Working on 22 year old rheem heat pumps. There are 4 systems. I just took over the work at this daycare for the HVAC. I have no background information on previous work other than what I gathered as I looked it over. I noticed 2 systems both freezing up at the accumulator up to the compressor and back to the reversing valve and slowly down the suction line. My suction pressure for both systems is right at 50psig. These are capillary tube systems. My suction line temp hovers between 27-35 degrees. My superheat averages 5 degrees. My first thought was that there is an airflow issue. The blowers all are single speed and appear to all be running exactly the same. I checked the capacitors and they were fine. I replaced every filter and checked all the evaporator coils. I cleaned all the condenser coils. On 1 system I backed refrigerant up and opened up the metering device at evaporator. Black. So I cleaned it up. Vacuumed system down and added acid away to the system. I discussed with owner of daycare to remove all refrigerant but that was too expensive. I was told to try the acid away first. So I did. That one particular system now intermittently freezes up in same spot at compressor/accumulator/etc.. I have done nothing to the other system that freezes up really bad at compressor/accumulator/etc.. The outdoor temperature was around 70 degrees as well as the indoor temperature. Humidity outside was around 47%. I do not know indoor humidity. And with the airflow I checked all fire dampers to make sure they were open. I just dont see this being a refrigerant problem. If it was undercharged my line would not immediately be freezing cold on start up. If it was overcharged I would expect to see much higher condenser pressure. My high side was around 220-225. So what do I do to fix this issue? Is there so much contamination in the system that it is now reduced system capacity? My solution would be to remove all refrigerant. Flush. Nitrogen. Evac. Weigh in charge. But expensive. Especially if that doesn't work.
freezing up at compressor/accumulator/reversing valve
NateBhvac
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Working on 22 year old rheem heat pumps. There are 4 systems. I just took over the work at this daycare for the HVAC. I have no background information on previous work other than what I gathered as I looked it over. I noticed 2 systems both freezing up at the accumulator up to the compressor and back to the reversing valve and slowly down the suction line. My suction pressure for both systems is right at 50psig. These are capillary tube systems. My suction line temp hovers between 27-35 degrees. My superheat averages 5 degrees. My first thought was that there is an airflow issue. The blowers all are single speed and appear to all be running exactly the same. I checked the capacitors and they were fine. I replaced every filter and checked all the evaporator coils. I cleaned all the condenser coils. On 1 system I backed refrigerant up and opened up the metering device at evaporator. Black. So I cleaned it up. Vacuumed system down and added acid away to the system. I discussed with owner of daycare to remove all refrigerant but that was too expensive. I was told to try the acid away first. So I did. That one particular system now intermittently freezes up in same spot at compressor/accumulator/etc.. I have done nothing to the other system that freezes up really bad at compressor/accumulator/etc.. The outdoor temperature was around 70 degrees as well as the indoor temperature. Humidity outside was around 47%. I do not know indoor humidity. And with the airflow I checked all fire dampers to make sure they were open. I just dont see this being a refrigerant problem. If it was undercharged my line would not immediately be freezing cold on start up. If it was overcharged I would expect to see much higher condenser pressure. My high side was around 220-225. So what do I do to fix this issue? Is there so much contamination in the system that it is now reduced system capacity? My solution would be to remove all refrigerant. Flush. Nitrogen. Evac. Weigh in charge. But expensive. Especially if that doesn't work.
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Best guess...
Assuming the 50 psi (26Ëš) and 5 Ëš superheat were measured with a defrosted coil, the problem is low air flow.
If you're confident the coils are truly clean, then there's something else interfering with the airflow.
A restricted metering situation would starve the evaporator (high superheat), which could eventually lead to all the icing if the system continues to run.
Those head pressures are high for 70Ëš OD. Been in your situation before. The previous servicer's kept adding freon to raise the head pressure which raises the suction pressure.
Assuming the 50 psi (26Ëš) and 5 Ëš superheat were measured with a defrosted coil, the problem is low air flow.
If you're confident the coils are truly clean, then there's something else interfering with the airflow.
A restricted metering situation would starve the evaporator (high superheat), which could eventually lead to all the icing if the system continues to run.
Those head pressures are high for 70Ëš OD. Been in your situation before. The previous servicer's kept adding freon to raise the head pressure which raises the suction pressure.
