Recommend a starting point for a garage A/C system ?

Mike vonB · July 2014

My situation:
Hi all - I'm a recently retired military guy who is now living in Sacramento (hoping I'll still be welcome here, because Nor Cal doesn't have a cool site like this one!). So my retirement hobby/pseudo-business is laser engraving, and my west-facing garage is the only real estate I have at the moment. The laser is best operated between at 60-70 F... and since the normal Sacramento temps are 90's+, I'd like to get a solar a/c unit to cool the garage, running only during the hot & sunny days (when I need the cooling).

I'm not really planning to work too much after sunset, and the rest of the year (minus a few days in 'winter') is temperate enough (using the sun to warm the west-facing garage). Garage size is about 25' x 25'.

What I'd like:
Solar system for a window/portable A/C unit running only when the sun is out. I'm guessing this would be considered an 'off-grid' setup.

Extent of solar knowledge:
I know I need some PV panels ...

... so just by reading the thread titles, now I'm needing to get smart on size os panels, batteries, fuses, inverters, cord size/gauge, and ... ???

So while I start to explore the forum, I'd appreciate any links to any similar threads to get me started, picture diagrams are great, youtube videos, etc, etc... as I didn't see a sticky with that info.

Thanks in advance!

mike95490 · July 2014

Re: Recommend a starting point for a garage A/C system ?

Any solar power going into a house, is going to need a permit & inspections. Homeowner can do the work per code.

What I would suggest is a small 2-5Kw Grid Tie system if your electric company allows them, and that would offset/unwind the new electric meter they will install. And it will reduce your monthly bill all year.

vtmaps · July 2014

Re: Recommend a starting point for a garage A/C system ?

Mike vonB wrote: »

What I'd like:
Solar system for a window/portable A/C unit running only when the sun is out. I'm guessing this would be considered an 'off-grid' setup.

Welcome to the forum,

You should know that an off-grid system will need a battery. Any battery based system will make your kilowatthours 5-10 times more expensive than what you pay the power company. As Mike95490 suggested, look into a grid-tied system. A grid-tie system can be cost effective, with a return on investment within a few years.

It's cheaper to conserve power than to generate it... in other words: be efficient. This means insulate and tighten the garage, and for the A/C, look into a mini-split system. The mini-split can provide heat as well as cooling.

--vtMaps

solar_dave · July 2014

Re: Recommend a starting point for a garage A/C system ?

Oh In California definitely do grid tie, no batteries to deal with, lower initial costs and you get the full benefit of every watt generated (not true on off-grid). Plus the net-metering plans out there seem to give a huge advantage to the home owner in that the crediting is in $$$$ and those on peak $$$$ can be used to purchase much cheaper off grid power at night or offset the higher cost on-peak.

Mike vonB · July 2014

Re: Recommend a starting point for a garage A/C system ?

Ok, so what I'm hearing is there is NOT a small garage-sized solar/air conditioner setup that works only when the sun is shining (and temps go up - hence the need for cooling) ?

vtmaps · July 2014

Re: Recommend a starting point for a garage A/C system ?

Mike vonB wrote: »

Ok, so what I'm hearing is there is NOT a small garage-sized solar/air conditioner setup that works only when the sun is shining (and temps go up - hence the need for cooling) ?

Small is relative... sure there are small systems. But if they require batteries, they are not cost effective.

Did you see this recent thread about a hybrid air conditioning unit?
http://forum.solar-electric.com/showthread.php?24023

I know nothing about it, or its price... but it is an interesting concept. It does require 240 volt AC.

--vtMaps

solar_dave · July 2014

Re: Recommend a starting point for a garage A/C system ?

Mike,
AC is about one of the heaviest users of electric (unless your heating with it and that is totally not recommended).

Grid tie will take into account all the watts the panels can make, if it isn't enough then the grid can make up the balance. If you are using a totally off grid setup you have to have batteries and a large enough inverter to run the AC plus you loose power recharging the batteries. If it is not adequate then you either over discharge the batteries or stop the operation until you get the batteries recharged.

Grid tie is much more cost effect and just plain easier to cope with.

Ks Solar · July 2014

Re: Recommend a starting point for a garage A/C system ?

Also if doing a grid tie I notice now the latest is to use a micro-inverter on each panel. It sends 240 volt AC directly to your house panel. Employ an automatic transfer switch to disconnect from the grid in case of a power failure.

jonr · July 2014

Re: Recommend a starting point for a garage A/C system ?

You could put together a battery-less system, but it's going to be easier to use a battery and a very conservative low voltage cutoff on the inverter such that it doesn't make much use of the battery. I'd get a small, 115V, inverter based mini-split (like a Fujitsu 9RL2). Plus insulate the garage.

Cariboocoot · July 2014

Re: Recommend a starting point for a garage A/C system ?

Ks Solar wrote: »

Also if doing a grid tie I notice now the latest is to use a micro-inverter on each panel. It sends 240 volt AC directly to your house panel. Employ an automatic transfer switch to disconnect from the grid in case of a power failure.

