Unvented heating system, unusual boiler fault

[Pauld1962]

I isolated the F&R at the boiler at 1.5bar and it held ...... Once the return was opened the pressure rose immediately and water meter was turning over ...

 

[chris watkins]

Drain & valve off cylinder coil in that way they can still use the immersion or Solar for domestic hot water.
The heating system pressure should stop rising. If so it is the coil & you will have to order a new cylinder.

 

[Best]

I isolated the F&R at the boiler at 1.5bar and it held .. Once the return was opened the pressure rose immediately and water meter was turning over .

Probably cylinder coil gone then.
Is it a copper unvented cylinder, or stainless steel?
If you are not G3 qualified, just be aware if no isolating valve on mains supply to unvented cylinder, then only install one BEFORE the combination valve. (Between the combination valve and cylinder must not have any valve)

 

[Pauld1962]

Thanks for all your input / answers guys I am going to call back to the customer and inform him ... That'll be fun ...!! .... Thanks again gents ...

 

[Pauld1962]

Apologies "Best" .... It's a stainless steel cylinder ...