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24v heat pumps?

Rednecktek

Rednecktek

Solar Wizard
Joined
Sep 8, 2021
Messages
5,538
Location
On a boat usually.
So I'm throwing this in here because of the nature of the power system, even though it's not mobile. Hopefully someone on here can point me in the right direction.

Here's the situation:

I'm going to be moving into a new place soon (fingers crossed!) that has an 8x8 utility shed in the back yard that I'm going to be installing solar onto. The solar system is based on a Growatt SPF 3000 24v inverter because I already own one in a box from a previous project that got scrapped. I'm thinking I can get 4x Yingli 255w panels on the roof in a 2s2p setup to feed it and the big investment will be the Trophy 24v battery to power everything (because cold and unattended) with some lights, outlets, etc. The shed will primarily be used for my solar hobbies and my roommate's combat robots so not a lot of heavy loads.

The issue I'm trying to get around now is climate control. AirCon in the summer and heat in the winter. Due to the size and lack of windows I can't get a small window unit in there, so I'm looking at the DC split systems but everything I'm finding is cooling only. If I want a proper heat pump I either have to go to a 48v system or get a full house size 12k BTU 120v system which is massively overkill for an 8x8 shed.

Has anyone seen/used/touched/heard rumors of a 24v DC based proper heating and cooling split system? I've only found 1 system that is small enough but that head unit is still huge and will take up a LOT of valuable space inside there.
 
Well your project sounds like the workshop for my newer house. I have a tp6048 sungold in there for the house's power and that sucker makes enough heat to keep the workshop warm from what I can tell so far. The ac I will be going with for the workshop is still undecided. I'm a big fan of ductless heatpumps but it does seem overkill for that size space. I'm leaning towards a 5,000 btu window unit since I have those in abundance here from ones my parents retired from use and ones I had left over too.
 
DC powered might be tough but I know there are on-wall 120 and 240 units that can ramp down from 6000 or 9000 BTU down to 1600 BTU which will be reduce the demand on the inverter and battery. At 1600 BTU and HSPF 14 that is like 125W. However I don’t think the on wall units will get much smaller in physical size.
 
If just a shed, why not cut a hole in the wall and install a window/wall unit running off the growatt?
 
ejfluhr said:
If just a shed, why not cut a hole in the wall and install a window/wall unit running off the growatt?
Click to expand...
i don't know if there are any window units that can run off VDC plus a mini-split heat pump will be much more energy efficient even the cheap ones that are around the same price as a window unit
 
It's 8x8=64sq ft. Even a 5K BTU window unit is 2.5x too big. A DC heat pump is 10x the cost. Spend the $ on more battery.
 
ejfluhr said:
It's 8x8=64sq ft. Even a 5K BTU window unit is 2.5x too big. A DC heat pump is 10x the cost. Spend the $ on more battery.
Click to expand...
Yeah, I was looking at the parking heaters but at $1000 for the cheap chinese units plus shipping, or $2000 for the Hot Spot, just getting a stand alone 120v AC unit and a whole other battery is more cost effective.
 
Q-Dog said:
Still can't find a 24 volt model. Please provide a link to the actual product.

I see their solar heat pumps/ACs use direct connect solar panels and grid backup. I see one DC model that is 48 volt DC.
Click to expand...
Designed to use 24v solar panels direct. Does not give a specific voltage. I believe the assumption is a 24v battery would also work fine overnight even if the design is to go to the inverter or grid.

https://www.hotspotenergy.com/solar-air-conditioner/HotSpot-ACDC12C.pdf
 
@Rednecktek and @Q-Dog
These guys have some 24Vdc and 48Vdc heat pumps both as window units and mini-splits. I'm looking for a 48Vdc mini split to cool and heat two very small container units (about 9'x9' each).

Any body have any experience with these or recommend something else? These are completely unbranded, no warranty indication, no supplier information which for the price seems a little concerning. I would like to find something that goes direct from battery.
fullbattery.com

24V & 48V DC Air Conditioner

Heat and cool your place with pure DC power without any inverters. Our Pure DC Heat Pumps are in stock and ship same day from our California warehouse — delivery in 3-5 days nationwide. The price includes shipping and tax, there is no extra fee for delivery to you and no waiting. Declare your...
fullbattery.com

The other option is telecom industry units which come in 24V and 48V models designed to heat enclosures. These are industrial grade though and prices tend to reflect: https://www.dcairco.com/product/emobility/dc-12502-24v-48v-400v-800v-wall-mounted-heat-pump

I don't see any 24v ones on the Hotspot Energy site referenced above but they do have direct 48v battery units. https://www.hotspotenergy.com/DC-air-conditioner/

And still need something smaller. All of those are too big for my needs or OP's.
 
Last edited:
I have some doubts that 1 kW of solar panels is going to be enough to either heat or cool your shed meaningfully.

In the winter it will take close to 1 kW of heat on average just to keep it at all warm, and at least 1/2 that much to keep it cool.

Depending on what "winter" means in the location, is Li the right choice for substantially unattended operation?

As far as AC vs DC, it will not make all that much difference in efficiency for a similar quality unit.

Perhaps look at the houghton units that are put on top of van roofs ?
 
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