Pressure release valve on converted vented system

[michcosg]

Folks

A customer pointed out a small drip from an overflow pipe coming from a pressure release valve of a heating system they have had converted from being a vented system. The issue would seem to be that the pressure release valve (3 bar is letting by).

My intention was simply to go in and replace their PRV. However it occurs to me that 3 bar seems a little low and is quite likely to blow with the least variation in the water pressure* and hence subsequently let by. Should I maybe install a slightly higher pressure PRV this time or perhaps you might have some other suggestion?

Many thanks

Michael

*They are mind you, 2/3 the way up on a hill which probably means that pressure is generally a little on the low side.

 

[SimonG]

You need to get somebody who knows what they are doing.

 

[diamondgas]

:iagree: your post shows up a great lack of knowledge michcosg. I'd advise that you go no further, explain to your customer that your knowledge is limited and would advise that they get someone else to look at the problem!!

 

[glenno1]

Call a Gas safe plumber

 

[bob the plumber]

michcosg, just wondering if you could tell us why the pressure 'relief' valve is 3 bar

 

[SafeGasInstall]

Hi MIchel ,

I know Michel we worked together on a site about three weeks ago . Michel does not have a much experience but is a good person .
Michel as above , it will be better if a heating engineer have a look .

Stan

 

[sheff paul]

Hi MIchel ,

I know Michel we worked together on a site about three weeks ago . Michel does not have a much experience but is a good person .
Michel as above , it will be better if a heating engineer have a look .

Stan

Must still be lots of work going on down there if ''Michel'' is still in work

 

[bob the plumber]

Must still be lots of work going on down there if ''Michel'' is still in work

Bit harsh, but its good to know your limits

 

[sheff paul]

Bit harsh, but its good to know your limits

ignore that one just me been annoyed cause nothing on next week

 

[diamondgas]

Hi MIchel ,

I know Michel we worked together on a site about three weeks ago . Michel does not have a much experience but is a good person .
Michel as above , it will be better if a heating engineer have a look .

Stan

I think Michel got the message Stan? Hopefully we haven't put him off coming back We've all got to learn somehow and this place offers the avenue to learn if you can take the flack now and again

 

[SafeGasInstall]

I spoke to Michel and invited him here to be regular as he will have ability to learn the theory hear , practice as I advised him I will take him on when I get some business going as I have finished the 8 houses and the builder is not doing any more

 

[SafeGasInstall]

ignore that one just me been annoyed cause nothing on next week

he is not good at plumbing as he is new to the plumbing but he is a good person !!!

 

[glenno1]

It all comes with experience i hope he gets the chance to achieve his goals in these tight times

 

[michcosg]

Yes OK its been about a month since I looked at this side issue whilst looking at a few other problems with their taps etc. And yes I accept I am not Gas Safe and have limited exposure to diagnosing a fault with a converted system such as this.

It would seem on reflection that I have confused the pressure release valve on a mains supply into an unvented cylinder with the pressure release valve on a now closed heating circuit.

To answer Bob the plumbers question: why do I think the pressure 'relief' valve is set to 3 bar - I would have said that is to protect the conventional copper cyclinder. Still seems a bit low to me but notice that the PRV on my combi is also 3 bar so I guess its about right!

However I would ask the question, is really necessary to have someone of considerably more experience in this area to swap out a faulty part? Non Gas Safe plumbers engage with heating systems in many ways I am sure. Have you always known so much about something you have explored? I accept I could do with some guidance. However are people suggesting, that given what I have now stated here, still betrays an unacceptable level of understanding?

That said I do appreciate the feedback and will consider passing this job to Gas Safe colleague if that seems to be the consensus.

Many thanks

 

[bob the plumber]

michcosg, i dont think theres anything wrong with changing a part. But i believe you need to know why it needs changing and what the implications are if you change it for something that is or isnt correct, thats where the training comes in. In this instance you looked at a converted open vented system, so prv is external to regular /standard boiler generally. It could have an expansion problem which has caused it to drip/pass albeit just a knackered prv?? in changing the prv to a higher limited prv say 6 bar or more it would be the entire system that has to contain that excess pressure thus putting massive strain on pipe work and the integrity of the boiler and parts. next thing you know prv has not blown off ...but part of the pipe work or boiler in the house causing a terrible mess at the least, and if its overheating its extremely dangerous!. know you limits, there is stuff out there that even myself as a qualified engineer would walk away from maybe because im not 100% sure and wouldnt take the risk, but im in a better postition to ask with my current experience and qualifications, its knowing your limits like i said...stick to what you know. safegas says your a good lad, so i know you will not mess around with it because you know know the risks enough to decided against it

 

[michcosg]

Thanks Bob

Yes that is a fair point, that there could be a problem with the expansion vessel and indeed so too are your concerns about installing a PRV with a higher pressure threshold. However withstanding my initial mis-description of the issue, part of the reason I think I checked before increasing the size of the valve, was because I realised this was a 'significant change' to the system and therefore needed checking. Changing a PRV (like for like) and indeed checking a pressure vessel are not in my view, significant changes.

