5200 BTU window A/C for doggies

SystemSystem Posts: 2,511 admin
Hi, at the moment I write this, I am the "newest guy" (girl). It may have been dumb but I went ahead and did it--I bought the Costco Sunforce 246 Watt Solar Power Back Up Kit with Sharp® Solar Modules Item# 253506.

What I need is a way to have emergency electricity at my house in case of an outage (etc) so that my dogs won't roast while I am at work. I am in central Texas with plenty of daily sun, even year round. I have a 5,200 BTU Energy Star A/C window unit for the dogs' room that I am installing (house has central air). The Costco solar kit says it will operate several items but doesn't say if it will do them all at once.

I probably should have done a lot more reading at this forum before buying the solar kit but my head was beginning to spin with all the info.

When the kit arrives, can I hook it up and hook it to the A/C unit (window 5200 BTU) and it will work? Am I way too naive on this???

Thanks for any help anyone can give me.

Phoenix and the 5 doggies


  • BB.BB. Super Moderators, Administrators Posts: 33,313 admin
    Re: 5200 BTU window A/C for doggies

    I am sorry--but you will not achieve any of your goals with this system...

    A/C is a pretty large electric load--and the amount of solar panels, battery storage, and size of inverter are beyond this sunforce system...

    Could you make a small A/C system run with this system... Sort of yes--perhaps for 1 hour per day. But, I assume, that would not be useful for you.

    So--go back and define your goals/requirements. And do it with energy conservation in mind.

    Normally, I do not recommend the solar roof fans--they can be done just about as well with just placing more vents in the roof (along the eaves, and at the peak). If you have a bit of wind--even add some wind turbines (may not look nice on your home--but may be OK for a dog house).

    Costco, currently is selling a solar roof fan for ~$270-$320 dollars (both in-store in our area, and online). You could place that on the roof of your dogs' home at get some positive ventilation (basically-if there is direct sun on the home--there is air movement). The solar panel can be dismounted and moved ~10-15' away if the dog facility is shaded. It would not be a bad solution if positive airflow meets yours and your pet's needs.

    Also--conservation would recommend creating shade for your pet's home. That will greatly reduce the self-heating, and the amount of cooling needed to keep the place at a safe temperature.

    --So, what is the real requirement? Shade and some positive ventilation, or do you really need A/C?

    And if you need A/C--how much backup/emergency power do you need... If you just need 24 hours of backup power a few times a year--an automatic genset (starting at ~$5,000) would not be a bad investment (and could power your home too). Look at what fuel sources make sense for your area (natural gas, propane, etc.). Even a small 10kW genset, when running (you need automatic start and auto-transfer switch), will use a lot of fuel for small loads (very roughly $1.00 per hour or so at current pricing). But, compared to the expense of installing solar panels and batteries (which require maintenance)--it is not bad compromise--plus with the genset you have a lot of "extra power" for home backup too.

    Basically, solar PV electricity makes good sense (worth the money) if you are using the power nearly every day for 9 months, or more, of the year. If you want to setup a backup solar power system to run 1 week out of the year--the solar panels, charge controller, batteries, inverter, transfer switch, etc. make for a very expensive backup system.

    If your area requires A/C for your pets, and you will be using the A/C for 3-6 months out of the year anyway... Take a look at the Sanyo or Fujitsu Mini-Split A/C systems. The run at 20-26 SEER and, the Sanyo, is very genrator/off-grid friendly.

    Based on what I am guessing here--how would you like to proceed. We are more than happy to give you some estimates for equipment and a sample list of components.

    But, be aware, building an Off-Grid capable solar system that can run, even a small A/C system, is neither small or "cheap".

    Please feel free to ask questions--I am guessing at your needs for the moment.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: 5200 BTU window A/C for doggies

    i think what is needed is just a home backups. a quality sine wave inverter with a built in charger and of course enough of the batteries to power things for as long as you deem and design it for. the pvs you bought can still be used to supplement the system and more can be added, but be aware that a window a/c unit going 24hrs will huge to design for if on solar only.
    many also opt for a generator with an ability to kick on during an outage. the drawback is the gasoline needed for long term use and it does not store well.
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: 5200 BTU window A/C for doggies

    Think about a well insulated "cool room". Thermal mass,, like a concrete floor,, well shaded from the outside,, maybe with a water circ system in a slab to keep the K-9's cool.

    Bill and Neil have it about dialed in terms of running any ac off of your small panel system. What you could run is a series of fans,, a pump for a misting system for evaporative cooling,, or a circulation system for cool water in a slab.

    For the number of times that you 'really' need a system,, a small auto start generator and transfer switch is probably the best way to go. One that is powered by either Propane or Natural gas,,, and has an auto exercise cycle built in would be nice. On the other hand,, if coming home is an option to start the system,, a smaller simpler system could be done quite cheaper.

