Heat Pump Retrofit Assistance Needed

[Bentherm]

I recently replaced the outdoor unit on an older heat pump installation for a family member. Unit used to be an R22 3T and I replaced it with an R410A 3.5T, replaced the lines after flushing the coil and also replaced the TXV indoors with one matched to the outdoor unit. The air handler fan has been replaced and is running in high speed. Lines were evacuated for an hour and held down to 500 microns before charge was released. Refrigerant charge has been topped-off to account for the 55' of pipe as per the installation manual.

It is 87'F outside today and I tried firing up the heat pump in heating mode to see whether it would work. I put my new digital manifold on and fired her up. It appeared to be working fine for the first 15 minutes or so before it tripped-out on hard lockout. Note that the indoor temp had risen to 95'F. I noticed that the suction line temp had risen dramatically up to 256'F and that the glue on the pipe insulation had melted. I also recorded the gauge readings just before the unit shut off and they were 110/283 PSI. The liquid line temp was 89'F. There is also a low vibration coming through the lines into the house.

I am not a refrigeration tech but work in the field enough to be dangerous. I would like some suggestions as to what the most likely causes for a problem might be. Here are some variables that I can come up with:

- The older indoor coil is not large enough
- I somehow botched-up the TXV installation inside the AH and may have caused some restriction despite the fact that it is being bypassed by the internal check valve in heating mode. Note that the sight glass after the TXV was clear and did not show any signs of flashing.
- The new blower is running at too high a speed.

That kind of covers the areas I might have screwed-up on. Your suggestions on what may be happening would be greatly appreciated.

[Brian_UK]

Outside air temperature too high perhaps?

[Bentherm]

Could be but I've never seen it happen before. Figured I must have mismatched the coil or done something wrong. Does high OAT explain the the pressures and temps?