I'll keep looking into an airflow problem. The evap coil was defrosted and I didn't see anything on the evaporator coil. It looked spotless. Usually I would see what looked like a dog sucked up on evap coil so I was shocked to see a clean evap with this situation. I don't think there were dampers in the lay ins but something to check. And I'll check for collapsed inner liner in return flex. I'll figure it out but thanks for reply. It helps.
If you think you have an airflow problem, you surely should know your static pressure, not just look at pressures.
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6,045 Posts
Assuming the RH is the same inside as outside, your target SH should be 10-7 degrees. Your head pressure is also high for 70 degree ambient. I would try removing some refrigerant before anything else.
How long are you letting these systems run? Does the accumulator and compressor ice over completely or are you seeing light frost? Typically, frost will form on the accumulator and suction line in the first 10-15 minutes as liquid refrigerant boils out of the accumulator. Frost will also form on the evaporator coil and suction line if conditions are mild (low load).
How long are you letting these systems run? Does the accumulator and compressor ice over completely or are you seeing light frost? Typically, frost will form on the accumulator and suction line in the first 10-15 minutes as liquid refrigerant boils out of the accumulator. Frost will also form on the evaporator coil and suction line if conditions are mild (low load).
The problem you're really having is in guessing what the problem is. First find out the static, next figure the cfm over the coil. There's really no way to properly figure the refrigerant charge until the air flow is correct or at least close to correct.
Quick example; I had a customer call basically kick the installing contractor off the job (they called the cops). The guy had removed a low boy oil and replaced with an up flow gas with A coil. The new furnace was turned in such as way as the back of the A coil now blocked 90% of the air flow into the trunk duct. Dumb move, however this fellow was sure the charge was wrong and had added an additional 19 pounds of R-22 above the factory charge to a 4 ton unit. I know this seems impossible, but I did recover 19 pounds extra.
The homeowner who was also the assistant to the Attorney General in PA, had seen this job degenerate into insanity. First the refrigerant, next more refrigerant, then thawzone added, next florescent leak check, next more refrigerant, then a hard start kit, and finally the compressor hydraulically locked up and tripped the breaker. The customer was told the house 100 amp service needed to be upgraded to 200 amp. After that was accomplished the compressor continued to trip the breaker.
I get the call, walk into the basement recommend replacing the entire system, to include adapting all near ducting and sealing all other exposed ducting. He says go for it, we install two tons and 70k of heat removing 4 tons and 125k of heat. Customer sues first guy, for all money spent with first contractor and of course wins.
The moral of the story don't guess based on preconceptions of what is wrong. Btw, every once in a while I am lazy and do so, and most times it does not work out well.
Quick example; I had a customer call basically kick the installing contractor off the job (they called the cops). The guy had removed a low boy oil and replaced with an up flow gas with A coil. The new furnace was turned in such as way as the back of the A coil now blocked 90% of the air flow into the trunk duct. Dumb move, however this fellow was sure the charge was wrong and had added an additional 19 pounds of R-22 above the factory charge to a 4 ton unit. I know this seems impossible, but I did recover 19 pounds extra.
The homeowner who was also the assistant to the Attorney General in PA, had seen this job degenerate into insanity. First the refrigerant, next more refrigerant, then thawzone added, next florescent leak check, next more refrigerant, then a hard start kit, and finally the compressor hydraulically locked up and tripped the breaker. The customer was told the house 100 amp service needed to be upgraded to 200 amp. After that was accomplished the compressor continued to trip the breaker.
I get the call, walk into the basement recommend replacing the entire system, to include adapting all near ducting and sealing all other exposed ducting. He says go for it, we install two tons and 70k of heat removing 4 tons and 125k of heat. Customer sues first guy, for all money spent with first contractor and of course wins.
The moral of the story don't guess based on preconceptions of what is wrong. Btw, every once in a while I am lazy and do so, and most times it does not work out well.
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1 Posts
So did you get it fixed?
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54,330 Posts
After 3 1/2 years I hope so.
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I saw him frying chicken at Chicken Express today.
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6,045 Posts
Good for him. Probably more along the lines of his comfort zone.
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8 Posts
Check static and td on the outside and indoor coil 5 degrees sh is crazy low if it's that low during the day it's definitely slurping on liquid during the night....take a wet bulb at the return and use your charts
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