Shop A/C... DC Air Conditioner?

Piper Ted · September 2010

Hi all, first post, been lurking a little, trying to understand.

I'm wanting to get an A/C for the woodworking shop, around 750 square feet, I know a standard A/C would be a huge power drain on a solar system, but I'm looking at using a DC powered air conditioner?

I'm wanting to know how many solar panels and batteries that I would need to power the system, and what other components would be needed. They would be strictly for the A/C system only.

I'm hesitant to give the link as some forums don't allow or like it, and I can't remeber seeing anything in the TOS.

Here are the specs on one of the A/C units I'm interested in.

Maximum (Continuous Duty)Cooling Capacity
11,000 BTU / HR

Maximum Heating
N/A

Input Voltage
48 VDC (42.5 – 56)

Power Consumption
880 watts / HR Maximum
610 watts @ 70% Duty Cycle

Recommended Batteries
AGM Deep Cycle or Lithium

Recommended Battery Bank
110 Ah @ 48VDC per 5 hour run time @ 70% Duty Cycle

Refrigerant
R134A - 2.9 LBS (43OZ)

Oil (With Green Dye for Leak Detection)
PAG100 – 8 oz

Compressor
Brushless DC (BLDC) Rotary – Hermetically Sealed

Low Voltage Protection
Yes – 21VDC / 41.5VDC

Sound
58 dB Maximum Condenser Unit

SEER
18.03

Controls
Thermostat Standard / Lead Lag (series) optional

Thanks in advance.
Ted

PS:
1. Would it be better to store the batteries in the shop to keep them away from the heat?
2. The panels will more than likely be mounted on the roof of my metal building barn which is located about 200 feet from the shop.
3. Would it be advisable to be able to charge the batteries or run the A/C with the shop power, just in case?

Cariboocoot · September 2010

Re: Shop A/C... DC Air Conditioner?

Is there no grid power available?
Frankly, that's still a massive amount of power for "off grid" production.
Look at the recommended "110 Amp hours per 5 hours operation".
So how many hours per day would it need to run? Perhaps 20? That would be 440 Amp hours. Unless I'm interpreting it wrong (doesn't say "battery size") that would be X2 or an 880 Amp hour, 48 Volt bank.

110 Amp hours @ 48 Volts = 5280 Watt hours divided by "5 hours running" = 1056 watts, which is pretty close to the Watt rating given.

You'd need about 6000 Watts of array to charge that, unless I've done the math horribly wrong.

Why do you want to run AC off solar?
If your answer is "to save money" ... it won't.

Take a look at this thread on AC: http://forum.solar-electric.com/showthread.php?t=5104

Piper Ted · September 2010

Re: Shop A/C... DC Air Conditioner?

Cariboocoot wrote: »

Is there no grid power available?
Frankly, that's still a massive amount of power for "off grid" production.
Look at the recommended "110 Amp hours per 5 hours operation".
So how many hours per day would it need to run? Perhaps 20? That would be 440 Amp hours. Unless I'm interpreting it wrong (doesn't say "battery size") that would be X2 or an 880 Amp hour, 48 Volt bank.

110 Amp hours @ 48 Volts = 5280 Watt hours divided by "5 hours running" = 1056 watts, which is pretty close to the Watt rating given.

You'd need about 6000 Watts of array to charge that, unless I've done the math horribly wrong.

Why do you want to run AC off solar?
If your answer is "to save money" ... it won't.

Take a look at this thread on AC: http://forum.solar-electric.com/showthread.php?t=5104

Yes I have power in the shop, for the power tools...

Just looking for a way to add A/C to the wood shop to make it bearable over the long haul.

If I were to put a Mini Split Air Conditioner in the shop it's going to cost about $1500, and then it's going to cost an extra $100 a month to power it. Over a 5 year period it brings the cost to $7,500 and money still ongoing to the elelctric company every month.

I'm trying to figure out the cost factor differences and how much would a solar powered system run me to power a DC A/C unit.

