p & t valve faulty?

[sasik]

The p&t valve on a Direct Unvented Cylinder is discharging hot water when the element in the cylinder is working. How can I find out if the p&t valve is faulty or the problem is the stat in the heating element?

Thanks

sasi

 

[Mike Jackson]

There are other issues to look at as well. Is the pressure relief valve correctly fitted and set correctly. The pressure relief function on the T&P relief valve should be a back up to the pressure relief but if the PRV is not working or set to a higher pressure the T&P would discharge first in the event of overpressurisation (caused by exp vessel fault, faulty pressure reducing valve or loss of air gap in megaflo).

If it is discharging due to a temperature malfunction (unlikely as the stat and overheat stat would both have to fail) the water discharging will be at 95C or higher and the airing cupboard would be full of steam.

If Everything else is correct then it is probably faulty. If it is faulty it will have to be relaced with the correct unit as specified by the manufacturer and the work will need to be carried out by a G3 approved installer.

Mike

 

[sasik]

Hi Mike

Thanks for your reply, I took on board all your comments.
The cyilinder have an external expanssion vessel and the pressure set correctly.
On this cylinder there is only T&P relief valve (temp set 90-95 and pressure set at 7 bar). So no PRV.
I do aggree with you about the unlikley hood of the failier of both temprature safety devises.
I am G3 approved insteller and I am going tomorrow to have a look at this cylinder, I will let you know the out come!

Thanks Sasi