Old HVAC tech needs Heat Pump advice

[Oak54]

Hello everyone, I’m and old commercial HVAC tech that has been out of the game for awhile. I am working on my buddies Trane XR12 Heat Pump and came across some strange pressure readings. His unit is operating fine in A/C mode but in Heat Mode the pressures are running 280 on the low side and 650 on the high side. It would hit 650 then shut down on the high pressure switch and come back on when it got below 500. The unit is a 410a system and I did the normal checks on air flow through both coils making sure there was no obstructions. I went ahead and took a super heat reading and it was at 10 which is ok if I remember on these units. Could the reversing valve be leaking through? I am real rusty on diagnosing these units so any help would be appreciated.

[pecmsg]

Air Flow issue indoors or overcharged.
Pull and weigh the total charge.

How did you check indoor air flow?

[Oak54]

I pulled the front Coil housing and did a flashlight check seemed clean but I know there could be something I might not be seeing. Is there a better way I could check it? Seems like if I’m pegging that high side Pressure switch I would see a lower pressure on the suction side during A/C mode if my coil is plugged? Thanks for the quick reply

[Vinnie_NJ]

I was going to say overcharge as well.
Being you have been out of the field for some while are you familiar with the temperamental 410a?
What was your cooling pressures along with outdoor ambient temp and return air temp.

Sent from my SM-G960U using Tapatalk

[Oak54]

They were just switching over the R-22 units when I got out of the field so I don’t have a ton of experience with them. The unit in A/C mode was running 125 on the suction and 330 on the high side. Indoor return temp was 72 and it was 80 outside.

[pecmsg]

They were just switching over the R-22 units when I got out of the field so I don’t have a ton of experience with them. The unit in A/C mode was running 125 on the suction and 330 on the high side. Indoor return temp was 72 and it was 80 outside.

You cant run in heat mode at those temperatures!

[Vinnie_NJ]

You cant run in heat mode at those temperatures!

He's right

Sent from my SM-G960U using Tapatalk

[sgraefe]

You cant run in heat mode at those temperatures!

That's what I was going to say.

Unless you shut off the Outdoor Fan Motor in the heat mode, thus reducing the heat absorbed by the Outdoor Coil, which would be the Evaporator in the Heat Mode.

[lzenglish]

I agree with all that has been said here so far, and would like to add another thought if i may. When you have a situation like this, with many unknowns, it best to play it safe, and check the refrigerant charge PURITY, before you charge it back in the unit, after recovery. Cross contaminated refrigerants can also produce high head pressure readings, so re-charge with virgin gas "If You Are In Doubt", and Welcome to the Site.

[Oak54]

You cant run in heat mode at those temperatures!

He said this was happening in the dead of winter and never had anybody check it out. How could I simulate it to check out Heat mode?

[Oak54]

Thanks for the info, I have a old bottle so I probably will weigh it in tomorrow when I go back out there.

[pecmsg]

He said this was happening in the dead of winter and never had anybody check it out. How could I simulate it to check out Heat mode?

Heat pumps are charged in cooling mode. A S S U M I N G the evaporator coil and air handler are sized and installed properly with NO duct issues that's good enough!

[Artietech]

Is the airflow set correctly for the heat mode? Airflow may be too low, remember that in heat mode the inside unit turns into the condenser and the outside unit turns into the evaporator.

Now, what symptoms can cause high head?

[Oak54]

I checked the numbers and everything seems sized right. Even though it was 80 out I can’t see the pressure pegging to 650 after a couple of minutes running in heat mode. I will try unhooking the outdoor fan and get some pressure readings when I go back out there.

[Oak54]

I will check the indoor fan in both modes but I don’t believe I heard a difference between both modes when I was out there. Thanks for the advice

[pecmsg]

I checked the numbers and everything seems sized right. Even though it was 80 out I can’t see the pressure pegging to 650 after a couple of minutes running in heat mode. I will try unhooking the outdoor fan and get some pressure readings when I go back out there.

Please Do Not run in heat mode at those temperatures.

Read and understand the manual...….Heat pump charges are checked in cooling!!!!!!!!!!!!

[Oak54]

Please Do Not run in heat mode at those temperatures.

Read and understand the manual...….Heat pump charges are checked in cooling!!!!!!!!!!!!

So is it impossible to check the heat mode in the summer?

[Artietech]

You can turn off the outside fan, as mentioned earlier, but you will not be able to recreate the issue. If it is running fine in cooling mode, I would wait for either a really cool evening, or September...

[pecmsg]

So is it impossible to check the heat mode in the summer?

At your level YES

Its clearly stated in the manual Don't do it...…

I don't know what your going to gain?

[Oak54]

I will weigh in new refrigerant this week and see if it helps the situation. Thanks for all the info. I will update after the recharge