Vaillant Eco Tec 824 pressure increasing on heating

[abc_plumb]

Nope the system is the same. No radiators added or taken away.
I've disconnected the filling loop and told the customer not to use the heating.
Filled the system to 0.8bar.
I got a feeling could be a very small pin hole in the domestic heat exchanger.
Let's wait a see......

 

[wards]

silly question but i take it you cleaned out the magnaclean?

 

[jtsplumbing]

Just use a foot pump with gauge, but what i have done is fit a longer hose on to pump,(2Mtrs) used same method for years.

 

[abc_plumb]

I wanted to but the customer didnt have the key. The lid was very tight, no chance of opening it, wothout a key. But I don't think there is much on there as I opened the filter in the flow pipe and that was clean. I'm gonna give it a day and wait for the feedback from the customer

 

[arran197]

How big is this system? If it's too big, the vessel won't cope.

 

[buckley plumb]

you could fit an external vessel or easier just to try and check isolate one radioator and drain it . then only open one valve so rad acts as a large expansion vessel as temp measure and see if the pressure still rises if not you have found the issue

 

[abc_plumb]

Just had an update from the customer. It was a faulty dhw heat exchanger. The orignal pressure vessel tank had no pressure.
brought a new Regin pump and pumped the original tank to 1bar, and replaced the heat exchanger.
So glad it's sorted.
Thanks guys for all your help.