Low/ No Gas pressure...please help

[sara275]

Thanks Millsy. This could be a possibility as the pipes were exposed during plastering. So just for my reference, when we say blocked pipes, we mean pipes from the first fix?

thanks a bunch

What make and model are both boilers? Will it work if the other boiler is not running? I have worked in a block of 4 flats which runs off a domestic meter and has sub meters (additional for each flat) and the boilers would run when all were on so although you may need a bigger meter it probably wont stop it firing up unless other boiler is running.

To me it sounds like pipework is undersized/Blocked/squashed I have seen all 3 when working it only takes a careless plasterer to get a good lump of plaster in a pipe or somebody to drop something on a pipe to kink it stopping the gas from coming through. You might have an inexperianced gas man but it could be something else I would check them out just for peace of mind but if it is 1 of the last 2 it could happen to anybody. (I now always solder cap ends on to stop plasterers filling the pipes)

Do you know where they have taken the gas pipe from if it was me I would run a seperate feed from near the gas meter or put a good sized pipe from meter until they tee off.

 

[Millsy 82]

Yes it will be pipes put in on the first fix.

I have also put a 22 mm elbow in which had a 15mm cap end in but that blocked completely but would say first fix.

 

[sara275]

hiya

i would prefer a blockage then anything more "complicated". Just for clarification, there is already a boiler in he property. The problem boiler is the second one.

cheers

Hi sara :welcome: to the forum

You're guy needs to check the working pressure at the meter with the boiler on! dropping to zero at the boiler I'd say he's got a blockage somewhere!! A U6 meter will supply about 64kW/hr ... Your guy if he's GSR will know all this. If he's running just the one boiler and the inlet is dropping to zero then he's got a restriction somewhere IMHO! Putting a bigger meter in wouldn't make a hapworth of difference if that's the case IMHO

 

[AWheating]

Hi Sara, don't worry i've had the same treatment on this forum after choosing a 'so called' Gas Safe Registered company to do work and things didn't go right. Stick around and you should eventually get some useful advice!

I agree that it can feel a bit intimidating and like a pack of lions ganging up on you when asking basic questions on here! I can (somewhat) understand the frustration from experienced GSR forum members when others carry out sub-standard work.

the usefull advice is to get a competent engineer, too many so called plumbers give poorly judged answers to questions they dont seem to understand or comprehend the safety issues of. The only correct advise here is to get somebody competent to sort it out.

 

[diamondgas]

hiya

i would prefer a blockage then anything more "complicated". Just for clarification, there is already a boiler in he property. The problem boiler is the second one.

cheers

It maybe that you'll need a larger meter to accommodate the 2 boilers and any other additional appliances, cookers, fires you may have fitted Sara ... However even with them all on that would not account for zero at the boiler though, you'd expect some

Just realised I'm echoing your posts Millsy 82

 

[Resolute]

Having read the further info you've now posted I would suggest taking a working pressure on the original boiler, if this is fine then you can rule out anything wrong with the existing meter and regulator. Then turn off all appliances except the new boiler and see if it fires. If standing pressure is 21mb but drops to zero when it fires it would suggest to me that there is a blockage/restriction in the new pipe run.

 

[Bernie2]

It does seem a bit of an unusual problem. Basically you are looking at two problems I suppose, if you are getting 21mb at the boiler.
If for instance you had a very small pipe going to the boiler, you may still get 21mb, conversely if you had a large pipe you would still get 21mb. The difference being that the large pipe can deliver a lot more gas at 21mb than a small pipe can. So the size of pipe is important. And of course making sure there is nothing blocking the inside of the pipe. I am afraid it is all to common for the likes of plaster to fall down pipes when left open while other trades work in the areas surrounding them. Also solid joints are not uncommon if to much solder has been used.

The usual pressure is 20mb coming out the meter with a permissible 1 mb drop at the appliance. I can't comment on the pipe sizing without a lot more information but just supposing its okay, then why is the boiler not firing?

I assume any air has been released out the gas line? I would have a few bob for every time I had tried to start a boiler on a new install without checking that.

