is 28mm pipe required to supply gas to 25kw combi boiler?

[Zehroni]

I have been inviting gas engineers for quote to replace the boiler and fit couple of radiators in a 2-bed mid terraced house and need help with 2 issues
1- There is already 22 mm pipe suppling the gas to the boiler and the boiler is approx. 10 m away from the gas meter which is outside the house. One gas of the gas engineer quote including replacing the 22mm pipe with 28mm for the gas supply. The reason given is that the boiler is to far from the gas meter and the gas pressure will be reduced from 22mbar to 18mbar by the time it reaches the boiler.
2- All recommended running plastic pipe instead of cooper. I have not worked with plastic pipe.
a. How reliable are they?
b. do they leak?

 

[Jurassicspark]

25kw for a 2 bed house?

 

[flameport]

One gas of the gas engineer quote including replacing the 22mm pipe with 28mm for the gas supply

Distance, number of bends, other appliances and so on. Those that have visited the property will have this information - no one here will.

All recommended running plastic pipe instead of cooper. I have not worked with plastic pipe.

Hopefully that's plastic for water and radiators, and certainly not for any gas.

Plastic pipes and the joints for them do not leak when installed properly.
If installed incorrectly, such as not secured, joints left hanging with the weight of wonky pipes pulling on them and so on, then leaks are inevitable.

 

[Murdochcat]

Are you thinking that you will be running all the pipes ?

 

[Zehroni]

Distance, number of bends, other appliances and so on. Those that have visited the property will have this information - no one here will.


Hopefully that's plastic for water and radiators, and certainly not for any gas.

Plastic pipes and the joints for them do not leak when installed properly.
If installed incorrectly, such as not secured, joints left hanging with the weight of wonky pipes pulling on them and so on, then leaks are inevitable.

Distance, number of bends, other appliances and so on. Those that have visited the property will have this information - no one here will.

Regulations are regulations and should not be subjected to personal option. Why 3 engineers think 22mm pipe is ok but only one thinks 28mm should be fitted. That is what I need to understand

plastic for CH only, copper for gas

 

[Zehroni]

Plastic pipes and the joints for them do not leak when installed properly.

what is the best brand

 

[Zehroni]

25kw for a 2 bed house?

is this too much or too little for 2 bed with shower

 

[RandomGrinch]

is this too much or too little for 2 bed with shower

A 25kW combi should be fine for a 2 bed mid-terrace with a shower.

 

[johnny2007]

what is the best brand

I've used hep2o and find it very good.
Many jobs done in the past 10 years and no leaks.
Make sure you support all pipes properly and don't forget the inserts.
Don't mix brands.

 

[flameport]

is this too much or too little for 2 bed with shower

For hot water it will do what's required.
For heating, it's grossly oversized.

That's how combination boilers are. It's an inherent limitation of them.

 

[Jurassicspark]

is this too much or too little for 2 bed with shower

You need a heat loss calculation carried out to ensure the best efficiency and boiler size.

 

[RandomGrinch]

You need a heat loss calculation carried out to ensure the best efficiency and boiler size.

Usually a heat loss calculation is prudent. However, in this case and as flameport suggests; a 25kW boiler is about the smallest combi that can be purchased. This is a size that would produce a good shower in a one bathroom house - the boiler is sized for the hot water output.
25kW would easily supply heat only, to a very large property.

 

[fixitflav]

Why 3 engineers think 22mm pipe is ok but only one thinks 28mm should be fitted.

That's the first mention of the 3 who think 22mm is OK. According to my calc, unless you have a large number of bends and fittings, or something unusual, 22mm is fine - less than 1mb pressure drop.

 

[Harry Bloomfield]

The pressure drop, needs to be calculated, not guessed at. Some gas fitters just play safe and guess. What Kw of combi do you have installed at the moment?

 

[johnny2007]

Some gas engineer don't want to waste time do the calculations and just go for the bigger size (bigger job maybe?)
I would like to think they all know how to calculate the pipe size, but who knows.
When I had my boiler replaced a couple of years ago, one plumber said I needed all new pipework with some at 28mm, all on top of his head.
Another came, measured, designed all the bends, checked gas hob supply and measured and made calculations which took him 20 minutes.
Result: 22mm more than appropriate.
I used him since.