Fluctuating Kriwan resistance value

[Peter_1]

Scroll ZH56K4E-TWD-524, Air/Water heatpump, installed begin 2016.
Kriwan fault, sometimes 5:day, sometimes no shut down in some days.
LP and HP are very stable (-1°C, 52°C), SH also stable
Current Stable 14,2 en 14,8A.
Bridged Kriwan, disconnected sensors and measured internal sensors.
Resistance varies from 1kohm to 30 kohm within 30 seconds
Sounds varies as well.

Link
https://www.youtube.com/watch?v=jGVf4lEqnEg&feature=youtu.be

What do you think is happening?

[nike123]

It looks like thermistors inside are faulty. I recommend installation of electronic motor protection.

https://www.schneider-electric.com/en/product/LR9D32/tesys-lrd---electronic-thermal-overload-relay---3p---6.4...32-a/?range=761-tesys-lr9-–-lr9d---lr9d&node=166389188-electronic-thermal-overload-relays

Also, I would advise usage of discharge pipe manually reset thermostat of 110°C in series with that thermal overload.

[Peter_1]

Thanks Nike 123... discharge temperatures stay also very stable around 95°C.
SH is also low, so windings are cooled very good I suppose.
Overload was already installed.
We suspect also erratic thermistors.

[nike123]

Thermistors are semiconductors end when they are erratically (jumping in values) then it is certain that they are faulty, since temperature cannot change that fast and fluctuate that much.