The Manufactured Housing Forums

I don't know anything at all about central air conditioning. We are buying a 1300 sf, 3 bedroom ranch modular with central air. How big should the system be? Do we need to worry about the AC manufacturer--or are they all pretty much the same? I'd love some help with this. Thanks.

How big the system should be depends on the home, windows, doors, insulation, lot placement (shade or no shade), typical weather extremes for your area, etc.. there is no scale to say ok, a 1300 sf home needs a x ton ac and x btu heat, there are too many variables.

If you want a guess, I'd say something around 3 tons or less for temps up to about 95 degrees.

Forgot to add, whatever you get, make sure it's a high SEER unit, this is where they can really go cheap on you.. 10 is about the lowest, 17 or so the highest. The higher the number, the less it costs to run.

Dealers usually go by sq feet,about 1 ton for every 500 sq ft.That may not be the correct way to figure it but thats about as techinical their going to get with it.Just to add also, don't oversize the unit,if anythin go a little smaller then you think you need ,in your case probably about 2 to 2 1/2 1/2 tons should be plenty.

The first thing you need to do is to look at your HUD Data Label. It will tell you how many btus your duct system can handle. It would not make any sense to purchase a unit that has more btus than what your duct system would handle.

Next is to have a dealer (either manf home or ac) do a manual J on your home. You don't want to guess on the size. If the unit is too big, you will not be comfortable; it will not run long enough to remove the humidity. If it is too small, again you will not be comfortable and the unit will run all the time.

The last thing is if you have a furnace, get a matching brand of air conditioning. Many contractors will tell yu that their unit will work with your furnace, but in reality it has never been tested or listed to work with that furnace. Make sure the air conditioner or heat pump is HUD approved.

Ducts are rated by how many cubic feet per minute (cpm) they can handle, not BTUs. They don't care whether they deliver warm air or cool air.

3 ton is fine, and almost any brand is ok. Just check the warranty to make sure you get the best warranty. I would purchase either a 10 or 12 SEER product. Yes there are higher SEERs, but they also cost many more dollars and sometimes the payback may not be there.

This is good advise! I had the geothermal contractor install my geothermal, and he obviously neglected to do a Manual J; likewise, he neglected to adhere to the HUD Label; otherwise, he would have complied to the "up to 37,900 btu/hour." Now, I am wondering how hard it will be to get HUD to force compliance with their code? The unit runs all of the time, i.e., it cycles on, and off in the afternoon, and it ices up in the A Coil, and water runs off of it in the floor. The utility bill is excessive, as much, or more than, the conventional homes I have compared it with. I live in Illinois, and am attempting to contact HUD. He placed a (4) four ton unit in the Manufactured Home with a (3) three ton air exchanger. This is my understanding why the A Coil ices up.

Sorry this is the homeowners responsibility..to know your homes heat loss characteristics..HUD would only force the original dealer or manufacturer to adhere to the rule..never a aftermarket person.....Have you tried talking to the a/c contractor about your problems...in most state they have to have a license...check with your states professional board for advice on how to file a complaint...

This could never be the homeowners' responsibility! Afterall, he/she is a layman in the HVAC field, and retain the services of a professional; therefore, it would be the responsibility of the professional [person who does it for a living] to adhere to the rules, and regulations. Afterall, rules, and regulations of any agency, are considered law.