Just moved in to a new house with an 824E combi boiler and I'm sure its pressure relief valve is faulty because the cold pressure has dropped since moving in and water slowly accumulates in the plastic bag I tied over the end of the discharge pipe, outside, to check. Although a competent DIY plumber, this is my first combi and I've only just got used to the complex user manual! From the spare parts diagram, and what I've seen online, the physical replacement of the valve seems only to involve unscrewing the discharge tube from it, removing the valve by unclipping the retaining clip, slipping in the new valve (which I have) and reversing the above procedures. All this is simple enough, but I need help about what needs switching off and on, and in what sequence it should be performed, since I'd like to avoid either water everywhere or air locks in the boiler. If this could all be in the form of step-by-step instructions for the simple minded, then I'd be very grateful indeed. Many thanks.
HELP WANTED IN REPLACING VAILLANT 824E COMBI PRESSURE RELIEF
- Thread starter sukitawdry
- Start date
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as you said basic plumbing, although not a hard task as the book suggests!
it is also a task for the qualified people of the world as it is the internalls of a GAS boiler.
it is also a task for the qualified people of the world as it is the internalls of a GAS boiler.
Thanks for the reply. If you go Forum > Plumbing & Central Heating > Announcement : DIY Gas, you will see the following "Water carrying parts of a boiler unrelated to gas or airflow, can be worked on without gas training, though you still have to be competent, for example electrically." What I'm proposing covers only the water side, without touching the gas or electrical components.
If you know so much, why bother to ask? 
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Your question sounds reasonable enough to me
I don't know your particular boiler, but generally, you have to drain down the boiler first, usually by isolating the feed and return pipes to the radiators using the quarter-turn valves, and then undoing a drain cock under the boiler. Note that the quarter-turn valves may leak a bit afterwards, but tend to seal up again if you're lucky. The PRV can then be removed and a replacement fitted.
I'm not sure how yours is attached, but complete instructions about how to do this are probably in the manufacturer's installation & servicing booklet, which is often downloadable from their website. Well worth reading.
AFAIK, you're right about what you can and can't do as a DIYer, but note that replacement of some seemingly-DIYable parts involves removal of gas-carrying parts or the combustion chamber cover, which would mean that the job is not actually something that you can safely attempt yourself.
Note that I'm only a keen DIY person, not an expert on these things!
Good luck.
EDIT... just realised you said PRV not AAV so have changed what I said
I don't know your particular boiler, but generally, you have to drain down the boiler first, usually by isolating the feed and return pipes to the radiators using the quarter-turn valves, and then undoing a drain cock under the boiler. Note that the quarter-turn valves may leak a bit afterwards, but tend to seal up again if you're lucky. The PRV can then be removed and a replacement fitted.
I'm not sure how yours is attached, but complete instructions about how to do this are probably in the manufacturer's installation & servicing booklet, which is often downloadable from their website. Well worth reading.
AFAIK, you're right about what you can and can't do as a DIYer, but note that replacement of some seemingly-DIYable parts involves removal of gas-carrying parts or the combustion chamber cover, which would mean that the job is not actually something that you can safely attempt yourself.
Note that I'm only a keen DIY person, not an expert on these things!
Good luck.
EDIT... just realised you said PRV not AAV so have changed what I said
Dan_Robinson - Thanks for the incredibly witty and perceptive comment. Tremendously helpful!
ChrisOxford - Thanks for the reply. I think that's right, although I'd tend to favour switching off the cold mains as well as the radiator feed & return! That's three valves to switch off. Can't see a boiler drain plug in the installation manual, but the PRV looks to be about the lowest component, so maybe this does double duty. Could it be as easy as switching the three valves off, removing PVR with a basin underneath, replacing it and switching the three valves back on, refilling via the loop to bring pressure up again and then bleeding radiators, the boiler being self venting? Is it as straightforward as this, you Vaillant experts out there?
ChrisOxford - Thanks for the reply. I think that's right, although I'd tend to favour switching off the cold mains as well as the radiator feed & return! That's three valves to switch off. Can't see a boiler drain plug in the installation manual, but the PRV looks to be about the lowest component, so maybe this does double duty. Could it be as easy as switching the three valves off, removing PVR with a basin underneath, replacing it and switching the three valves back on, refilling via the loop to bring pressure up again and then bleeding radiators, the boiler being self venting? Is it as straightforward as this, you Vaillant experts out there?
You missed the point of my post, as you are talking about an 800 series when you remove the front door it is in essence the combustion chamber seal, the boiler takes it air to burn fro this area, therefor you have affected the sealed combustion chamber. Also in changing the prv you would care to notice a rubber ring round it which is also an integral part of the combustion chamber seal.
Therefor as much as it's only a water part you could inturn damage combustion seals therefor are obliged to carry out regulation 26.9 of the gsiur regulations,
That is probably the reason we seem to be unhelpfull.
