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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Baxi Combi Instant 105e - DHW pressure valve https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1284799074 Message started by markjsmith2000 on Sep 18^th, 2010, 9:37am

Title: Baxi Combi Instant 105e - DHW pressure valve
Post by markjsmith2000 on Sep 18^th, 2010, 9:37am

Hi All,

The pushrod on the DHW pressure differential valve wasnt operating when hot water was called for, so I replaced the valve assembly including diaphragm but it still doesnt operate.

I've removed and cleaned the cold water inlet filter gauze and the filter in the inlet/return manifold. I've also removed and cleaned the small copper tubes that go between the inlet/return manifold and the diaphragm assembly but still the pushrod doesnt operate. There's plenty of flow at the hot tap so I'm stumped as to where the blockage might be.

Could a brand new pressure differential valve have a sticking pushrod? I didnt check it was free before installing it and now I'm wondering....

Any other suggestions?

Cheers,
Mark

Title: Re: Baxi Combi Instant 105e - DHW pressure valve
Post by The_Trician on Sep 18^th, 2010, 1:03pm

Mark,
I had similar problems with my BAXI 105e combi - it turned out to be the pump inside the boiler - don't ask why though, since the pump only circulates and does not create any pressure. I changed the pump and everything worked fine after that.

TT

Title: Re: Baxi Combi Instant 105e - DHW pressure valve
Post by markjsmith2000 on Sep 18^th, 2010, 8:31pm

Thanks TT. I read something similar in another post but didnt think it sounded possible, but maybe a faulty pump affects the correct operation of the pressure differential system? Also, I have heard the pump make some strange noises in the past 6 months so I think I'll try that.

Mark

Title: Re: Baxi Combi Instant 105e - DHW pressure valve
Post by markjsmith2000 on Sep 19^th, 2010, 6:49pm

The problem turned out to be my school boy error! ...

When I re-connected the positive and negative pressure pipes to the DHW differential valve, I connected them them to the wrong connections. Doh!

The correct way is as follows:

1. Front connection on DHW pressure differential valve > Right hand connection on hydraulic inlet assembly.
2. Rear connection on DHW pressure differential valve > Left hand connection on hydraulic inlet assembly.

Hopefully my little error will help someone else..