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9k BTU Heat Pump Advice

JBoffgrid2022

JBoffgrid2022

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Oct 28, 2022
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153
Hello All,
Looking for advice on getting a heat pump for providing strictly AC (No heat) to our off grid camp. We recently installed the following setup and it has been working great so far. Ideally, I'd love a setup that could grab DC power from either my battery bank or solar panels. But if that isn't possible, does anyone have recommendations on a good, AC powered air conditioner unit that is less than 500 watts? I tried using a 300 watt / 5000BTU window unit last year but it couldn't keep our camp cool enough. Also, on sunny days, my current system will be able to put out roughly 28kWh-35kWh per day. The usage of the camp (not including any air conditioner/heat pump) will not exceed 5kWh on any given day which would leave plenty of power for a cooling system. Thank you!

Here is my setup:
EG4 6kW Off-Grid Split Phase Inverter (1)
EG4 LifePower4 Lithium Battery | 48V 100AH (4)
EG4 Enclosed Battery Rack (1)
SunPower 450W Mono Solar Panel (Silver) A-Series Solar Panel (16) 2S8P
TIGO TS4-A-O Optimizers with CCA
 
We use a Senville 9,000BTU mini-split for our camper - https://senville.com/9000-btu-mini-split-air-conditioner-senl-09cd/ It peaks at ~1100w if and if used in *extreme* conditions (near the limits of capability / runs continuously) it can reach ~18kwh/day. Otherwise it's more like 10kwh/24hr period to heat/cool a 100sq ft trailer with 1" insulation in moderate temps relative to it's operating range.

Not pushing this brand as it requires a vacuum compressor and fitting to install but it does work / been reliable for 3 yrs now.

A 9,000 BTU Mr Cool would likely be similar - https://www.homedepot.com/p/MRCOOL-...ith-Line-Guard-115V-A-09-HP-115B-LG/320378942

These are both 115vac models.
 
Last edited:
JBoffgrid2022 said:
Hello All,
Looking for advice on getting a heat pump for providing strictly AC (No heat) to our off grid camp. We recently installed the following setup and it has been working great so far. Ideally, I'd love a setup that could grab DC power from either my battery bank or solar panels. But if that isn't possible, does anyone have recommendations on a good, AC powered air conditioner unit that is less than 500 watts? I tried using a 300 watt / 5000BTU window unit last year but it couldn't keep our camp cool enough. Also, on sunny days, my current system will be able to put out roughly 28kWh-35kWh per day. The usage of the camp (not including any air conditioner/heat pump) will not exceed 5kWh on any given day which would leave plenty of power for a cooling system. Thank you!

Here is my setup:
EG4 6kW Off-Grid Split Phase Inverter (1)
EG4 LifePower4 Lithium Battery | 48V 100AH (4)
EG4 Enclosed Battery Rack (1)
SunPower 450W Mono Solar Panel (Silver) A-Series Solar Panel (16) 2S8P
TIGO TS4-A-O Optimizers with CCA
Click to expand...
Any inverter style AC split will modulate it’s operating point to the actual required cooling. I’ve got a 12K in my office that runs about 225 watts 24X7 and an 18K one in a 20x50 living room, kitchen, pantry that runs about 600W. One mistake a lot of people make is to oversize the units (I should have a 9K in my office, for instance). I have Mitsubishi heat pumps (professionally installed) and I love the ‘dry’ mode, allows the temperature to get up to 80 or so while keeping ghe RH under 60%, which is really comfortable.
 
Since you mentioned using a window unit, the Midea U shaped window units have a variable speed compressor and will slow down once maintaining temperature. They make 3 sizes and they work a lot like a mini split but fits into a window. They do not make heat but they do have dehumidify and fan settings in addition to cooling.

On high our 12K btu Midea will use about as much power as any other window shaker, but on low it draws between 150 - 250 watts to maintain temps. We love it.
 
Q-Dog said:
Since you mentioned using a window unit, the Midea U shaped window units have a variable speed compressor and will slow down once maintaining temperature. They make 3 sizes and they work a lot like a mini split but fits into a window. They do not make heat but they do have dehumidify and fan settings in addition to cooling.

On high our 12K btu Midea will use about as much power as any other window shaker, but on low it draws between 150 - 250 watts to maintain temps. We love it.
Click to expand...
Just installed an 8000 BTU Midea U-shaped in a window last weekend.
That thing is great! Very quiet, more than enough cooling. 120V
 
JB. We easily run a 15,000 btu and a 6,000 btu mitsubishi on our 5,000 watts of solar with 390 ah Discover lithium batteries.

Today temps in the 80’s F. Sitting and sleeping in 70 degree comfort🙂
 
OffGridInTheCity said:
We use a Senville 9,000BTU mini-split for our camper - https://senville.com/9000-btu-mini-split-air-conditioner-senl-09cd/ It peaks at ~1100w if and if used in *extreme* conditions (near the limits of capability / runs continuously) it can reach ~18kwh/day. Otherwise it's more like 10kwh/24hr period to heat/cool a 100sq ft trailer with 1" insulation in moderate temps relative to it's operating range.

Not pushing this brand as it requires a vacuum compressor and fitting to install but it does work / been reliable for 3 yrs now.

A 9,000 BTU Mr Cool would likely be similar - https://www.homedepot.com/p/MRCOOL-...ith-Line-Guard-115V-A-09-HP-115B-LG/320378942

These are both 115vac models.
Click to expand...
Very helpful! I will look into these units. Are they considered "DIY" or would I need to hire a professional to install them?
 
timselectric said:
I've been running a 12k hotspot 48vdc mini split for almost a year. Working perfectly.
I will be getting at least 2 more.

