Turning HW on turns heat right down

[laverstock]

Fairly standard open vent system. CH by itself works fine. When I turn HW on, the boiler will only fire for 60 seconds and then goes off for 5 minutes then on for 60 seconds etc. amost no heat comes out of either side of mid position valve. Help!

 

[kevplumb]

bugger the crystal ball is flat again

forgot to recharge it

 

[Softus]

Don't be so obtuse Kev - if this isn't an installation problem then it's obviously a fault with the plumbing, or the boiler, or the fuel supply, or the air supply, or the flue.

 

[gas4you]

Mid pos valve head fault. Not opening for hot water. Boiler cycling just to heat the water within its self with no flow going through it. Have you a bypass fitted to the circuit?

 

[Softus]

Mid pos valve head fault. Not opening for hot water. Boiler cycling just to heat the water within its self with no flow going through it.

Yeah, those mid position valves are renowned for closing off both ports at once.