slightly naughty gas engineer

[nickelarsed]

afternoon all, a question for gsr's. I'm doing my gas hours at the moment and got a call the other day from a gsr I know asking me if I wanted to help the with a boiler install. I went along and helped. We replaced an old ariston with a new glowworm (both 24). When I commissioned it there was a 2mb drop on working pressure. We did the rest of the commissioning tests and all analysis etc was fine. He just shrugged his shoulders and left it at that. Now I know it's only meant to be 1mb, and that the pipe was too small. How bad is this? What would others have done in this situation. I'm asking because I want to know the right way of doing things, and would like once I'm gsr to use best practice. Thanks for any replies.

 

[southcoastboile]

Obviously that was to low so idealy you would upgrade the pipewok, if there are other gas appliances it could potentialy drop even more. Boilers will operate correctly on a 2mbar drop so although it's wrong, if the fga was ok it should be fine

 

[mfgs]

Was the inlet pressure tested at the gas valve? Some boiler manufacturers allow a drop internally on the boiler. For example Worcester say that from the inlet on the boiler connection to the gas valve can cause a 1.5mb drop due to restrictions inside the boiler.

 

[nickelarsed]

Thanks for the replies. It was the only appliance in the house. And it was the inlet pressure tested. But I want to check I'm understanding you right mfgs. It's a zero governor and there were two test nipples on the valve leading up to it. I tested from the first one, before it passed through the valve. Do you mean that on a worcester I could have 1.5 drop because of restrictions? tbh I didn't get a chance to read mi's on this one.

 

[mcniven]

the inlet pressure, and working pressure, are tested on the same test point at the appliance mfgs.

 

[southcoastboile]

the inlet pressure, and working pressure, are tested on the same test point at the appliance mfgs.

standing and wp can be checked at the same test point. Think he is refering to the test nipple on the iscolation valve compared to the test nipple on the gas valve inlet

 

[GrahamM]

Ideally when doing an install, a test point should be installed immediately before gas valve connection. This is where you should take your WP from.

It is now widely accepted that taking WP from gas valve inlet test point (P1) can result in a further decreases of 1-1.5 mbar on your WP reading.

If you are getting full gas rate and FGA all good. Don't worry about it.

 

[nickelarsed]

Thanks for all the help everyone, good to know.

 

[mfgs]

the inlet pressure, and working pressure, are tested on the same test point at the appliance mfgs.

Yeah I know that, but some boilers now have a test point on the isolation valve aswel as on the gas valve. I was trying to determine which one was used, if the boiler had one. As we all know you get a loss through the boiler, so 2mb at gas valve, could be infact be 1mb at the isolation valve and therefor it would be ok.

 

[kirkgas]

P1 to test inlet pressure, and P2 to test what a lot of engineers wrongly call BP, (which on a zero governer is 0mb) its all about the way the interpretate it, we use P2 to demo the operation of the gas valve, if you connect u gauge to P2 and turn on boiler you should get it drawing the gas to about -4mb or so, then as soon as it lights it drops to 0mb

 

[nickelarsed]

I wondered why there was a p2 on a zero governor, since we never seem to test anything from there. Just so I understand on the older gas valves that was where you took burner pressure from. but on a zero governor it will be zero (hence the name?). When you say it's a good way to show demo the operation, is it also a good place to check if it's operating correctly? Or am I just complicating things.

 

[kirkgas]

I wondered why there was a p2 on a zero governor, since we never seem to test anything from there. Just so I understand on the older gas valves that was where you took burner pressure from. but on a zero governor it will be zero (hence the name?). When you say it's a good way to show demo the operation, is it also a good place to check if it's operating correctly? Or am I just complicating things.

to a point it proves its working, but gas rating and FGA will confirm boiler is working correctly

 

[dboi78]

if pipe sizing was done then there would not be any query regarding correct pipe size, even easier with only one appliance, what is the p for on p1/p2 is it pressure or point ?

 

[kirkgas]

if pipe sizing was done then there would not be any query regarding correct pipe size, even easier with only one appliance, what is the p for on p1/p2 is it pressure or point ?

i dont know TBH