Here are the ones I'm looking at but wonder which is better??
(I see on the other thread that link were posted... so)

http://solcoolstore.net/index.php?main_page=product_info&cPath=5&products_id=10

This link doesn't give a price online, so I'm waiting for a quote to come back from the company.
http://www.securusair.com/

With electricity rates going up it adds up. Isn't one of the reasons to use solar "to save money"?
Ted

BB. · September 2010

Re: Shop A/C... DC Air Conditioner?

Feel free post links to the sites that have product information that you are asking about...

What we tend to avoid is the Hey--Look at THIS!!!!

:D:D A wonderful product... type posts.

The pure DC A/C units can be very pricey... There have been some people that have looked at the new Mini-Split AC systems from Sanyo (and other mfg.) that use internal "Inverters" to controller the compressors (really VFD's --- Variable Frequency Drives). Can be very efficient and very "friendly" to run from an AC inverter on off-grid systems...

But you still need enough solar panels and batteries to run them for XX hours per day at whatever settings.

Sanyo mini split AC (inverter/variable speed)
More panels & window AC or efficient mini split AC?
smallest, most efficient A/C ?
Is Running and Air Conditioner possible with solar power? - Solar
Thoughts on system

At least those are the threads I could find with a quick search about various options for off-grid solar....

-Bill

niel · September 2010

Re: Shop A/C... DC Air Conditioner?

it might be better to just get the best a/c for grid tie and then put a gt solar system in to offset the running costs some.

solar_dave · September 2010

Re: Shop A/C... DC Air Conditioner?

I just put one of these in:
http://www.friedrich.com/products/ductless-splits/wall-mounted/overview/
http://www.friedrich.com/products/ModelOverview.php?model=M36TYF2

I have no hard data on power consumption yet but soon:
Model Specifications:
BTU Cooling 35100
BTU Heat 38100
SEER 15.0
Moisture Removal 3.7/3.7/3.7 pints/hour
Net Weight 222 lbs
Volts 230/208
Cooling Watts 3980
Room Air Circulation 355/355/355 CFM
Circuit Breaker Rating 30

I originally planned a Trane ground mount but because there was a garage involved the code monkeys would not allow ducting a garage/shop/office on one system, this was the logical solution (after paying an additional $110 for permit change). The unit is made by an American manufacturer, and has the inverter technology. It also has an ultra quiet mode which is really whisper quiet. My AC guy installed the base and 3 wall units in about 5-6 hours. A 3-inch hole in the wall was all that was required for each indoor unit.

Heat pump systems from 30,000-36,000 BTU/h. SEER rating 15.0

No expensive, messy and disruptive duct construction.

Unlike traditional window air conditioners, ductless split systems leave window views unobstructed. And, because these are permanent installations, there is nothing to remove or store over the winter.

Exceptional energy efficiency is the result of high tech Inverter Technology. Systems use only the power they need to reach the desired set point. Turn off units in unoccupied rooms to save even more.

Ductless systems keep the operating noise of the condenser unit outdoors.

Auto-swing louvers and air sweep operation keep cool air circulating throughout the room.

Auto-shut flaps maintain a sleek appearance when the unit is not running.

Wireless remote controls with 24-hour timer and sleep timer for independent operation of each indoor unit allows easy operation regardless of where you choose to place your indoor units.

Piper Ted · September 2010

Re: Shop A/C... DC Air Conditioner?

solar_dave wrote: »

I just put one of these in:
http://www.friedrich.com/products/ductless-splits/wall-mounted/overview/
http://www.friedrich.com/products/ModelOverview.php?model=M36TYF2

I have no hard data on power consumption yet but soon:
Model Specifications:
BTU Cooling 35100
BTU Heat 38100
SEER 15.0
Moisture Removal 3.7/3.7/3.7 pints/hour
Net Weight 222 lbs
Volts 230/208
Cooling Watts 3980
Room Air Circulation 355/355/355 CFM
Circuit Breaker Rating 30

I originally planned a Trane ground mount but because there was a garage involved the code monkeys would not allow ducting a garage/shop/office on one system, this was the logical solution (after paying an additional $110 for permit change). The unit is made by an American manufacturer, and has the inverter technology. It also has an ultra quiet mode which is really whisper quiet. My AC guy installed the base and 3 wall units in about 5-6 hours. A 3-inch hole in the wall was all that was required for each indoor unit.