Therefor as much as it's only a water part you could inturn damage combustion seals therefor are obliged to carry out regulation 26.9 of the gsiur regulations,
That is probably the reason we seem to be unhelpfull.
Exactly, those who know about boilers realise whats involved.
We are bound by common sense and the forum rules not to give advice on DIY work which should correctly be done by a gas registered person.
Unfortunately, some DIYers like Chris above, will unknowingly give advice which is not correct.
Its a pity the site does not allow those who are gas registered to put the logo after their name.
Tony
We are bound by common sense and the forum rules not to give advice on DIY work which should correctly be done by a gas registered person.
Unfortunately, some DIYers like Chris above, will unknowingly give advice which is not correct.
Its a pity the site does not allow those who are gas registered to put the logo after their name.
Tony
Hi Tony,
But I did take the trouble to emphasise:
and
and to thank Bell824 for his second post which was all the OP needed to know.
It would have been great if that had been said earlier on in the thread. The first two posts weren't of any help to the OP.
Keep up the good work, I always enjoy reading your posts.
C.
Yes, well said.
But I did take the trouble to emphasise:
and
and to thank Bell824 for his second post which was all the OP needed to know.
It would have been great if that had been said earlier on in the thread. The first two posts weren't of any help to the OP.
Keep up the good work, I always enjoy reading your posts.
C.
I bet you could... one of the regulars here seems to have a pic of a foreign Vaillant van appear after every post they make.
That will be the bunnyman witht the van, it isn't foriegn it's the van of old that vaillant engineers used.
As i have pointed out it's not that we don't want to be helpfull, but as agile has said we are duty bound on this one,
Chris if you a regular reader of this forum you will see that tony and dan post very usefull comment's were they can. I must admit like myself thay can get cranky when asked for advice on something diy enthusiasts shouldn't be doing, but as i get the chance to have regular thread conversations in the combustion chamber with them, and also reading their open forum post's i can confirm they are very knowlegable and are willing to help were they can.
Just like most of us.
As i have pointed out it's not that we don't want to be helpfull, but as agile has said we are duty bound on this one,
Chris if you a regular reader of this forum you will see that tony and dan post very usefull comment's were they can. I must admit like myself thay can get cranky when asked for advice on something diy enthusiasts shouldn't be doing, but as i get the chance to have regular thread conversations in the combustion chamber with them, and also reading their open forum post's i can confirm they are very knowlegable and are willing to help were they can.
Just like most of us.
bell824 - No, I don't think I missed the point of it at all. It said, essentially, GAS! - leave it to the professionals. So, reasonably enough, I referred you to the announcement at the head of the P&CH Forum and made clear that I intended only to work on the water side of things.
But I am grateful for your second post, since it explains rather a lot about the familiar protestations of those with vested interests - I take it that you're a professional.
About forty years ago, I designed and installed an open vented gas central heating system. In those days, there was little in the way of legal obligations placed on us amateurs. Of course, I wouldn't have dreamt of doing any such thing without getting the design OKd, the pipework and wiring checked and the commissioning undertaken by a professional heating engineer. It saved me quite a bit of money. And, since then, I've tried to take an intelligent interest in such matters, finding Tolley's particularly useful concerning gas installation, not that I've thought of doing any since that first attempt, so complex have devices become, so endless the legislation and so threatening the penalties.
In all those pages, I cannot recall the definition of a combustion chamber ever being quite so extravagantly extended as to include an unsealed boiler casing! Now, it is true that Vaillant recognise the difference in the %age of CO2 present according to whether the front casing is on or off the boiler, but this difference is as little as 0.2%, while the tolerance allowed for both eventualities is plus or minus 1%! Even so, nothing in Vaillant literature, Tolley's or common sense suggests that the air inside the cabinet, completely "unsealed" from that in the kitchen (and what about all those other leaky holes in the bottom plate, through which pipes pass?) constitutes a "combustion chamber".
Similarly, to claim that the O ring around the seat of the PVR is to provide a gas seal, rather than the stunningly obvious water seal it is, seems, pardon me, arrant nonsense.
I'm not really interested in engaging with those who feel deeply threatened by the slightest suggestion that a water side component replacement is a serious breach of the regulations. As I said, this is my first combi boiler and I had wondered, in all innocence, if anybody could tell me if I'd got it right (as above) or not. Any takers?
But I am grateful for your second post, since it explains rather a lot about the familiar protestations of those with vested interests - I take it that you're a professional.
About forty years ago, I designed and installed an open vented gas central heating system. In those days, there was little in the way of legal obligations placed on us amateurs. Of course, I wouldn't have dreamt of doing any such thing without getting the design OKd, the pipework and wiring checked and the commissioning undertaken by a professional heating engineer. It saved me quite a bit of money. And, since then, I've tried to take an intelligent interest in such matters, finding Tolley's particularly useful concerning gas installation, not that I've thought of doing any since that first attempt, so complex have devices become, so endless the legislation and so threatening the penalties.
