On 29 Aug 2003 15:33:43 -0700,
(E-Mail Removed) wrote:
>I've been given three different statements by Corgi fitters with
>regards to the length of pipework running from an old boiler to the
>mains in the flat my fiancé bought six months ago.
>Currently the run is an excessive one on 15mm pipe (over 30m all told
>with multiple 90 degree bends and a hob spurring off). As all three
>have commented, the boiler and hob should have gone bang by now. There
>are no other gas appliances.
>A: replace the run with a new shorter run of 22mm pipe from the point
>of entry to the house to the boiler. 15mm spur to hob. This gives a
>total run of 17m in the house, 4m to the mains outside, with 10x 90
>degree bends. He says anything under 30m in total, taking bends as
>0.5m is acceptable.
>B: replace the lot from the mains into the house with 1" pipe most of
>the way (up to about 6m from the boiler).
>C: Move the boiler.
>What I can't get clear from them is what the safe/legal/most cost
>effective option is.
>A would be the easiest option as the run from the mains to the house
>would be untouched (it steps down from 22mm to 15mm about two feet
>into the house) and this is an awkward section to re-fit. I've punched
>holes for the run of pipe already so it should be a fast job. But
>would it be safe/legal?
>B is really more than I can afford. The written quote isn't in yet,
>but verbally quoted 3 days work with one day just for replacing the
>22mm mains to the house section
>C is not an easy option. It's a basement flat so the only walls
>available to vent are front and back. It's a Listed building, so the
>front wall is no go. On the back wall I could fit a new boiler
>slightly nearer. The run would then be 13m with 6x 90 degree bends,
>plus 4m to the mains outside, and a 15mmm spur to the hob. Would this
>be possible on a 22mm run of pipe to the boiler?
>
>I don't know which of the fitters to believe, so any advice, links,
>recommendations or comments would be an enormous help.
>
>John Bennett.
In order to work this out, the maximum ratings of both appliances are
needed, as well as the meter position relative to this lot.
Almost certainly, with typical appliances, one can say that 15mm tube
over the distances mentioned are not enough.
http://www.cda.org.uk/Megab2/build/pub124/default.htm
has information and a worked example, so you can at least get an idea
of what is involved.
The pipework should be designed so that the pressure drop between the
outlet of the meter and the appliance does not exceed 1mbar at maximum
flow conditions.
Option A *may* be adequate if the boiler is relatively small, but you
would need to do the sums.
Same for Option B although again the calculations are required. This
would likely be required for a larger or combi boiler, and I suspect
the calaculations would show it to be belt and braces for a smaller
boiler.
Option C seems similar to Option A.
Getting the pressures right is important both for operational and
safety reasons.
From the perspective of doing any DIY work, the law requires you to be
competent if you want to do your own fitting work, but does not define
it. Professional fitters are required to be CORGI members.
There are a bunch of issues associated with installing a hob as well
as installing a boiler that have to do with fitting arrangements,
flues, ventilation and so on. The fact that the pipe sizing issue is
probably wrong invites the question as to whether anything else is
wrong.
There is more information in Ed Sirett's gas fitting FAQ
Gas fitting FAQ
http://www.makewrite.demon.co.uk/GasFitting.html
..andy
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