home a/c efficiency

It feels too cool until you get used to it.

I don’t mind going down to the in law’s for weekend dinners for that reason .

5F is tough for a standard unit, but a 2 stage one, it does it no problem.

 

How’s the outside unit look? Any buildup around the cage? How’s the temp on the fan that blows the warm air out?

 

One of my outdoor thermometers logged 101°F today, hottest I’ve ever been home for in PA. 86% humidity to go with. Somehow the murder statistics didn’t go up with it, but the night is young...

 

Even dust on the coils can affect the efficiency .

If you have a compressor for something like filling tires, take it out and try blowing on a section of the coil. I bet some dust is removed .

If you have a IR gun, or something similar, you can shoot the area above the fan and see the temp difference. Or just feel it and see how warm it is.

 

Most A/C units in the home have holes on either side of the A-coil where you can insert a thermometer. This is typically used by the installers to measure the delta-T across the coils, which is a fairly direct measure of how much work the A/C unit is doing to remove heat. For a given airflow, the higher the delta-T, the more heat being removed. This is more accurate than measuring the temperature above the fan unit on the exterior of the home (too many variables out there).

 

Warmer than the air it is replacing .

So if it feels the same as the air around it, the efficiency of heat transfer isn’t good.

Our unit has air that is typically 15-20 degrees warmer, but I’m not at home right now.

Enjoy 73 F indoor temps at the in law’s with some nice red wine.

 

Sounds like your unit is sized according to your house.

When we sized ours, we “upgraded” from what was previously there, which gave us more capacity .

Even on over 100 degree days out here, it does the job well, but a conscious decision at the time of purchase .

 

You sure that isn’t Doctor guy with a hammer and a pair of pliers?

Around here a fancy setup like that will get you pegged as a neurosurgeon.

 

The cost to upgrade was $1200. So we went with it.

Having a unit run below capacity rather than closer to capacity should yield longer tenure into service .

I’m a big picture, total cost of ownership type with a CFO that supports keep things for a long while.

 

Check with various ac companies at the next replacement interval. We’re multi quoters when it comes to large expenses. So we had 4 quotes on replacements and we didn’t go with the cheapest.

Some have knowledgeable sales staff that come out and they talk intelligently about the options they have. Quiz them on what you’re thinking as well as what they would recommend. Then tell them some of the things that bother you about your current setup.

Some listen better than others, and their quotes show that.

 

The correct way to size an HVAC system is to do a heat gain/loss calculation for the house, then put in a unit that is sized for that load. Sales people aren’t doing this calculation, and they will typically sell you a larger unit. My home has a 3 ton Trane, and the Carrier rep was working hard to sell me a 4 ton. No data to support it, he said it’s what they ”normally install”.

A perfectly sized A/C unit runs constantly on the hottest day. It doesn’t hurt these units to run constantly when needed, and an oversized unit will have lots of off-cycle losses from starting and stopping.

Hire an HVAC engineer to do the sizing calc for you, then buy that size.

 

I battled that sort of inertia too. Our house had no air when we moved in. We added minisplits to the bedrooms upstairs, and as soon as I said I wanted those instead of a forced air system I started getting all kinds of pushback from the sales guys.