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Now that I know I can safely but briefly run a scroll type AC compressor in the winter I have some Heat pump questions. We have the ocean breeze for AC, so I see mostly heat pumps here.

I ocassionally come across an antique 20 year old unit that is still pumping out heat. How can I tell if it has a piston type compressor?

If a heat pump outdoor unit does not respond to the thermostat and the emergency heat comes on instead, what are some simple tests to narrow down the problem?

If a heat pump outdoor unit fan is spinning, mild weather but the coils are covered with frost and there's no heat, what is likely to be the problem?

If a heat pump or AC unit has sat unused for 2 years, is there any precaution before turning it on?

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Scroll on the left and recip on the right. In short the scroll will be tall and skinny and the recip will be short and fat!

You can also stop by just about any HVAC store that sells compressors and ask them for a book. You can look up the model number on top the compressor and it will tell you what it is.

Copeland Scroll refrigeration compressors (such as ZRxxKA-PFV) are designated by a "Z" in the first position of the model number. Copeland Reciprocating compressors (such as CRxxKA-PFV) are designated by a "C" in the first position of the model number.

The second position determines the application range (R = high/medium temperature, S = medium temperature, F = low temperature).

The third and fourth positions represent the first two digits of the capacity of the compressor at its standard rating conditions and the fifth position gives the multiplier for the capacity (C = 100, K = 1,000, and M = 10,000). The sixth position designates the compressor's model generation.

If there is a seventh position before the dash prior to the electrical designation, it will be an E (Polyol Ester oil) or an L (shipped less oil). If there is nothing in the seventh position, the compressor has mineral oil in it. Electrical designations (such as PFV) are the same as other Copeland? models.

If the outdoor unit is frosted up you must get a snickers! once it defrost it will start again. Some heat pumps have a low temp lock out so once the outdoor temp goes below the set point it will not let the refrigeration package go into heat pump mode, but if its frozen up then that means it was just running so just let it go through the defrost cycle.

If you are in a cold location then the unit should have a heater in the bottom of the compressor. Ensure the power is on at the disconnect for the outdoor unit for a few hours before you test the unit. The heater warms the oil in the compressor and keeps the refrigerant from getting dissolved into the oil.

The reason you do not want the refrigerant to be dissolved into the oil is if the compressor has a oil pump when it starts pumping it will fuzz like a coke and damage the oil pump. Another thing it will do if the refrigerant is dissolved in the oil it will push all the oil out the compressor this is bad for all the rotating parts plus it oil loges the indoor coil and that is kinda a itch to get back to the outdoor unit if the tubing run is poorly designed.

Sam

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Now that I know I can safely but briefly run a scroll type AC compressor in the winter I have some Heat pump questions. We have the ocean breeze for AC, so I see mostly heat pumps here.

I occasionally come across an antique 20 year old unit that is still pumping out heat. How can I tell if it has a piston type compressor?

What Sam said.

If a heat pump outdoor unit does not respond to the thermostat and the emergency heat comes on instead, what are some simple tests to narrow down the problem?

It's not a problem. On my thermo, the emerge heat is engaged whenever the set temperature is more than a few degrees above the indoor temperature. So if you don't want the emerg heat engaging, set it just above the indoor temp. That's easy on a digital thermo. For an analog, just monitor the emerg indicator.

If a heat pump outdoor unit fan is spinning, mild weather but the coils are covered with frost and there's no heat, what is likely to be the problem?

Maybe it's in defrost mode. It'll do that to get rid of ice. It switches to cool mode and emerg heat at the same time until the outdoor sensor says the ice is gone.

If a heat pump or AC unit has sat unused for 2 years, is there any precaution before turning it on?

Not that I know of.

Marc

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Thanks.

Sam, the Payne heat pump today has a tall compressor and says 'piston' on the label.

I guess for every rule, there is an exception to the rule, eh? [:)]

Actually, I don't think it has a piston, just says it does.

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Yeah, that oil tank's sprung a bit of a leak.

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I find that a lot of heat pumps don't start if you raise the stat one degree--the air handler and the emergency heat come on. I'm looking for energy efficiency issues, and that's definitely a big one in houses where the owner likes to goose the stat when they feel cold, so I normally check that and advise them if that's what they have. If they're amenable, I leave the front door open for a few minutes so the system starts itself, then check to see that it's in heat pump mode. I see a lot of systems where the heat pump is performing poorly, or isn't performing at all even though the fan is running. IR is very handy for looking at heat pumps.

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Thanks.

Sam, the Payne heat pump today has a tall compressor and says 'piston' on the label.

I guess for every rule, there is an exception to the rule, eh? [:)]

Actually, I don't think it has a piston, just says it does.

Click to Enlarge
tn_20142131238_payne1.jpg

29.04 KB

Click to Enlarge
tn_20142131317_payne2.jpg

58.83 KB

Yeah, that oil tank's sprung a bit of a leak.

Click to Enlarge
tn_20142131335_payne3.jpg

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That compressor is a scroll, If you had looked at the first letter of the model number on the compressor it would have been a "Z"

Look at you photo of the outdoor unit information tag, Do you see where it says metering device?

That is telling you it has a TXV on the indoor coil and and a #61 piston on the outdoor coil

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Sam

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It is normal for a heat pump to have a build up of white frost on the outside coil during cold damp weather. The build up can completely cover the outdoor unit. If you have a heavy build up clear ice, you probably need to call for service. A heat pump will change to defrost mode automatically every 30-90 minutes depending on how the unit is set-up. However, unless you are watching the outdoor unit when it defrosts, you may never notice that it has defrosted, because it will begin to frost up again as soon as it changes back to heating mode.

A heat pump that is not defrosting normally is more expensive to operate and extended operation with a heavy build up of ice could possibly damage the unit.

Some conditions that can make icing worse can include, rain dripping from the roof directly into the outdoor unit, dirty coils, coils covered with leaves, grass, etc...

If water is dripping from the roof into the outdoor unit, this will cause the unit to ice up more than normal and maybe even to the point, it can not remove all the ice during the defrost cycle. To help reduce this, a simple piece of metal can be added to the second row of shingles that is about 2 feet wider than the unit and it will force to water to drain to each side of the metal strip and miss the outdoor unit. Gutters will also eliminate this problem.

Never cover your outdoor unit with anything in an attempt to keep moisture out as this will only reduce air flow and make the situation worse. You could also cause permanent damage to your unit.

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