Boiler and unvented hot water servicing question.

[Mottie]

Possibly a silly question but my boiler is up for its first service and I also have an unvented hot water system that’s well overdue for a service (about 2 1/2 years old). I would like to use the person who installed the boiler to service the boiler but looking on the gas safe register I see he is not certified for unvented systems.

I'm assuming it would be cheapest to get one person to do both services at the same time but unvented engineers are not as common as I thought - of the first two pages in the register nearest to me, only three are registered for unvented. This would mean that if the original installer serviced the boiler I’d need to get another engineer out for the unvented service.

Now my silly question. What is so special about an unvented installer - is it a legal requirement or should a competent gas safe installer be able to carry out a service on one (as opposed to actual installing one).

Thanks

 

[ianmcd]

Call your installer and ask him if he is G3 (unvented) qualified, when you complete ACS courses the element is automatically added to the Gas Safe website, but with unvented you have to send in your qualification and request that it is added, lots have the qualification but dont bother notifying gas safe

 

[bernardgreen]

What is so special about an unvented installer -

an unvented installer is going to be full of self inflated ego......

but seriously..... A poor installation could become a hazard to the safety of people and/or property if the essential safety devices are not fitted or fitted incorrectly

 

[Mottie]

an unvented installer is going to be full of self inflated ego......

but seriously..... A poor installation could become a hazard to the safety of people and/or property if the essential safety devices are not fitted or fitted incorrectly

Understood. It was installed by an unvented registered firm so installation is all good. Just wondered what is actually involved in servicing them - perhaps there is no 'servicing only' qualification, just the full monty and that’s why installers are few and far between? From what I’ve read, servicing consists of repressurising the expansion vessel, cleaning out a gauze filter and checking the pressure relief valve is working or are there other elements of it? I would imagine repressurising the cylinder to be straightforward - there’s enough advice on this forum to do that - and as I've read that most pr valves leak after you test them, perhaps it’s just easier to fit a new valve body complete with valve and filter and be done with it!

 

[bernardgreen]

and checking the pressure relief valve is working

Just how do you test a pressure relief valve that is set to open at say 3 bar pressure when the incoming mains is only at 2 bar pressure at the time of testing ?

Perhaps the air side of expansion vessel can be pumped up to put 3 bar pressure onto the water and see if that opens the valve..

 

[ianmcd]

Just how do you test a pressure relief valve that is set to open at say 3 bar pressure when the incoming mains is only at 2 bar pressure at the time of testing ?

Perhaps the air side of expansion vessel can be pumped up to put 3 bar pressure onto the water and see if that opens the valve..

Nope wouldnt have any bearing on the actual water pressure

 

[Mottie]

I think it’s to release pressure from inside the hot water cylinder. Must surely have some sort of a one-way valve incorporated in the system otherwise hot water under expansion when heated would go back into the mains surely?

 

[bernardgreen]

Nope wouldnt have any bearing on the actual water pressure

Are you saying that increasing the air pressure acting on one side of the membrane will not affect the pressure of the fluid on the other side of the membrane ? This would be true if the membrane was rigid and did not flex as the air pressure varied.

But the question remains un-answered as to how to test a pressure relief valve and ensure it will open at the rated pressure.

 

[ianmcd]

Are you saying that increasing the air pressure acting on one side of the membrane will not affect the pressure of the fluid on the other side of the membrane ?

yep

 

[Mottie]

Both my valves say 6 and 7 bar. Serious question, I’d quite like to know how close to that pressure the hot water system builds up to. If I was to fit a pressure gauge (similar to the one I have for my heating) anywhere on the hot water side of the system, would that give me a true indication of the working pressure in the hot water cylinder and pipes?

 

[ianmcd]

No because the inlet control group will have a pressure reducing valve on it, usually set at 3 Bar, the pressure releif valve is there in case this valve fails and will vent to release excess pressure in the event of a failure

 

[fezster]

Both my valves say 6 and 7 bar. Serious question, I’d quite like to know how close to that pressure the hot water system builds up to. If I was to fit a pressure gauge (similar to the one I have for my heating) anywhere on the hot water side of the system, would that give me a true indication of the working pressure in the hot water cylinder and pipes?

If your EV fails (or your air bubble needs replenishing), you will quickly see the pressure rise on the HW inlet when the cylinder is heating. You will also hear your Pressure Relief Valve slowly start to trickle to release this pressure.