Need to cool small shed with 24V

ryann

I've got a small (6'x6') well insulated instrumentation shed I've got to keep below 85F. This is in Coastal NC on a beach, so ambient temperatures don't get above mid-90s. The instruments generate about 150W of heat.

The shed has unreliable 110vAC, but I'm only allowed to use it for my 30A @ 24VDC Charles battery charger.
I've got eight Rolls D600 batteries, 1500 Watts of solar, and AirBreeze and a mindnight classic charge controller all wired up at 24V.

My options seem to be:

• Simple but expensive ($3400) 24VDC mini-split unit.
• Less expensive ($1300) and more efficient 48VDC with 90% efficient 24-48 DC boost converter ($?).
• Least expensive ($800?) and most efficient 110V inverter mini-split and 85% efficient 24VDC-110VAC inverter ($<1000)

Unfortunately, converting from 24VDC to 48VDC is not an option.
For all of these options , I'm looking in the 8000 - 10000 BTU range, although I think smaller would be fine.
Right now I'm leaning towards the last option but I'm not sure what model to get, where to get it, and how big of an inverter I need. Reading old forum posts, it looks like Sanyo was the favorite, but they no longer seem to be available.

Can anyone suggest a 110AC inverter mini-split unit and a vendor?

Does anyone have experience running this off of an inverter and if so, what size? Sine wave or modified? It sounds like start-up load is not a problem with inverter AC units, but what about inductive load vs resistive?

ryann

Re: Need to cool small shed with 24V

Here are some of the small 115V inverter high-SEER mini-split units I've found:

Energy Star(?) - DCE-09 - 22 SEER
http://www.thermospace.com/ductless_split/ymgi/energy-star-9000-btu-inverter-ductless-split.php

Friedrich M09CJ - 21.5 SEER
http://friedrich.com/products/commercial/ductless-split-systems/wall-mounted/model-specifications

Fujitsu - all high SEER are 230VAC

Gree Neo GWH09MA-A3DNA3A - 22 SEER - 7 amps
http://www.greecomfort.com/literature/Gree-NEO.pdf

Lennox MS8C - 22 SEER
http://www.lennox.com/pdfs/brochures/Lennox_MS8C-MS8H_Mini-Split_Systems.pdf

Mistubishi - High seer in 230V only


Thermocore(?) T125S-H109 - 24.5 SEER
http://www.thermospace.com/ductless_split/thermocore-t125s-h109.php

YMGI WMMS-09K-V2A/B(58)(2) - 22 SEER
http://www.ymgigroup.com/product/2013518145246363.pdf

It looks like the higher SEER units require 230VAC. I suppose I could find a 24VDC to 230VAC inverter.

Photowhit

Re: Need to cool small shed with 24V

I believe someone had posted here that they had run a small window unit on a 1100watt Exeltech inverter. Exeltechs are well made and handle motor starting very well, that said, I've only just purchased one to play with. I should be able to tell you if it can handle my window unit with in a week.

I've run a 5200btu Kenworth on a cheap 1400watt inverter and regularly do on an 1800 watt Prosine(6 years and counting) If the shed is well insulated at that tiny size it should be no problem with your system, though you haven't discussed your other loads.

There also was some rumor here, that Xantrex was going to make a 24v version of their cheap and popular 1800/2000 watt cheapy inverter, might have to check for that myself.

verdigo

Re: Need to cool small shed with 24V

I am way down the latter as far as expertise here but for 6'x6' may be a 5000 btu 120v window unit might suffice? $<100.00 at most big box stores.

ryann

Re: Need to cool small shed with 24V

verdigo wrote: »

I am way down the latter as far as expertise here but for 6'x6' may be a 5000 btu 120v window unit might suffice? $<100.00 at most big box stores.

Due to the nature of the project, I really would rather not cut a big hole in the side of the structure. Cost isn't as big a factor as value.

I'm also now seriously considering a 24VDC to 230VAC inverter with a 230V split unit. This gets me a substantially higher SEER value and some brands I've actually heard of before like Fujitsu and Mitsubishi.

The Fujitsu 9RLS2 is rated at 27.2 SEER and is $1500.

Slappy

Re: Need to cool small shed with 24V

The 1100 watt exeltech does run a 5000 btu with no problem. Mine is running as im typing this plus a small chest freezer and other stuff. These are great inverters.

Blackcherry04

Re: Need to cool small shed with 24V

ryann wrote: »

Due to the nature of the project, I really would rather not cut a big hole in the side of the structure. Cost isn't as big a factor as value.

I'm also now seriously considering a 24VDC to 230VAC inverter with a 230V split unit. This gets me a substantially higher SEER value and some brands I've actually heard of before like Fujitsu and Mitsubishi.