Oh,
Got a reply to the Securus Unit that I linked to in my 2nd post...

Hi Ted - The 18000 BTU attached should be sufficient and the solar PV/battery bank calculation is below.

A good rule of thumb for the Securus hardware is .085 watts of power use per
BTU so the 18000 BTU Securus uses 1530 watts per hour to cool at max. At a
48vdc power current that would be approximately 32 amps per hour. If you
want to run the Securus 18000 BTU system for 10 hours at night you will need
320 amp hours of useable battery bank, (a total of 550 amp hour battery
bank) at 48vdc, (320ahx48vdc=15360 watts). You will also need approximately
3500 watts of solar panels to run the system all day and charge the battery
bank for night use. Approximate off-grid battery/solar PV hardware wholesale
cost per hour to run the 18000 BTU cooling for the Securus is estimated at
USD$2000 plus freight. A minimum of four hours is recommended.

He mentions "night use" of the A/C system, but if it's running also during the day I imagine I'll need more panels and batteries.

It seems to me with the $2000 cost for that A/C system, plus solar panels and batteries and whatever other items that would be needed, the cost would be at least $12K and that doesn't include installation. Which is more than what I was expecting or wanting to pay.
What would the panels and batteries cost, is my estmate close?

On the brighter side...
Thanks to solar dave for the Friedrich link and info. I like the option of being able to add on to the Ductless Split System with another indoor unit. I was planning on building another shop right next door to my current one and with the Friedrich system I could just add an indoor unit in the new shop and use the same outdoor condensors for both buildings.

It's also a 19 seer unit...

http://www.appliancesconnection.com/i71206-friedrich-m18yf.html?ref=rap&mkwid=s9dUjm0WN&pcrid=4782878036

Listed on EBAY

Ted

Dave Angelini · September 2010

Re: Shop A/C... DC Air Conditioner?

I looked thru this string and never understood if you plan to use this 750 sq ft shop at night. In Houston you have challenges different than where many of my offgrid homes are up in the mountains. If you have some time go over to the energy portion of the forum and look at what we did in the topic " Sanyo mini split AC."

It basically is a strategy that works during the day only and asumes the house has natural cooling at night. If you are not using the shop at night and your morning temperature is not too high it might be worth considering. Drop me an e-mail I am arround this week-end.

dwh · September 2010

Re: Shop A/C... DC Air Conditioner?

Piper Ted wrote: »

He mentions "night use" of the A/C system, but if it's running also during the day I imagine I'll need more panels and batteries.

No, he's figuring that the unit uses 1500w on max, that having double that in solar will provide enough to run the unit *and* charge the batteries during the day, and then run the unit off the batteries at night.

I think he's overly optimistic in his calculations, since he's not accounting for things like system losses. In reality you would probably need somewhat more solar. At least he did differentiate *usuable* battery bank and more or less said you need double the capacity of whatever the unit will end up using.

It seems to me with the $2000 cost for that A/C system, plus solar panels and batteries and whatever other items that would be needed, the cost would be at least $12K and that doesn't include installation. Which is more than what I was expecting or wanting to pay.
What would the panels and batteries cost, is my estmate close?

NAWS does have some quote estimates on their store site under the System Design & Consulting section that might give you a more accurate view of the price range.

Piper Ted · September 2010

Re: Shop A/C... DC Air Conditioner?

Dave Sparks wrote: »

I looked thru this string and never understood if you plan to use this 750 sq ft shop at night. In Houston you have challenges different than where many of my offgrid homes are up in the mountains. If you have some time go over to the energy portion of the forum and look at what we did in the topic " Sanyo mini split AC."

It basically is a strategy that works during the day only and asumes the house has natural cooling at night. If you are not using the shop at night and your morning temperature is not too high it might be worth considering. Drop me an e-mail I am arround this week-end.

Dave, No, I don't plan to use the shop alot at night, maybe for an hour or two after I get home from work. Primary use will be during the day, mostly on the weekends. I do have a day job that I'll be wanting to get some sleep time in to accomplish that.

