Highflow 400 high pressure problem

[cwrtcoed]

hi
I currently have a high pressure problem in my highflow 400 electronic boiler. It's running at 3 bar which triggers the PRV so I got constant dripping water ( and I'm on a water meter).
Plumber has come up and he changed the expansion tank, but the next day pressure was back up. He's changed the heat exchanger and the problem still exists. Isolated the filling loop and again the problem is still there.
The system has been drained and repressurised, radiators been bled and I'm still having the same issue. Soon as the cold water feed supply is turned on this is when the pressure goes up high.
My plumber reckons it's mixing somewhere forcing the pressure up. He has spoken to worchester to see if they have any ideas to what it could be, and they are stumped. The plumber can only think of two other places where this problem could be and this is the top and bottom manifolds where the heat exchanger is attached to, these are the only place the water could mix if there's a crack or leak in there.
Worchester said they have never had a problem with any of their manifolds, but I suppose there's always a first time.
Can anyone else think where else the issue may be. When the boilers off the dripping water is cold, soon as the central heating is on the dripping water becomes very hot

 

[omega015]

You don't have a faulty PRV do you? Couple of questions if you can answer

What pressure is the system being filled to when off/cold?
Does the pressure only climb when either CH running or when filling up with the filling loop?
Is the dripping water the water from the PVR attached to the central heating pipes?
You haven't turned off all radiators have you? Therefore possibly no bypass for return water.

 

[cwrtcoed]

Norm set pressure to just over 1 bar, but soon as you open the cold feed it goes straight to 3 bar, if you turn the CH feed and return pipes on, the pressure is ok (without turning in the actual boiler on).
Soon as you put cold feed via loop it more or less goes to 3 bar
I think the PRV is attached to the CH via a manifold which is all
Linked to the heat exchanger and cold feed etc
All rads are on ok

 

[omega015]

That cold feed via the loop is only used to fill the central heating to a specific point (i.e. the 1bar) it should then be switched off at both ends (and technically removed) therefore there will be no more cold main feed into the central heating part. Unless you are meaning the cold feed into the boiler for hot water and not the central heating (two different parts of a combi boiler)

 

[ollski]

Expansion vessel flexi connector pipe blocked?

 

[cwrtcoed]

Hi
Cold feed has been disconnected
Yes cold feed for the hot water supply, sorry I only been watching what the plumber been doing.
There was a slight kink in the flexi hose but it doesn't look totally blocked.
Is there any other places where the feeds mix, he said that's the only thing he thinks it is

 

[omega015]

No there should be no other places where the central heating water mixes with the mains/hot water except the cold water inlet into the central heating. If there is any other mixing then there is a real danger of contaminated water supply from central heating chemicals etc...

If you are getting over pressure only when hot water cold feed is on then you have a deeper issue. And to confirm, the loop from the cold water to the central heating is only to be used to top up the water in the central heating system and should be shut off at both ends when at the required pressure.

 

[cwrtcoed]

I know I was thinking about the contamination issue.
I can Confirm that the loop fill has been disconnected.
What other issue could it be if it's when the cold feed for the hot water is putting the pressure up?
Only the manifolds are left, it's only costing £40 for the both manifolds cause he said that he just as well change the top and bottom manifolds whilst it's in bits,
Charging me £100 to do the job which isn't a bad price considering he need to take it all apart.
Can you think of anywhere else the problem could be?
Is there a water pressure sensor in the system somewhere that shuts of the supply when the pressure gets high?? And it could be faulty.

 

[omega015]

This just doesn't make any sense. How long has it been like this for? have you had any recent work done on the plumbing? do you have any storage tanks in your loft or anything?

 

[cwrtcoed]

It's been like this for weeks, nobody has touched the boiler. The boiler has its own storage at the base of the boiler, Worcester said the problem shouldn't be there. because there's nothing that can mix together so we are stumped. Hence why the manifold change