have gone a different way....

 

[k490]

If you want to permit best way would be a EG4-6000XP it's UL listed meets the requirements the cost to buy a battery is higher. That's what I'm doing I have 12 panels going to ground mount on the side of my house. It will run shed AC, garage mini split, refrigerator, and act as a UPS for my computers. I'm not permitting, but going to build it to code best I can. We get such high heat in mid summer most AC units running at max power SEER doesn't mean much until it's cooler out.

 

[Luk88]

I see you already decided to to a different route, but few things seem worth discussing a bit more.

Please note I'm not in the USA, but the electric code there is of interest to me.

Issue #2: Since it's high voltage, the neutral current carrying connector (B-) must be bonded to the equipment grounding connector. If this does not happen within the heat pump itself (similar to the way inverters handle this) then I must proving a bonding lead somewhere. Within the roof top junction box perhaps? So I assume I can just connect the B- box in & box out leads to the EGC terminal block or must I use a wire nut?

You can't refer to DC- as neutral. There is no neutral in a DC system. The part of the NEC that deals with PV systems is 690. It gives 6 system configurations to choose from in 690.41 A. One of them is indeed "2 wire circuits with one functionally grounded conductor", but there is also " isolated" and this will be a huge majority of all PV systems installed.

Related to Issue #2: IF the heat pump DOES bond the B- to EGC internally, then that means that the suggested way to connect it to AC using a standard 120v 3-prong plug (for 12KBtu and smaller units) will NOT meet code. Unplugging the unit would break the B- to EGC bond. So I still need a hard wired service disconnect. (Awaiting a tech reply from Airspool - who has been very responsive BTW).

It seems insane if any device did that. It is essentially bonding PV - to its enclosure. Now you don't need to be exposed to both PV conductors to get shocked. Just a + will be enough... But as mentioned above NEC allows for one functionally grounded conductor. I would expect a huge warning label if a device did that as well as it being on the first page of the manual.

Issue #3: Since the high voltage DC must use a bonded B- conductor, the NEC requires that wire color to be either Grey or White. The cable sets offered in the kits are all red & black. So no using pre-made cables with MC4 connectors - I'll have to make my own. Crimpers, connectors, etc are now added to the list.....

If you wanted to ground one of the PV legs yes, it should be white or grey. Can such PV cables be bought in US?