No transfer switch is needed with grid-tie inverters. They have anti-islanding circuitry which causes them to shut down in the event of grid failure, preventing them from trying to energize the whole neighbourhood. They produce no power during an outage.

TucsonAZ · July 2014

Re: Recommend a starting point for a garage A/C system ?

Mike, things can get confusing beyond comprehension fairly quickly in here. If you just want to have some fun and play around with solar, not have a "grid-tie" system, not worry about "code" as it isn't going to be inspected, there's no issue with that.

1) Figure out when you're going to use the power, if only when the sun is up, that's much easier.
2) Get a Kill-O-Watt meter, hook it up to what you intend to run and log the data, remember, you may want to completely unplug the unit so you have correct info on hours/usage.
3) Figure out how many panels you will need to supply that power.
4) Figure out how many batteries you will need to equalize the mercurial natural of solar power (clouds, leaves on panels, shadows).
5) Get the supplies you need to be safe, a charge controller, some cable, an inverter sized to your AC unit (account of surge at start up).

You may also want to look into a mini-split, less cost to run, makes things less costly on the power supply end.

Good luck!

Cariboocoot · July 2014

Re: Recommend a starting point for a garage A/C system ?

TucsonAZ wrote: »

Mike, things can get confusing beyond comprehension fairly quickly in here. If you just want to have some fun and play around with solar, not have a "grid-tie" system, not worry about "code" as it isn't going to be inspected, there's no issue with that.

1) Figure out when you're going to use the power, if only when the sun is up, that's much easier.
2) Get a Kill-O-Watt meter, hook it up to what you intend to run and log the data, remember, you may want to completely unplug the unit so you have correct info on hours/usage.
3) Figure out how many panels you will need to supply that power.
4) Figure out how many batteries you will need to equalize the mercurial natural of solar power (clouds, leaves on panels, shadows).
5) Get the supplies you need to be safe, a charge controller, some cable, an inverter sized to your AC unit (account of surge at start up).

You may also want to look into a mini-split, less cost to run, makes things less costly on the power supply end.

Good luck!

Except that with battery-based inverters you figure out how much battery you need to supply the power and how many panels you need to recharge the batteries. You'll be much happier with the result, even if you only want to run in daylight hours.

Ks Solar · July 2014

Re: Recommend a starting point for a garage A/C system ?

Cariboocoot wrote: »

No transfer switch is needed with grid-tie inverters. They have anti-islanding circuitry which causes them to shut down in the event of grid failure, preventing them from trying to energize the whole neighbourhood. They produce no power during an outage.

I did not know that. I would want my solar working for me if the power is out.

Cariboocoot · July 2014

Re: Recommend a starting point for a garage A/C system ?

Ks Solar wrote: »

I did not know that. I would want my solar working for me if the power is out.

Then you need batteries, or a generator, or the SMA GTI with the built-in emergency outlet which can provide a small amount of power during daylight hours.

Skippy · July 2014

Re: Recommend a starting point for a garage A/C system ?

I started out with the idea of going to batteries, but then changed my mind too go grid tied. If you are not worried about the pay back or just want to play with it, go for it. I have an old window a/c unit that draws a full 15 amps - I tried to use a regular extension cord with it, and the cord heated up . . NOT GOOD ! . . on the other hand, I also have one of those stand alone units that have the two hoses that feed out the window. It does a really good job at cooling, and it only uses 700 watts - full blast.

Get yourself a kill-a-watt meter, and have fun with your sunny experiment.

drraptor · July 2014

Re: Recommend a starting point for a garage A/C system ?

Cariboocoot wrote: »

Then you need batteries, or a generator, or the SMA GTI with the built-in emergency outlet which can provide a small amount of power during daylight hours.

How about a grid interactive Inverter with batteries for backup e.g Outback Radian ?

Cariboocoot · July 2014

Re: Recommend a starting point for a garage A/C system ?

drraptor wrote: »

How about a grid interactive Inverter with batteries for backup e.g Outback Radian ?

Yes, and that falls under the first segment "you need batteries".

Raj174 · July 2014

Re: Recommend a starting point for a garage A/C system ?

Hi Mike, You said your garage is 25x25 feet. That's 625 sq/ft and your going to need an 18000 BTU A/C to cool that space, and that space does need to have some insulation. As many have said here the mini-split system is the way to go. I found a 16 seer unit as an example. It is 220 volt as they all are at that size, and it draws about 7 amps per leg and is rated at 1500 watts. If your house is within a couple of hundred feet of the garage you might look into having a 220 volt line pulled to the garage. It think it would be much cheaper than a solar solution. If the solar project is just as important as the A/C project then the guys on this forum can definitely tell you what you need to power this unit. Here is information on the unit.

http://www.thermospace.com/ductless_split/senville-leto-senl18.php

Hope this helps……Rick

Recommend a starting point for a garage A/C system ?

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