The Fujitsu 9RLS2 is rated at 27.2 SEER and is $1500.

Buying a A/C unit designed to cool a space 4 times the size your trying to cool is just going to short cycle the compressor on and off so many times a day that all the SEER goes away.

Photowhit

Re: Need to cool small shed with 24V

Blackcherry04 wrote: »

Buying a A/C unit designed to cool a space 4 times the size your trying to cool is just going to short cycle the compressor on and off so many times a day that all the SEER goes away.

I think the newer electronic controller energy saver features is that you can increase the temperature differential to help prevent the frequent cycling. I skipped over that section of the manual, but recall seeing something about that.

FWIW- there aren't many options below 4800btu, a mini split run on low, would be in the low 4000's.

Blackcherry04

Re: Need to cool small shed with 24V

Photowhit wrote: »

I think the newer electronic controller energy saver features is that you can increase the temperature differential to help prevent the frequent cycling. I skipped over that section of the manual, but recall seeing something about that.

In a 6'x6' room ?? It wouldn't take 2,000 btu to cool it. He'd be better off with a portable unit with a hose out a dryer vent.

verdigo

Re: Need to cool small shed with 24V

Blackcherry04 wrote: »

In a 6'x6' room ?? It wouldn't take 2,000 btu to cool it. He'd be better off with a portable unit with a hose out a dryer vent.

Hadn't thought of those. Most I have been around are pretty quiet too.

Photowhit

Re: Need to cool small shed with 24V

Blackcherry04 wrote: »

In a 6'x6' room ?? It wouldn't take 2,000 btu to cool it. He'd be better off with a portable unit with a hose out a dryer vent.

I have looked before, if you have a link to a unit smaller than 4800btu, I'd like to see it. I have seen the dog kennel units but they have no rating and running every thing outside nad piping air inside would seam to be many times less efficient to me.

jcheil

Re: Need to cool small shed with 24V

Photowhit wrote: »

I have looked before, if you have a link to a unit smaller than 4800btu, I'd like to see it. I have seen the dog kennel units but they have no rating and running every thing outside nad piping air inside would seam to be many times less efficient to me.

I'd like to find one also. I have a 9x10 room and the 5000btu window unit in there now is way too big for it.

Blackcherry04

Re: Need to cool small shed with 24V

Photowhit wrote: »

I have looked before, if you have a link to a unit smaller than 4800btu, I'd like to see it. I have seen the dog kennel units but they have no rating and running every thing outside nad piping air inside would seam to be many times less efficient to me.

Put a Mini split in they put out 4,000 btu on low. I mentioned them ( portable ) as a ROI, a 240v A/C and a split phase Inverter. Your talking about $4,000 of value installed. The OP said he doesn't want to cut a hole.

Slappy

Re: Need to cool small shed with 24V

http://www.iceqube.com/default2.asp units as low as 1000 btu come in ac/dc. "A" rating with the BBB

jcheil

Re: Need to cool small shed with 24V

Slappy wrote: »

http://www.iceqube.com/default2.asp units as low as 1000 btu come in ac/dc. "A" rating with the BBB

I am speaking with them now, getting some quotes. They look rather interesting from a power consumption rating and physical size.
Would definitely be an alternative to a mini-split especially since you do not need an AC technician to connect it up. They are package units. Just mount to the outside of your wall and vent thru to the inside.

However, the price remains to be seen...that will determining factor. Should know more in a few.

ryann

Re: Need to cool small shed with 24V

Slappy wrote: »

http://www.iceqube.com/default2.asp units as low as 1000 btu come in ac/dc. "A" rating with the BBB

That's very interesting, they even have a 24 volt version.

My thought on an "oversized" 9000BTU split unit was that the new inverter style would run at a low speed rather than cycling.

jcheil

Re: Need to cool small shed with 24V

ryann wrote: »

That's very interesting, they even have a 24 volt version.

My thought on an "oversized" 9000BTU split unit was that the new inverter style would run at a low speed rather than cycling.

..and a 48v DC version too!

Regarding the mini-split on low, that might be the case, but even 4000btu may be excessive for a 10x10 or an 8x8 room.
We'll have to see how the prices come in. I mean, if 3 individual of these 3000 units are cheaper (both money and power) than the 9000 mini-split then we'd really have to look at it more closely. I'll prolly get one regardless (unless the price is a joke) and see how it goes.

mike95490

Re: Need to cool small shed with 24V

If ambient never goes over 90F, why do AC ? A fan on the heat sink, and another fan to blow hot air out should keep things below 90F. Insulate the roof so it's not a Hot Box in there.

Slappy

Re: Need to cool small shed with 24V

Please let us know on the pricing.

jcheil

Re: Need to cool small shed with 24V

Slappy wrote: »

Please let us know on the pricing.