    Good luck,

  • System2System2 Posts: 6,290 admin
    Re: 5200 BTU window A/C for doggies

    Wow, you guys are great. These suggestions really have me thinking. And lots of good info. I am embarassed I didn't know how much of a hog an A/C unit might be. I have a friend with a motor home and she does run it (including AC) on a generator at times. Noisy.

    The dogs have their own room in the house (for when I'm not home) and I have had the house a year (built in 1970) and added insulation (blown in attic) & the attic solar fan. Okay they talked me into it :-( Also the radiant barrier. I had an energy audit and they said I lose most of my cool/heat thru the windows but it would be too expensive for me to replace all the windows (many of them are about 7-8 ft x 5 ft). As I bought the place 'for' the dogs, there is a huge yard with lots of big shade trees--one shades the dogs' room (on the north) most of the day. Still, if the air goes off in the summer (outside temps 100+) the heat in the house seems to rise fast. I have a friend with a newer, better built, brick house and you get the feeling in that place, that it would take a day or two for the heat to get unbearable if the AC went off. Not at my place.

    I was worried about storage of gasoline for a generator. But maybe a propane tank? The other thing about the solar panels, I DO want to be green and not so dependent on "the man" (i.e. the grid). Anybody has more info and suggestions, I am here to learn. PHX
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: 5200 BTU window A/C for doggies

    Awnings,, insulated shades,, hanging blankets over the windows to reduce "cool loss" or prevent heat gain. Do everything the energy auditor suggests starting with the cheapest. Those of us "northerners" have a difficult time getting our heads around "cooling loss" or heat gain in this concept,,, but it is all the same physics...

    You have two issues,, direct heat gain from ambient air,,, and solar gain. It seems your biggest short term issue (power outage) is solar heat gain. Do every thing to reduce it,, add as much shade,,, and insulate the attic as much as possible

    Good luck,, welcome to the forum,, read and learn,,, there are some pretty sharp folks here!

  • System2System2 Posts: 6,290 admin
    Re: 5200 BTU window A/C for doggies

    ...got all excited about how fun it was to fly and ignored his dad's instructions not to fly too close to the sun. It melted his wings and he fell to his death :-(

    I just love the handle you chose--is there a reason you like it?

    I am already learning a lot from you folks. PHX
  • BB.BB. Super Moderators, Administrators Posts: 33,313 admin
    Re: 5200 BTU window A/C for doggies

    My two cents (remember, this is the Internet--$0.02 is about the right value). :roll:

    I live in a relatively moderate climate--there are others here that can correct me on the details. Some suggestions are probably not practical (or only practical for a single guy :D ).

    Start by insulating the heck out of the one room (at least).

    Make sure you attic has something like 19"+ worth of insulation (R44?). And make sure the attic has proper ventilation to keep it from getting too hot.

    If the exterior walls are not insulated, insulate them--and I would also insulate the interior walls of the pet room with blown in insulation (and under floor crawl space--if applicable)--if you can keep the door to the room closed during the day.

    Replace the exterior windows with, at least double pane vinyl windows with Low-E glass.

    If you need ventilation in the room--look into a Heat Recovery Ventilator. Basically, it runs the cool interior air in a metal heat exchanger with the hot air coming in from outside--The cool air leaving gets hot, and the hot air coming in gets cool... Just has a fan inside (works fine by doing the opposite in cold weather).

    Any lighting in the room--change to CFL or LED (less heat into the room, the slower it will get hot).

    And as Tony Says--eliminate any direct sunlight on the exterior of the room (and the other windows of the home--as possible). Heavy drapes, Styrofoam cutouts in the windows for rooms not used much during the day (take the foam out on weekends when friends are over, etc.).

    Reduce energy use in the rest of the house during the day (turn off computers, printers, etc.). Close doors to "hot rooms" (kitchen + fridge, etc.) to keep rest of home cool. Get a Kill-A-Watt meter to check where you may be "wasting power" (old TVs and stereos consume quite a bit of power in standby).

    Keep the rest of the house cooler as best you can (notice--this is all "standard" conservation 101--not a bad thing to do anyway).

    Install (probably) the Sanyo Mini-Split A/C in the room... You can efficiently over-cool the pet room a bit on a hot day--will take longer to overheat.

