Low inlet gas pressure - Worcester Greenstar 42CDI bolier

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I've just had a Worcester Bosch Greenstar 42CDI combi boiler installed (replacing my old traditional system). The problem we've got is that the gas fitter (who's Corgi registered etc) only measures 14 mb of gas pressure at the meter - he needs 18mb in order to commission the boiler. We called Transco and they came round and said there's no problem with the supply - they measured 30mb from the pipe going into the house and according to them they're only obliged to supply 19mb, so there's nothing they can do. They reckoned the boiler's too big (and that modern combi boilers are putting too much demand on existing domestic systems), although it was 8pm on a saturday night and they were on call so I'm reluctant to believe all they say. I've got a three bed semi, which I could easily put a loft extension with en suite into so I should be entitled to use a larger domestic boiler. Either way, I'm stuck with a boiler on my wall that we can't return but we also can't use as the gas fitter can't sign it off. Has anyone had a similar experience or got any advice? Is there a part that can be changed to downgrade it to a 37CDI for example?Cheers.
 
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JB277 said:
I've just had a Worcester Bosch Greenstar 42CDI combi boiler installed (replacing my old traditional system). The problem we've got is that the gas fitter (who's Corgi registered etc) only measures 14 mb of gas pressure at the meter - he needs 18mb in order to commission the boiler. We called Transco and they came round and said there's no problem with the supply - they measured 30mb from the pipe going into the house and according to them they're only obliged to supply 19mb, so there's nothing they can do. They reckoned the boiler's too big (and that modern combi boilers are putting too much demand on existing domestic systems), although it was 8pm on a saturday night and they were on call so I'm reluctant to believe all they say. I've got a three bed semi, which I could easily put a loft extension with en suite into so I should be entitled to use a larger domestic boiler. Either way, I'm stuck with a boiler on my wall that we can't return but we also can't use as the gas fitter can't sign it off. Has anyone had a similar experience or got any advice? Is there a part that can be changed to downgrade it to a 37CDI for example?Cheers.

You should expect a reading of at least 21mbar at meter as a working pressure, if you have not got this then your regulator is faulty. It needs to be changed. If your fitter has a reading of 14mbar, after Transco have already told you that your pressure at the meter is 30mbar I would suggest changing your gas installer, preferably to someone who has a clue.
 
You're not the first and won't be the last.

The Transco guy:

They reckoned the boiler's too big (and that modern combi boilers are putting too much demand on existing domestic systems),

Although not really qualified to comment is not completely wrong.

IMHO if people want more hot water they should use a system that doesn't need nearly three times the gas supply that was the case with older style systems. Its just plain silly. a 35kW combi is more than powerful enough for properties that suite a combination boiler. If it does not provide the volume of water then you should have a more appropiate system fitted.

To give you more practical advise then I would suggest you need a larger supply pipe brought in from the street.

You'll be wishing for a Megaflo once you see the costs of that.. :eek:


Lecture over - sorry...
 
Standing pressure is largely irrelevant - if the dynamic pressure at the meter is low despite a new reg being fitted then the service pipes are too small.

42Kw is silly for a combi IMHO and most domestic pipes will struggle as they simply weren't ever meant to carry that much gas.
 
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Dan_Robinson said:
You're not the first and won't be the last.

The Transco guy:

They reckoned the boiler's too big (and that modern combi boilers are putting too much demand on existing domestic systems),

Although not really qualified to comment is not completely wrong.

IMHO if people want more hot water they should use a system that doesn't need nearly three times the gas supply that was the case with older style systems. Its just plain silly. a 35kW combi is more than powerful enough for properties that suite a combination boiler. If it does not provide the volume of water then you should have a more appropiate system fitted.

To give you more practical advise then I would suggest you need a larger supply pipe brought in from the street.

You'll be wishing for a Megaflo once you see the costs of that.. :eek:


Lecture over - sorry...

Sorry you are missing the point. Transco have told the customer that his meter is delivering more than the required gas pressure. The gas fitter is saying that his meter isn`t. Should I draw you a picture Dan the Man? ;)

I meant your working pressure should be at least 21mbar, sorry for my confusion.
 
I have to disagree with the above comments and am assuming your installer correctly knows how to mesure the working pressure at the meter outlet.

Firstly Transco (now Southern Gas Networks) quality of "engineers" can vary in their abilities by a considerable margin (I had 7 out on one job before they understood the problem - its real hit and miss affair).

They have measured the street pressure at 30 mbar which is fine.

Your installer measured 14 mbar working pressure at the meter which is very low - it should be 21 plus/minus 2 mbar.

There is either a problem with the governor on the meter or the service pipe from the street main to your meter is partially blocked. Transco engineers frequently do NOT know how to distinguish between the two faults.

Call Transco back and get them to resolve the problem. A domestic gas supply will easily handle your boiler. Unless they start to print anything to the contrary in your gas supply contract they are just making excuses.

It is often worth getting your installer to visit the surrounding properties to check the working pressures - you can then get a genuine idea of the street pressures. Sometimes if you are on the end of the distribution pipework the street pressure can be very low (14 mbar) and it is true to say there is nothing that can be done until the network is upgraded. Some parts of Mitcham experience these low pressures. However your street pressure appears OK.

