Modern condensing boilers and microbore

[choco]

Are they reasonably compatible? I had a look at a job today where a new combi system is required to replace the existing hot and cold storage. It's a third floor 3-bed flat where all the 8mm and 10mm microbore CH pipes are buried in screed. The custie wants a few rads moved, so I'm more inclined to start from scratch with 15/22mm pipe runs and do a bit of digging.

 

[johnnyplumb]

microbore is fine as long as there is no sludge in the system. 8/10 mm pipe can clog up easier and can be harder to powerflush or clean. is there any problems with rads not heating up ?

 

[choco]

I think the CH system still works reasonably well, but the whole apartment is being modernised from a granny flat to a bachelor pad. There's a conventional flue Ideal Mexico (floor standing), HW cylinder and CW storage tank they want ripped and replaced with a combi.
There's a ton of other work going on in the flat while it's empty, so replacing the pipework could be viable.
If anything, I've got more concerns over the cold main water pressure. It seems pretty lame to run two bathrooms and a kitchen.

 

[Mike Jackson]

Microbore is fine on a modern boiler but I wouldn't be pressurisng pipes buried in screed. Too high a chance of a leak for me.

 

[stevetheplumber]

id run some cleaner round the exiating sytem for a few days then pull the boiler cylinder and tank out and preasure test the pipework before you start dropping the rads if its copper chances are it will be fine

 

[Bernie2]

I think that perhaps your question was more about the fact that it is a modern condensing boiler and would mini/micro bore pipework be as effective as 15mm small bore at getting a temperature drop across the system. Obviously with mini bore you may need higher pressures to get it to circulate and that would mean faster water flow. The question is would it be too fast to meet the flow and return temperature difference required for a condenser boiler to condense? I imagine it should be okay, if you fiddle about and balance it enough and as you say you are adding more rad's which in turn will help lower return temperatures.

 

[Billy Bob Bob]

there is no problem at all with using 10mm minibore on a sealed system condensing or otherwise i only use 10mm on rads unless BTU,S dictate otherwise as per mikes post when pipes go in screed this is one application where plastic is very suitable

 

[Howsie]

I'm wit Gasman!

 

[Mickyplumb]

I've done plenty of new boilers onto existing micro bore. Always been fine.