CH heats up then cuts out.

[big stu]

My problem is;

The central heating was being put on the other day for the first time since the winter. I found that the motor in the drayton mid position valve was burnt out, I replaced this and fired the system up. Everything appeared to be working ok. However after 40min the pump stops running and the boiler will only fire up for a few minutes at a time, Cutting in and out on the boiler thermostat. This will continue and the radiators upstairs will heat up slightly and the ones downstair will cool down completly.

I checked the connections on the pump and there is no power there.

The water heating works fine.

The boiler is a glowwarm,
The mid position valve is a Drayton lo3030
It uses a drayton timer and room thermostat.

Any help would be great.

Cheers

Stu

 

[oilman]

The pump should run in either position of the valve as long as the stats are calling for heat. The boiler shuts down becuse the pump's not running. The fault is electrical, so you need to find where the power stops on it's way to the pump.

 

[ChrisR]

Are you sure the motorized valve mchanical and wet bits are working properly? feel for heat to go through the pipes when it should open to a "new" route. Has to be checked from cold.

The HW WILL work - valve doesn't have to open for that!

Could be the new motor didn't go in properly or something got pushed...

 

[big stu]

I tried removing the motor and jamming the valve in the central heating position, it did the same thing. Heated up for about 40 min, all radiators then for some reason the pump stopped. Could it be that the water is bypassing into the hot water tank and the thermostat on that is cutting it out. Should I try replacing the entire mid position valve? Anyone know any good plumbers????

 

[ChrisR]

Boiler and pump will stop when it gets hot! Check the voltage onthe Orange(probably) wire coming from the 3 port valve. Goes to Switched live on the boiler.


"Could it be that the water is bypassing into the hot water tank and the thermostat on that is cutting it out. " No, assuming you have a full programmer and room stat.

where are you?

 

[big stu]

Right... as I siad I replaced the mid position valve, it functions correctly, ie when water is selected it does nothing, when they are both selected it moves to the mid position, and when ch is selected it moves to the H positon. I wired the pump up to a 240v plug and plugged it in.

Sysytem functions correctly appart from it will not reset itself, ie when the program is finished the boiler will continue to light.... any ideas...

 

[oilman]

Did you replace the valve head, or just the motor? It sounds like a connection is missing from the valve to the boiler, "BOILER INTERLOCK".

Look for this and Y-plan here