5,841 posts, read 5,490,171 times Crappy situation I'm in, compounded by me being on maternity leave and bleeding savings by the hour... It's 102 here in TX and woke up to NO AIR. I thought it was probably due to Freon leakage or something, but found out that the worst case scenario - the compressor being hosed -- is now a reality. We have two AC units, one is a replacement (the downstairs unit's compressor also got hosed last year and was replaced) and the other is the original 6 year builder's grade Carrier. This is the one that has died. Should we both purchasing a new compressor, or should we get a new unit? Some more factoids: we found out that the tonnage for the existing AC is not proper for our size home -- 2.5! It uses Freon, whereas Freon is going the way of the Dodo. New unit would be in full compliance with new refrigerant and energy efficient. Price difference between compressor and new unit is 2.5K. We're really bummed out over this. 1,323 posts, read 2,934,142 times

445 posts, read 1,086,035 times 694 posts, read 2,327,427 times 6,939 posts, read 14,640,995 times Originally Posted by riaelise Wow, the baby must be walking by now! Air Handler mismatch with compressor I have a situation where the air handler is 5 ton and the compressor is 3.5 ton (both 2009 models) The HVAC guy says that this was done in order to meet the SEER requirements or something to that effect.....5000 btu ac unit room size Does this make sense? wall air conditioner smells like vinegarCan the system be really more efficient under this scenario?car air conditioning repair coventry Thanks for you input! Need a home inspection in Nevada? listing of Nevada certified home inspectors.

Re: Air Handler mismatch with compressorThis is how you obtain a higher SEER rating. The air handler will be oversized to meet the SEER rating. And yes it will be more efficient. Why did you not believe the AC contractor? Originally Posted by rmurphy1 I smell smoke when you say ahu does that mean refrigerant coil or blower or both. Standard protocol worst case is to never mismatch more than 1/2 ton over or under between the compressor and the refrigerant coil The CFM of the blower is also calculated to match As the Master HVAC Mechanic (retired) states - Protocols are such that the mismatch shouldn't be more than 1/2 ton... Why didn't I believe the HVAC contractor? Because I have known them to be wrong and the above stated protocols have been in our toolbox. I haven't disagreed with the man, I am merely finding out if what he is saying is correct. If the systems are so much more efficient this way - Why aren't all systems installed in such a manner?

I am NOT an HVAC professional. I am trying to improve my knowledge base here. Is it not right to call out the mismatch and refer it to a professional? Sure if you want to use engineering formulas like this oneThe polynomial equation that shall be used to represent the tabular data is a third degree equation of ten coefficients in the form of: X = C1 +C2 � (S) + C3 � D +C4 � (S2 ) + C5 � (S�D) + C6 � (D2 ) + C7 � (S3 ) + C8 � (D�S2 ) +C9 � (S�D2 ) + C10 � (D3 C = Equation coefficient, represents compressor performance S = Suction dew point temperature, F [C] D = Discharge dew point temperature, F [C] Originally Posted by wsiegel Back in the late 70's and early 80's that's how Coleman was achieving their high SEER rating. They were selling them as a package deal. We installed a lot of 3 ton condensing units matched with 5 ton A coils plus a liquid line shut off solenoid valve and an indoor blower time delay relay in those days.

I had one in my own house until 3 or 4 years ago. As I recall the SEER was 12.4 or so then. Of course you can't (shouldn't) go the other way and use a smaller A coil. Originally Posted by sparksnmore We installed a lot of 3 ton condensing units matched with 5 ton A coils What was the sweat line on the coil I have a hard time believing that a 3 ton condensing unit can hold enough liquid in its condenser to prevent a 5 ton coil from being starved. I was taught in two different A/C schools that you never over size the A-coil by more than 1/2 ton. To be honest I have never seen a MFG increase the size of the indoor coil to achieve a higher Seer rating but I am not a mechanical Engineer either. My observation has always been to increase the size of the outdoor condenser on the high seer units. Carrier was very famous for this when seer rating became a issue. They increased the size of the outdoor condenser X3 over a standard 12 seer unit, and had this little compressor wrapped in a blanket could barely see it.

BTW Trane also did the same thing monster condensing unit same size coil She lives in a small, simple house in southern Mississippi. It's only 1700 square feet. Why then, she wondered, were her summer electricity bills running more than $600? She didn't have anything that could be a big energy hog, like a swimming pool, and she didn't do stupid things like leave all the doors and windows open while she ran the air conditioner. She called her electric company, one of the co-ops in Mississippi, and they sent someone out to investigate. Utility companies get calls like this all the time, and they've learned from experience what most of the main causes of high bills are. When the utility investigator arrived arrived at the house, he asked her to tell him anything she knew that might help him. "Well," she said, "the air conditioner runs all the time, but the house won't even cool down to 80 degrees." "Ah, that helps to narrow it down a bit." He went to work, and it didn't take him long to find the problem.

He measured the temperature drop across the air conditioner coil and found that the air on the 'cool' side wasn't much lower than the air on the warm side. And both were much warmer than they should be. OK, that could be a disconnected duct in the attic, he thought, like the one from a different house that you see above. A look in the attic, however, showed that wasn't the case here. Besides, a disconnected duct would increase the bill, but it almost certainly wouldn't quadruple it. His next step was to turn off the breaker to the electric resistance heat (a.k.a. strip heat) in the HVAC system. This is basically a giant toaster inside the air handler. Heat pumps use it for supplemental heat. In some homes, it's used as the primary heat source. It's not cheap, though, especially considering that the same electricity going into a heat pump will yield two or three times more heat. Anyway, the utility investigator turned off the breaker to the strip heat and watched what happened to the meter.

In the summer time, turning off the strip heat should have no effect at all on how fast the meter spins because it shouldn't be running. Strip heat is for cold weather. In this case, the meter went from spinning fast enough to saw wood to moving as slow as a horned passalus (photo at right) going for a walk in the woods. "Well, we found your problem, ma'am," he told her. "Your heating and cooling system was doing both at the same time, making you spend a lot of money to stay uncomfortable." This problem often results from a thermostat wired incorrectly so that the system kicks on the strip heat when it shouldn't. Since anyone can go down to the home improvement store or the Interwebs and buy a thermostat, a good number of these problems result from DIY jobs. It seems crazy to think that someone wouldn't notice that the heat is running in their home in summer, but they don't feel heat coming out of the vents. That heat gets mixed with the cool air from the air conditioner.