RSpermo

Erby, As you know a lot of aspects go into sizing a HVAC unit. I am presently air conditioning my 4100 sq ft 2 floor house in south central Texas mostly with a 3 ton unit. I do have a 4 ton unit that is zoned that comes on very sparingly. As others have said the insulation, the infiltration rate, the sensible/latent split and other aspects must be considered. Have a reputable HVAC contractor run a load calculation. As least then you will have a recognized number.

I don't think it is the lid switch. I just replaced my lid switch because the washer would stop when it got to the rinse cycle. Moving the knob still had no effect. I think when the lid switch goes it shuts down the rinse and spin cycles completely.

Let's look at some simple math. Before the math is the attic ceiling insulated? I will assume it is and just concentrate on the 2 uninsulated walls. If the 2 walls are 40 feet long and 8 feet high that would be a total of 640 sq ft of uninsulated walls. Using a formula of BTUs of heat lost = U factor (assume .33) x sq ft (640) x temperature difference between indoors and outdoors (50 degrees), the answer is 10560 btus of heat lost per hour or 253,440 btus of heat lost per day which is 2.5 therms. For 30 days you have lost 75 therms right there! I am also betting your attic/ceiling is insufficiently insulated.

I think the guy is incompetent and has opened himself up to lawsuits by the home owner! He is trying to sound like a competent HVAC contractor but has failed to do so! I would charge $250 - $300 to do a load calculation (requires a lot of onsite measurements, etc).

Anyone interested in doing an inspection in Lancaster, Va for a 3800 sq ft home? It is for my daughter's father-in-law. Call Bob @ 210 385-1209

I do blower door leakage tests in south Texas in the summer. I have used my IR camera during the test. Its benefit is that with the IR camera it does highlight the hot air that is being pulled into the inetrior through leakage holes. Would I buy an iR camera just for this purpose? No! I would only buy an IR camera if I was willing to get proper training and I had some valid uses for it.

Phillip - Exactly why I went out and earned my Texas HVAC Contractor's license. I can now give my clients a more thorough inspection. By the way taking static pressure only requires a "pitot tube" and a pressure measuring gauge.

Phillip, Have you checked the static pressure in all configurations (different dampers opened and closed)? It may very well be that in the worst case the static pressure is approximately .5"WC.

I recently installed a damper and zoned system with a barometric bypass duct from the supply plenum to the return plenum. The bypass duct functions basically on the static pressure in the supply plenum. I took the static pressure and got .55"WC. That was my goal - around .5. I installed 3 dampers and when one zone is called for it goes full open and the other 2 still remain 50% open. So I think the bypass duct may depend on what the dampers do when that zone that is not the primary zone. You also have to ensure that the bypass duct does not put too much cold air back into the return system. By the way I used 800 KwHrs less this July than last (temps about the same - high 90s - 100 all month).

I would ask Carrier if the coil and the condenser are allowed to be used (matched) together. The final answer rests with the manufacturer.

The best way to size a HVAC system is to do the full manual J, S and D. Short cuts and other methgods can lead to mis-sizing.

Mike, I just talked to the head code compliance officer for HVAC for the state of Texas at the Department of Licensing. In Texas only the homeowner or a licensed HVAC technician can repair (seal ducts with tape or mastic). Anyone else that repairs ducts would be in violation of the state licensing laws and subject to a large fine. While I have no idea what the laws are in Va I would certainly check before I do any more repairs.

Nolan, I am interested in the protocol that this "auditor" follows. Would you please post after the audit exactly what the "auditor" did.

There are many companies in the weatherization business that are having success by blowing cellulose into the wall cavities from the exterior. I have seen it done in 40 - 50 year old houses. By the way while you may have R-13 insulation in the walls your wall is probably closer to R-8.

I would be careful in calling a unit too small if I had not done Manual J calculations. You really need to address alot of factors (insulation, house siting, overhangs, windows, etc) before calling it undersized. Oversized is more of a problem especially in regards to removal of moisture.