Just had a Vaillant 831 installed..Installer having problems and vaillant said it was gas. Error F28. Bear with me as don't know much about this but it's bugging me. There is 22millbars of gas at meter and drops to 21mb when hob is turned on so guvnor is ok. However, at boiler pressure is 22mb and when boiler turns on drops to zero. There is 22 inch pipe from gas metre for about 5metres and then it changes to 15inch to the boiler for about 3 metres so we thought this was the problem. So we changed to 22 inch all way to boiler and pressure is still dropping from 22 to zero.. it hasn't made an ounce of difference. The boiler was dropped by the courier, could it have broken something inside. Vaillant insissited it's gas and don't want to change to inch pipe for it still not to work. Installer will sort this but just want to hear what people think as it's driving me crazy as I'd like to understand it a bit more.
New Vaillant Boiler - no working pressure!!
- Thread starter taragee
- Start date
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has your installer checked all the pipework run to the boiler it sounds like something has got in there causing a restriction possibly dirt. id check the isolation under the boiler it wont harm in taking the flex pipe connecting on the gasvalve.
Hope you get it sorted
nath
Hope you get it sorted
nath
What is the working pressure at the meter when the boiler tries to fire up?
I could tell you in one second what it is but it's gas related so need to get your installer back to sort it he should be able to fix if not, get a rgi out that can and charge the installer. Oh just so you know its not the boilers fault it's install fault and don't think the pipe size is a issue
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think it was about 21.. I know nothing about boilers but from what I've listened to these guys over last week.. I just don't understand how it drops to zero.
they were talking about changing all the pipe to one inch which will cost me a fortune and wreck my house.. am I still going to have the problem? it's hard with these people as I don't know what I'm talking about you have to take their word for it..
Still trolling joe?
It drops to zero because when your appliance fires it pulls gas through to the burner however if you have a restriction then you will not get the correct working pressure. if you have 22mbar at the meter then you should have no less than 21mbar as you are allowed to lose 1mbar across you pipework. me personally thinks theres something in the pipe.
thanks Bellair...
The gas goes from meter to the hob then to the bolier. My old boiler (not combi) worked fine and the hob works fine. Could a blockage be in that pipe as maybe the hob and old boiler didn't need much pressure so I never noticed there was a problem?
I don't think blockage from hob to boiler as they tested a new 22 pipe from hob to boiler today and still dropped to zero..
it's a shame you can't test pressure at hob to see if it's still 22 there...I did ask that and they said there isn't a test point, that would tell me if the block was between the meter and the hob.. all the pipe between these two points are under floorboards and then there's chipboard under floorboards.. trying to avoid wrecking my house and preventing the pulling up of floors..
The gas goes from meter to the hob then to the bolier. My old boiler (not combi) worked fine and the hob works fine. Could a blockage be in that pipe as maybe the hob and old boiler didn't need much pressure so I never noticed there was a problem?
I don't think blockage from hob to boiler as they tested a new 22 pipe from hob to boiler today and still dropped to zero..
it's a shame you can't test pressure at hob to see if it's still 22 there...I did ask that and they said there isn't a test point, that would tell me if the block was between the meter and the hob.. all the pipe between these two points are under floorboards and then there's chipboard under floorboards.. trying to avoid wrecking my house and preventing the pulling up of floors..
F
fishhead1
He maybe testing at the wrong point 
oops,didn't see the f28
oops,didn't see the f28
I've had this before but had 4 mb at the boiler on a glowworm combi, it turned out to be 7 3" 10 screws in the gas pipe. Or a blockage/restricted service pipe.
As said it's not the pipe if it gose to zero!!!! You can test the hobs working pressure. The installer said he would fix it so let him. The blockage isn't in the pipe but would be caused by the pipe vails suffer from it because they are not turd so protect them selves. Can I ask are you a unregistered installer trying to fix your cowboyness by coming on a forum before you get caught? You seem to be asking for a fix on the problem and have all the values from meter to boiler and so on???
