CH pipes only 15mm from boiler

[nigelad]

I'm going to have my combi boiler replaced, but fitters who have looked say current 15mm pipes on CH flow and return are too small. One suggested replacing about 1m up and 1m down [from the boiler] with 22mm to help heat travel away from boiler. Do you think this would make a difference? Does it depend on the boiler fitted? It would be either Vaillant Ecotec plus 831, Worcester 30si or Alpha 28K.
Thanks .

 

[THECURE1]

you may have this sorted by now but it is a good idea to have as much 22mm pipe as possible

 

[BGEngineer]

All depends how big your place is and what boiler is going on. Went to a customer the other day who had a Potterton Performa 28 and he had a 3 bedroom house. The installer had done the flow and returns in 15 and I said straight away you can't have that. Allthough on reading the installation instructions it didn't say the pipework had to be in 22 and the heating worked perfectly well. Its good practice to do them in 22 but not necesary.

 

[nigelad]

Thanks for replies.
House is 3 bed terrace, 10 rads including 5 small ones. Got cavity wall ins, loft ins = double glazing so not hard house to heat.
Still not sorted out as fitters who have quoted all want to install Alpha boilers, and I want a Vaillant or WB. When I ask them to update their quote for this they don't get back to us.
Gonna have to go with someone soon as it's getting cold...

 

[gas4you]

Generally with 10 rads I would expect the first part of the heating circuit to be in 22mm.

15mm pipe will handle approx 4Kw of rads comfortably, above this you would need the 22mm.

Whats all this with Alphas recently? Nothing too wrong with them, but not up to the Vaillant quality.

Must be on cheap offers somewhere.