New Heat Pump Advice for Noob

[mrsunshine]

OK, so I'm a total noob when it comes to HVAC. I was hoping someone could give me some advice. I have a 14 yo Trane 2 ton heat pump. It currently has a problem with heating (compressor consistently shuts off after 10 minutes when heating), which (coupled with the tax credit) led me to think that it might be time for a new system. Cooling does seem to work OK, but still, the unit is 14 yo.

I've gotten numerous quotes, but how do I find a contractor to trust? I've read some of the other posts on the forum and none of the contractors that have come to my house have done a manual "J" or "D". Are those always done for a replacement system? One note, the area I live in (St Pete, FL) has a large # of houses with similar configurations. That is 2 or 3 bedroom block ranches. I have a 2 bedroom 918 sf block ranch, so how much effort is required to size a replacement system & ducts when my house has the mostly the same configuration as all the other houses in the area?

Also, it seems reasonable to stick with a 2 ton unit, but I'm wondering if I need a new return. I have 1 18x24 return in the side dining room wall. 1 contractor recommended another return. He stated that I have 600 CFM and need 800 CFM. But my house has had this set up for years. Do the new hi-efficiency units require more precise ductwork?

[jeff520]

400 CFM per ton is the suggested airflow for most installations, but in Florida you might want to drop this to 350 or so in order to get better humidity removal. In any case it would be a good idea to go with the contractor who was smart enough to see that your return was somewhat undersized.

A bigger return will lead to a quieter system and a very slight drop in energy consumption even if no other changes are made.

If 2 tons has worked for you up to this point then going with the same size should have no bad effects. Going up in size if you do not need it will certainly be uncomfortable both to your wallet and to the environment in the house. A good contractor will want to do a Manual J in any case, but be very cynical if an increase of more than half a ton is suggested and ask for a detailed explanation of why.

[ccservicefitter]

I agree with installing an additional return in a central location. Stick with the two tons. Also if you spend more on a high seer unit you get a variable speed air handler that with help draw out the humidity on a summer day. However a correct thermostat has to be in place for the unit to dehumidify correctly. Good luck!

[TwincamDave]

Sounds as if the unit is over charged and this condition will show up in heating(which is less forgiving) rather than in cooling.Has anybody added refrigerant in the last year to the unit or have you had a repair to the system in the last year? If so have a different set of eyes look at it and correct the charge to the proper level.The return is plenty big.The calculation is CFM/2.08= the square inches of the required filter size. So
800cfm/2.08=384sqin. of filter space. An 18x24 fliter has 432 sqin.(18x24=432)Hope this helps,Dave...