Unvented problem

[clarky101]

Got a Gledhill 180L slim unvented cylinder passing water through the tundish, now this was fitted in december 11, custards a bit of a knowall & played with the valve on the expansion vessel when it passed water about a month back....so i reset the vessell to 3bar & today hes phoned saying its passing again....The pressure reducing valve is set on 2.75bar on the incoming main but theres no gauge on the combination valve...tested the pressure vessel which was 4.75 bar which is right for the prssure relief valve
Any ideas why this keeps hapening, should i change the Vessell or the Combination valve or are the mixer valves for bath/shower causing this.....

 

[snowhead]

If the mixer has unregulated cold then it could be passing higher pressure cold across to the hot side, assuming the incoming cold is higher and the hot at the mixer doesn't have a nrv

 

[mountainman]

Spot on answer Snowhead.

 

[clarky101]

The pressure reducing valve is just above the stopcock, then the T to the combination valve, on the branch of the T & continuing up to the rest of the house..

 

[clarky101]

Cheers for the quick response, BTW should of said its passing cold water through the Tundish, custard also says its when the H/W is on at the boiler, but it doesnt do it when the CH is on.....

 

[AWheating]

faulty expansion vessel?

 

[clarky101]

On one shower mixer ther is a 22mm hot feed & a 15 cold feed, bit the main is now set at 3bar

 

[Dannypipe]

The most common cause of this is as snowhead pointed out. If you have a pressure reducing valve on the stopcock before any draw offs, then you have eliminated that possibility.

You've checked the pressure in the expansion vessel with the system un pressurised right?

Then check the pressure of the system to acertain that the pressure reducing valve is doing it's job.

If no problems with that....then I guess you'd have to assume a faulty pressure relief vavle.