They may change the governor (low cost to them) and still find a problem. That leaves a blocked service pipe (expensive repair to them) so they are often reluctant and make excuses. Last time a customer of mine had a problem they had the road up and a weeks work to sort out.


42Kw is nothing for a domestic meter, its equivalent to a "normal" sized combi and a cooker...routine installation.
 
Gasguru said:
I have to disagree with the above comments and am assuming your installer correctly knows how to mesure the working pressure at the meter outlet.

Firstly Transco (now Southern Gas Networks) quality of "engineers" can vary in their abilities by a considerable margin (I had 7 out on one job before they understood the problem - its real hit and miss affair).

They have measured the street pressure at 30 mbar which is fine.

Your installer measured 14 mbar working pressure at the meter which is very low - it should be 21 plus/minus 2 mbar.

There is either a problem with the governor on the meter or the service pipe from the street main to your meter is partially blocked. Transco engineers frequently do NOT know how to distinguish between the two faults.

Call Transco back and get them to resolve the problem. A domestic gas supply will easily handle your boiler. Unless they start to print anything to the contrary in your gas supply contract they are just making excuses.

It is often worth getting your installer to visit the surrounding properties to check the working pressures - you can then get a genuine idea of the street pressures. Sometimes if you are on the end of the distribution pipework the street pressure can be very low (14 mbar) and it is true to say there is nothing that can be done until the network is upgraded. Some parts of Mitcham experience these low pressures. However your street pressure appears OK.

They may change the governor (low cost to them) and still find a problem. That leaves a blocked service pipe (expensive repair to them) so they are often reluctant and make excuses. Last time a customer of mine had a problem they had the road up and a weeks work to sort out.


42Kw is nothing for a domestic meter, its equivalent to a "normal" sized combi and a cooker...routine installation.

I know, read my apology above. ;)
 
I read it that the meter is NOT delivering the required gas. They have 30mBar standing (so what?) and 14mBar working at the meter.

Obviously if this is 14mBar at the boeilr then the installer is a plank and they need a new internal supply.
 
Cheers Dan & Bambergaspipe, Dan's actually right though - the 14mb was when the boiler's running full whack and the 30mb was the standing pressure, so I don't think my gas fitter's wrong in that respect. However, it does seem that the boiler I've got is way bigger than I need - I didn't realise there was this gas flow issue when I chose the boiler, otherwise I'd have gone for a slightly smaller one. Hindsight is a wonderful thing. But do you know if I can get a part changed to convert the boiler down to a 37CDI? I don't want to go down the road of laying larger inlet pipes etc etc.
 
Is the 14mBar DEFINATELY being measured at the meter? if not then it could be a problem with your house supply pipe rather than hte national grid's end.

I doubt there is an easy conversion - but the wall frame is probably the same (haven't got time to check the documents) so it MIGHT be an easy swap. If your pressure is that low though even a 37CDi might be too much still.
 
JB277 said:
I didn't realise there was this gas flow issue when I chose the boiler

There isn't a gas flow issue normally when choosing a boiler. You have a domestic sized boiler that will happily work off a domestic meter and supply.

The street pressure is 30 mbar. The working pressure at the meter is 14mbar.

EITHER the governor on the meter is faulty OR the service pipe from the street main to your meter is blocked.

Call Tansco and get it sorted. As I said Transco "engineers" often havn't a clue when it comes to blocked service pipework. Get your installer to talk to them - this is routine stuff and digging up the road and garden to renew the pipework is sometimes necessary but very expensive for them so they like to make excuses.


What area of London are you?
 
JB277 said:
Cheers Dan & Bambergaspipe, Dan's actually right though - the 14mb was when the boiler's running full whack and the 30mb was the standing pressure, so I don't think my gas fitter's wrong in that respect. However, it does seem that the boiler I've got is way bigger than I need - I didn't realise there was this gas flow issue when I chose the boiler, otherwise I'd have gone for a slightly smaller one. Hindsight is a wonderful thing. But do you know if I can get a part changed to convert the boiler down to a 37CDI? I don't want to go down the road of laying larger inlet pipes etc etc.

Sorry for the misleading information on my part, the fact is that your gas pipework is undersized to suit your boilers needs, it will need to be upgraded usually from your meter to boiler in 22mm pipework. Depending on the amount of gas appliances you have it may need to be upgraded to 28mm to your first appliance & then reduced to 22mm then 15mm to serve the rest.

Sorry again, but it`s definitely a faulty governor. :rolleyes: forget pipe sizes :rolleyes:
 
JB277 said:
The problem we've got is that the gas fitter only measures 14 mb of gas pressure at the meter

Confirm if this is definately correct. At the meter or at the boiler?
 
Possibly more than 28mm Bamber remember we can do 35mm(?) on a domestic ticket...

I doubt that they will get their service pipe upgraded for free - although it is certainly worth a shot.
 
In response to various questions above:

The boiler is right next to the gas meter and has all new 22mm pipe work (would switching to 28mm help?)

The only other appliance is the cooker and that's in the next room.

The governor was replaced by Transco but this didn't seem to help.

The 30mb standing pressure was going into the meter, not out in the street.

I live in North Cheam / Worcester Park and the main in the road is new apparantly. The pipe coming into mine and my neighbour's house is plastic rather than cast iron so must be fairly new.

Cheers guys!
 

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