Chrishutt, I know from previous posts that you don't agree with me, but the length of pipe from the meter to the cooker tee off must be doubled when working out the pipe sizing, so each appliance only gets 0.5 mBar drop and if there were 3 appliances then it would have to be tripled, as we are all taught in our ccn1.
Gas pipe to boiler
- Thread starter dp123
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Actually that's 100% out, not 50%. The tables say that 25 metres of 22mm should give a drop of 1 mbar at 2.5 m³/h. You're getting that on just 12 metres, so the drop over 25 metres would be 2 mbar, double what the tables say, so 100% out (which is the same as ChrisR says).
That's wrong I'm afraid, and it's not what I've read in textbooks either. As long as the total drop to each appliance is no more than 1 mbar, it's OK, irrespective of how much of the drop happens on the shared section.
Sorry ChrisH, but if you look in your corgi 'essential gas safety book' P79, 'Guide for sizing gas supplies (natural gas)', the section in italics proves and states exactly what I said previuosly about the number of appliances/sections and the multiplication factors needed.
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Point taken. That is indeed what he said. I was thinking of what I thought he meant! Nevertheless in terms of the accuracy of the tables, it does suggest that they are 100% out.Chrishutt wrote
He didn't say 50 percent out but rather 50 percent over the actual flowrate which is different.
You're right, it does say that. I take that as a suggested way of approaching the problem, a rule-of-thumb. But it isn't necessary to do it that way. To take the £orgi manual diagram as an example, section A-B from the meter to the first T could have a drop of 0.5 mbar (rather than 0.25 as they suggest). Providing the remaining run to the combi had a drop of no more than 0.5 mbar that would be fine, although as ChrisR said it might be prudent to leave some spare capacity in the common pipework from the meter.
Me thinks you need a gas installation engineer- not a glass bending artist!
Why has nobody mentioned the prevailing gas pressure- is this fixed all over the country?
Sounds like it would be cheaper to bump up the pressure and fit a 10 mm pipe
Why has nobody mentioned the prevailing gas pressure- is this fixed all over the country?
Sounds like it would be cheaper to bump up the pressure and fit a 10 mm pipe
Same specs everywhere, yes.
But the poiint is it's the same Regulation everywhere. That's what Corgis have to abide by.
Wouldn't work, because unregulated appliances can share the same pipe - explained above, by moi.
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