Heat pump not hitting target temp
I have a heat pump and had many problems with the original install. The service techs were back every time I switched between heating and cooling to tweak the system to get it to work. Each time they made adjustments, it did work and would cool to the desired temperature.
This cooling season, when the cooling was once again not working (the coils/pipes would completely freeze up and the cool air would stop) I got fedup and called another service company.
The new company raised the coil within the furnace (the heat pump is an add on to an oil furnace) and increased the blower motor size to increase the overall air flow. They also replaced a sensor that I guess tells the system when the coil is about to freeze up and thaws it out before freezing.
The frozen coil issue has been fixed, the problem now is the AC never hits the desired temperatures. The latest company says that is normal and heat pumps are designed to do the best they can, but it is not uncommon for them to not hit the target temperature. I don't live in an extremenly hot climate, dor example mid 30's is considered a really hot day, with most hot days being between 28 and 32 outside. When the temperature is that outside, if I set the inside thermostat for 18, the system will only cool to 20ish. It actually does not cool, but rather hold an existing temperature - what I need to do is leave the heat pump running all night set at 18, then when I wake up it will be around that temperature and I'll leave it running all day and the temperature inside will slowly rise up to 20 - 21, but will not hold at 18. Furthermore, there are times when it is actually cooler outside than inside (it'll be 20 outside, I'lll have the heat pump set at 18 inside and it will only cool to 21). This does not seem normal to me. Does anyone have any suggestions as to how to increase the cool air being produced by the system?
Just FYI - the techs spent several days coming back and changing the coolant, adjusting this and that - I ended up spending approxmitaly 1/3rd the cost of a new heat pump to date with the recent round of servicing.