Connection between boiler and gas supply

[sebastienj]

Hi,


I am currently having a few quotes done to replace my boiler+cylinder with a combi and one of the plumber who offered to fit either atag or a vieassmann said that I can't have a boiler that supply 30kw because my connection for the gas supply is provided through a 22mm pipe. He told me that I can have a boiler that is less powerful or upgrade the pipes. The problem with upgrading the pipes is that the gas meter is on the other side of the flat so this is not an option. Having a less powerful boiler would mean I could not run both showers at the same time. I need to boiler to run 2 showers at the same time.


I went on the Atag website and looked at the documentation
http://goo.gl/SK22cU
and searched for the gas supply connection


In section 9.5 gas connection in general - it says the following
The boiler connection is provided with an isolation valve with 22mm compression fitting, into which the gas line can be fitted


Does the mean that the boiler can indeed work with a 22mm gas supply ?


The other plumbers (vaillant, worcester) did not raise this as being a problem - who is right? Was this overlooked?


Thanks

 

[Dotty]

He's right. I'd go with him as he seems the most conscientious so far.

Also, any combi will probably struggle to run two showers, it's not the kw output, it's the flowrate

 

[chris watkins]

Almost certainly the guy suggesting the gas supply is replace in 28mm but we would need to see the gas run.

It is all about the amount of gas that you can get out of the end of a gas pipe and this is effected by a number of things but mainly the length of the run & the amount of bends which restrict the flow due to friction, it is not just about the size of the pipe.

So you are likely to have a 22mm connection to the boiler & a 22mm outlet from the gas meter but 28mm will be needed to achieve the mount of gas required so that the boiler can heat the mount of hot water you require to run 2 showers.

So you need to ask yourself a couple of questions -
1. Will I actually have two showers running at the same time?
2. If two fittings will need hot water at the same time is a combination boiler the right equipment for the job?

Warning, if any of the boilers are connected to an undersized gas supply they will still work but may not provide the amount of hot water you require or the manufacture states they can produce.

 

[ShaunCorbs]

I'm sorry to say before you start looking as croppie has said no combi boiler will run two showers at the same time

The only way is have a storage combi but there big very big

Could the gas pipe be run external if your in a flat ?

 

[sebastienj]

yes the current pipes going from the meter to the boiler is 22mm.

we can't run new pipes because it will need to go through the corridor and 2 bathrooms. plus i don't really want the pipes to be apparent.

we really need the extra space that's why we wanted to get rid of the cylinder.

 

[ShaunCorbs]

yes the current pipes going from the meter to the boiler is 22mm.

we can't run new pipes because it will need to go through the corridor and 2 bathrooms. plus i don't really want the pipes to be apparent.

we really need the extra space that's why we wanted to get rid of the cylinder.

sorry to say your stuck with your cylinder then

 

[sebastienj]

ok so if we do want get a combi while using the 22mm pipes what are the options in terms of boiler power we can have?

I read on some other sites that you could get worcester
https://www.mybuilder.com/questions/v/11360/does-a-combi-boiler-need-a-bigger-gas-pipe-than-boiler-with-large-water-tank

could this be an option?

would a one shower and a tap at least work?

 

[ShaunCorbs]

ok so if we do want get a combi while using the 22mm pipes what are the options in terms of boiler power we can have?

I read on some other sites that you could get worcester
https://www.mybuilder.com/questions/v/11360/does-a-combi-boiler-need-a-bigger-gas-pipe-than-boiler-with-large-water-tank

could this be an option?

would a one shower and a tap at least work?

thats with every boiler gas flow and pressure is key

and no as the flow would be split say your boiler can supply 20 lpm and you open 1 tap that will be 10lpm in your shower and 10lpm at your tap (about)

 

[AlexGas]

Is it the time to close the thread!?

 

[joni os]

If you have a gas cooker this will further restrict your boiler Kw sizing. Either upgrade to 28mm as advised, or stay with cylinder.

 

[sebastienj]

Is it the time to close the thread!?

don't be rude I am trying to understand my options

 

[sebastienj]

ok thanks the responses. i am sure I will have other question as i get more understanding. thanks

 

[AlexGas]

don't be rude I am trying to understand my options

We cant give out gas safety related advice to non qualified people this includes all aspects of gas installation and repair.

 

[Dotty]

No, we can't. However this thread can stay open because I think it's vital that the general public understand that there's a danger associated with an undersized gas supply. As long as no one gets too technical.

Sebastienj

We never ever size a boiler according to the existing gas supply. We always size the gas to suit the boiler and there's a rake of calculations to do this.

I'm sorry but you will probably need to substantially re-evaluate your expectations.