In all those pages, I cannot recall the definition of a combustion chamber ever being quite so extravagantly extended as to include an unsealed boiler casing! Now, it is true that Vaillant recognise the difference in the %age of CO2 present according to whether the front casing is on or off the boiler, but this difference is as little as 0.2%, while the tolerance allowed for both eventualities is plus or minus 1%! Even so, nothing in Vaillant literature, Tolley's or common sense suggests that the air inside the cabinet, completely "unsealed" from that in the kitchen (and what about all those other leaky holes in the bottom plate, through which pipes pass?) constitutes a "combustion chamber".
Similarly, to claim that the O ring around the seat of the PVR is to provide a gas seal, rather than the stunningly obvious water seal it is, seems, pardon me, arrant nonsense.
I'm not really interested in engaging with those who feel deeply threatened by the slightest suggestion that a water side component replacement is a serious breach of the regulations. As I said, this is my first combi boiler and I had wondered, in all innocence, if anybody could tell me if I'd got it right (as above) or not. Any takers?
As you rightly said yes i am a proffesional, and in fact repair vaillants for a living.
As for what the mi's say about the co2% tolerances being differnt for the case off or on and swing in % is to confirm correctly set up gas valve.
As for those holes is the bottom of the appliance where the pipes pass through i think you will also find these have what are known as back nuts that bring to pieces together tightly around the casing.
As for the glaringly obvious(as you put it) rubber seat around the prv as it exits thhe boiler it is indeed not a water seal and is infact a seal for the combustion chamber, if you would care to notice the same seals are used under the left hand side of the boiler for the cable entry points.
As for the fact YOU don't understand why these are all classed as combustion chamber seals and if tampered with could potentially lead to a dangerous situation, i will explain that they are there so that the fan only takes it air from the combustion box that is drawn in from the outer flue, unlike older boiler's were the combustion chamber and water sections were totally seperate, the diy on water sections is easier to explain in those.
I will repeat that yes i am a proffesional and as such know that this type of work on this boiler requires regulation 26.9 of the gas safety installation and use regulations needs to be satisfied as you couls have impaired the safe working of this appliance.
In no uncertain term's am i being podantic or flippant about this but trying to get you to understand that this is not diy'able work is diffucult.
You have probably removed any other proffesional persons interest in assisting you with the comments you have returned to us when we are just trying to inform you it is not diy work.
Serious breach it may not be but a breach just the same, and in your innocence of asking the question i feel i have done all i can to point you in the right direction.
As for what the mi's say about the co2% tolerances being differnt for the case off or on and swing in % is to confirm correctly set up gas valve.
As for those holes is the bottom of the appliance where the pipes pass through i think you will also find these have what are known as back nuts that bring to pieces together tightly around the casing.
As for the glaringly obvious(as you put it) rubber seat around the prv as it exits thhe boiler it is indeed not a water seal and is infact a seal for the combustion chamber, if you would care to notice the same seals are used under the left hand side of the boiler for the cable entry points.
As for the fact YOU don't understand why these are all classed as combustion chamber seals and if tampered with could potentially lead to a dangerous situation, i will explain that they are there so that the fan only takes it air from the combustion box that is drawn in from the outer flue, unlike older boiler's were the combustion chamber and water sections were totally seperate, the diy on water sections is easier to explain in those.
I will repeat that yes i am a proffesional and as such know that this type of work on this boiler requires regulation 26.9 of the gas safety installation and use regulations needs to be satisfied as you couls have impaired the safe working of this appliance.
In no uncertain term's am i being podantic or flippant about this but trying to get you to understand that this is not diy'able work is diffucult.
You have probably removed any other proffesional persons interest in assisting you with the comments you have returned to us when we are just trying to inform you it is not diy work.
Serious breach it may not be but a breach just the same, and in your innocence of asking the question i feel i have done all i can to point you in the right direction.
bell824 - Apologies, we are at cross purposes! The O ring I referred to is item 35 in diagram 08 Connection parts (Hydroblock) in the Vaillant spares catalogue for the 824E, clearly a water seal, but you are referring to the grommet, item 37. Also, it doesn't help matters that I'm writing all this away from home, with only online diagrams to light the way and no boiler in front of me. Never a good idea.
I do appreciate from your last post that you are only trying to do what's right, for which I thank you. But, what it comes down to is this. Someone who has had the satisfaction of designing and installing a CH system simply can't be trusted to replace a PVR AND ensure that an O ring and grommet are properly seated. I'm afraid that, as I get older, I no longer recognise this madhouse as the country I grew up in.
Many thanks to everyone who contributed to this thread.
I do appreciate from your last post that you are only trying to do what's right, for which I thank you. But, what it comes down to is this. Someone who has had the satisfaction of designing and installing a CH system simply can't be trusted to replace a PVR AND ensure that an O ring and grommet are properly seated. I'm afraid that, as I get older, I no longer recognise this madhouse as the country I grew up in.
Many thanks to everyone who contributed to this thread.
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