Why is 1mb drop dangerous

[jase158]

I understand the regs and that we have to follow them no matter what, however

I don't understand why a 1.2mb drop would be dangerous!!

surely it aint dangerous!!! Turning something off and telling customer it is "Immediately dangerous" or "at Risk" (depending on how u would classify it) is just wrong, surely it is NCS at best!

Maybe a 5-6mb drop!!

but surely we should have a better test then this!! for instance

• Turn on all Gas appliances and make sure the gas appliances are getting the correct amount of gas as set out in MI's

Surely there should be an easier way to work it out as well!! column e-f and column h-g aren't very scientific!!!

 

[AWheating]

its because appliances are designed and manufactured based on the inlet being correct, 20mb inlet, 21 at meter so you are allowed up to a 1mb drop.

you have to have consistency.

as for being dangerous, use your engineering judgement and experience.

 

[jase158]

but most boilers are manufactured to 14mb ish aren't they??

 

[arran197]

Got the wrong end of the stick, ignore me.

 

[AWheating]

but most boilers are manufactured to 14mb ish aren't they??

where you hear that rubbish?

dont forget boilers only make up 1/3 of most houses appliances.

 

[jase158]

where you hear that rubbish?

dont forget boilers only make up 1/3 of most houses appliances.

Most boilers have a minimum inlet pressure of around 14mb (may be wrong) but surely they need to allow for 4mb drop of meter!!

 

[bigads28]

The way premix burners work its essential they have the correct inlet pressures or the mix won't be correct. It also ensures all appliances have enough pressure to work properly.

On old boilers where you set the heat input then as long as the minimum bp could be achieved then I think it was NCS can't quite remember if I'm honest.

But if somebody is moaning about .2 mb then they need to get a grip! Use a water gauge and the .2 will evaporate lol!

 

[jase158]

for example!!
say you had a house with no cooker or fire, only a 12kw heat only boiler and a 2mb drop!! MI say working pressure must be 14mb minimum.

meter working pressure is 21mb, at boiler 19mb,

 

[mfgs]

for example!!
say you had a house with no cooker or fire, only a 12kw heat only boiler and a 2mb drop!! MI say working pressure must be 14mb minimum.

meter working pressure is 21mb, at boiler 19mb,

The its NCS if you are servicing it. You cant install it that way though.

 

[AWheating]

Most boilers have a minimum inlet pressure of around 14mb (may be wrong) but surely they need to allow for 4mb drop of meter!!

incorrect, they are all different from around 16.5mb to around 14mb but this normally depends on the pressure drop inside the appliances components (loss though gas pipework,filters etc...) and if you have 16mb at the meter at "peak demand"

 

[AWheating]

for example!!
say you had a house with no cooker or fire, only a 12kw heat only boiler and a 2mb drop!! MI say working pressure must be 14mb minimum.

meter working pressure is 21mb, at boiler 19mb,

i would be asking why would i want to do my job incorrectly? assuming your installing it.

 

[jase158]

i would be asking why would i want to do my job incorrectly? assuming your installing it.

Hence why I am asking,
Went to a boiler service other day. Started doing service as you do and went to gas meter (all in garage) couldn't see gas pipe to boiler so moved a few things and 6-7 metres to boiler, I know the 12RI's can be installed using 15mm but MI's say 22mm for anything bigger. Had a look and it was 24kw, fitted with 15mm gas pipe 9 metres (including fittings) from meter. With cooker and gas fire (obviously capped and turned off) but got me thinking about why we do it!! The worst thing is that it was someone I know who installed it, so may be getting a call next week!!

 

[Ermintrude]

Not sure what to say; boilers gas rate calculated for 19mbar. Reps say it will function at 14 to make it some how appealing! They will start to malfunction below 14mbar.
They are safe and designed for 19. I don't believe it's dangerous its ncs. It's AR if it's sucking out appliances .

 

[AWheating]

what if somebody comes along and refits a cooker, tests it, its all good. then when in use the boiler fires up and the gas cooker goes out. Yes its all if and buts, but there are reasons why we must do things correctly, mainly because its safe if done correctly. Some installers use the boilers min to excuse shyt work.

 

[villa_tom]

I don't make the rules, I just follow them

if I found a 1mb drop I'd personally NTCS it and check it with other appliances on full pelt, I've yet to find one that stopped another appliance working, but I'd imagine I will eventually.