Click to expand...
Does this setup require a dedicated panel/battery power source? Or could it be powered by my battery bank? I currently have a 20kwh EG4 LifePower4 battery bank that is being used by my EG4 inverter. I could potentially separate some of the panels and/or batteries from that system and devote them to power this DC heat pump. Any thoughts on that?
 
Q-Dog said:
Since you mentioned using a window unit, the Midea U shaped window units have a variable speed compressor and will slow down once maintaining temperature. They make 3 sizes and they work a lot like a mini split but fits into a window. They do not make heat but they do have dehumidify and fan settings in addition to cooling.

On high our 12K btu Midea will use about as much power as any other window shaker, but on low it draws between 150 - 250 watts to maintain temps. We love it.
Click to expand...
Unfortunately I don't have any windows at our camp big enough to fit anything but a very small window unit:( But thanks for the repy!
 
JBoffgrid2022 said:
Does this setup require a dedicated panel/battery power source? Or could it be powered by my battery bank? I currently have a 20kwh EG4 LifePower4 battery bank that is being used by my EG4 inverter. I could potentially separate some of the panels and/or batteries from that system and devote them to power this DC heat pump. Any thoughts on that?
Click to expand...
It's runs on your existing battery bank.
This is why I chose it. Nothing extra needed.
But I will warn you that it's more expensive than other options. $2,100 US.
 
Just pot lucking A/C size is an expensive way to determine heat load for an air-conditioned area. If 5k btu fixed speed unit was not enough it is likely 9k mini-split will not be enough either.

Mini-splits can actually draw more power compared to equivalent rated btu size conventional unit if run at their maximum output all the time. Mini-splits have 8 to 12% of input power going to inverter losses at full rated btu output not present on conventional fixed speed units. Mini-splits win when heat loading goes down and they reduce their operating speed.

Smaller btu mini-splits operating on 120vac often have high peak current crest factor with poor power factor which is not good for running from a battery powered inverter.

You should oversize btu capability when selecting a mini-split.

BTU loading varies in time by 3x to 5x over conditions of the given area. Initially, hot and humid area eats up the btu's. Initially, 30% of the btu's can be consumed just removing humidity (latent heat). Once humidity is brought down more of the btu's goes to cooling down air temp (sensible heat).

Amount of insulation and windows highly effects heat loading. Just going by room size is not a good way to select btu size required.

BTU Calculator

Two free calculators estimate the number of BTUs needed to cool or heat a room or house based on its size, insulation, and some other conditions.
www.calculator.net www.calculator.net
 
Last edited:
timselectric said:
It's runs on your existing battery bank.
This is why I chose it. Nothing extra needed.
But I will warn you that it's more expensive than other options. $2,100 US.
Click to expand...
Ok, that sounds like the best option for me. The costs actually isn't terrible, worth it's weight in gold if it ends up working!
Would you make any recommendations or is there someone on DIY solar that could help me design and size my wiring to power this unit? I would most likely keep the outdoor unit close to the battery bank so I can help reduce any power loss. Thanks for your input once again!
 
JBoffgrid2022 said:
Ok, that sounds like the best option for me. The costs actually isn't terrible, worth it's weight in gold if it ends up working!
Would you make any recommendations or is there someone on DIY solar that could help me design and size my wiring to power this unit? I would most likely keep the outdoor unit close to the battery bank so I can help reduce any power loss. Thanks for your input once again!
Click to expand...
If you are familiar with mini splits, it's basically the same setup. The only difference is where the power source originates from. (Battery instead of AC service panel)
Mine is about 30' (wire length), from my battery bank.
#10 AWG is more than adequate. (21a max draw)
 
I am somewhat familiar, thank you! I would like to tie the +/- power leads from the server rack bus bars to a DC breaker, and from that to the heat pump. #10AWG should be plenty considering the distance will be less than 15' from the battery bank.
 
JBoffgrid2022 said:
I am somewhat familiar, thank you! I would like to tie the +/- power leads from the server rack bus bars to a DC breaker, and from that to the heat pump. #10AWG should be plenty considering the distance will be less than 15' from the battery bank.
Click to expand...
If you have a shunt in your system. Make sure that you connect the negative on the load side of it.
Otherwise, your good.
 
JBoffgrid2022 said:
Very helpful! I will look into these units. Are they considered "DIY" or would I need to hire a professional to install them?
Click to expand...
DIY. There are multiple youtubes full of details and links to needed vacuum pump w/R410A adapter ($70) - https://www.amazon.com/ZENY-Single-...ner-Refrigerant/dp/B012CFTYX4/ref=as_li_ss_tl

It has refrigerant in the outdoor unit (like Mr Cool) but you need to get air out of the line between the outdoor and indoor unit before releasing the refrigerant so you vacuum pump the line - takes about 15min. Then let it sit a few hours to check for leaks using the gauges on the vacuum pump before releasing refrigerant. This ensures that you have a leak free copper pipe connection / things will work.

For me, the vacuum gauges took a little time to get used to, several passes thru that section of the youtube - but in the end, it's actually quite easy to do and you can do it multiple times till you're comfortable as long as you don't release the refrigerant till you're totally done getting the vacuum in the line. Tip - you have to put the provided oil into the vacuum pump else it won't work properly - I didn't read instructions :)
 
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I did the installs on our two Mitsubishi units. Not too hard. I found the you tube videos from “AC Service Tech LLC” to be very useful.

You’ll need to buy, borrow or rent some equipment, which is likely less than having a professional come out to do the install. Other neighbors are using the DIY splits.

Those window units are pretty nice. If you can enlarge a current window or install a new hole in your wall, the window units do the job.

BTW we are VERY off-grid out here so it’s a diy world for us. Closest professionals are 90 miles away, expensive and do t always get it done right.
 
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