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Discuss Symptoms and problems associated with low inlet working pressure (forced draught). in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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bennygas

Alright?

i've been wondering. we're all hell bent on getting the correct minimum inlet working pressure at appliances, all the more so it seems as many more of us tend to be more and more concerned in meeting the requirements for seemingly bigger and bigger combis in an environment of ever increasing accountability and professionalism. Now, in the days of atmospheric burners, the repercussions of low inlet working pressure were manifest by poor combustion, possible lighting back and various other issues. My question is, what are people finding to be the symptoms and faults that people are finding as a result of undergassed condensing boilers? given the construction of modern burners, is lightback something people have found to be occurring? how have people found combustion to have been affected in these cases? has anyone had any complete howlers?

For example, I used to do some audit work, and got called to an address where a 6 month old ecotec was about to be replaced because it kept locking out, numerous major parts had been exchanged, and the next step by the contractor was replacement. It was evident that the inlet wp at sFb was low at 8mb (knocking the hob and fire out of operation at times - how someone didn't put 2 and 2 together amazes me), but the only symptom was the boiler going to lockout. So it seems the only way the low wp manifested itself was problematic ignition and maintenance of lit gas at the burner, together with the adverse affect upon other connected appliances. forgetting other connected appliances, my query is about the observed effects upon condensing boilers of low inlet wp. what have people been finding?
 
Re: Symptoms and problems associated with low inlet working pressure (forced draught)

Like yourself bennygas I have only had experience of it affecting other appliances. I gas rated an Isar 30HE that took the wp down to 9mbar and it was spot on so getting the correct amount of gas through! I must admit I didn't check out the gas valve to see if it was maintaining 0mbar? Worth knowing! You certainly wouldn't get lightback as there's be excess air in the pre mix I'd imagine which would result in flame lift yeh?
 
Re: Symptoms and problems associated with low inlet working pressure (forced draught)

good point mate - can't say as I'm totally boned up with premix technology, hence my query on here (just wanted to find out out what sort of problems were being manifested out in the wild). I read yesterday about a problem with the ceramic burners on the baxi 105HE I think it was, and it got my mind thinking...this premix stuff certainly puts a different slant on things eh?
 
Re: Symptoms and problems associated with low inlet working pressure (forced draught)

re the flame lift - in such a case, with large amounts of excess air, I guess the likelihood of light back or flame lift is going to be governed by just how lean the mix has been made, together with how any pockets of combustible mixture and are being moved around the place and what temperatures they're subject to - which I guess is going to be affected by fan speed, the volume of gas coming in plus god knows how many other variables. bit beyond me to make any assessment in that respect - that's kind of why I was kind of hoping if people had examples of things that had gone wrong, I might be able to form an opinion as to how and what things affect the behaviour of this part of the boiler. Given all the things that could go wrong - it seems pretty resilient (again, I stand (nay, I hope) to be corrected!).
 
Re: Symptoms and problems associated with low inlet working pressure (forced draught)

Premix burners have been around a long time as you may well know ... The commercial market has had 'package' burners since i can remember! Explosive ignition is certainly an issue as the gas builds up to an eventual mixture to ignite ... That's probably why commercial flame detection in 1 second thereabouts and a post purge before re trying to light!

The reason for the requirements for correct inlet pressure has always been and will always be to maintain a safe gas supply pressure to all appliances throughout the installation yeh?

Are you GSR registered bennygas? This discussion really could be of more benefit in the GSR only section in IMHO there's kind of a limit to what is safe to discuss out here in the open, if you know what I mean :)
 
Re: Symptoms and problems associated with low inlet working pressure (forced draught)

mate, cos of the redundancy, I can't afford to renew this year. got a letter through me door this morning saying I'm off the register on the 5th unless I give 'em some lolly. gutted mate. ACS is valid till 2015 though - do they accept that for access? is the gas bit that different? who's the man to see?
 
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Re: Symptoms and problems associated with low inlet working pressure (forced draught)

re the 20mb - I believe so - think that's more or less what bs6891 suggests/states. re the package burners - was quite new to me when it hit the domestic market, my background's only domestic, so I guess that's why. i did some work at an acs centre, and so kind of got involved with the commercial side of things a bit more then, that's when I became aware of just how old and proven the technology is. couldn't hand on heart say i knew it inside out though. got a rough idea, but i aint god's gift like.
 
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Re: Symptoms and problems associated with low inlet working pressure (forced draught)

No one is bennygas and will never be .. thats what I know anyways .. this medium of gas is continually changing and evolving. I doubt we'll ever know it all!

Sorry to hear about your hard times ... I hope it picks up :)
 
Re: Symptoms and problems associated with low inlet working pressure (forced draught)

yea mate - sure it will - always does. never knowing all there is to know? best part of the job - each days different, always learning. better than being in an office.
 
Re: Symptoms and problems associated with low inlet working pressure (forced draught)

yea mate - sure it will - always does. never knowing all there is to know? best part of the job - each days different, always learning. better than being in an office.

Totally agree regards an office! The boss is to freekin close all the time!!!

Regards learning, it never ends IMHO ... I now know more useless stuff than ever and am playing catch-up with new technology just about every day :)
 
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