boiler install gas pipe size

[g35brit]

I need a new boiler and would prefer a 35KW combi boiler but wanted to know if my existing gas pipe will allow it. I wanted to check this first so i can look at my boiler options before getting somebody around.
I don't have any other gas appliances and my existing pipe is 22mm. The gas meter is located next to our front door in a box at ground level. I have no wish to take up my Oak floor to lay a new pipe.
I have attached a rough sketch of the gas pipe run and would appreciate any advise. Thanks .

 

[Scott_D]

How many elbows & tees on the gas run

 

[g35brit]

How many elbows & tees on the gas run

Seven elbows no tees as shown on the sketch I attached.

 

[SimonG]

Your gas safe engineer will take care of all that. Get them in early.

 

[Scott_D]

20m of 22mm isn’t big enough for a 35kw boiler

 

[steadyon]

1. Your gas run is roughly 20 metres.
2. You appear to have 7 elbows. I'd suggest you count this as 10 (allowing for ones by the meter which may have been missed), so a further equivalent 5 metres.
3. The manufacturer's data will tell you exactly, but a 35 kW boiler will require around 3.8 cubic metres of gas per hour.
4. A 25 metre run of 22 mm pipe will only support a flow rate of 2.6 m cubic metres / hour, so is inadequate.
5. Subject to a specific site survey, you would need 28 mm pipe for the run.
6. Because gas is compressible, a required flow rate may be achievable with a mixture of pipe sizes. This would need a precise on the spot calculation. It can't be done over the internet. However, it MIGHT allow you to avoid damaging a floor.
7. For those who might consider this too much information, all the above is freely available on the internet. Mostly at https://copperplumbing.org.uk/sites...achments/domestic-gas-planning-and-sizing.pdf

 

[ShaunCorbs]

Gut feeling 28mm required as it’s around 20m

24kw is pushing it for 20m on 22mm

 

[g35brit]

Ok thanks all. New pipe was my gut feeling but it's a real pain having to lift an oak floor and chase across a newly tiled kitchen floor.
I was looking at a 35k Worcester greenstar 8000 lifestyle as we have a Bosch Worcester floor mounted 400 high flow at the moment, the difference being the floor mounted has a hot water storage tank in it.
I have 5 bedrooms, one bathroom and one shower room and no other gas appliances so maybe a smaller KW would be ok. What do you think?