Ted

BilljustBill · September 2010

Re: Shop A/C... DC Air Conditioner?

Dave Sparks wrote: »

I looked thru this string and never understood if you plan to use this 750 sq ft shop at night. In Houston you have challenges different than where many of my offgrid homes are up in the mountains. If you have some time go over to the energy portion of the forum and look at what we did in the topic " Sanyo mini split AC."

It basically is a strategy that works during the day only and asumes the house has natural cooling at night. If you are not using the shop at night and your morning temperature is not too high it might be worth considering. Drop me an e-mail I am arround this week-end.

Dave,

Would he be any better off, if he could, to call his workshop a "business" and use some of those IRS guidelines to fund his solar cooling project?

Would the short depreciation factor allow for more money, rather than the one time 30% residential tax credit?

Bill

Piper Ted · September 2010

Re: Shop A/C... DC Air Conditioner?

Dave Sparks wrote: »

I looked thru this string and never understood if you plan to use this 750 sq ft shop at night. In Houston you have challenges different than where many of my offgrid homes are up in the mountains. If you have some time go over to the energy portion of the forum and look at what we did in the topic " Sanyo mini split AC."

It basically is a strategy that works during the day only and asumes the house has natural cooling at night. If you are not using the shop at night and your morning temperature is not too high it might be worth considering. Drop me an e-mail I am arround this week-end.

dwh wrote: »

No, he's figuring that the unit uses 1500w on max, that having double that in solar will provide enough to run the unit *and* charge the batteries during the day, and then run the unit off the batteries at night.

I think he's overly optimistic in his calculations, since he's not accounting for things like system losses. In reality you would probably need somewhat more solar. At least he did differentiate *usuable* battery bank and more or less said you need double the capacity of whatever the unit will end up using.

NAWS does have some quote estimates on their store site under the System Design & Consulting section that might give you a more accurate view of the price range.

Just a thought...
Since the A/C unit is DC powered I'm assumiog it uses less power to run it than an AC powered unit? Does that mean It would need some sort of converter to run it, on household current?

Ted

BB. · September 2010

Re: Shop A/C... DC Air Conditioner?

A low voltage DC a/c system may or may not use less power than a very efficient 120/240 VAC system... You have to look at the specifications and compare.

My two cents, for large loads, you are generally better off going with 120/240 VAC inverters vs a 24 or 48 volt DC system... The issues of sending lots of low voltage DC current any distance will require lots of heavy copper cables. Also, the 120/240 VAC systems may end up costing less (including the inverter) because of high volume and "high tech" efficient designs (like the "Inverter A/C" systems from Sanyo/etc.).

-Bill

Cariboocoot · September 2010

Re: Shop A/C... DC Air Conditioner?

I agree with Bill.

There's already utility power to the shop. Buying a DC air conditioner and installing expensive solar electric system just doesn't make $ sense.

Lots of people get the notion that AC should be run from solar. On the surface it makes sense, since the panels would be putting out their maximum when the AC is needed most. But so far no one has built a direct-from-panel AC unit à la the water pumps available from SunPumps or Grundfos. But then water pumps can supply to a reservoir as available and used when needed. Can't do that with AC.

Maybe some day ...

Dave Angelini · September 2010

Re: Shop A/C... DC Air Conditioner?

BB. wrote: »

A low voltage DC a/c system may or may not use less power than a very efficient 120/240 VAC system... You have to look at the specifications and compare.

My two cents, for large loads, you are generally better off going with 120/240 VAC inverters vs a 24 or 48 volt DC system... The issues of sending lots of low voltage DC current any distance will require lots of heavy copper cables. Also, the 120/240 VAC systems may end up costing less (including the inverter) because of high volume and "high tech" efficient designs (like the "Inverter A/C" systems from Sanyo/etc.).

-Bill

This may be changing very soon, I hope they decide to go past a successful beta test. Stay tuned!

Piper Ted · September 2010

Re: Shop A/C... DC Air Conditioner?

niel wrote: »

it might be better to just get the best a/c for grid tie and then put a gt solar system in to offset the running costs some.

