15mm or 22m for correct gas pressure

[fixitflav]

Afraid fixitflav you are well out of your depths here. And the giving out of gas advise outside of the combustion chamber is not allowed under the forum rules. you can do as much fishing as you like on google but i'm afraid certain information is restricted and is not available on the internet unless you have certain passwords/ memberships for various sites to gain access. This is done so illegal gas work is not encouraged, and untrained/unqualified can't find the answers.

I think I understand gas flow calcs as well as anybody on this forum.
Apart from re-iterating the 1mbar max pipe pressure loss, I can't see any other posts which help the OP with his query. I wasn't encouraging the him to do gas work, the work would be done by his fitter. I was hoping to give him a few basics so he can have an informed discussion.
I said more the once that his fitter needs to check the pressure drops, and that nobody could give a definite answer without knowing full details of the system.
If you think I've said anything which is incorrect, please tell me what.
I still think reference to internal pressure drop after the boiler inlet test point is a red herring. As I asked earlier, if there is this loss, how do you separate it from the pipe loss, to determine whether the latter is within spec? (obviously there is a pressure drop from boiler inlet to burner inlet).
My boiler manual says "A minimum working pressure of 20mbar MUST be available at the boiler inlet". (that's suspect for a start, as the pressure can be 18mbar within the regs). There are 2 tapping points, boiler inlet and burner inlet. It says to adjust the burner inlet pressure on commissioning. It doesn't say to check the boiler inlet pressure, but the clear implication is that they want 20mbar at that point.

 

[ianmcd]

you wont get the answer as @snb has already said we cant give advice on Gas work in this open forum, and you are very wrong in your thinking and you keep posting stuff that people will read and think you know what you are talking about

 

[Dan Robinson]

My boiler manual says "

Well if your boiler manual says it, then it must be true for all the tens of thousands of other different models still in operation out there.


Burner pressure test point I hear you say? How many boilers fitted in the last 13 years have one of those I wonder?

FFS.

 

[nwgs]

I think I understand gas flow calcs as well as anybody on this forum.

No you don’t.

 

[fixitflav]

you wont get the answer as @snb has already said we cant give advice on Gas work in this open forum, and you are very wrong in your thinking and you keep posting stuff that people will read and think you know what you are talking about

I wasn't giving gas advice, just making some comments which might help the OP. There isn't enough detail to make a firm decision anyway. As I said, it's up to the gas fitter to do the calcs and make the final recommendation.

If I'm very wrong and don't know what I'm talking about, will you tell me what I've said that's wrong? I'm always happy to learn and if I'm wrong about something I'm capable of admitting it.

 

[fixitflav]

No you don’t.

Yes I do.

 

[Dan Robinson]

I'm always happy to learn

Then buy the relevant books and read them.

if I'm wrong about something I'm capable of admitting it.

It's patently obvious that you are not.

 

[Dan Robinson]

I wasn't giving gas advice, just making some comments which might help the OP

You were talking bo||ocks and some poor sod might take it as solid advice.

 

[bernardgreen]

.

The pipe length between Meter and Appliance is the same in the two examples. Is there a given minimum value for distance d below which the two elbows have to be considered as a complex and not as two simple elbows when calculating pipe sizes.

 

[nwgs]

Yes I do.

You don’t and I’ve no idea why you pretend.

 

[fixitflav]

You don’t and I’ve no idea why you pretend.

How do you know I'm pretending?

 

[fixitflav]

It's patently obvious that you are not.

But you haven't told me where I'm wrong yet.

 

[Dan Robinson]

I'm not here to teach you your ACS.

Buy the books and teach yourself.

 

[fixitflav]

Well if your boiler manual says it, then it must be true for all the tens of thousands of other different models still in operation out there.

OK, I had meant to add words to the effect that not all boilers are the same, but then I forgot. I see now some boilers have a pressure tapping on or near the iso valve which allows pipe loss to be measured. But what I said was right for my boiler.
But bringing in internal pressure loss between boiler inlet and gas valve inlet is irrelevant to sizing the gas pipe. It doesn't help the OP and might cause confusion. The gas pipe still has to give < 1mbar loss to comply with the regs.
I was just giving some idea of the pipe set-up to give that sort of loss. Have you or anybody else done pressure loss estimates? If so, what do you get? Does anybody disagree that if there is a pipe length buried in concrete with a 22mm branch downstream, it's not likely to be less than 22mm? But as I said more than once, it's up to the fitter to check.
It would be good to hear from the OP, but if he was happy to leave it entirely to the fitter he wouldn't have posted in the first place.

 

[rhinosaw]

sorry for the can of worms that I appear to have opened.
I think that I am none the wiser,
A line in the estimate (it does highlight that its an estimate of works only) says 'use existing gas supply as long as 16.5 mb operating pressure can be achieved from the gas valve of the new boiler', just really checking if that sentence makes sense to a pro