Emailed them again today. Hopefully I will have some prices soon!

unseenone

Re: Need to cool small shed with 24V

You could line the shed with truprotect, this will cut down on the heat extremely. The testing and specs on the product are on the web site. This will cut down on your cooling requirements by a huge margin.

jcheil

Re: Need to cool small shed with 24V

jcheil wrote: »

Emailed them again today. Hopefully I will have some prices soon!

Quote came back, and unfortunately even though their energy usage seems good, they are WAY overpriced:

1000btu, 48v = $2,036
2200btu, 48v $2,722
1300btu 9120v) = $ 1,021
2200btu (120v) = $1,121

Well, it was worth a try

vtmaps

Re: Need to cool small shed with 24V

jcheil wrote: »

Quote came back, and unfortunately even though their energy usage seems good, they are WAY overpriced:

If the cooler is an essential part of a RE system, it might be eligible for a 30% fed tax credit

--vtMaps

Dave Angelini

Re: Need to cool small shed with 24V

I tried this advice of fixing the building when I lived there. In my opinion one can't cook in a home once the air is above 82F. It did not work. Too humid and too darn hot. Look at the LG 28 SEER heat pump and it will be the best money you spent. We went thru the DC based AC with a client and it was just not that good vs power consumed. Give $75 to an HVAC person keep the receipt and you are good for 5 years and 7 on the compressor.

I like the idea of claiming it for federal solar credit. If it is a home and you were audited it would probably not fly. But a power shed might....If you did this it probably would have to be part of an installed solar system and not by itself, if you want to survive an audit.

mike95490 wrote: »

If ambient never goes over 90F, why do AC ? A fan on the heat sink, and another fan to blow hot air out should keep things below 90F. Insulate the roof so it's not a Hot Box in there.

Kgelles

Re: Need to cool small shed with 24V

I am cooling my kitchen with a 6000btu frigidaire I picked up from Lowes. I believe it's model FRE06L3Q1. It is being powered by an Exeltech xp1100. This is my 2nd year doing so and I have no problems so far.

Kgelles

Re: Need to cool small shed with 24V

Sorry, that's model: FFRE06L3Q1

RandomJoe

Re: Need to cool small shed with 24V

Blackcherry04 wrote: »

In a 6'x6' room ?? It wouldn't take 2,000 btu to cool it. He'd be better off with a portable unit with a hose out a dryer vent.

I'm a bit late but...

I'd suggest if you try one of these portable units, be sure to get one that uses TWO dryer vents - the condenser is isolated, uses outside air to cool itself, air in one hose then out the other.

I bought a Maytag portable unit for my "server closet" at home (small walk-in closet that I had a bunch of computers in). The unit runs just fine, however it was a single-hose unit so the condenser was drawing air from the room to cool itself, then blowing it outside. Of course that meant unconditioned air was constantly being drawn into the room. The unit NEVER cycled off once the house was warm. (I wanted to be able to turn off the main house AC while gone.)

jtdiesel65

Re: Need to cool small shed with 24V

mike95490 wrote: »

If ambient never goes over 90F, why do AC ? A fan on the heat sink, and another fan to blow hot air out should keep things below 90F. Insulate the roof so it's not a Hot Box in there.

My plan is to put a slightly above ground level intake on the shaded side of the shed and a vent above the equipment with a larger 24v dc computer type fan pushing the air out. So something similar to a Powervent. I have all the parts, but forget the exact size of fan. When I bought the fan, I figured out the fan cfm would exchange the air every few minutes or something like that.

bmet

Re: Need to cool small shed with 24V

verdigo wrote: »

Hadn't thought of those. Most I have been around are pretty quiet too.

Portable A/C units are power hogs, and high maintenance. I've owned 3(Panasonic, LG, and Samsung). The smaller ones start in the 9,000 btu and do not operate as efficiently as a 7500 btu window unit. The exhaust hose, if not set properly, will make the unit work harder. None of my 3 portables are quiet.
Next, it's more of a challenge to dispose of the condensate when the reservoir is full. If you don't empty them regularly, mildew gets a hold. Lastly, the programming options are not as flexible as their window-unit-relatives of same btu. They are a last resort in my book.

inetdog

Re: Need to cool small shed with 24V

bmet wrote: »

Next, it's more of a challenge to dispose of the condensate when the reservoir is full. If you don't empty them regularly, mildew gets a hold.

The single tube ones I have seen use a splash of condensate onto the condenser coil to improve efficiency and get rid of extra water. Since the air going into that process is dehumidified inside air, they can always be sure of sending the extra water back outside.
Two tube units (which I have not seen) may not be able to count on this process. Window units that use splash cooling are able to just let any excess drain out the back.