Plumbing my central heating?

[amason79]

I am going to be plumbing my central heating (not the boiler).

I am not sure if I should use 15mm or 10mm from the main runs to the radiators!

As I see it there are Pros and Cons to each, as I see them:

10mm (microbore) is easier to work with, requires less notching of joists, and I can burry it easily in conduit in the wall and there is less water in the system to heat up (reducing the cost of warm up).
But its not much cheaper than 15mm, it comes on coils and can be messy, I have my doubts if it can deliver to any radiator over 2500 BTU and I wonder if the radiators will take longer to heat up in addition the heat loss will be greater than from a 15mm pipe.

15mm it neater (straight lengths) it can definitely supply upto 10000 BTU, it looses less heat and should get the radiators quick faster.
But it is difficult to run through 20mm conduit and 25mm conduit in stone is hard damn work (I don't want it in chunky trunking cause that looks worse than the pipes directly on the surface). Also I am heating a lot of water during the warm up phase that I do not need to.

All of this is based on my limited knowledge, any advice would be much appreciated. Which system is more efficient?

Do you get cool rads with 10mm (I know you do with 8mm)?

Thanks


andy

 

[Johndug]

I installed my 10mm microbore system 35 years ago. Originally I used 3/4 inch stainless steel tubing from the boiler to the manifolds, one on the 2nd floor landing, the other on the groundfloor. The reason for using steel tubing in 1971 was because of a world copper shortage. From the manifolds to the rads I used 10mm copper. Over the years I've extended the system into a kitchen extension and also into a loft conversion. Over the 35 years the controls have been updated and only recently have I taken out all the steel tubing and replaced it with 22mm copper. The 10mm tube is original. The system is now on it's third boiler and I find it all very satisfactory.

 

[ChrisR]

I'd stick with 15mm if it was for me!
Major reason is the heat losses. Under suspended floors these are truly massive for 10mm, and insulation is hard to get.
Surprisingly it's cheaper to use 22mm with proper insulation than 15, so you see what I mean.
We see lots of dirty sysems, and increased problems with smaller pipes. OK if you make sure it never gets dirty.

 

[petelewis]

Hi, I work on new builds, we use 10mm for radiators which are pulled back to a 22mm run for the central heating. As long as you have a 22mm run it doesn't matter if you have 10 or 15mm to radiators.[/b]