Occasional hum

[CageyH]

Thanks Jim.
It is a 100Hz and 200Hz noise, so for me, it is mains based.
I don’t use a fixed phone anymore, so the base stations have been unplugged a long time ago.
The internet router has been turned off, and it made no difference.
I tried all of this when the family was out, and also turned off the mobile phones.

The noise was still there.
It is intermittent, and low level. My money is it being my air source heat pump, so I need a way of filtering this noise.

[CageyH]

I have been reading up about this, and it seems that this is due to the full inverter in my heart pump, injecting harmonics back into my mains, and it is suggested that a line reactor may fix it.

I thought lune reactors were a three phase thing? Any thoughts on this?

[Barry]

I assume "heart pump" is a misspelling of heat pump.

A mains conditioner will be of little help as they have to pass the mains components of up to a few hundred Hz to allow rapid transient switch-on rise times.

It would seem that your heat pump uses a variable speed motor (VSD) and use an inverter, which as you have found out will cause switching spikes at harmonics of the nominal mains frequency. I think you will need to consult a qualified electrician for advice, as anything designed for audio use will be inadequate.

[CageyH]

Heart pump is indeed an autocorrect.

I am looking at solving the issue, rather than curing the effect, so I think you are correct. A qualified electrician will be required