I accept though this is new ground for me. I do have some training however - unvented and solar tickets but admit have only applied them to a limited extent. Still maybe I should get a more experienced colleague to at least check my intentions on this occassion.

Thanks again for you input.

M.

 

[cr0ft]

Yes OK its been about a month since I looked at this side issue whilst looking at a few other problems with their taps etc. And yes I accept I am not Gas Safe and have limited exposure to diagnosing a fault with a converted system such as this.

It would seem on reflection that I have confused the pressure release valve on a mains supply into an unvented cylinder with the pressure release valve on a now closed heating circuit.

To answer Bob the plumbers question: why do I think the pressure 'relief' valve is set to 3 bar - I would have said that is to protect the conventional copper cyclinder. Still seems a bit low to me but notice that the PRV on my combi is also 3 bar so I guess its about right!

However I would ask the question, is really necessary to have someone of considerably more experience in this area to swap out a faulty part? Non Gas Safe plumbers engage with heating systems in many ways I am sure. Have you always known so much about something you have explored? I accept I could do with some guidance. However are people suggesting, that given what I have now stated here, still betrays an unacceptable level of understanding?

That said I do appreciate the feedback and will consider passing this job to Gas Safe colleague if that seems to be the consensus.

Many thanks

Michcosg,

I appreciate you have an unvented ticket but if you don't know what the root causes of a T/PRV leak can be, I would get someone in. There are 6 things that would cause the pressure relief valve to leak: -

1.) Pressure reducing valve on inlet control group has failed.
2.) Expansion valve has scaled up, stopping the seal from seating.
3.) Expansion vessel has lost it's charge (maybe air has not been topped up or air/water seal has ruptured).
4.) Cylinder is being back-pressured by mixer taps/showers that don't have a balanced feed.
5.) Expansion vessel installed upstream of the check valve on the inlet control group (I have seen this before).
6.) Cylinder high temperature. This will cause an increase in pressure that will activate the pressure relief valve (it opens at a lower pressure than the TRV).

As you can see there is a lot to investigate. If you are at all in doubt get someone in to help with more experience. Your idea of replacing the EV with one rated for a higher pressure is extremely dangerous. The fact you would even consider it says that (I'm sure with the best intentions) you should not be working on this yourself.

You don't need a gas safe registered engineer for this as the problem is nothing to do with any gas appliance. You just need a competent plumber with an unvented ticket to help you out. Get them in and learn from them. As you are new it may be handy to have a more experienced plumber in your area that you can pass jobs too when you are out of your depth, on the understanding that you can learn from them (i.e. watch and ask questions).

Please get someone else in and learn from them on this one!

 

[secret squirrel]

Michcosg,

I appreciate you have an unvented ticket but if you don't know what the root causes of a T/PRV leak can be, I would get someone in. There are 6 things that would cause the pressure relief valve to leak: -

1.) Pressure reducing valve on inlet control group has failed.
2.) Expansion valve has scaled up, stopping the seal from seating.
3.) Expansion vessel has lost it's charge (maybe air has not been topped up or air/water seal has ruptured).
4.) Cylinder is being back-pressured by mixer taps/showers that don't have a balanced feed.
5.) Expansion vessel installed upstream of the check valve on the inlet control group (I have seen this before).
6.) Cylinder high temperature. This will cause an increase in pressure that will activate the pressure relief valve (it opens at a lower pressure than the TRV).

As you can see there is a lot to investigate. If you are at all in doubt get someone in to help with more experience. Your idea of replacing the EV with one rated for a higher pressure is extremely dangerous. The fact you would even consider it says that (I'm sure with the best intentions) you should not be working on this yourself.

You don't need a gas safe registered engineer for this as the problem is nothing to do with any gas appliance. You just need a competent plumber with an unvented ticket to help you out. Get them in and learn from them. As you are new it may be handy to have a more experienced plumber in your area that you can pass jobs too when you are out of your depth, on the understanding that you can learn from them (i.e. watch and ask questions).

Please get someone else in and learn from them on this one!

Excellent post, saved me getting on my soap box, people having a go at the op, must be gas safe etc.

I'm glad I continued to read the answers people had posted.

