16mbar pressure at boiler as opposed to 18 minimum

Corrado · 7 Sep 2006

Hi All

I have a Worcester Bosch 35HE plus condensing combi boiler

I had a service call today and was told that the gas pressure is too low. The boiler is in the loft and the meter is in the garage. He said that the minimum pressure should be 18mbar and it is in fact 16. He has suggested that I upgrade the 22mm pipework to 28mm in one section in the garage to remedy this. Will this help to solve this? I am not able to upgrade all of the pipework as much of it has now been boxed in.

The boiler was originally situated in the garage and worked at 18mbar I am sure. The pipework has just been extended into the loft to move the boiler.

I was unaware that there was a drop in pressure until the service engineer pointed it out to me on a routine service call.

As this is running at 16mbar, should I get this sorted as a matter of urgency?

Many thanks in advance.

Baxmax · 7 Sep 2006

Hot water hot enough ?.Radiators heating up to a good temperature ?Bliss

Corrado · 7 Sep 2006

Yes, the heating seems okay and the hot water is hot as hell! The service engineer told me that I could end up de-calibrating my boiler with the low pressure, which worried me a bit.

Will enlarging a piece of the pipe on the 22mm run actually make a difference??

Baxmax · 7 Sep 2006

Hot water hot enough ?.Radiators heating up to a good temperature ?Bliss

kevplumb · 7 Sep 2006

Corrado said:
Yes, the heating seems okay and the hot water is hot as hell! The service engineer told me that I could end up de-calibrating my boiler with the low pressure, which worried me a bit.

Will enlarding a piece of the pipe on the 22mm run actually make a difference??

have to ask

how do you decalibrate a boiler

Corrado · 7 Sep 2006

HE told me that it would decalibrate itself and would have trouble recalibrating.

Paul Barker · 7 Sep 2006

It isn't safe to use with insufficient working pressure, and the supply has to be adequate for the maximum power of the boiler whether it is range rated or not.

You have to have the pipesize increased. The person who moved the boiler should have performed a calculation to ensure pipesizing was adequate. Evenb if they didn't do that they should have gas rated the boiler or checked the working pressure which would have highlighted the problem, then the installation should have been brough up to safe standards acording to manufacturers instructions. You have told us that standard in this instance is 18mBar.

ratonnastick · 7 Sep 2006

here is a spanner in the works . went to a greenstar 35 boiler for service 2 meters from gas meter 28 mm pipework 16 mbar working pressure! after investigation and getting the gas provider in they only have to supply 16mbar working pressure if its on a pinch point . Spoke to corgi and they confirmed this. The installation only works at 16 mbar even with 1 burner on a hob running.

bster · 7 Sep 2006

what do you mean 'pinch point' and 'working pressure' is at the meter with an appliance on. -yes?

just recapping college starts next week

ratonnastick · 7 Sep 2006

A point where the gas main is not large enough and they don't have the money or can't be bothered to upgrade the gas main.

Biggles.. · 7 Sep 2006

Had same problem with a 133HE, 28mm from meter to boiler and could still only get 16mbar working pressure.As ratonnastick said thats the minimum transco have to provide and if thats all you've got heyho. 16mbar is plenty for most modulating combis anyway to perform as per MI's.

bster · 7 Sep 2006

so 'pinch' = penny pinching

It's safe to run, say 20mb rated inlet, appliances then on 16mb. I take it overgassing is far more dangerous than undergassing?

bripl · 7 Sep 2006

bster if you look long and hard you will find all the info you need

even easier join www.argi.uk where experienced gas installers will keep you right and answer any queries on gas related matters,even telling you things like how low the working pressure has to be before it starts affecting its performance

ratonnastick · 7 Sep 2006

that's what you have to do, given all the information by corgi,the regs and the manufacturer, make a decision is it safe or not. At installation you should always try to abide by the regs but try telling people they cant have a boiler because the gas provider does not supply enough pressure. it is obvious that some installers don't even check or don't care.

Agile · 8 Sep 2006

Just by chance I have been asked to go to an installation where the pressure at the meter alledgedly drops to 15 mB when the 32 kW boiler is on full power.

This gives a potential problem because the boiler is only guaranteed to work if the inlet pressure varies by less than 2 mB between minimum and maximum power, ie 12 kW to 35 kW.

The problem is as usual CORGI who treat a gas supply at the boiler inlet less than 18 mB as At Risk regardless of what the manufacturer or gas transporter say. The CORGI argument is that a low gas supply pressure could cause the pilot light ot go out. That is eroneous because few boilers now have pilot lights anyway and if a pilot goes out then the magnetovalve trips the supply to the pilot.

Since Transco, National Grid, Pooper Scooper or whatever they call themselves tomorrow, say ( but only if asked ) that they only have to provide 16 mB at the meter then it leaves a 3 mB uncharted gap where the installer should turn off the boiler and the gas transporter say the supply is in accordance with their legal obligations.

Tony

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16mbar pressure at boiler as opposed to 18 minimum

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