Heat pump problem, attempt fix or replace

[honcho]

11 year old Trane XL System. Noticed that system seemed to running constantly even though the thermostat is set at 66 deg. Been hanging out in basement using a space heater so really didn't notice any problems with temps elsewhere in the house. It was the constant running of the air handler that got my attention. Turned the system off and then restarted. Outdoor unit seemed to start up ok, on startup heard/felt what seemed to be refrigerant running in line by air handler. No appreciable heating of refrigerant line into air handler.

original installer no longer in business, neighbor provided with name and number of their HVAC guy. Called and they promptly came out and spent close to three hours diagnosing, which included trying to add refrigerant. Technician said they were unable to get the system to accept any appreciable amount of refrigerant. Also said original installers had not installed a filter/dryer on the lines. Suggested that there was a blockage somewhere in the system and that they could disconnect lines and attempt to clear condenser, line set and air handler or replace line set and check indoor and outdoor units for passage of refrigerant. Expensive option is replace system although if we can put it off until in the new year a $2k tax credit will be available. Question is whether trying to clear the system will work or just add cost to buying a new system if they are unable to clear the system.

Heat strips are working so not without heat, albeit expensive heat.

Thoughts on next steps? Thanks much and Happy Holidays.

 

[justinjoyal]

The first question is why were they trying to add refrigerant ?

 

[Jim greengo]

Is there a factory installed drier inside unit someplace?

 

[bonneyman]

The first question is why were they trying to add refrigerant ?

Maybe the pressure readings they were getting didn't correspond to the unit's charging chart?

Did the system work satisfactorily last summer while cooling? If so, maybe the reversing valve is worn and hanging up. Some of the working gas is being rerouted and not giving you full delivery. The RV moves every time it goes into defrost (even in the summer on energized in cooling applications) so it gets alot of wear and tear. Those plastic seals in there can get pretty worn after 11 years - could be your problem. Pressures won't be right if it's mid-positioned - maybe that's what they saw?

RV operating issues can be real tricky to nail down, as it is a system "gremlin" of sorts. Usually working fine while the technician's there and then acting up while no one's looking. It takes a real sharp tech to catch them in the act. And even if they determine that is the problem, RV replacement is an expensive, time consuming process. Most companies will just try and replace the unit - especially if it's not warranty.

 

[honcho]

Maybe the pressure readings they were getting didn't correspond to the unit's charging chart?

Did the system work satisfactorily last summer while cooling? If so, maybe the reversing valve is worn and hanging up. Some of the working gas is being rerouted and not giving you full delivery. The RV moves every time it goes into defrost (even in the summer on energized in cooling applications) so it gets alot of wear and tear. Those plastic seals in there can get pretty worn after 11 years - could be your problem. Pressures won't be right if it's mid-positioned - maybe that's what they saw?

RV operating issues can be real tricky to nail down, as it is a system "gremlin" of sorts. Usually working fine while the technician's there and then acting up while no one's looking. It takes a real sharp tech to catch them in the act. And even if they determine that is the problem, RV replacement is an expensive, time consuming process. Most companies will just try and replace the unit - especially if it's not warranty.

It has worked fine without any service calls for the past 11 years. I don't know exactly how good the technicians were that checked out the system. I hope they knew what they were doing but given the many different system manufacturers and multiple configurations possible, who knows what they actually were knowledgeable about and able to successfully check.

Thank you for your response.

 

[bonneyman]

You're welcome. I try and help where I can.

If you get the problem sorted out, please let us know.

 

[danski0224]

A blockage or obstruction will show up on gauges and temperature readings. A digital gauge set is invaluable.

It is quite difficult in comparison to do the same troubleshooting with analog gauges, temperature sensors and a PT chart. Especially if the readings are changing.

You don't know how well it's been "working" without any maintenance. The equipment will still appear to operate with a declining refrigerant charge. You will not notice gradually changing run time or performance loss until it just about won't work anymore.

Setting the refrigerant charge on a heat pump in heating season is just about impossible. Good luck with that. I have one and messed around with plastic bags and whatnot, but never got it right. Had to do it in cooling season, with a proper load.

A regular AC unit with an outdoor ambient kit will routinely shut off the condenser fan to keep pressures where they should be.

I'd guess that it's low on charge.

The easiest way to check is to reclaim what's in the equipment, then weigh in new based upon nameplate factory charge and adding for lineset length.

The reclaimed charge can be weighed, looking for a discrepancy against what's supposed to be in there.

Then recheck in cooling season.

Or spring for a new one. Will still need to dial in the charge in cooling season, for a traditional split system.

