CH only works when the HW is on.

[Bp89]

Hello. I discovered yesterday that my CH wasn't working but if I switched on the HW the radiators heated up. This morning when CH was called for the boiler did not ignite but I could hear a trickle of water in the vicinity of the boiler. On switching on the HW the boiler fired up.

Last summer I had the reverse situation- for the HW to fire up I had to switch on the CH. I found that the Honeywell 2-way valve needed replacing and once replaced everything worked well. Surely the valve hasn't failed already? I should add that the pump is very hot. Hotter than I thought it should get.

I have a Worcester Bosch boiler and a Heatrae Sadia cylinder plus a Potterton EP 2002 timer. The expansion tank is reading a very low pressure but has done for some time.

Help, please.

 

[exedon2]

First bring system pressure up to correct level
Assuming you have 2 2 port valves and you changed the dhw one this time it's the heating valve .
Maybe time to have it checked out make sure there is not a underlying cause of micro switchs burning out.

 

[Bp89]

First bring system pressure up to correct level
Assuming you have 2 2 port valves and you changed the dhw one this time it's the heating valve .
Maybe time to have it checked out make sure there is not a underlying cause of micro switchs burning out.

Thanks for that. As far as I know, there is only one two-port valve. I should have added that once the hot water reaches temperature the boiler switches off so the CH is only on for a short time.

 

[Bp89]

First bring system pressure up to correct level
Assuming you have 2 2 port valves and you changed the dhw one this time it's the heating valve .
Maybe time to have it checked out make sure there is not a underlying cause of micro switchs burning out.

The problem would appear to be solved, although it's confusing. After the morning setting on the timer of 'timed' I moved the switch to 'on' with the HW on as well. The HW and CH combined heated the rads until the HW eventually reached temperature and switched off and the rads lost temperature. Sometime later I decided to reset the boiler, although there was no indication on the blue light at the front of the boiler that there was a fault and resetting was needed. I didn't get any sense that resetting had occurred. I then moved the timer switch from 'on' to 'timed' and the boiler fired. I assumed that there was a fault with the timer contacts but I'm not convinced.