    Seems strange--but add anything Massive/Heavy into the room... For example, 200 gallons of water (4x 55 gallon drums) weigh about 1,600 lbs. If they "heat" 1 degree Fahrenheit -- that is 1,600 BTU. If the room starts at 70F and heats to 90F (and the drums change from 70-90F) that is 20Fx1,600BTUstorage=32,00BTU -- Or:

    32,000BTU/5,200 BTU per Hour A/C = 6 hours of "passive A/C"

    Now, 200 gallons of water in 55 gallon drums may not be the best room decor--but anything heavy (wood, ceramic, fish tanks, drums of water, etc.) will help give you that passive cooling (pets can curl up next to cool objects if it gets warm.

    If you can get the room where it is more thermally "stable"--you can get a small gasoline/propane genset with manual start and know that you can wait until you return home and everyone will be safe. Now instead of a big/expensive automatic installation, you can get smaller (more fuel efficient) and cheaper manual genset (pull start, electric start) that you can run your small A/C unit on instead.

    If propane is an appropriate fuel for your area--go for it.

    Our home--70 years old--we installed wall insulation, double pane vinyl windows, afternoon shade from trees/garage to the west (actually, I also insulated my garage too), Energy Star Fridge, no large "standby loads", CFL lighting, added skylights (double pane low E) for interior lighting, etc. (more or less, just "normal" remodeling stuff)--and our home can be 25F less vs our first hot 95F-100F day (we don't have A/C--so we kind of work to keep the house cool/cool at night). Before, it was always hotter than the air outside (on hot days).

    Just the insulation, some exterior shade, and normal thermal mass of a wood frame home is enough to keep our home very cool--except when we have a week of extended heat (and the evenings are warm).

    In our previous home, we only had some ceiling insulation and stucco walls (no insulation in walls) in our west facing bedrooms. I just changed a set of windows in both bedrooms (d-pane, low-E glass)--and it made "night vs day" change. After changing the windows (still no insulation in walls)--and the west facing rooms where no hotter than the rest of the house (and a ~18F-20F lag on a 95F-100F day).

    The Windows (if single pane, leaky wood/aluminum) and Attic/Ceiling Insulation (if it is lacking) are the two place to put your conservation funds first (in my humble opinion).

    Your thoughts?


    PS: I should also ask the size of the dogs... An adult human "dissipates" an average of 100 watts = 341 BTU / hour...

    Five good size dogs--and you will have to take "them" into account when looking at your heat loads for the room.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: 5200 BTU window A/C for doggies

    hmmm, doing all this for 1 room is tricky and complicated. it isn't always as easy to isolate 1 room. for example if there are air ducts for whole house, be it for a/c or heat, the cooler air from the room will escape to the rest of the house. i think that even though it is costly to do all of the windows, that you can't do right now, but doing a few may help and may be within your means now. also, keep in mind that losses/gains also occur through crawl spaces or basements under the home. the insulation need not be as elaborate for this, but some should go in.
    now i have a window air conditioner that is 6000 btus and on its nameplate a 9.7 eer and 5.5a at 115vac. my kill-a-watt meter shows about 4.4a at 122.6vac and about 440w and 560va on high. it calculates to about 540w going v x a. confusing i know, but we'll take the marked 5.5a as worst case and use this as an example for you. if this goes 24hrs (constant running is possible if temps outside are that high even with putting the thermostat to roughly 80 degrees) this is 24 x 5.5a = 132ah. for the wattage this is 132ah x 115vac = 15,180wh or 15.18kwh. the batteries used must be rated at least twice as many kwh as your loads will be for 30.36kwh. if it's a 12v battery bank (not recommended due to wiring losses and costs) this will be 2530ah in batteries and is sizable. if placing a timer for say running 12hrs per day this can be cut in half and mind you you have no power for the next day if power hasn't been restored. for a 24v battery bank you'll need 1265ah in capacity. and finally a 48v battery bank will need 632.5ah in capacity.
    now i know you said you will use a smaller a/c unit, but you also indicated you were running other items with it and i didn't include anything else so these figures may be in the ball park of your needs. remember that batteries need at least 5% of the battery ah capacity to charge so multiply that times those capacities reveals quite a few pvs needed to charge this and it can't recover all of it's power losses every day at a 5% charge rate. this may be closer to the 20-25% charge rate to achieve that and that means batteries that can take a high charge. speaking of high charges, standard lead acid batteries will off gas and it could be significant with the high charge rates creating a hydrogen gas danger. higher quality agms would better suite in this case imho.
    i am probably throwing out too much for you and confusing you somewhat, but you can now see how much an a/c unit can suck up in power and the elaborate numbers of batteries needed to supply it.
  • System2System2 Posts: 6,290 admin
    Re: 5200 BTU window A/C for doggies

    BB., niel, icarus:

    Thanks for all the great suggestions. I have printed them off and am going to start implementing them or checking if I have already done them well enough. I will keep you posted on my progress. Very selfless of you guys to help people out like this, I am grateful.

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