Then of course you have to have a meter that will deliver the required amount of gas for all the flats. The problem is you still need 20mb in the loft with all the other gas appliances turned on. If the pipe is to small or the meter too small you will struggle to get that probably. You can get bigger meters of course but you may come on a different gas price rate if the meter is required to be overly big. It also depends on a few other things as well such as incoming mains sizes and pressures. So its not easy to give you a proper answer. Incidentally I think the meter comes under customs and excise as well as the supplier. I can assure you you do not want customs and excise after you for connecting in the gas main before they have metered it for VAT on the gas.

Try turning all the other gas appliances off in all the flats and then try the boiler. That at least may tell you that the pipe run to the boiler may be okay. What you are actually doing of course is running one boiler off the meter and the meter should be able to cope with that. If the air has not been purged, you can do it yourself by continually firing the boiler until you get a light or if it has a manual gas valve holding the button in flicking the piezo until the pilot light lights. It may take sometime as well, I must admit though the installer should have already done all this for you. Anyway if I can help just post some more and I will try to be a bit more specific.

 

[Millsy 82]

It does seem a bit of an unusual problem. Basically you are looking at two problems I suppose, if you are getting 21mb at the boiler.
If for instance you had a very small pipe going to the boiler, you may still get 21mb, conversely if you had a large pipe you would still get 21mb. The difference being that the large pipe can deliver a lot more gas at 21mb than a small pipe can. So the size of pipe is important. And of course making sure there is nothing blocking the inside of the pipe. I am afraid it is all to common for the likes of plaster to fall down pipes when left open while other trades work in the areas surrounding them. Also solid joints are not uncommon if to much solder has been used.

The usual pressure is 20mb coming out the meter with a permissible 1 mb drop at the appliance. I can't comment on the pipe sizing without a lot more information but just supposing its okay, then why is the boiler not firing?

I assume any air has been released out the gas line? I would have a few bob for every time I had tried to start a boiler on a new install without checking that.

Then of course you have to have a meter that will deliver the required amount of gas for all the flats. The problem is you still need 20mb in the loft with all the other gas appliances turned on. If the pipe is to small or the meter too small you will struggle to get that probably. You can get bigger meters of course but you may come on a different gas price rate if the meter is required to be overly big. It also depends on a few other things as well such as incoming mains sizes and pressures. So its not easy to give you a proper answer. Incidentally I think the meter comes under customs and excise as well as the supplier. I can assure you you do not want customs and excise after you for connecting in the gas main before they have metered it for VAT on the gas.

Try turning all the other gas appliances off in all the flats and then try the boiler. That at least may tell you that the pipe run to the boiler may be okay. What you are actually doing of course is running one boiler off the meter and the meter should be able to cope with that. If the air has not been purged, you can do it yourself by continually firing the boiler until you get a light or if it has a manual gas valve holding the button in flicking the piezo until the pilot light lights. It may take sometime as well, I must admit though the installer should have already done all this for you. Anyway if I can help just post some more and I will try to be a bit more specific.

Or you could test working pressure at meter. If you have 21mbar at meter working and nothing at boiler it will not and can not be air in the pipe as the air will be replaced from gas coming through the meter at between 19-23mbar (21mbar+/- 2) if the other appliances are working it may be that they use alot less gas. An old vaillant vcw gb 242 eh runs at 6.0 mbar high flame so would cope with undersized pipes better than an ecotec plus 831, But if the pressure drops to zero and you have working pressure at meter it will be blocked.

Also if you try to purge a gas pipe through a pilot be prepared to wait a long time. ( there is a proper way to purge but I wont say it here)

 

[AWheating]

Having read the further info you've now posted I would suggest taking a working pressure on the original boiler, if this is fine then you can rule out anything wrong with the existing meter and regulator. Then turn off all appliances except the new boiler and see if it fires. If standing pressure is 21mb but drops to zero when it fires it would suggest to me that there is a blockage/restriction in the new pipe run.

this should be common sense to any gas engineer. This engineer is either an idiot or not a gas engineer??

 

[sara275]

hi all

i can't thank you all enough for the info you have provided so far. Its a lil late now so i cant contact him to get any more info but will hopefully get onto it tomorrow to have him answer/ consider the points mentioned.

i'll sleep a bit better tonight knowing i've had second opinion from some great guys!!!

thanks again