New boiler install with low gas pressure

[Agile]

"Bare or "bear" ?

The simple fact is that we have no detailed information on pressures there.

The RGI correctly warned the client of the possibility of low pressure. So he acted correctly.

Also calculations can often give loss figures which are found to be three times higher when measured.

Few people reamer the pipe ends for example! Calculations assume perfect joints!

Tony

 

[Steelmasons]

Stop backtracking Tony , you stated the installer was way out with his calculations , too often on this forum you slate installers along with an attitude that you are the best engineer in the field , you know as well as I do this is not the case so behave yourself.

xxxxx

 

[JulianP]

I have a question which I hope is OK to ask here as it seems appropriate: Why do we supply appliances like boilers with such a seemingly pitiful gas pressure? Not that I have a clue really but you'd think about 25psi or thereabouts would be better, you could use micro bore pipe throughout and never run into low pressure problems.

I guess leakage may be more of a worry but if we can contain mains water pressure in lead pipe then 25psi should be easy enough? What pressure is the gas at in the pipe under the pavement?

Julian

 

[Dan Robinson]

Christ.

Half of London struggles to get its water pressure that high

 

[Agile]

Gas supply pressure is partly historic based on how we have stored gas in the gas holders and partly because a high pressure supply could cause severe problems if a leak became ignited.

There are the occasional cases of gas mains leaking and igniting. You can see some on Youtube!

Street pressure is usually about 30 mbar although a higher pressure of 75 mbar is becoming more common as it enables more gas to be carried by existing size pipes.

Tony

 

[JulianP]

That makes sense, so it dates back to town gas and the old gasometers.

I was thinking a bit more about it: Those little Camping Gaz stoves that run direct from the disposable bottle. They make a fair old hissing sound from the burners so that would become annoying on a domestic gas cooker. So far better to use a much lower pressure couples with a correspondingly bigger jet to get a decent flame that makes little noise?

Julian

 

[Steelmasons]

Service pressure is around 75/80mb , the reason for low pressures is due to increased demand.

High gas pressures=smaller injectors=blockage.

 

[Agile]

The street pressure is reduced by a regulator at the meter to 21 mbar for use within the property.

That is a very low pressure and you can strongly blow at that pressure!

Tony

 

[sloppytom]

 Though they should have issued a "Not to CurrentStandards" notice regarding the low pressure.) On a (probably more modern)boiler requiring a burner pressure closer to the inlet pressure then low inlet pressure could cause an incorrect gas mixture and incorrect combustion which would be a safety issue. Producing high CO levels

 

[Steelmasons]

Pre-aerated burners then not an issue regarding low inlet pressure when stand alone.

The boiler in question is a premix so burner pressure would be a moot point.

 

[JBPHS]

One thing to be said about some Keston boilers where they had a low pressure gas switch. If gas inlet pressure was too low, boiler wouldn't fire or remain lit. Simples.

James.

 

[Steelmasons]

Pressure switches were set to around 8/10 mb if I recall? , pretty much standard with regard to commercial burners.

 

[Dan Robinson]

boiler wouldn't fire or remain lit. Simples.

James.

That is just ****uation normal for those piles of crap.

If they worked at all tehy tended to surprise themselves into prompt and spectacular failure.

Often including leaks, tears and gnashing of teeth.

 

[JBPHS]

I'd only seen the low pressure switches on the K series.

Kestons are primitive looking things, not yet had the misfortune of looking at any of the new ones.

James.

 

[manbackh]

Tony , the installer advised the client gas supply may be undersized before any work was undertaken , client pays for an upgrade period.

FWIW I always fit a test nipple at isso valve.

Too many try to put the blame on installer including fellow gas installers , been in this situation many a time.

It doesn't look so simple from the other side of the fence guys. All depends on how the warning is given. If the *expert* says 'it may be borderline', but recommends to go ahead, as was case here, the customer is likely to go with it. Different case if the expert says 'it may be borderline, and if it isn't enough its going to mean £XXX of work will have to be redone'.

This is the problem with quotes being non-binding really. If anything changes its going to fall on customer, so tradesman isn't really under any pressure to make sure the customer is fully informed of eventualities. Not saying that is always the case, but I've seen it often enough.

Thats the view from my side anyway...