Set the Temperature on Your Air Conditioning System

LESLIE: George in South Carolina, you’ve got The Money Pit. What can we do for you today?

GEORGE: Yes. What it is is that we had an air handler replaced in the loft and the outside heat pump was also replaced.

TOM: OK.

GEORGE: The air handler was replaced and the outside heat pump was replaced.

TOM: OK.

GEORGE: We have a 2,400-square-foot house. My question is, it’s not getting as cold or cool as it should be on a hot day as I’m losing ground.

TOM: OK.

GEORGE: And what I wanted to know – the question was what should be the temperature coming out of that register inside the home when I sit on…

TOM: Oh, good question. It depends, George, on what you set the thermostat at but more important that the temperature that comes out is the difference between the air coming out and the air going back in. What you want to do is measure the temperature of the air at the supply and measure the air temperature at the return register and the difference should be 15 to 20 degrees.

So for example, if it is going back into the register at, say, you know, 85, 88 degrees, it ought to be coming out at 70 degrees.

GEORGE: Yeah.

TOM: And if you don’t have 15 to 20 degree differential, then your system is not working right and you need to give it some attention. And in that case, I would call a pro.

GEORGE: Yeah. Is there any question on these – an air handler and the heat pump not being compatible as far – they’re three-and-a-half ton units, both of them.

TOM: OK. And they were both replaced and so if the HVAC pro did their job right, then they would have put back in the same size units that they took out.

GEORGE: Well, yes. That’s true. That is true.

TOM: Mm-hmm.

GEORGE: But the fact is that they’re a different brand.

TOM: That doesn’t matter.

GEORGE: OK.

TOM: Yeah, not as much. I tend to think that this is an issue with refrigerant more than anything else. That’s why I would measure the supply and the return air and see if you get that 15 to 20 degree difference. If you don’t, get it fixed.

GEORGE: Alright. Yeah.

TOM: Before it runs out of warranty too.