Gas pressure problems, use of MDPE pipe outside?

[Brian99]

Hi,

I've just had a new combi boiler fitted in my bungalow (37kW) and the existing 22mm pipe (routed through the loft) is not good enough to maintain the pressure and support the gas flow (the many elbows don't help here and the loft is now converted so cant gain access easily!). Gas meter is outside on gable end.

My only option seems to be to run an external 28m pipe round the outside from the meter position to the boiler (approx 20m) but I do not like idea of an external copper pipe on grounds of electrical safety, asthetics and the very real threat of copper theft.

So, my question is, can I lay an underground MDPE plastic pipe and have this made off onto the meter and boiler? What joints are required and can MDPE be brought into the hosue? My plumber suggests plastic cnnot be used, but as its all UG I can't see why not. :icon12:

Incidentally, the gas board were called in as the presure at the meter was also way too low and they have instaled a biger plastic pipe in place of the not so old plastic pipe. They were prompt though.

Thanks.

 

[fuzzy]

whats wrong with copper outside?

dont think you can use any plastic after meter, must be metal

 

[Brian99]

Hi,

Thanks for your interest.

Besides the fact that copper theft is rife, the wiring regs do not allow earth bonding to be taken outside a building if on a PME supply. As a copper pipe would be bonded inside, the 20m of exposed copper pipe back to the meter would present an electrical touch potential hazard in the event of a neutral fault. I know its done, but its not always safe and besides that 20m of copper running along the building will look awful. Far safer to burry it, hence my question about using plastic, just like the incoming service.

 

[SimonJohns]

Plastic can be used

You will have to have someone with a commercial ticket thou. I think you will def exceed a Dom ticket for installation

It will have to be of the yellow mdpe. And will need to be installed to the regs, of which there are many.

 

[mikimac]

The answer is fairly simple if you are gas qualified and have access to a G1. I also think that if your plumber is gas qualified & used the pipe sizing given in the G1 they would have told you prior to the installation of the new 37kw boiler that a 22mm run of "approx 20m" was insufficient. Also, By giving you the answers to the questions you have asked & the fact that you seem to intend to carry out this work yourself would mean as a Gas Safe Registered engineer, I would be in contravention of the regulations & liable to prosecution. My advice is simpler still.. Get a Gas Safe Registered engineer.

 

[Brian99]

It would appear you are suggesting I shouldn't have had a 37kW boiler fitted? The gas pressure problem was always a possibility and now its here a solution is sought. I am not Gas Safe Registered and do not intend to touch or alter any gas connections and will employ a gas safe registered person to do this (preferably the plumber who installed the boiler). However, I would like to explore the options with open minded experts before committing to one solution or another and discuss the relative technical constraints. I thought that was the purpose of forums such as this?

By the way, how many copper pipes have you left exposed outside that are connected to internal house bonding on a PME service? I don't want you to worry about it and I'm quite happy to share my concerns without fear of prosecution.

 

[Gray0689]

I guess you was told gas supply was inadequate but you still went ahead with it did not want to spend the money I guess well your plumber should not of installed the boiler with out upgrading the gas supply great plumber I'd love him to work on my house lol NOT

 

[stevetheplumber]

it can be buried in mdpe copper or steel and can be done with a domestic qualification

 

[mikimac]

No, there's nothing wrong with having a 37kw boiler fitted but as i said in the previous post the correct sizing for the pipework & the materials to be used should have been carried out PRE installation of the boiler & your plumber (if he is GSR) should have done this simple calculation. The gas pressure problem wasn't so much a possibility but rather a guaranteed fact & a GSR plumber would have known this straight away.

I'd suggest you give the plumber who installed the boiler a call & firstly verify his Gas Safe Registration & then go over what you want doing. Failing that, the Gas Safe Register website has a find a registered engineer page where you can input your postcode & a list of engineers in your area who are qualified to carry out this work will be happy to help you.

 

[Hardy1]

for a 20m run of external pipework then going into a bungalow, i would be running 32mm mdpe, has your engineer not checked his pipe sizing?( just saying cause i had to run a external MDPE run with a engineer about 2 weeks ago and we run 32mm and it was about a 18m run.

 

[fuzzy]

Hi,

Thanks for your interest.

