Unvented cylinder relief valve letting by

[John.g]

There are two or threes things about G3.

1. people who do it and mess with your system take a legal responsibility for your system as they are designated 'competent'.
2. doing an exam (it's open book by the way) is only the start. Any good engineer applies their knowledge & intelligence as you have. They are harder to find...
3. many people who attend these courses have not the first idea about the systems they are then legal to work on. The people teaching often have zero idea either. Their job is to get the 'bum on the seat' out the door and recommending. Welcome to education 21st century stylie!

I've been doing UVCs for many years. I knew immediately what the issue was and yet tonight I learned even more. Thank you John.G

Thanks, I have attached a extract from a S.Sheet calculation that I did 100? years ago, I think you and others may find it interesting. John

 

[Bwani]

Thanks All.
John.g, there are only two relief valves -one at 3.5 and the tprv at 4.5. I presume you mean the latter by 'tribune relief valve' , or perhaps you refer to newer systems that have additional third valve ?

 

[John.g]

Thanks All.
John.g, there are only two relief valves -one at 3.5 and the tprv at 4.5. I presume you mean the latter by 'tribune relief valve' , or perhaps you refer to newer systems that have additional third valve ?

Yes, I'm referring to the tprv.

 

[Welder]

tprv is the Temperature & Pressure relief valve. The last line of defence...

 

[John.g]

Many thanks.

These are exactly the parameters i need to know and expect a g3 would be able to know

It explains why even 2.8 would blow the relief valve.

Perplexing how someone can pass g3 and not realize this immediately.

Thank you for this.

What you say is consistent with the spec label.

At correct pressure charge the 24 litr i have is adequate.

Thermostat has only gradings with no temp indication but it is a 3 kw and says not to exceed 65 which is then near maximum presumably. Measured at hot tap it is around 45 deg with a fever thermometer . This includes losses in the pipe and inaccuracies . So 60-70 in tank is about right.


The mistake is clearly that the plumber charged it up to 3.5 so of course leaves no space fo expansion. Prior to servicing it was 2. 8, still too high. I am stumped why instead of putting to 2 he raised to 3.5.

I believe he did shut off water and open a tap when charging up oherwise the pump would not budge I imagine.

Bottom line is :
get someone else to
Confirm mains is 2
Shut water and open tap
Bring down recharge pressure to 2.1
Refill and reheat.
I doubt new relief valve is faulty. Likely the other was not faulty either !

I am 400 quid poorer and not fixed yet. At least i deserve a g3 more than these cowboys surely .

Thank you for this.

What you say is consistent with the spec label.

At correct pressure charge the 24 litr i have is adequate.

Thermostat has only gradings with no temp indication but it is a 3 kw and says not to exceed 65 which is then near maximum presumably. Measured at hot tap it is around 45 deg with a fever thermometer . This includes losses in the pipe and inaccuracies . So 60-70 in tank is about right.


The mistake is clearly that the plumber charged it up to 3.5 so of course leaves no space fo expansion. Prior to servicing it was 2. 8, still too high. I am stumped why instead of putting to 2 he raised to 3.5.

I believe he did shut off water and open a tap when charging up oherwise the pump would not budge I imagine.

Bottom line is :
get someone else to
Confirm mains is 2
Shut water and open tap
Bring down recharge pressure to 2.1
Refill and reheat.
I doubt new relief valve is faulty. Likely the other was not faulty either !

I am 400 quid poorer and not fixed yet. At least i deserve a g3 more than these cowboys surely .

Assuming cold water relief valve still lifting/feathering and
ONLY until you get some competent person in and while I am always mindful of safety requirements etc I don,t think you would be contravening any safety regulations per se by doing the following, if not already done so....with no hot water usage and ensuring "whole" cylinder heating on, and near or at cut out temperature (both, or bottom immersion on) slowly release the E.vessel air pressure until the PRV (cold water) reseats. ( I am assuming no pressure gauge fitted anywhere)