24K BTU EG4 solar mini-split sizing questions

[G20]

I have a question about sizing solar panels to power EG4's 24K BTU mini-splits.

The specs give an input watt range [190 - 2250 watt] and max VOC <380V.

EG4 Hybrid Solar Mini-Split Air Conditioner Heat Pump AC/DC| 24000 BTU

I have local options for smaller 270 watt panels and larger 540 watt panels. More of the smaller panels will get me closer to <380VOC spec where fewer of the larger panels will get me to the 2250 watt spec at half the 380VOC spec in a serial string.

Which is preferable for the solar mini-split and why ?

I understand higher voltage equates to less line loss, but are there other considerations that outweigh the relative line loss in these 2 options ?

Thanks much.

 

[Supervstech]

I have a question about sizing solar panels to power EG4's 24K BTU mini-splits.

The specs give an input watt range [190 - 2250 watt] and max VOC <380V.

EG4 Hybrid Solar Mini-Split Air Conditioner Heat Pump AC/DC| 24000 BTU

I have local options for smaller 270 watt panels and larger 540 watt panels. More of the smaller panels will get me closer to <380VOC spec where fewer of the larger panels will get me to the 2250 watt spec at half the 380VOC spec in a serial string.

Which is preferable for the solar mini-split and why ?

I understand higher voltage equates to less line loss, but are there other considerations that outweigh the relative line loss in these 2 options ?

Thanks much.

You don't want to shoot for VOC, you want to ABSOLUTELY POSITIVELY BE CERTAIN IT NEVER EXCEEDS IT...
you want to shoot for double the minimum voltage which would be 180V
But be sure your weather low temp will never cause thw string to exceed the voc number.

 

[G20]

You don't want to shoot for VOC, you want to ABSOLUTELY POSITIVELY BE CERTAIN IT NEVER EXCEEDS IT...
...
But be sure your weather low temp will never cause thw string to exceed the voc number.

Thanks much for the quick response.

I was under the impression you wanted to approach max VOC including the cold weather gain while not exceeding it to compensate for overcast and partial shade issues and minimize line losses.

According to the voltage drop calculator, twice the voltage at half the amperage is @ 400% less line loss compared to half the voltage at double the amperage.

4 of the 540 watt panels would be @ 199 VOC.

 

[SolarScott]

I have a question about sizing solar panels to power EG4's 24K BTU mini-splits.

The specs give an input watt range [190 - 2250 watt] and max VOC <380V.

EG4 Hybrid Solar Mini-Split Air Conditioner Heat Pump AC/DC| 24000 BTU

I have local options for smaller 270 watt panels and larger 540 watt panels. More of the smaller panels will get me closer to <380VOC spec where fewer of the larger panels will get me to the 2250 watt spec at half the 380VOC spec in a serial string.

Which is preferable for the solar mini-split and why ?

I understand higher voltage equates to less line loss, but are there other considerations that outweigh the relative line loss in these 2 options ?

Thanks much.

I'm running seven used Sharp 245 watt panels to my 24K.......I can't remember the exact highest wattage but I know I have seen at least 1600 watts from them, maybe even more.

 

[Plum Crazy Rob]

Keep getting a security error uploading an image, but use info at deyesolar.com - 2500-3000W of panels is easy tolerable and I feel preferred for low light. I have 2700W, have seen 2600W on Heat and 2200 on Air...

 

[G20]

Keep getting a security error uploading an image, but use info at deyesolar.com - 2500-3000W of panels is easy tolerable and I feel preferred for low light. I have 2700W, have seen 2600W on Heat and 2200 on Air...

Their chart indicates a lot of 500w panels for their 24K BTU unit. It looks like they are maxing out the VOC and over-paneling/watting (7 x 400 = 2800 watts, 7 x 500 = 3500 watts).

DGWA1-ACDCBLW-24K WiFi

24000btu 3.0Hp 2.0Ton

80V-380V

</=10A

1790(300-3200) W

Deye hybrid ACDC unit suit for both Poly and mono solar panel on the market from 250w to 450w. But all the solar panel should be in series connection, parallel is not allowed.

 

[Plum Crazy Rob]

Yes. According to 380V x 12A Isc, you could have 4560W of incoming Solar (don't do THAT lol)

 

[740GLE]

So much PV wasted when the unit isn’t needing it, alas in the world of cheap PV it’s better than grid tied.

 

[Plum Crazy Rob]

Yes I was just going to joke individuals from diysolarforum.com will make a Citizens Arrest of underutilized panels over 3000W

 

[G20]

Yes. According to 380V x 12A Isc, you could have 4560W of incoming Solar (don't do THAT lol)

I have 2 locations for ground mounts. One favors morning/mid day, one favors afternoon, later evening.

