We had our AC repaired a bit over a month ago, new evaporator coil & expansion valve installed.
Prior to that it was running constantly just to hold temp, usually around 74.

Now, it holds temp well, but if I bump it down, the temperature increases in the house...

I have an appt for Wednesday, scheduled follow up post service. Just curious.

I set it to 72 this morning & it held that all day. Bumped it to 70 around 5pm & the temp has increased to 74.

What would cause temps to go the opposite way & take hours to cool.
Really hoping I don't have another leak somewhere in the system, as the evaporator coil was a pricey repair already.

t-stat problem possibly?

Did you set it back up to see if the temp came back down.
Does sound like a thermostat issue.

If it can't get the space down to your selected temp and it runs without a break, it could be freezing up. Check the air flow at a vent near the fan unit after it has runs for a couple of hours or more. Is it pushing the same as you are used to when it first starts up early when its not as hot out?

Also, did it cycle off at all when set to 72?

You are also near Houston, it's harder for the system to cool down with higher humidity.

If you stay still outside too long in Houston, moss will grow on the north side of your leg.

Obviously, you forgot to reverse the polarity of your battery connections.

I agree with 83V45Magna, you are running your system hard enough that it's freezing up. I also sort of agree with his choice of motorcycles except in my case it's an 83 Sabre.

BTW, I am a BIG believer in acclimatizing yourself for the prevailing conditions. As in my AC is set to 80 degrees and when it's in the mid 90's for the Michigan State Skeet championship I'll barely break a sweat while most of the shooters will complaining endlessly. Hopefully this will give me a bit of an edge over those dependent on air conditioning.

My point is that if you turn your thermostat UP you won't have issues with the AC freezing up. Because the cooling cycles will be short enough it will have time to thaw out when it's not running. You'll also save a lot on your electric bill and become a lot less dependent on artificial climates.

I've never had an AC unit freeze up unless there was a problem with it .

Undercharged
Guy said this is why they do a 1 month follow up.
Added freon after cleaning the outside unit & letting it dry out.
Cooling better already.

quote:

Originally posted by P250UA5:
Undercharged
Guy said this is why they do a 1 month follow up.
Added freon after cleaning the outside unit & letting it dry out.
Cooling better already.

So it's got a leak?

Only two ways for a system to be undercharged. Either they did not put in enough when it was first started, or it leaked out. If they improperly charged it in the first place it would not have performed well from the start. If there is a leak, and nothing was done to repair it, only adding more refrigerant, the system will leak down and freeze up again in about the same time it did last time. The rub if there is a leak will be if it is on the new work or the portion of the system that was not replaced. Are they warrantying the system or just the indoor coil?

Guy said that it wasn't uncommon to need an additional charge after part replacement like we had.

We'll see if it keeps working like normal.

They only replaced the evap coil & exp valve before.

quote:

Originally posted by architect:

Obviously, you forgot to reverse the polarity of your battery connections.

Another possible cause:

Man, 72 degrees and I'm putting on a jacket. I'm pretty comfortable at 78. Rarely do I set it below that.

BTW, where is Excam_Man?

Comfortable at 78?! Heck no. We definitely couldn't be roommates, Q.

I keep my AC on 68 during the summer, and my heater on 62 in winter. And it's not uncommon for me to sleep with my windows open during the fall and spring when the overnight low is in the 40-60 degree temp range.

quote:

Originally posted by RogueJSK:
Comfortable at 78? Heck no.

I keep my AC on 68 during the summer, and my heater on 62 in winter.

74 daytime, 68 nighttime for us

quote:

Originally posted by 12131:
BTW, where is Excam_Man?

I figured he would show up in this thread. Maybe he's on a nice tropical vacation?

I've learned a lot about HVAC goods from Excam_Man and Warhorse.

Funny, my dad is even worse. His place is set at 79. I turn on the ceiling fan when I'm there, and he has to put on his winter jacket. Not just a light one but a real thick winter jacket. Too cold for him. Lol.

quote:

Originally posted by 12131:

BTW, where is Excam_Man?

He’s tired of fighting misinformation in these types of threads. He is very good at what he does.

stlhead statement is correct.
Refrigerant has a pressure temperature relationship. Air flow impacts this, as does the temperature of the air. Earlier P250 said as he lowered the setpoint the system got worse. It appears due to the low charge condition, the pressure was near saturation temperature of 32°, thus ice starts to form on the coil. When operating with colder return air, this causes the pressure too fall ( get colder ), This impacts heat transfer, thus cooling capacity. Ice will reduce the heat transfer ( insulate ) and start to restrict the air flow, equivalent of lowering the volume of air, also reducing capacity.
Forgive my poor explanation of thermodynamics, its been a long day.
The repair contractor should of performed a pressure test with nitrogen to confirm the connections and system holds. Then evacuation to proper levels, not to simply remove moisture and non-condensables but also observe system integrity. Hopefully the technician that performed the initial charge, simply did not properly execute the task.

That makes sense, thanks for the simple explanation

Hvac may as well be witchcraft to me