low gas inlet pressure? is this a major problem???

[n3il101]

Hi I had a new Worcester greenstar 37CDi fitted 20 months ago. At the time the fitter said he had to fit a new larger gas supply pipe annd fitted a 22mm pipe.

I had a friend of the family (works for one of the big companies servicing boilers) service the boiler today as we had been having problems with the CH. That seems to have sorted the problem but he said that the supply working pressure at the boiler was only 15mbar (which he said was a bit low), he checked it at the meter and it was 19mbar.

I have been searching about this and figure that the reduction is due to the diameter, length and bends in the pipe. (As I said it is 22mm, about 13m long and I think it has got 4 elbows)

The friend who serviced it said it was a bit low but not to worry about it.

What I want to know is should I be worried?

What effect will it have?

I have looked at the instruction manual and it says the minimum inlet pressure should be 18mbar. Should I be trying to chase up the original installer and getting him to add a section of larger diameter pipe? (I feel a bit awkward as it is the husband of a friend of my mums so feel bad saying he hasn't done his job properly, if that is the case)

would replacing a 7m section at the start with larger diameter help? ( I ask as that is the easiest section to access as though I am about to fit Karndean flooring over all of this section so access will be harder if I don't sort it now)

Thanks for any help. I have tried to settle my worries by searching the net but can't seem to find anything definitive.

 

[sooey]

Like your friend said that is too low, did he test it with the boiler on full and the other gas appliances running?

 

[n3il101]

The only gas appliance in the house is the boiler (there is a T joint going off with 15mm that supplied the old boiler but that has been blanked off). Yeah I THINK he had pressed the boost button on the boiler to have it going at full whack when he tested the pressure at the boiler, he definately had me have the hot water tap running when he tested the pressure at the gas meter (and got 19mbar)

If it is a problem I don't get why he has said not to worry about it, unless he just thinks he is saving me having/paying for work to be done which I can live without.

But i'd rather sorted it out if it is a serious problem.

 

[n3il101]

plus I have seen people saying that at the gas meter it should be 21mbar.

Is this correct? If i got the gas board to sort that out would that make it 17mbar at the boiler and less of a problem?

 

[sooey]

The fact that you've got no other appliances to be affected makes it less of a problem, though it is a fair old drop you've got, and close to the minimum that boilers are tested down to.
I can understand why he said don't worry about it but like you surmised it would be a lot better with a couple of lengths of 28 mm coming from the meter. (assuming there are no blockages in the pipe further up)
At the meter it should be 21mb + or - 2mb, so 19 is ok.

 

[n3il101]

Would it be reasonable to expect the original installer to come back and add the 28mm pipe or is he able to say he installed it acceptably?

 

[sooey]

Would it be reasonable to expect the original installer to come back and add the 28mm pipe or is he able to say he installed it acceptably?

In point of fact yes it would, (gas safe would make him if you asked them) though it would go down a lot better if you offered to pay for the pipe and fittings.

 

[joe-90]

He'll use the existing pipe elsewhere so only offer to pay the difference.

 

[sooey]

There's a feller in the gardening section needs some advice joe...he's got some sh**e to shovel.

 

[joe-90]

What are you waiting for?

 

[n3il101]

Could there be anything else causing such a big drop in the pressure (from 19mbar - 15mbar) because that seems pretty large a drop if to get the required pressure it is only allowed to drop 1mbar?

Would replacing half of the piping with 28mm be sufficient?

 

[Dan Robinson]

because that seems pretty large a drop

What makes you say that?

 

[Razor900]

You're allowed to go down to 16.5mbar at the test point on these boilers so it's not massively undersized although it's still not right

 

[ALEC1]

Worcester Bosch also say the pipe shoukd be a minimum of 22mm uninterrupted between the meter and the boiler...How many meters away is the meter...I reckon about 10m..

 

[joe-90]

Has anyone done the maths to see if a section of larger diameter pipe will make any realistic difference? Pressure has nothing to do with volume other than with a miniscule amount of friction.