unvented hot water cylinder

[princeknight]

got an unvented cylinder, not heating up water, just very tepid. two port valve working okay. connected to vailant system boiler which is always losing pressure, and when using filling loop does not fill over 1.2bar???? mains water pressure ok so dont understand y this is.

supect that thermostat needs replacing but would like verification by you guys if anything else needs to be checked before hand just incase this is not the correct diagnosis.

thanks

 

[Bernie2]

Hi! Prince Knight,

Have you thought about indirect boiler coil inside unvented cylinder leaking?

Turn off cold main to unvented and run off taps.

Boiler pressure should drop as water from the boilers system leaks into unvented cylinder.

Do it cold system of course. But also bear in mind it may only leak when hot.

But this is only a rough guide. To test coils of course you need an air test on it.

May explain having to top up so often. That is of course providing there is no indicators of any other kind of leak.

The 1.2 bar pressure may be all there is on the cold main.

 

[princeknight]

Hi Bernie

i will test coil tomorrow and check, if lets say the coil is fine, any other suggestions?

i would of thought that the hot water would have been contaminated with dirty water colour if the boiler was leaking into cylinder.

i can not identify any leaks on the boiler system, but what your saying sounds that that is the problem.

i thought it might of been the thermosat.

just thought if coil leaking wouldnt the water be hotter?
at present it is just luke warm

 

[Bernie2]

The colour of the water depends on whether there is much corrosion in the system. Often a sealed system doesn't corrode as much as people may think.

It may seem logical for the water to get hotter in the cylinder by mixing with the hot water in the coil. But its amounts really, compared to the amount of water in an unvented cylinder a sealed system boiler doesn't hold much and of course not all of it would be leaking into the cylinder, if both are at the same mains pressure the leak would probably be pretty slow.

So if not much sealed system hot water is going into the cylinder, its temperature would be diluted in the colder volume of water in the cylinder producing tepid water.

The thing is of course all this is only consideration, its possible the thermostats may be at fault as well or even any mixing valves fitted. Its a case of looking at everything, if the fault is not so easy to find.

 

[Plucky]

In this case you could disconnect flow and return pipes at cylinder and pressure test

 

[princeknight]

YEP, i got unvented on my ticket, just to let you guys know got the damn thing sorted.

following faults found when inspected closer, bit of a tight squeeze where it was but managed to do it.

1. air pocket was leaking on cylinder, where stat fits onto cylinder
2. thermostat not working
3. coil had small pitted holes in it

thanks to you guys for ALL the advise and help that you have all given.

cheers