T
Truman
Boiler is a Viessmann 100 combi, installed about 8 months ago. After the CH has been on, and the boiler shuts off, - the fan and pump (?) continue to overrun for a couple of minutes as expected, but when the last thing shuts off (whatever it may be), there's a loud hum which varies in pitch for about 10 seconds or so as the boiler finally shuts off. It sounds like an electrical hum but the noise goes randomly quieter and louder, like it's hunting/searching.
Also, like most combis, when there's been no heating demand for 24 hours, something must be coded into the unit to run the pump (?) for a few seconds - and the humming noise happens then as well for 10 seconds or so. It's almost as if whatever it is that is kicking in at this point is struggling/failing and I doubt it actually spins the pump at this stage.
There are no humming noises when HW is being used (either on or shutting off). Regardless of all the above, the boiler continues to operate OK for CH and HW (and is quite quiet in operation) so I'm just wondering if anyone has come across this before or knows what it could be. It's been doing this for several months at least, don't think it did it when first installed.
Also, like most combis, when there's been no heating demand for 24 hours, something must be coded into the unit to run the pump (?) for a few seconds - and the humming noise happens then as well for 10 seconds or so. It's almost as if whatever it is that is kicking in at this point is struggling/failing and I doubt it actually spins the pump at this stage.
There are no humming noises when HW is being used (either on or shutting off). Regardless of all the above, the boiler continues to operate OK for CH and HW (and is quite quiet in operation) so I'm just wondering if anyone has come across this before or knows what it could be. It's been doing this for several months at least, don't think it did it when first installed.