 

[Mike Jackson]

Michcosg,

I appreciate you have an unvented ticket but if you don't know what the root causes of a T/PRV leak can be, I would get someone in. There are 6 things that would cause the pressure relief valve to leak: -

1.) Pressure reducing valve on inlet control group has failed.
2.) Expansion valve has scaled up, stopping the seal from seating.
3.) Expansion vessel has lost it's charge (maybe air has not been topped up or air/water seal has ruptured).
4.) Cylinder is being back-pressured by mixer taps/showers that don't have a balanced feed.
5.) Expansion vessel installed upstream of the check valve on the inlet control group (I have seen this before).
6.) Cylinder high temperature. This will cause an increase in pressure that will activate the pressure relief valve (it opens at a lower pressure than the TRV).

As you can see there is a lot to investigate. If you are at all in doubt get someone in to help with more experience. Your idea of replacing the EV with one rated for a higher pressure is extremely dangerous. The fact you would even consider it says that (I'm sure with the best intentions) you should not be working on this yourself.

You don't need a gas safe registered engineer for this as the problem is nothing to do with any gas appliance. You just need a competent plumber with an unvented ticket to help you out. Get them in and learn from them. As you are new it may be handy to have a more experienced plumber in your area that you can pass jobs too when you are out of your depth, on the understanding that you can learn from them (i.e. watch and ask questions).

Please get someone else in and learn from them on this one!

All very informative but not actually pertinent in this case as the leak is from a PRV on a sealed heating system.

 

[cr0ft]

My understanding is he thought it was then realised it was coming from an unvented cylinder setup. If I'm wrong then my post is indeed fairly useless!

 

[SimonG]

I that it was heating, then i thought it was unvented

 

[cr0ft]

Yes OK its been about a month since I looked at this side issue whilst looking at a few other problems with their taps etc. And yes I accept I am not Gas Safe and have limited exposure to diagnosing a fault with a converted system such as this.

It would seem on reflection that I have confused the pressure release valve on a mains supply into an unvented cylinder with the pressure release valve on a now closed heating circuit.

To answer Bob the plumbers question: why do I think the pressure 'relief' valve is set to 3 bar - I would have said that is to protect the conventional copper cyclinder. Still seems a bit low to me but notice that the PRV on my combi is also 3 bar so I guess its about right!

However I would ask the question, is really necessary to have someone of considerably more experience in this area to swap out a faulty part? Non Gas Safe plumbers engage with heating systems in many ways I am sure. Have you always known so much about something you have explored? I accept I could do with some guidance. However are people suggesting, that given what I have now stated here, still betrays an unacceptable level of understanding?

That said I do appreciate the feedback and will consider passing this job to Gas Safe colleague if that seems to be the consensus.

Many thanks

As he stated in his post above, he initially thought it was as Mike Jackson suggested but his later post indicates that it's the pressure relief valve on an unvented cylinder...

 

[mprotsa]

You have to ask yourself what has caused it to leak? Has the boiler/system overheated? What has caused it to over heat? Is the expansion vessel correctly sized? But usually when changing prv's on domestic systems, especially when converted they are specified at 3bar. I would not advise fitting a higher bar eg. 5 bar prv. Higher bar prv's are usually fitted on unvented systems.

 

[Mike Jackson]

Rereading has further post I still think it is on the heating.

 

[mprotsa]

Ignore my previous message. did not follow through all posts

 

[cr0ft]

Rereading has further post I still think it is on the heating.

I guess the key issue is that we would both know how to fix it and the OP clearly doesn't so my advice would be the same in either case. Get someone in who knows their stuff. PRVs of either type are safety devices and messing around with them if you don't know what you are doing can be very dangerous.

 

[SafeGasInstall]

Up date !!!
Went around today . Incorrect conversion from open vent to sealed system !
Combi boiler expansion vesel installed on the hot water flow to cylinder after three port valve ! Expansion vesel connected via a flexy tapconector 15mm and it was twisted so no expansion could be taken ! Advised customer of what need to be done and will be submitting quote to do some work in the house !

 

[SafeGasInstall]

and another thing ,

in the same house there is 4 boilers , but customer is only using 3 as one of the floors in the house is sold to some one else . Loft conversion had a leaking pump valve , long story short .... pump was wired in incorrect and it was changed 15 years ago .

live to live on the pump
neutral to earth on the pump
earth to neutral on the pump

they had very old electrical consumer unit , why did it not trip anything over this time ???????

 

[PlumbBobBob]

probably had an old nail instead of the fuse wire

 

[SafeGasInstall]

my concern was that mains 230v was leaking down the earth and probably due to good earth bond there were no fatality,
I did have a look how it was wired to the wiring center and it was correct but the other end did shocked me as i never seen one before