combi v system

so minimum 18mb at the boiler inlet. So on that basis 13.5 and 16.5mb don't meet the regs, whether or not the boilers would work fine at those pressures.
So, at 16.5mb the boiler works fine within the makers spec's. So you would rip apart the house to needlessly install a lager bore gas pipe. After this expensive new larger bore pipe is installed, with much disruption, the boiler's performance is exactly the same.
 
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Load of rubbish. Assuming the tapping point is equivalent on the 2 boilers ie at the boiler inlet, before any internal losses, and the meter is unchanged, if the old one showed 13.5mb the only way the new one could show 16.5mb is if the gas flow is lower. That's possible if the efficiency is higher (and maybe the output lower, he didn't say otherwise) but not because the new boiler works differently.
And, as has come up a few times on the forum, pressure must be 21+/-2 mb at the meter outlet, max 1mb pipe loss so minimum 18mb at the boiler inlet. So on that basis 13.5 and 16.5mb don't meet the regs, whether or not the boilers would work fine at those pressures.
Also a 21.5mb reading was thrown in without comment. We need to know the pressure at the meter to make any sense of that.
Why don't you go to the Youtube vids site and ask them. All you have to do is click on the words "Youtube" as its playing. They may reply. If they do you can report back what they say. They only fit W-B selling a lot of their kit, so W-B must agree with them, otherwise they would object telling them to remove the vid.
It looks like three GasSafe fellows there.
 
Why don't you go to the Youtube vids site and ask them. All you have to do is click on the words "Youtube" as its playing. They may reply. If they do you can report back what they say. They only fit W-B selling a lot of their kit, so W-B must agree with them, otherwise they would object telling them to remove the vid.
It looks like three GasSafe fellows there.
No thanks, I've got better things to do. If you disagree with my comments, what do you think about the claims made?
 
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It will only take a few minutes to ask them. Less than replying to us. You disagree with their gauge readings - ask them.
Look at the facts in the vid:
  • Old boiler: 13.5mb working pressure. Shown on the gauge.
  • W-B state a minimum of 16.5mb working pressure for the new boiler.
  • New boiler: 21.5mb working pressure. Shown on the gauge.
He emphasised it was working pressure.
 
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pressure must be 21+/-2 mb at the meter outlet, max 1mb pipe loss so minimum 18mb at the boiler inlet. So on that basis 13.5 and 16.5mb don't meet the regs, whether or not the boilers would work fine at those pressures.
The regs say (or is it recommend?) that 18mb must be at the boiler's inlet. But the makers may say the boiler works perfectly at 16.5mb at the boiler's inlet - as do W-B with some of their models. Who is right? The maker, or regs which are clearly outdated.

The makers care not a jot what pressures there are at the meter, they only care what is at the appliance.
 
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if the old one showed 13.5mb the only way the new one could show 16.5mb is if the gas flow is lower. That's possible if the efficiency is higher (and maybe the output lower, he didn't say otherwise) but not because the new boiler works differently.
The new boiler works very differently, that point he was emphasising. I assume a negative pressure gas valve of some description to draw the gas through the pipe from the meter.

W-B, and other makers, must like this vid as it means people can have a boiler change with all the work only being at the boiler with no new lengths of pipework through the house with carpets ripped up, etc.
 
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I assume a negative pressure gas valve of some description

I think what you are refering to is a gas injector feeding into a venturi in the combustion air feed circuit. The pressure in the venturi could be a few millibar below atmospheric pressure and thus would add a few millibar to the effective gas pressure at the injector nozzle..

Hint
that 18mb must be at the boiler's inlet.
which is 18mb above atmospheric pressure.
 
The regs say (or is it recommend?) that 18mb must be at the boiler's inlet. But the makers may say the boiler works perfectly at 16.5mb at the boiler's inlet - as do W-B with some of their models. Who is right? The maker, or regs which are clearly outdated.

The makers care not a jot what pressures there are at the meter, they only care what is at the appliance.
Yes, I agree with you there. IMO it would be more logical if the boiler maker stated the pressure needed at the boiler, and left the installer to select the correct pipe size to give that pressure. Could be a requirement to work on minimum pressure at the meter, 19mb, if thought appropriate. But as I understand it the regs say the pipe loss must be not > 1mb, possibly leading to a bigger pipe. Whether it's mandatory or advisory I don't know, probably depends who you ask. Or whether installers take much notice anyway, or just do what works.
 
It will only take a few minutes to ask them. Less than replying to us. You disagree with their gauge readings - ask them.
Look at the facts in the vid:
  • Old boiler: 13.5mb working pressure. Shown on the gauge.
  • W-B state a minimum of 16.5mb working pressure for the new boiler.
  • New boiler: 21.5mb working pressure. Shown on the gauge.
He emphasised it was working pressure.
The new boiler works very differently, that point he was emphasising. I assume a negative pressure gas valve of some description to draw the gas through the pipe from the meter.

W-B, and other makers, must like this vid as it means people can have a boiler change with all the work only being at the boiler with no new lengths of pipework through the house with carpets ripped up, etc.
It doesn't matter how the boiler works, or what type of valve it has. For a given flow the pressure at boiler inlet is what it is - meter pressure minus pipe loss. If that pressure is say 13.5mb, and that particular boiler needs 13.5mb to work, it's OK. If a different boiler (same gas flow) with a negative pressure valve or something could work with a lower pressure at that point, it doesn't change anything. The actual pressure at that point is still 13.5mb.
 
So, at 16.5mb the boiler works fine within the makers spec's. So you would rip apart the house to needlessly install a lager bore gas pipe. After this expensive new larger bore pipe is installed, with much disruption, the boiler's performance is exactly the same.
I wouldn't expect anything. I was merely making some comments. See also my #70.
 
Whether it's mandatory or advisory I don't know
Probably advisory. I recall a boiler (only a boiler off the meter nothing else) had a working pressure just below the makers spec'. We broke the seal on the meter regulator opening the regulator slightly until the minimum mb at the boiler, plus a bit more. It worked. Transco men (at the time) didn't care a hoot if the seal was broken.
 
You are questioning their findings. They did show the gauge readings.
All I'm saying is - those readings aren't due to differences in boiler design, only to reduced gas flow or maybe higher pressure at the meter (which would be dishonest, to put it mildly).
 

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