Neil,
I think your right, actually everyone that has responded is.

So, does a grid tie system have to interact with my incoming utility, or can it be used solely for just the A/C unit? I am prohibited to feed any excess power produced by a solar array back to the utility grid, per my utility provider.

Ted

Not that I will get a system that will exeed my usage. If our power would go down any power produced by the solar array cannot feed into the grid.

niel · September 2010

Re: Shop A/C... DC Air Conditioner?

"I am prohibited to feed any excess power produced by a solar array back to the utility grid, per my utility provider."

what exactly does this mean? if it truly means excess as in turning the meter backwards at any given moment then just don't put so much pv in to do that. for example if you draw 1kw while producing 600w then it certainly won't go backwards as it would show a net usage of 400w. however, if it just means you are not to be allowed to have a 0 or negative usage on the average or in other words producing more per month than you use then again don't put in enough to do that. if they are saying no gt systems allowed then i'm not sure they can legally make such a blanket statement like that.

Piper Ted · September 2010

Re: Shop A/C... DC Air Conditioner?

niel wrote: »

"I am prohibited to feed any excess power produced by a solar array back to the utility grid, per my utility provider."

what exactly does this mean? if it truly means excess as in turning the meter backwards at any given moment then just don't put so much pv in to do that. for example if you draw 1kw while producing 600w then it certainly won't go backwards as it would show a net usage of 400w. however, if it just means you are not to be allowed to have a 0 or negative usage on the average or in other words producing more per month than you use then again don't put in enough to do that. if they are saying no gt systems allowed then i'm not sure they can legally make such a blanket statement like that.

Someone posed this question a few years back to our Co-op's newsletter. The reply was something along the line of: ...we can't have a grid tie system attached, because in the event of a power outage any energy we are generating during the outage could flow back into the grid, for safety reasons. For example: If a power line were to go down, a grid tie system could feed into the grid and possible cause injury to repair personnell trying to repair the lines.

Seems to me that if they had some sort of equipment at the meter that could sense if there was no power incoming it would shut down any power feeding out, but what do I know?

Ted

Ralph Day · September 2010

Re: Shop A/C... DC Air Conditioner?

Ted,
It seems the co-op needs a little education . Any grid tie inverters will drop/stop production within 1 or 2 cycles (I think) of power interruption or instability...UL1741 or something. It's a standard that equipment has to meet. Most grid ties have a monster/master disconnect which the utility can come and shut off and lock out while they are working in the neighbourhood. This information should be brought to the attention of the co-op. (Plus I understand there's federal legislation that requires utilities to net meter small producers in the US. I'm in Canada so not sure about that)

How do you feel about fighting city hall, so to speak?

Ralph

Piper Ted · September 2010

Re: Shop A/C... DC Air Conditioner?

Ralph Day wrote: »

Ted,
It seems the co-op needs a little education . Any grid tie inverters will drop/stop production within 1 or 2 cycles (I think) of power interruption or instability...UL1741 or something. It's a standard that equipment has to meet. Most grid ties have a monster/master disconnect which the utility can come and shut off and lock out while they are working in the neighbourhood. This information should be brought to the attention of the co-op. (Plus I understand there's federal legislation that requires utilities to net meter small producers in the US. I'm in Canada so not sure about that)

How do you feel about fighting city hall, so to speak?

Ralph

After I made that post I decided to go to the Co-op's website to see if I could find the statement anywhere. There was a FAQ section but tit didn't mention anything, so I decided to pose the question on the on-line "additional questions" link, which after I posted it crashed my bowser, all three times. This morning I get a call from the director of the Co-op on my cell. The message never went thru but my name and phone number did all three times, and he asked what I wanted to know. He said they do allow grid tie systems, but in order to install they would meter it differenty. Something about adding a meter to measure any outgoing power as it is metered and charged differently than the incoming power meter, but they do allow a grid tie hook-up. So apparently I was wrong about that or misread something, that was also 3 years ago... a mind is a terrible thing.

Ted

Shop A/C... DC Air Conditioner?

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