m still working on getting my system sized and installed and am at the point where I need some experienced input.All,repeat ALL the contractors I had quote all did the rule of thumb thing.I asked a couple of other contractors,one a very latge commercial/industrial shop owned by a cousin,and the fellow I talked to there said he had only heard of the load calculations for residential being done for rental(ie;townhouse)type units.So,I downloaded the trial one from your home page but had some probs.I was then fortunate enoughthat I was able to get someone to take my info and run it on their program(hes a tech in on of the industrial plant here in town;I don't know what program it was but here are the results..(all measurement are in BTUH..sensible gain-20878...latent gain-2715...total heat gain-23593...total heat loss-57159. (From the way its stated I suspect he may be using Don S 's program)Now,heres my question,can anybody point me in the direction of funace(HE gas)and AC unit size I should expect from these figures?Sorry for being so long winded and a little dense in this matter but the more info I can get the better the choice I can make.Thanks profusely in advance to any and all.
You are looking for an A/C with an ARI rating more than your heat gain. If you keep the indoor temp same has the computer program was set, I'd say a 2 ton but be sure it is close to 24,000 BTU. If you like it cooler, better bump up to a 2.5 ton. Many 2.5 ton units are more like 2.25 anyway.
Heat wise, that would be a furnace with an output more than your loss. A 75K 80% furnace has an output around 60,000 so that would be what you need.
What was your indoor and outdoor design temperatures for cooling?
VERY disappointed to hear the majority of contractors still refusing to utilize a vital tool in our industry, i.e. Manual J load calculation. There is no reason, NO REASON, except laziness for someone NOT to perform this service. It is for THEIR benefit as well as YOURS. Just my 2 cents worth. Sounds like the correct size recommendations (not knowing anymore than what we do.) What did your contractor recommend? Be cautious when upsizing to be sure your air distribution system can properly handle it.
read lots here
numbers can be slanted depending upon the design temps -- eg: do you want 65F in the summer? or, are you willing to let temp drift to 80 or 85F if it is 100F outside? are you in area having lots of hi RH%, like Huntsville AL ( we had low this week = 47%! )
letting it drift is ok, esp if you plan to live there long time -- maybe not if you plan to sell soon --
do you know what insulation is existing?
ask the contractors -- but, have a list of questions, so you don't waste their time ( = $ )