15mm or 22m for correct gas pressure

[Dan Robinson]

It does make sense depending on the boiler in question

 

[fixitflav]

I think that I am none the wiser

Perhaps no wiser, m'lud, but vastly better informed, as a QC once said to the judge

'use existing gas supply as long as 16.5 mb operating pressure can be achieved from the gas valve of the new boiler'

That sounds as if it means at the inlet to the boiler, before any internal pressure drop (see earlier discussion). If the boiler supplier is happy with that, no reason to think it won't be OK. But strictly speaking it doesn't meet the regs, which give minimum 18mbar at that point, meter outlet 21+/-2mbar, max 1 mbar pipe loss. Different if it means a point further downstream inside the boiler, be worth asking.
But in any case it seems he's putting the onus on you to decide what the pressure at that point will be. That doesn't sound right, presumably you're employing him to design the system, including assessment of the pressure drop in the existing. Though it would expected he'd have caveats about the bits he can't see, like the section buried under concrete.

Is the existing boiler still operable? If so, the pressure can be measured. Even if the kW rating is different from the new one, it will give a good idea.

That's my take on it, but I'd be surprised if somebody doesn't disagree vehemently (to put it politely!)

 

[Grumpy Gasman]

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

A bold statement wouldn’t you say?
I can assure you that you don’t.

 

[Grumpy Gasman]

That sounds as if it means at the inlet to the boiler, before any internal pressure drop (see earlier discussion). If the boiler supplier is happy with that, no reason to think it won't be OK. But strictly speaking it doesn't meet the regs, which give minimum 18mbar at that point, meter outlet 21+/-2mbar, max 1 mbar pipe loss. Different if it means a point further downstream inside the boiler, be worth asking.
But in any case it seems he's putting the onus on you to decide what the pressure at that point will be. That doesn't sound right, presumably you're employing him to design the system, including assessment of the pressure drop in the existing.

I rest my case.

 

[fixitflav]

A bold statement wouldn’t you say?
I can assure you that you don’t.

OK then, what's your estimate of the pressure drop for the system I referred to?

 

[fixitflav]

I rest my case.

Here we go again, derogatory remarks without saying what you think's wrong with it, or what you think would be right. When are you, or anybody else, going to say something that might be useful to the OP? He came here for help, not to listen to guys trying to show how clever they are.
I'm out of this thread. Too many critics who rudely claim others are wrong, but without being specific, and keep safe by not saying anything themselves which could be challenged.

 

[Dan Robinson]

Jesus H christ on a bike.

 

[Grumpy Gasman]

OK then, what's your estimate of the pressure drop for the system I referred to?

If you happen to think “gas flow calcs” only relate to discharge rates/pressure loss then you are sadly mid-informed.
To make the statement that you are as knowledgeable with regard to “gas flow calcs” as any other member on this forum is ludicrous.
If this were the case then you wouldn’t have to defend yourself in this way.
The only one trying to be clever is yourself.

 

[fixitflav]

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

Any developments on this?

 

[rhinosaw]

Thanks for asking F, no further developments, was going to get another couple of quotes anyway

 

[fixitflav]

Thanks for asking F, no further developments, was going to get another couple of quotes anyway

OK keep me posted

 

[hard-work]

This is how three GasSafe men assessed the size of the gas supply pipe:

 

[Grumpy Gasman]

I know the charlatan in that video personally (used to manage a leak detection company).
His knowledge regarding the gas industry is pitiful as is demonstrated in the video.
Burner pressure was being measured on the existing boiler and NOT gas operating/working pressure.
I doubt whether gas operating/working pressure for the replacement boiler was measured correctly with the appliance at full load as this would not yield a pressure of 21.5 mb.
The video is totally misleading.
Hard-work is a clown who gleans his knowledge from internet fools.
To state that the zero governor/1.1 valve ‘sucks gas’ from the supply pipework is laughable.

 

[hard-work]

The only clown is you. I never made the video or commented on whether they were right or wrong, just posting it. That company is a very large customer of W-B. If it compromised their sales or appliances in any way W-B would have had a few words with them I am sure.

Insulting the man is not enough. It would be nice if you could give us a blow by blow account of what, or where, these three GasSafe men when wrong.

 

[Dan Robinson]

Didn't we already cover this arse wipe and this ridiculous video?