Pipe size required for combi ???

[MartinJohnson]

I am trying to get a small combi fitted in a new house and am confused because of conflicting advice from 2 gas safe registered fitters. One says a valient eco tec pro 24 will be fine using existing pipework which includes a 15mm section of piping going upstairs with a few bends, for about 10-15 meters from street source. The other says won't get enough gas to the boiler.
I'm obviously trying to do this safely so any help me working out who is right much appreciated. Thanks,

 

[Whn1]

May work correctly with he original pipe work but doubt it, you should definitely listen to the 2nd engineer and the the gas upgraded!

 

[smtplumbing]

where is your meter, from your meter to your gas boiler how many meters is it is there any other gas appliance on a the line.

Tbh like me and most the GSR boys we upgrade the gas to 22mm saves any problems in future, as you might add more gas appliances

 

[GasmanxxxR1]

22mm gas for sure

 

[AlexGas]

Get a 3rd one in!?