I could see a use case using more panels to lengthen the solar day which could serve as a stop-gap approach to a growing system (start with a DC only heating/cooling and then add inverters/charge controllers/batteries over time as budget allows).

I have added a lot of insulation over time so the house is used as a thermal battery not requiring 24 hour heating/cooling except on very rare occasions.

 

[Shimmy220]

Since these are most advantageous to people without an existing solar system it seems like Signature Solar should be selling a kit that comes with the mini split and panels.

 

[Supervstech]

Keep getting a security error uploading an image, but use info at deyesolar.com - 2500-3000W of panels is easy tolerable and I feel preferred for low light. I have 2700W, have seen 2600W on Heat and 2200 on Air...

Text the pic to yourself, save the texted pic, then attach the edited pic here.

 

[Plum Crazy Rob]

I have 2 locations for ground mounts. One favors morning/mid day, one favors afternoon, later evening

Before I have an answer, any favor for heating/cooling or equal split?

 

[740GLE]

Afternoons are always warmer, but depending on solar gain of the house that may not correlate with higher AC needs in the summer.

 

[G20]

Before I have an answer, any favor for heating/cooling or equal split?

I have whole house fans (2 attics, 2 fans). In the summer, it normally drops down at night (30-40 degree swings in 24 hours) so we open up the house , put on the whole house fans which quickly evacuates the house and attics/broilers (charges the thermal battery) and then close up the house for the rest of the day. Do the opposite in the winter to warm the house. It has drastically dropped the electric bills for a couple of decades, but the savings hasn't kept pace with the electric price increases.

The A/C/heat would just retard the depletion of the thermal battery in a 24 hour span and in extreme conditions, handle the periods that fall out of the normal pattern (e.g. sustained periods with no nightly drops or nearby wildfires bringing in smoke into the area preventing house ventilation).

In the past, cooling was more of an issue than heating with high electric and tolerable natural gas prices, but with electric and natural gas prices both skyrocketing and an unseasonable cold winter, last winter reversed the trend so now it was @ 50/50.

I have a 3-tier electrical bill with the 2nd and 3rd tiers having the same price, 32, 41 and 41 cents plus all of the additional taxes and fees.

 

[Danke]

Since these are most advantageous to people without an existing solar system it seems like Signature Solar should be selling a kit that comes with the mini split and panels.

I’m buying some from China that are exactly that.

 

[G20]

Afternoons are always warmer, but depending on solar gain of the house that may not correlate with higher AC needs in the summer.

I have added attic foil radiant barrier to my lower attic, fire caulked seams and holes in the drywall (around HVAC boots, seams, wiring chases, etc.), replaced the fiberglass with R53 rockwool, added attic fans and more eave venting. This has significantly diminished the solar gains in the lower attic and the subsequent broiler effect that would extend long into the night. Would love for the attic fans to be solar, but the ones I have seen don't move much air.

Unfortunately, the HVAC ducts are in the attic and not in conditioned spaces like a basement. Terribly inefficient design to have HVAC ducts in unconditioned spaces.

On a 90 degree day, an attic can get up to 165 degrees. The radiant barrier can't reduce the temp below ambient, but it can minimize the gain above that. The last time I was up there, the floor of the attic was 90 and the bottom of the roof was 145. The heat rolls up the chase (between the roof and radiant barrier) and out the attic fans, but you need proper eave inlet venting to make it work.

I initially thought it would not work, but it is noticeably hotter standing under a section of roof without the radiant barrier versus one with the radiant barrier.

I am currently doing the same to the upper attic when temps permit.

FWIW, this July was hotter than July of last year. The electrical usage went down 13% for the same period with the aforementioned changes (but the electric bill didn't drop accordingly).

 

[740GLE]

Do you have any insulation right on the sheeting? Or is it just stagnant air baking all day?

 

[G20]

Do you have any insulation right on the sheeting? Or is it just stagnant air baking all day?

Don't quite understand the question.

There is no insulation on the radiant barrier. The radiant barrier makes a 6" deep chase between the roof and the radiant barrier with an inlet at the bottom and an outlet at the top. Convective currents create a draft that draw in ambient air from the eaves which then gain heat, rise to the crest of the roof and get exhausted out the attic via the attic fans (or appropriate passive vents).

It makes a vented shell. Computer motherboards have used similar approaches to cool their active circuity. ASUS called their version "THERMAL AMROR" but the radiant barrier prevents the additional heat from heating up the attic floor by reflecting radiant heat back into the vented chases.

You could do the same thing with foil backed Styrofoam insulation sheeting, but you need to provide venting at the bottom and top.

As mentioned before, the last time I was in the attic, the attic floor was 90 degrees compared to the underside of the roof at 145 degrees. That is a 55 degree delta that the insulation would have to cope with.

 

[740GLE]

Ah some how I didn’t think you had a ridge vents due to you having the attic fans.