Glow-worm Ultracom 38hxi Problem

[bw65587]

We have:

• Glow-worm Ultracom 38hxi boiler.
  Grundfos 'Super Selectric' UPS 15-60 130 pump (speed currently set to II).
  Glow-worm Climapro RF thermostat.
  Westherm TRV's on all radiators (except hallway where thermostat fitted and bathroom towel radiator).
  11 radiators.

The above replaced a floor-standing 36-year old Glow-worm boiler 12-months ago (wish we hadn't bothered now!).

I now know the boiler to have been massively over-sized for our house. I have calculated the radiators to be around 14,000 watts so have rated the boiler to 16kW allowing for 2kW for DHW.

We have the boiler temperature set at 80 degrees C and the flow and return temperatures at the boiler are 80 (d40) & 65 (d41) respectively.

We have no problem with heating the house or with heating the water.

We do have a problem in that the boiler seems to come on whenever it feels like it! We have the internal programmer disabled at the boiler as we have the Climapro RF installed.

We have the heating and water set to be on together from 05:30 to 07:30 in the morning and from 17:00 to 22:00 in the evening but the boiler will come on at times outside of these set times.

I have lost count of the number of occasions I have had to go downstairs between 00:00 and 05:30 to try and switch it off - it's driving us nuts! Often, we'll come home before 17:00 and we can tell it's been on!

Any ideas would be much appreciated as we need to regain our sanity?

As an aside, is speed setting II the correct setting for the pump?

Many thanks!

 

[glasgowgas]

in your timed off settings, what is the room temp set for?

 

[bw65587]

Eco is set to 15 degrees C. The house is a 1970's detached with cavity wall insulation and recent loft insulation fitted. I've never seen the room stat say less than 18.5 degees C in the last 12 months.

I thought it could have been that originally.

Also, it can't be the frost setting kicking in (I believe!) as the boiler is in the kitchen and I've never seen the water temp at the boiler less than around 35 degrees C.

Many thanks.