HVAC Guys, a little help please.

[threewood]

Dealing with a high pressure shutoff. This is a 3.5t Armstrong heat pump. Air filters are brand new, evap coil has just been cleaned, although it wasn't dirty. Plenty of airflow through the return.

Cool mode works fine, kicks on and kicks off when temp is hit. Screen shot of numbers below

Heat mode is a **** show. Head pressure continues to rise into the 500psi before it cuts off. Suction rises as well. The air handler has a piston orifice. Which should be for cool mode. Once heat mode is commanded, it switches to a txv on the condenser side. I'm leaning toward a bad txv valve. Is it possible for a piston orifice to stick in the housing? Another possibility for overpressure?
Heat mode...

 

[threewood]

You can see the temp on the discharge get to 146° which I don't think is normal.

 

[threewood]

Pulled 5lbs of r410a out and head pressure is still at 500.

 

[5.7 hemi]

Is the fan moving? No airflow would cause the high side pressure to go up. But I’m not a hvac guy.

 

[threewood]

Is the fan moving? No airflow would cause the high side pressure to go up. But I’m not a hvac guy.

Yep. Outdoor fan is going. Indoor fan is going. Oth coils are clean. It's got good air flow. No problems in cool. Only have issues in heat, where the flow is reversed.

 

[5.7 hemi]

Well, I’m no more help to ya.

 

[threewood]

I'm going to evacuate the system and check out both the piston orifice and thermal expansion valve. It's got to be one or the other.

 

[Moms68]

What's the amp draw on the compressor in heat mode?

 

[threewood]

What's the amp draw on the compressor in heat mode?

I'll hook up my meter and check. Do you think that the compressor could be on the way out?

 

[Burnout68]

Looks like you are getting a restriction in heat mode would check for temperature differences of your lines going through the reversing valve and then would definitely be troubleshooting the TXV some more

 

[threewood]

Looks like you are getting a restriction in heat mode would check for temperature differences of your lines going through the reversing valve and then would definitely be troubleshooting the TXV some more

Someone else mentioned the reversing valve. I can check it with the orange wire on the board. The system does cool in cool mode and heat in heat.

 

[Burnout68]

Someone else mentioned the reversing valve. I can check it with the orange wire on the board. The system does cool in cool mode and heat in heat.

It looks like you have a restriction in the refrigeration system so I would check the temperature differences if any on the line entering against leaving the valve & trouble shoot the TXV also, which may be the culprit causing the restriction

 

[threewood]

Success!!

Reversing valve is good.

I evacuated the system. Pulled out about 15lbs of r410 which is about 2.5 lbs over spec plus lineset. Replaced the drier and the outdoor txv (which was a pain in the arse to find). Checked the piston orifice at the indoor unit and there was no issue there.

Flowed argon while I brazed the fittings. Pulled vacuum down to 450 micron. Filled her up to 11.5lbs per spec sheet plus 1lb for lineset (estimate).

Kicked it on in a/c and let it run for 15 minutes. Besides gauge readings, I didn't get superheat or subcool (a/c runs off the piston, plus outdoor temp was 55 degrees) but it runs good and steady. No rise in headpressure. Good heat in heat mode. No high pressure lockout.