Too many rads off 15mm pipework?

[ms2004]

Hello, looking for an answer to this question please. 10 years ago we had CH installed after removing night storage heaters. Originally it was a combi but we changed to a regular boiler 2 years ago which is a Worcester Bosch oil 25kw. We currently have 12 rads, all of which are fed through 15mm pipework, the whole sytem is piped using 15mm. We want to add 2 more rads to the system now and potentially another 2 later in the year when we may build an extension (Not 100% sure about that at the moment).

My plumber rekons the 15mm pipework may not cope with an additional 2 rads and says "we can try". The house is a single storey.

Can anyone tell me whether they think the current pipework will cope? Right now all rads seem to work quite well. One or two are slightly cooler than others but I think balancing them properly may cure that. The flow and return to the majority of the rads furthest away from the boiler could be changed to 22mm without huge disruption but I would rather not do that if its not necessary. Also, given the boiler has been very good so far, I wouldnt want to cause any future problems to it by adding more rads to the system as it is currently.

Thanks for the advice.

 

[BigSnoopy01]

without seeing the system most engineers would advise on the increase in pipework size. 15 can feed 6-10kw depending on many factors which thoses with brains and a need can tell you about.

 

[mcmoby69]

just repiped a bungalow 6 rads all in 15mm. new 22mm's flow and return to a new boiler. no point fitting a new boiler and not correcting a badly designed system at the same time. boiler manufacturers are looking for easy way out of their excessive warranties they are offering.