Size Matters.
A lot of engineers I've come across have used whatever pipe size the entry to the boiler happens to be, for whatever run.
It could be that they have used 15mm to supply your appliance, but the run (total length) of pipe leading up to the appliance is incorrectly sized.
Incorrectly sized, or as mentioned, restricted in some way.
Your best bet is to get a tape measure, pen and some paper.
This will require some physical work, but it will all be worth it.
Go to your gas meter and draw a diagram of the pipework from the gas meter to ALL of your gas appliances.
Ideally, it would be good if you could break it up into A-B, B-C, B-D and so on...
A being your Meter, B being the joint between splitting off to your Hob (C) and your Boiler (D).
For every bend or tee, we add 0.5m to the total length (for arguments sake! I know it should be 0.3 and 0.6 blah blah blah)
Finally, we will need to calculate what amount of gas you require to get to each destination (C & D), something we will calculate for you.
Then its a case of working out how much pipe can carry the required amount of gas to each section.
If you notice anything, such as, as mentioned, a nail stuck into the pipe, then obviously this is your restriction and we can abort the mission
If not, and we calculate the pipes to be the sizes already installed, you will require your engineer/installer to physically check the installation for blockages.
A lot of engineers I've come across have used whatever pipe size the entry to the boiler happens to be, for whatever run.
It could be that they have used 15mm to supply your appliance, but the run (total length) of pipe leading up to the appliance is incorrectly sized.
Incorrectly sized, or as mentioned, restricted in some way.
Your best bet is to get a tape measure, pen and some paper.
This will require some physical work, but it will all be worth it.
Go to your gas meter and draw a diagram of the pipework from the gas meter to ALL of your gas appliances.
Ideally, it would be good if you could break it up into A-B, B-C, B-D and so on...
A being your Meter, B being the joint between splitting off to your Hob (C) and your Boiler (D).
For every bend or tee, we add 0.5m to the total length (for arguments sake! I know it should be 0.3 and 0.6 blah blah blah)
Finally, we will need to calculate what amount of gas you require to get to each destination (C & D), something we will calculate for you.
Then its a case of working out how much pipe can carry the required amount of gas to each section.
If you notice anything, such as, as mentioned, a nail stuck into the pipe, then obviously this is your restriction and we can abort the mission
If not, and we calculate the pipes to be the sizes already installed, you will require your engineer/installer to physically check the installation for blockages.
I'm flattered. I work in marketing for a mobile network and knew nothing about boilers since I had this thing fitted last week. I'm nosey and curious and don't like it when I don't know what's wrong. I know I don't know what I'm talkking about but I'm not stupid and logic tells me it isn't the pipe because of what they tested today as it made no difference. And it's bugging me as Vaillant also mentioned running a one inch pipe down the side of my house yesterday. I'm trying to prevent uneccessary ruin to my house and I don't trust any of them! Now if we were taliking mobile phones then I'd be running circles round the lot of you!
That's just it though.... You're being told by several qualified and experienced engineers, it is likely to be a fault with the gas pipework.
If VAILLANT are telling you, then I'd be inclined to pay attention... It is, after all, their boiler.
The fact that your hob works fine is completely irrelevant.
You need to calculate your pipework sizes, and confirm they are large enough to carry the amount of gas your Boiler requires when in operation.
If Vaillant have said you require 1inch diameter pipework, I have a distinct feeling it is currently 15mm pipework on a large run, and it's just not coping.
If VAILLANT are telling you, then I'd be inclined to pay attention... It is, after all, their boiler.
The fact that your hob works fine is completely irrelevant.
You need to calculate your pipework sizes, and confirm they are large enough to carry the amount of gas your Boiler requires when in operation.
If Vaillant have said you require 1inch diameter pipework, I have a distinct feeling it is currently 15mm pipework on a large run, and it's just not coping.
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