Besides the fact that copper theft is rife, the wiring regs do not allow earth bonding to be taken outside a building if on a PME supply. As a copper pipe would be bonded inside, the 20m of exposed copper pipe back to the meter would present an electrical touch potential hazard in the event of a neutral fault. I know its done, but its not always safe and besides that 20m of copper running along the building will look awful. Far safer to burry it, hence my question about using plastic, just like the incoming service.

gas pipes have main bonding and you say this cannot be run then outside? whats PME system in simple terms and how do we spot it

 

[Destroyer2813]

What about the numerous earth bonding cables taken outside and bonded within the meter box or is that not PME SUPPLY ?

 

[AWheating]

you can bond inside the meter box right?

pme = protective multiple earthing and its the most common used today. I have never read that the position of the bonding is different from one earting system to another, but its been a while since i opened the book.

normally its within 600mm of the meter or can be on entry into the building if the box is external or in the ground. Its unlikely in any event that the position of the bonding clamp be a huge factor in the safety of the installation especially with rcd's.

where is the exsisting bonding?

 

[fuzzy]

as they must be bonded anyway can anyone tell me what difference it makes to have the copper pipe run outside?

 

[AWheating]

nothing really.

 

[fuzzy]

thats the bit i dont get?

 

[fuzzy]

anyone shed any light?

 

[Halesowen1]

I cant see it either, if it has been bonded inside what difference is it then to run on an outside wall as it would be to run up an hallway wall where a child could touch??

 

[mikimac]

anyone shed any light?

Nope..If its bonded - its bonded it doesn't matter where it runs

 

[SimonJohns]

Would I be right in saying that it has to be bonded after the pipe enters the dwelling to prevent 'perceived shocks'

If it was to be bonded outside. There's is a possibility that any stray voltage could be picked up by someone outside the property and receive a shock. If it is bonded inside there is more chance the stray voltage would be picked up by the bond

Also bonding inside reduces the chance of corrosion of the bond

 

[stani]

Brian99, where abouts in the wiring regs does it say you cannot bond external on a PME system?

 

[mikimac]

@ Simonjohns, no, the gas pipe has to be bonded within 600mm of the meter to the point of entry into the building. So if possible it can be bonded in the meter box or on any exposed pipework within 600mm of the meter or at the nearest point where it has entered the property within 600mm of the meter box.

 

[mikimac]

Brian99, where abouts in the wiring regs does it say you cannot bond external on a PME system?

It doesn't :bucktooth:

 

[Destroyer2813]

Within first 600mm and before first tee

 

[fuzzy]

It doesn't :bucktooth:

ive never heard of this and i dont see the issue anyway, is he getting mixed up with were the boding is as opposed to where the pipe runs?
if you read his post he has kindly agreed to discuss this with us without fear of prosecution

 

[Halesowen1]

Must be a huge bungalow to require a 37kw boiler.

 

[fuzzy]

Must be a huge bungalow to require a 37kw boiler.

and an incredible amount of bonding required

there is no way that a bungalow unless greater than 8 bedrooms (even then?) would require 37kw for heating so it must be for hot water, begs the question why not fit unveneted?

 

[Halesowen1]

Seems there was no thought or planning into this job.

 

[fuzzy]

poor planning yet the issue is bonding

 

[Halesowen1]

I am looking at the gas supply, a huge run of 22mm to feed a gas thirsty 37kw boiler. Never stood a chance, I have seen 30KW boilers drop 3mb working pressure with 6m of 28mm in a 20m run.
Problem is this is a huge problem in our trade but many engineers dont have a clue how to check working pressures and gas rates etc, and many more cannot be bothered.
I have done a lot of inspecting and auditing in my time and half the boilers out there have more than 1mb drop in working pressure.

 

[fuzzy]

i have spoke to people who think there should be a 1mb drop, not that it is the max permissable!!!!!!!!

to be fair, in many cases you get away with it, if working pressure 23mb at meter and burner pressure needs to be 18mb you can get away with 5mb drop

i know the incoming could drop and it shouldnt be allowed but tis one of the reasons many ignore it

 

[Halesowen1]

You wont get away with it at any of my local councils nor on Warmfront scheme, if its got more than 1mb drop then you upgrade the gas.

 

[fuzzy]

You wont get away with it at any of my local councils nor on Warmfront scheme, if its got more than 1mb drop then you upgrade the gas.

wont get away with it, who checks?

 

[Halesowen1]

Inspectors.
Its in gas regs for a reason, aint it At Risk?

 

[fuzzy]

how many inspectors check your pressure drop across a system and on how many installations? you said people wont get away with it, but they do