Delonghi r410a Air Source Heat Pump High Pressure problem

[heatsave]

Hi
Looking for some technical assistance for a Delonghi Bran Air Source Heat Pump it's r410a.
It's tripping the high pressure switch when it gets to high outlet temperatures on hot water.
Measured 5 bar on low side and it is hitting the high side limit at 38 bar when water flow temperature is about 52oc.
Temperature at expansion valve seemed constant around -6oc.
Plenty of flow to hot water tank delta t of 5oc.
It's been in a year and worked fine, no sign of refrigerant leaks.
Wondering if it is a faulty expansion valve.
Ambient was 1oc today but was doing the same at 8oc.
Have about 20 of these installed all with same parameters and work fine and no problems running hot water up to 48oc

Thanks for any help

[heatsave]

Thanks for the help

[Rob White]

.

Start with the obvious.

What is the HP set to?

Is the water flow through the heat exchanger restricted?

Is there air in the water side?

38 bar is about 60 degsC so that is on the upper end of hot for
water flow at 50 degsC. What is the temp difference over the
heat exchanger?

Rob

.