Siemens 2 port valve bangs shut when off

[Basicbob]

Hi,

I was hoping to get some ideas to a problem I am having.

i have a megaflo with a sealed system and a Valliant boiler. I have 3 x 2 port valves in the loft. ( water, central heating and underfloor hearings) The system was installed 5 years ago and we never had a problem until now.

last week I noticed that's when just the central heating is on the 2 port valve closes with a loud bang and the pipes rattle. But when the central heating is on with either the water or underfloor heating you can't hear it close and everything is fine.

i have also noticed that's when just the central heating in on the pressure in boiler jumps from 1.1 cold to 2.3 and it never went this high before, again the pressure only increases dramatically when the central heating in on and it's fine otherwise.

for information I believe a bypass was fitted and we have 2 towel radiators without a TVR that are fully open.

Any ideas on the loud bang and sudden increase in boiler pressure when the central heating is on?

Would replacing the actuator head with an identical one solve the problem.

Like I said it's only an issue when the central heating is on otherwise everything is fine.

any advice or thoughts is most appreciated.

thanks in advance

 

[rpm]

Welcome along Bob, has there been any recent work carried out, boiler service or new radiators fitted? Anything at all that might help the guys answer.

 

[Unregistered]

Hi

Nothing has changed at all the banging just started now.

no changes have been made

 

[rpm]

Hi

Nothing has changed at all the banging just started now.

no changes have been made

Bob, need you to sign in again and this time tick the little box under your user name or it times out, just makes it easier for the guys to reply to you directly.

 

[Dotty]

If its the 2 port directly attached to the megaflo then you'll need a g3 qualified engineer to look at it.

 

[walterwhite]

When was the whole system last serviced? 5 years old - the exp vessels will need checking

 

[rpm]

If I had a sealed system then 2.3 on the pressure gauge would worry me enough to get a g3 guy in tbh.

 

[stevetheplumber]

sealed system needs a repair and have you checked the flow direction of the motorised valve it may be fitted reversed and as its got looser its now banging shut agaist the direction of flow

 

[Basicbob]

Hi

The valve is definitely in the right direction.

With the 2.3 boiler pressure am I right in assuming I have 2 problems ie expansion vessel in the boiler needs checking and the 2 port valve bagging is a separate issue and not related.

If I get the boiler serviced will they sort out the expansion vessel pressure?

 

[Dotty]

No. You need your unvented cylinder serviced by someone with G3.