Thermostat

jesuslord

Had a Goodman 14 Seer 4 ton A/C unit installed.Awesome power, cools great, but the darn thing runs an hour or more to reach the set temperature (minus 1). Here in South Texas, the usual temp. is 100, and I have the thermostat set at 77, when it hits 78 it kick starts and reach 77 in about 10 minutes, but it'll keep running till it reaches 76. In the afternoon, it'll take an hour or more to reach that 76 and shut down for about 25 minutes. Is there something wrong with the setting. Running for an hour, is that normal with a Goodman?

ratio

What kind of thermostat do you have? Maybe a pic of it if you can't see a model number.

It's nearly impossible to tell if the runtimes are unreasonable without detailed knowledge of your house & the AC system, but if it's 100 outside, long runtimes are expected, even desirable.

ChrisJ

As ratio said, long run times are a good thing.

Thermostat location has a huge effect on how the thermostat functions. There's also differences between thermostats obviously.
And, there's always the chance the thermostat isn't working right.

I like ratios idea of posting a picture of it.

Also, for your own curiosity, if you can, measure the temperature going into your largest return, and measure the temperature of the closest supply to the unit, and see what the temperature difference is.

For example, if the return is 80 degrees and the supply is 60 degrees, that's a 20 degree drop.

I just installed a system in my own house and there's days it'll run non-stop. There's often times it'll run for many hours at a time. That's what you want with air conditioning on hot days.

jesuslord

Thanks for the quick responses ratio and ChrisJ. The thermostat model is a Pro T701. It puzzling because my old A/C (23 year old Rheem) never ran non-stop for an hour even on the hottest days in South Texas. This Goodman pushes out alot of good cool air but takes a good hour or more to reach that set temp. minus 1. I'll someone come in and take temp. readings on the supply and return. I also have work planned for replacing the soft fits around the house. Also have sun screen being installed next week. Along with a new roof, 3 solar vents, and that new Goodman, the A/C still runs too long. Any suggestions would be greatly appreciated. Thanks!

ChrisJ

jesuslord said:

Thanks for the quick responses ratio and ChrisJ. The thermostat model is a Pro T701. It puzzling because my old A/C (23 year old Rheem) never ran non-stop for an hour even on the hottest days in South Texas. This Goodman pushes out alot of good cool air but takes a good hour or more to reach that set temp. minus 1. I'll someone come in and take temp. readings on the supply and return. I also have work planned for replacing the soft fits around the house. Also have sun screen being installed next week. Along with a new roof, 3 solar vents, and that new Goodman, the A/C still runs too long. Any suggestions would be greatly appreciated. Thanks!

What size (tonnage) was the old system? Was it also 4 ton?

Are you sure you're comparing the same outdoor conditions? 100+F is pretty toasty.

John Mills_5

Probably just the way Pro 1 stats do it. We don't use them, I've only installed one and it broken down within the first year.

Honeywell & Emerson would likely never leave the set temp but would be turning the stat on & off a bit more frequently to hold the temp closer and now allow the 2° swing.

When it is 100 out, it should run & run & run...

Big Ed_4

You use to have a system that ran R22 . Now your running R410A system .. It's not as pure but it works ..It's all good, nothing is wrong , it's just not the same ... Remember when our cars AC went from R12 to R134A

ratio

Why is the long runtime an issue? Wasn't like that before? Not comfortable? Makes too much noise when it's running?

Long runtimes means more dehumidification, which you want in the summer. However, big temperature swings are uncomfortable. Is the new system larger than the old one?

It sounds like you're using a setback. That doesn't always result in savings, especially with deep setbacks.

Is the house comfortable all the time? That's the primary test of your air conditioner. Everything else is secondary to that, unless you intentionally sacrifice comfort.

jesuslord

Thanks guys for the helpful comments. The old Rheem was a 4 ton unit,,it would run for about 15 minutes then shut off, for about 15. Even on hot 100 days, it may run for about 20 minutes but always shut off. I would set the temp. at 78 and was comfortable. I guess I'm expecting the same thing with this new Goodman. Would switching the thermostat to a Honeywell or Emerson be any better? Ratio,,,can you explain what you mean by a setback (deep setback)? Is it something I can control? Thanks!

ratio

Setback is when you use a programmable thermostat to change the temperatures at certain times. If you want it a degree or two cooler at night because you find it's more comfortable to sleep that way, that's one thing. But if you, say, have the temperature go up to 80 during the day to "save energy" because you're at work and the house is empty, it might not work out the way you think.

If you're comfortable, and the temperature is set just like it was before with the old system, then Big Ed is probably right—this may just be an artifact of how the new system operates. There are subtle differences in how the old refrigerant worked vs the new refrigerant.

If everything is working properly, I'd look at switching to a Honeywell thermostat. They have a config option for "cycles per hour", which tries to turn the system on for that number of equally-timed on/off cycles. A TH6110 if you want the cheaper model or a TH8110 if you want the fancy model, assuming you have a single stage furnace/AC.

newagedawn

not to be of topic, but everyone is taking about the tstat, what about the refrigeration side of things,if you replaced the tonage with the same, it sounds to me like the refrigerant charge could be off, is it TXV or captube, did the lineset get change??? it is important when changing to 410a

ChrisJ

newagedawn said:

not to be of topic, but everyone is taking about the tstat, what about the refrigeration side of things,if you replaced the tonage with the same, it sounds to me like the refrigerant charge could be off, is it TXV or captube, did the lineset get change??? it is important when changing to 410a

I've seen you say this a few times in different threads.
Why is it so important to change a lineset when going from 22 to 410?

JUGHNE

Residual oil would be incompatible with new oil/410A.
Also the old system may have had a compressor motor burn, leaving acid in old oil.
Also some old systems used 1/4 or 5/16 OD for liquid lines and would be considered too small for anything today.
Occasionally the suction line may be too small also.

ChrisJ

JUGHNE said:

Residual oil would be incompatible with new oil/410A.
Also the old system may have had a compressor motor burn, leaving acid in old oil.
Also some old systems used 1/4 or 5/16 OD for liquid lines and would be considered too small for anything today.
Occasionally the suction line may be too small also.

All of that is understood and I'd expect the guy doing the install to take all of that into consideration. I know, never assume or expect anything.

Mineral vs POE has been argued many times and my current understanding is a small amount of residual should have no harmful effects. If the lineset is run decently, and holds little to no oil I don't see why it would be ripped out "just because". Assuming it's an acceptable size and isn't contaminated of course.


Since you mentioned it, one thing has had me baffled for a while though. When repairing a system after burnout many recommend flushing the lineset and even installing a suction line drier which is to be checked and perhaps even replaced multiple times.

If the liquid line drier does it's job, why would a suction line drier even be needed? I have to assume there's a good reason but I'm not understanding what it is. Shouldn't the liquid line drier catch anything in the oil, including acids? What's making it past that point to assume the entire system is contaminated?

JUGHNE

IIRC, supposedly acids are easier to capture when the refrigerant is in a vapor state.
Also SLF are recommended as close to the replacement compressor as possible. On a heat pump between reversing valve and compressor, tight fit sometimes.

One case I know of was a 5 ton AC maybe 30 years old. Motor burn, new outside CU. Less than a year, that compressor burned.
Another year and the 3rd burned and was replaced. LLF only, installer told me you don't need SLF as the LLF does it all.
Who am I to argue, he was a pro commercial refrigeration serviceman.
It seems after a severe burn the problem snowballs if the rest of the ACR is contaminated.