Heard a rumour Vaillant are shelving the 7kw and brining out an 8kw. Wonder what the threshold is for getting our noisy units swapped.

The 7kW is (in terms of output) what most manufacturers would call an 8kW (or even 9), so this might just be a marketing exercise.  However they are launching a new range with, I believe, a different compressor, distinguished by a fashionably black case.

I did find out today that the sensors are exactly the same as the ones used on Vaillant boilers. As that’s what he had with him. You can remove them from the boiler clip and fit them to the heat pump clips.

I expect they are all made in the same factory in China!

What I’ve noticed is I’ve still got the 0.2c gap which I’m guessing is the wiring resistance possibly. I’m going to cover the sensors in some insulation to see if that helps. If not I’m assuming the sensors goto the main pcb box so might measure the resistance there. Why they don’t put some small trim pots or software adjustment on these I don’t know.

I suspect because the absolute value doesn't matter to the day to day operation and they don't guarantee the accuracy of energy or COP readings, which is the only thing materially dependent on them being matched!  Not entirely satisfactory I agree, it wouldn't be that difficult to calibrate them!

Couldn’t suggest a fix for the humming other than the installer should have used Vaillant flexis. Did say the installer could move the external pipe clamps which I think might also help.

If there are no flexis then fitting them may well help.  If he has just used third party ones then less likely.  If you can find something that is vibrating in time with the hum that may give a clue of a point to either isolate or clamp!

What I’ve noticed is I’ve still got the 0.2c gap which I’m guessing is the wiring resistance possibly. I’m going to cover the sensors in some insulation to see if that helps. If not I’m assuming the sensors goto the main pcb box so might measure the resistance there. Why they don’t put some small trim pots or software adjustment on these I don’t know.

I did find out today that the sensors are exactly the same as the ones used on Vaillant boilers. As that’s what he had with him. You can remove them from the boiler clip and fit them to the heat pump clips.

Sorting the sensors - get them to swap them round or put both on the same pipe to demonstrate that they are matched, otherwise they will probably put in two new equally random sensors.  Note the mismatch and which way round they go for future reference

Humming - make sure you know what triggers it so that the conditions can be created when they are present.  Otherwise sods law guarantees there will be no humming when they come.

im also wondering if they will bring any sensors with them as I’ve heard other people say one turned up with none, even though they were told it was a sensor fault, and the second visit by a different engineer only had one new one and one seemingly off another hp.

it was after their last email asking me to pay the balance that I sent them a list of faults with their installation and said id pay up when the list was cleared. That got the manager involved and she was a tyrant. I just kept my cool and we came to a compromise