Microbore principles

[ChrisLong]

Hi,

I was going to install a 15mm central heating system but am now considering 10mm microbore for ease of installation.

There will be 4 downstairs rads and 4 upstairs rads.

Have I got this right?

the 22mm flow pipe should end in a manifold, out of which would be 10mm pipes to the rads (4 10mm pipes for the groud floor). From the return valve of the rads the 10mm pipe would go to the return manifold connected to the 22mm return pipe. Is this right? OR do i form a loop in the 22mm flow and return as with 15mm and take of stems with manifolds on?

Also, is it best to split the 22mm flow pipe before the manifolds, one for upstars and one for downstairs.

Also, is it possible to use 10mm in the same way 15mm, without using manifolds?

Doesn't seem to be much info online. Help would be appreciated.

Thanks

Chris

 

[chrishutt]

Also, is it possible to use 10mm in the same way 15mm, without using manifolds?

Yes, and you can use 8mm too. The principles are exactly the same as for 15/22mm. The flow runs to all rads by the most convenient route, and returns likewise. Pipe resistance should be appropriate for heating load, so 8mm is fine for short connections to most rads, 10mm OK or longer connections and/or bigger rads, and 15mm can supply about 6 kW total load. But above that you might need 22mm. It's not always necessary to feed manifolds with 22mm, or even to use manifolds.

 

[ChrisLong]

thanks for the reply, thats a great help,

Another query, what are the maximum guidelines for the length of 10mm going to a rad? I know it will depend on the pump but is there an average that is 'safe'?

Chris

 

[chrishutt]

Try a Google search for the tables. I think CDA do them.

http://www.cda.org.uk/megab2/build/pub-33-copper-tube-in-domestic-water-services.pdf

 

[ChrisLong]

Thanks for the reply, a great help.

Last query. If I use manifolds then my plan would be this. To have the flow and return in 22mm. Half way along a manifold would feed two rads. At the end of the 22mm manifolds would feed 4 rads. Therefore, there would be 4 10 mm flows at the end of the 22mm. Is this right? It may be more cost effective than buying lots of T-convertors.

Chris

 

[Agile]

You may find it will work better and perhaps be cheaper if you limit the length of 10 mm to a rad distance of say 3 m otherwise you can get some widely varying flow resistances.

With such a small number of rads it may be easier and cheaper to just reduce or tee off 15 mm rather than using manifolds.

Its very important with microbore to use a cleanser and flush properly and then add a good quality inhibitor like X100.

Tony

 

[ChrisLong]

If i were to use manifolds, the manifold at the end of the 22mm flow pipe with 4 10mm outs would feed 4 rads. 3 of these would be within 3 metres, another would be within 4 - 5 metres. what do you think?

Alternatively I could lay 22mm and 15mm under the floor and then reduce further to 10mm to make it easier to get to the rads.

I was just considering manifolds because it would be neater with less joints to make.

To be honest, I feel happier using the 10mm micorbore as if it were a 22mm / 15mm system.

Chris

 

[fitz1]

i run 22 to 15 then 10. only use 10mm for short connection on upstairs and drop on downstairs. Hate it when you have to add a rad in conservatory and you have to find manifolds under chipboard floors.

 

[Agile]

If i were to use manifolds, the manifold at the end of the 22mm flow pipe with 4 10mm outs would feed 4 rads. 3 of these would be within 3 metres, another would be within 4 - 5 metres. what do you think?
Chris

If you must use a manifold then I would recommend that you feed the diistant rad with 15 mm until you are 3 m away.

The 10 mm tube gives considerable resistance and installers often seem to forget or perhaps do not appreciate that if you double the distance you halve the possible flow.

I would still suggest you use individual pipe bits unless its truly a radial situation. 10 mm is the same price as 15 mm.

Tony

 

[croydoncorgi]

And 10mm fittings usually cost MORE than 15mm!!

 

[ChrisLong]

thanks for the advice everyone, a great help

I'm going to reduce to 15mm where possible and then 10mm later keeping the distances as short as possible.

Thanks again

Chris

 

[Agile]

As I said earlier, in many ways its better to equalise the 10 mm distances.

That gives a kind of auto balance.

Tony

 

[chrishutt]

Even better to do it properly and use 8mm and 10mm in accordance with heat load (rad output) and length of run. Equal lengths of 10mm only makes sense if all rads are of similar output.