Grant Combi heating rads when set to hot water only?

[ajj]

Hi, we have a Grant Combi 90 mkii (indoor) boiler and about 3 months ago had issues with the hot water so replaced the 3 way diverter value, heat exchanger and thermostatic mixer valve. I have now noticed that the radiators are getting warm despite the boiler switch being set to hot water only. Our usual plumber is suggesting that we replace the boiler but having spent so much money on it recently I am reluctant to do so. Any assistance to diagnose the issue would be grateful received. many thanks.

 

[Terrywookfit]

Does your usual plumber do the boiler servicing and repairs.
Why was the PHE and DV changed?

Test that the check valve on Heating flow is not passing.

 

[ajj]

Hi Terry, unfortunately the plumber that installed the boiler (about 12 years ago) and has serviced it since retired last year. We found another local company and had them service the boiler in March this year. They said that the expansion vessel needed replacing (which it did as weighed a ton!) so we had that changed. End of July, heating would work but no hot water so they came back out and installed a new dv. Hot water was a bit erratic (going hot then cold) and we noticed the mixer value leaking so changed that too. They suggested changing the heat exchanger as for extra £80 we would have all new components on hot water side.

Thanks for the advice on the check valve. I will check that when I get home later.

 

[ajj]

Piping was hot both sides of check valve even though heating set to off. Will order new valve in the morning. Thanks for your help.

 

[oilboffin]

If you have a brass diverter valve then it's probably stuck you can get a kit to repair it.Bob

 

[oilhead]

If you turn off the cold water supply and remove the top of the diverter valve, you can check with a probe whether the diverter valve is free. If it is new, it is doubtful if it is faulty, but you never know.