 

[honcho]

A blockage or obstruction will show up on gauges and temperature readings. A digital gauge set is invaluable.

It is quite difficult in comparison to do the same troubleshooting with analog gauges, temperature sensors and a PT chart. Especially if the readings are changing.

You don't know how well it's been "working" without any maintenance. The equipment will still appear to operate with a declining refrigerant charge. You will not notice gradually changing run time or performance loss until it just about won't work anymore.

Setting the refrigerant charge on a heat pump in heating season is just about impossible. Good luck with that. I have one and messed around with plastic bags and whatnot, but never got it right. Had to do it in cooling season, with a proper load.

A regular AC unit with an outdoor ambient kit will routinely shut off the condenser fan to keep pressures where they should be.

I'd guess that it's low on charge.

The easiest way to check is to reclaim what's in the equipment, then weigh in new based upon nameplate factory charge and adding for lineset length.

The reclaimed charge can be weighed, looking for a discrepancy against what's supposed to be in there.

Then recheck in cooling season.

Or spring for a new one. Will still need to dial in the charge in cooling season, for a traditional split system.

The technicians were using a digital gauge and made mention of the challenge of checking refrigerant in the cold temperatures they were working in.

Thank you for your insights, maybe need to consider calling another technician before springing for a new system.

Choices, choices!

 

[danski0224]

The most expedient option is to reclaim and weigh what is in the system now, and compare to nameplate data plus the lineset allowance.

If it's off by a noticeable amount (say, 25%), then evacuate and weigh in new.

If it's not off, there is another problem.

Then there's attempted cold weather diagnostics, which is a pain.

I've never really received a definitive answer. Even factory start up guys that unplug the condenser fan revert to checking it later in cooling season.

Even if you crank the heat and try running the AC, the time window is very short for diagnostics.

 

[bonneyman]

A blockage or obstruction will show up on gauges and temperature readings. A digital gauge set is invaluable.

It is quite difficult in comparison to do the same troubleshooting with analog gauges, temperature sensors and a PT chart. Especially if the readings are changing.

You don't know how well it's been "working" without any maintenance. The equipment will still appear to operate with a declining refrigerant charge. You will not notice gradually changing run time or performance loss until it just about won't work anymore.

Setting the refrigerant charge on a heat pump in heating season is just about impossible. Good luck with that. I have one and messed around with plastic bags and whatnot, but never got it right. Had to do it in cooling season, with a proper load.

A regular AC unit with an outdoor ambient kit will routinely shut off the condenser fan to keep pressures where they should be.

I'd guess that it's low on charge.

The easiest way to check is to reclaim what's in the equipment, then weigh in new based upon nameplate factory charge and adding for lineset length.

The reclaimed charge can be weighed, looking for a discrepancy against what's supposed to be in there.

Then recheck in cooling season.

Or spring for a new one. Will still need to dial in the charge in cooling season, for a traditional split system.

Definitely! On split systems I used a roll of plastic sheeting to check HP charges in mild conditions. It was a nifty idea, as the suction force of the condenser fan will "hold" the plastic against the outside of the coil. I could slowly and confidently raise or lower the overhang of the plastic till I got around 95 deg equivalent (around 300PSIG) and then checked subcooling and superheat. It would get you close - close enough for government work.

With package units the only precise method is reclaim and weigh in the right charge from the nameplate.

I'd also ask the customer if they noticed a gradual decline in performance over time, or did it just one day stopped making warm air. Not always helpful, as alot of customers typically not notice a gradual decline. But I did get lucky fairly regularly, and more than one customer commented how they liked how I seemed more interested in their unit than other techs.

 

[rooster59]

One easy check, take off the cover to the indoor a-coil. Is it full of ice when it’s been running?

 

[fitter30]

Dryers would not be installed unless the has been other problems. Heat pump wouldn't have a standard one direction dryer installed in the line have to be bi directional. Heat pump systems will either have access on suction side of the compressor or 3 rd access valve on the outside of the cabinet. Not a mini split.

 

[honcho]

Lots of good information. Unfortunately, I'm a customer not a technician so not exactly in the best position to be telling the technicians what to check for or how to do their job. Plus, it becomes a question of economics and time with how many service calls do we pay for in search of a definitive answer/repair. I guess for the moment we'll live with using the heat strips as the weather gets nasty for Christmas.

 

[danski0224]

Should be able to suggest and get a quote to reclaim into an empty cylinder and weigh it. Then either weigh in a new charge if there's a discrepancy or reinstall what was reclaimed if not.

Either way, should be no more than 4 hours of labor, plus trip charge, plus refrigerant if needed.

If there's a hard start kit, that can mask a failed run capacitor and will result in reduced performance.