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sizing gas pipe for boilers
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User2050
Posts: 20 Forumite
Got 2 quotes on the replacement of my combi-boiler.
One of them mentioned that gas pipe needs to be 22mm. However, the other didn't even mention gas pipe at all.
I assume the latter just assumed if the old boiler works, the same pipe will work for the new boiler.
I don't know much about combi-boilers, so can anyone explain to me the possibilities if the gas pipes is not increased to 22mm (parts of it is already
22mm, but not all of it)? I just think the gas pressure may not be enough, but what's the resulting situation?
Furthermore, how can I estimate how big the gas pipe need to be (in case even 22mm is not enough in the future), any quick guides?
Thanks everyone
One of them mentioned that gas pipe needs to be 22mm. However, the other didn't even mention gas pipe at all.
I assume the latter just assumed if the old boiler works, the same pipe will work for the new boiler.
I don't know much about combi-boilers, so can anyone explain to me the possibilities if the gas pipes is not increased to 22mm (parts of it is already
22mm, but not all of it)? I just think the gas pressure may not be enough, but what's the resulting situation?
Furthermore, how can I estimate how big the gas pipe need to be (in case even 22mm is not enough in the future), any quick guides?
Thanks everyone
0
Comments
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15mm gas pipe will only carry 15000 btu,s.
so vitually all modern domestic gas boilers will require a 22mm gas supply pipe.
esp if feeding say a gas cooker too.Get some gorm.0 -
15mm gas pipe will only carry 15000 btu,s.
so vitually all modern domestic gas boilers will require a 22mm gas supply pipe.
esp if feeding say a gas cooker too.
Strange. My boiler input is 100,000 to 114,000 BTU's
It is fed by a 15mm gas pipe.
My house has solid stone walls, no double glazing and it's very warm.0 -
Ormus, you are getting confused with the heat carrying capacity of 15mm pipe for radiators.
Gas pipe sizing has to be done taking into account the input power of all the appliances, length of pipe run, number of elbows/bends in the pipe etc etc.
Gloomendoom, unless your boiler is withing approx 3m of the gas meter, your gas pipe is undoubtedly undersized for that power boiler.
Just because it may seem to work ok, the power input will be less than it needs to be and the pressure drop between meter and appliance will be greater than regs allow.0 -
Gloomendoom, unless your boiler is withing approx 3m of the gas meter, your gas pipe is undoubtedly undersized for that power boiler.
Just because it may seem to work ok, the power input will be less than it needs to be and the pressure drop between meter and appliance will be greater than regs allow.
I've been told this before. The meter is in the front garden and the boiler is in an an outbuilding at the back of the house. Part of the run is 22mm but the last 10/12m are 15mm pipe. Theoretically the boiler (an ancient 70's Potterton) is well matched to the size of the house and, in practice, it heats it perfectly well even in the coldest winters.
If the power in was too low, then one would expect the power out to be correspondingly low. It isn't. :huh:
.
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.0 -
Yours is a very common scenario with boilers fitted years ago.
The chances are the boiler was oversized when fitted anyway. Even if the burner pressure may be set correct the boiler output may be low.
You need to gas rate the boiler. If you have a metric meter, see how much gas is used in 2 minutes. If am imperial meter, see how long it takes for one revolution of the dial, then post back results.0 -
Yours is a very common scenario with boilers fitted years ago.
The chances are the boiler was oversized when fitted anyway. Even if the burner pressure may be set correct the boiler output may be low.
You need to gas rate the boiler. If you have a metric meter, see how much gas is used in 2 minutes. If am imperial meter, see how long it takes for one revolution of the dial, then post back results.
Cheers.
I'll give it a go at the weekend. I don't run it with the boiler thermostat turned up full. I suppose it would use more gas if I did.0 -
Thanks for your input.
I now understand what really matters here is the gas pressure, am I right?
If gas presure is low, what will happen? I can think of,
1. lower input power, hence lower output power --->
2. bath water is not hot or takes longer to get hot; and heating is not warm enough.
what else? Will the boiler stop functioning? - as I am starting to think maybe my current boiler looks sick just because of this - not enough gas pressure?
Any gas engineer willing to explain?
Thanks again0 -
With the hot water running, take a reading at your meter as in #6 and post the results back. Someone will calculate the heat input for you, but will not be able to advise on pressure drop from the meter.0
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