central heating

[andy116]

hi there
i have a siemens rwb9 programmer and a potterton suprima 40L boiler on a pumped system.
when we turn hot water on, boiler does not light, green light on boiler flashes and pump runs but when we turn central heating on, boiler lights ok.
also if hot water heating is turned on while cetral heating is on, it heats ok.
any ideas please

thanks in advance

in answer to your questions it is a siemens 3pmp v22 3 port motorized valve thanks again

 

[D_Hailsham]

Do you have a Y-plan (one 3-port motorized valve) or an S-plan (two 2-port motorized valves)?

 

[Meldrew's mate]

My guess, given the limited information, is that the "HW OFF" signal is missing (wire missing? from terminal 1 on the programmer?), or the HW two port valve is not generating the "I'm open" signal on its orange wire.

MM

 

[D_Hailsham]

My guess, given the limited information, is that the "HW OFF" signal is missing (wire missing? from terminal 1 on the programmer?)

But, if that was true, the OP would have had this problem from the beginning. From what he says it is a new problem.

, or the HW two port valve is not generating the "I'm open" signal on its orange wire.

I agree that the problem could be the switch within the MV, but we don't know if the OP's system has a three port or two 2-port valves.