Heat Pump questions (outside fan stopped)

[Kevin O'Neill]

Yes, great info Kevin O'neill and Waterloo!!!! Kevin would you be able to tell me, if a heat pump has a timed defrost to initilize the start of a defrost cycle, what signals the end of the defrost cycle? Is it a preset time or another condition that ends the defrost. I'm just wondering. Lately, my heat pump seems to defrost quicker then other times.

thorton
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Common sense isn't that common

Thorton,

It depends. Most terminate after 10 to 11 minutes max, regardless of coil conditions, but usually there is another way to terminate as well.

Most (Time/Temperature Defrost) also have a coil thermostat that terminates after the coil warms up to between 60 and 75 degrees.

Some (with demand defrost) have a coil thermistor that electronically senses the coil and outdoor air, then terminates after the coil warms a certain amount above the outdoor air temperature.

Trane & York use mostly demand defrost.

Lennox and Carrier use some time/temperature & some demand.

Most other brands that I am familiar with use time/temperature terminate.

[thorton]

Thorton,

It depends. Most terminate after 10 to 11 minutes max, regardless of coil conditions, but usually there is another way to terminate as well.

Most (Time/Temperature Defrost) also have a coil thermostat that terminates after the coil warms up to between 60 and 75 degrees.

Some (with demand defrost) have a coil thermistor that electronically senses the coil and outdoor air, then terminates after the coil warms a certain amount above the outdoor air temperature.

Trane & York use mostly demand defrost.

Lennox and Carrier use some time/temperature & some demand.

Most other brands that I am familiar with use time/temperature terminate.

Thank-you, sir!!! Yes, my heat pump is a Carrier 38YZA which is a 410A unit. I knew the defrost initialization was a pre-selected time. I have mine set to defrost every 50 mins. But I didn't know what terminated the defrost. It must be a time/temperature and demand that does it, as you suggested. This particular heat pump seems to be behaving diferently this heating season. My local refridgeration mechanic checked the sub-cooling about a month ago and he added some 410A refridgerant. The heat pump seems to be working really, really great. Better then other years. The condenser is quieter, even less noise in the linesets and like I said seems to be defrosting quicker. This is the first time the heat pump sub-cooling was checked since initial install. Every time previously, it was serviced in cool or cold weather and you know as well as I do that pressures are the only way you can check refridgerant charge in cold weather. So I'm begining to believe that the charge has been incorrect since day one. It's probably my fault, as I never had the heat pump serviced the first 5 years in the warm months. The reason for this is it always worked awesome in cooling mode. All the problams I have had has been when it was in heating.

Thanks again for taking the time to give me a very good explanation.

thorton
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My wife always gives sound advice
99% sound… 1% advice

[kccustom]

UPDATE

Just heard back from the contractor, they said my unit needs a muffler that is installed on newer models after Feb '07 (mine was from Jan.) go figure.

They also said repair has to be done in weather above 60 degrees. I wonder why?

[Waterloo]

UPDATE

Just heard back from the contractor, they said my unit needs a muffler that is installed on newer models after Feb '07 (mine was from Jan.) go figure.

They also said repair has to be done in weather above 60 degrees. I wonder why?

I believe the answer is related to being able to check subcooling and superheat. Both are done in A/C mode, and would have to be done above 60*.

Pros - What is this "muffler"?

[kccustom]

Last Update:

Muffler installed, I can barely hear it running.

Guy came by and hooked it up while I was at work and had it ready to turn on when I pulled up.

[Waterloo]

Last Update:

Muffler installed, I can barely hear it running.

Guy came by and hooked it up while I was at work and had it ready to turn on when I pulled up.

Is it anything more than a tightly wrapped foam wrapper on the suction line?

I had my installer out yesterday to finish up some stuff. Found that the unit was overcharged and removed some refrigerant. But, with the temps at 70 yesterday, I was unable to check. It seemed to also help.

[kccustom]

I will do one better with some picture goodness!

[gary_g]

I have mine set to defrost every 50 mins.

My new Goodman heat pump condenser was set at 60 minutes defrost time. I changed it to 90 minutes.

[Airmechanical]

My new Goodman heat pump condenser was set at 60 minutes defrost time. I changed it to 90 minutes.

that was pretty ballsy!



.

[jrbenny]

that was pretty ballsy!



.

Really? I have mine set for two hours.