Voltage drop problem not resolved with bigger cable

[Shoei]

Measurements in the pump room - with pool pump only running 220v and 4.3 amps, with pool pump and heat pump it drops to 197v and current shoots up to 29amps. The instructions for the heat pump show normal working current to be 16amps.

Agree with you, that points to a faulty heat pump. I'd measure volts and current at the heat pump alone and compare readings to the spec, sounds like it's taking an excessive amount of power.

 

[TingleFingers]

If the voltage at the incoming supply terminals is 218/230/230 then it sounds like there may be a supply problem.

Have you tried moving this onto a different phase temporarily to rule that out?

Next thing on my list!! Cheers.
[automerge]1571478876[/automerge]

Agree with you, that points to a faulty heat pump. I'd measure volts and current at the heat pump alone and compare readings to the spec, sounds like it's taking an excessive amount of power.

Will do, it hasn’t been serviced in a couple of years either. I’ll check connections inside the heat pump in case there’s a problem there too.

 

[marconi]

If it is a conventional compressor motor using switched start winding and a run winding I suggest you check that the start winding is being switched off once the motor is running. You can ampclamp the start winding to find out. If both are energised it might explain you higher than 16A current draw. If it is not the starter module may be defective. Starter modules use a number of techniques which we can go in to if you find the module is defective.

The same thinking applies to the fan motor.

 

[marconi]

Is there an RCD 'up-front'?

 

[dmxtothemax]

Are you sure that the local grid has the power to power the heat pump ?.
It could simply be that the local supply grid is maxed out,
And therefore the power just aint there !
To know for sure, you need to measure the voltage at the main panel as well and compare.

 

[Deleted member 105166]

Are you sure that the local grid has the power to power the heat pump ?.
It could simply be that the local supply grid is maxed out,
And therefore the power just aint there !

The heat pump referred to is only 4kW

 

[Lucien Nunes]

The main panel voltages are given in post #6. L3, serving the heat pump, is low at 218V, but that is a separate issue to the unaccountable drop in the heat pump circuit.

 

[marconi]

Further thoughts:

It is a swimming pool heat pump so I'd expect long periods of running.

Maybe:

1. Bearings are failing/have failed in compressor or its motor or both.
2. Low lub oil level in compressor.
3. High pressure fault in refrigerant circuit not detected by faulty HP pressure sensor.

All would cause comp motor to work harder and draw more current.

 

[davesparks]

The main panel voltages are given in post #6. L3, serving the heat pump, is low at 218V, but that is a separate issue to the unaccountable drop in the heat pump circuit.

It doesn't seem clear to me whether the OP has measured that incoming voltage with the heat pump running or not.
My thoughts at the moment are that if the incoming voltage is dropping to, or near to, 197V when the heat pump is running then that will be relevant.

 

[marconi]

Re my #18: I forgot to add a fourth:

4. Check that water flow through the condenser ( an heat exchanger) - which transfers the heat of the hot pressurised refrigerant vapour to the circulating pool water - is not restricted or throttled by defective valves or valves not fully open. Also check that the pool pump is running at its correct speed and the pump is not restricted - is there a strainer which needs clearing/replacing? If the volumetric flow of the pool water is lower than it should be, the refrigerant in the condenser will be at a higher temperature than it is designed to be at which means a higher back pressure at the compressor outlet. The compressor will have to work harder - more amps - to pump the refrigerant into the condenser.