Air Conditioning - Replace compressor?

I have a 10 year old carrier heat-pump that still cools, however I had it checked out and the tech added 1 lb of refrigerent however he told me that the unit was struggling to keep up and that I needed a new compressor. However he recommended that I replace the whole outside unit.

I found that I can get a replacement compressor (Copeland ZR40K3) for about $650. It's about $3500 to replace the outside unit.

Any recommendations? I haven't got a quote yet on replacing the compressor.

Does it cool the home??? Does it run ok??? Then let it alone. If the big copper line is cold and wet the small copper line warm to hot you should be ok. Most units run 15 years. If you will stay in the home for the next 10 years.
Down the line look at both inside coil and outside condenser new with a SEER over 15. One lb freon in 10years is not bad. If he has to come back make sure he looks for the leak

It cools and runs OK now however we've not hit the summer heat yet. I have compared it the the other unit beside it that cools the downstairs. The cold line outside does not sweat very well and it's not nearly as cold as the other unit's large line. Also recently I had to change out the filter for the upstairs unit to cool properly as ice was forming on the upstairs small line in the attic. Also the small line in the upstairs unit in the attic drips a lot more water than the downstairs unit.

The unit that does not have as cold a suction line as the other could be bad based on this temperature difference.
It could also be doing this because of being slightly undersized for the area it cools or even because of a problem unrelated to the compressor.
The tech should have given you a better explanation than "struggling to keep up" to help make a decision on this.
A better description might be something like: "the readings I get on my guages show that the suction valves on your compressor are bad and will not allow the compressor to properly lower the suction pressure".

It would not be unreasonable to call and speak to the technician directly and ask for a technical explanation of the problem and write down exactly what he says.

Come back and let us know what he says.

"Also recently I had to change out the filter for the upstairs unit to cool properly as ice was forming on the upstairs small line in the attic. Also the small line in the upstairs unit in the attic drips a lot more water than the downstairs unit."

Ice on one small line (about 3/8"?) and drips on both upstairs and down!

Both units are undercharged!

The small line is called the liquid line and should never sweat, drip, or freeze. It should be warm all the way to the indoor coil becuase it sshould be full of liquid refrigerant all the way to the metering device. If it isn't it's because the charge is low and the liquid refrigerant is "flashing" into gas in the line and not at the metering device as it should.

Anyone ever heard of the predetermined point in the evap where the refrigerant turns from saturated vaper to gas??????????

The two sentences I quoted tell me that the upstairs unit is very short on refrigerant and the downstairs unit is also undercharged but not as bad.

But, and of course there always is a but. The condenser coils could be dirty and not providing enough subcooling.

mjs7 (my daughter has the same initials) the last tech was an idiot! Call another company and have the condenser coils cleaned and then the charge checked.

Chris

Both units use pistons at the point where the small lines enter the condenser in the attic. Upstairs unit condenser was checked and it was not dirty. I had sprayed it with some condenser cleaner I got at Home Depot previously.

Problem was descrbed as valves going bad in the compressor on Upstairs unit.

Downstairs unit: S -> 62psi, L -> 225psi
Good sweating and cold large line at outside compressor
No dripping from small line where it enters condenser in attic

Upstairs unit: S -> 45psi, L -> 185psi :: before adding refrigerant
S -> 50psi, L -> 225psi :: after adding refrigerant
No sweating and not cold large line (maybe cool) at outside compressor
Dripping water from small line where it enters condenser in attic

It's from Jarredsdad@myemail

Do you have any temperature readings from the lines where the pressures were taken from?

Look at the small line for the upstairs unit. Any sharp bends or kinks before the indoor unit?

If the valves were "going bad" I'd expect the suction and discharge pressures to be closer. Higher suction and lower discharge, indicateing leaking valves.

Chris

Unfortuneately no temperatures were written down, however the tech was measuring the temps

No sharp bends in upstairs unit small line.

I took a candy thermometer and held it at the large lines outside:

downstairs approximately 60 degrees

upstairs unit approximately 74 degrees

Since you can't give real time pressure and temperature measurements I have to use old presure with new temperature.

Using old downstairs pressure of 62 and new temp of 60 degrees, comes out to 24 degrees superheat. Pretty high, low charge. Upstairs old pressure 50 and new temp of 74 degrees comes out to 47 degrees superheat. VERY high.

Mike, the manual I sent indicates to check the charge for subcooling (small line temp and pressure). As I said in a a past post the tech was an idiot. Probably couldn't buy a clue if you gave him a blank check.

Both units are low on charge, period. Maybe the cheapest thing to do if to find a company that will come out and correctly charge the units and add refrigerant dye. Adding dye makes finding the leaks (if there is one other than allowable leak rate) much easier. The dye mixes with the oil that is also moving through the system with the refrigerant glow bright green under a UV light. Kind of like a big neon sign saying "here I am, fix me". Checking with an electronic detector can take some time which adds to the bill.

Since your systems are 10 years old you could be looking at an improper install and allowable leak rate (1/4 to 1/2 ounce per year). Best case.

Your probably wondering "What the heck is superheat and subcooling?". If we keep this up you'll know more than change the compressor guy.

R-22 boils at -41 degrees, water boils at 212 degrees. Using water, if you heat it to make steam at 212 you change the the "state" from liquid to vapor. If you heat that steam to 222, you have what is called superheated stem at 10 superheat. The temp of the steam above what temp is needed to change state from liquid to vapor. The same is true in reverse. Steam will condense into water below 212, so if you condense steam back to water at a temp of 202 the steam (now water) is subcooled 10 degrees.

I imagine your thinking what the heck is this idiot trying to tell me :-).

The function of subcooling the R-22 at the condenser (refer to the manual) is to ensure that the refrigerant remains in liquid form all the way to the piston. Superheat ensures that the R-22 is all gas when it returns to the compressor and is liquid free. Compressors fail when they try to compress liquid.

Bottom line again is the systems are low on charge and your upstairs unit doesn't need a new comperessor.

But, and there always is one, that doesn't mean that once the systems are charged correctly that a compressor will not fail now that it has the correct charge. I've checked systems in the past that were working like textbook examples and a week later it was dead.

Chris

I remember that the tech said that it could not take any more charge on the upstairs unit - that the lower pressure was not rising but the upper pressure was and apparently he thought that the ceiling on that should be 225. He didn't bother charging the downstairs unit. At first he seemed to think that the system was blocked.

What would textbook temps and pressures be in this case for one of the units?

If there was a blockage in the system it would be pretty apparent. Were it on the low side very low pressure, high side very high pressure.

But he went from blockage to change the compressor due to valves. And everything I've read from you indicates undercharged. For, I think, the third time the tech was and idiot.

Again get another company to check both systems.

Chris