Planning a Microbore system

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I'm planning a retrofit 10mm microbore system for a small house. I know that the standard method is to run individual circuits to each radiator from a manifold on a 22mm pipe, although I have put two radiators on one sub-circuit before without any problems. However, in this case, it's going to be difficult to use the standard system on the Ground Floor. If I take the 22mm pipe as close as I can, am I likely to have any problems if I then connect four radiators on one 10mm microbore sub-circuit ? Maximum distance from the 22mm pipe is going to be about 10 metres.
 
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You seem to be planning to do something that no heating expert would ever approve.

Only you know just why you think that you can do something that no professional would ever do.

Is it that you think that you know better than any professional or is it just that you cannot see that we do it in a particular way for a good reason?

Tony
 
Thanks for the replies. That's the whole point. I couldn't find anything that told me whether it was possible or not, so I thought I'd try and get some advice. Clearly it's not possible, so thanks for telling me. The only reason I'm contemplating microbore is that it would make the retrofit a whole lot easier. If I can't use it on the ground floor, it's not the end of the world. Microbore would still make life a lot easier on the first floor, so the next question is can I mix standard two pipe 15mm on the ground floor, and standard 10mm microbore (one circuit per radiator) on the first ? Your plainly stated advice, as before, would be much appreciated.
 
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You can but balancing will be more tricky.

You have not explained why you are so keen to use 10 mm pipework.

The most that I would recommend if it was any advantage is to feed the last 1 m to the rad in 10mm. But again I cannot see why you would want to do that!

Tony
 
Tony,

Thanks for the reply. Sorry for delay in response - been away.

The only reason for thinking of 10mm on the Ground floor was being able to avoid making messy chases into walls - they're dry lined, but there isn't enough gap for 15mm. As it's not going to work, then so be it.

On the first floor, the joist spans are quite large, and where I'm going to have to cross them it seems structurally better to drill small holes in the centre of the joist and feed 10mm through, then notch them for 15mm - and 10mm is just easier to work with - but if it's going to cause me more problems than it's worth, then again, so be it.
 
Drilling neat holes in the middle is better anyway. Make sure you drill in the right place; nicely in the middle of the height, and between 25% and 40% of the span, measured from either side. Holes can be twice as big as notches, so apart from very rare situations, 20 mm holes in joists are fine, and lots of room to work.
The hole should never be less than 50 mm from top or bottom, and measure out at a minimum of 4 times diameter from each other, preferably more.
 
usually with 10mm, rule of thumb is it will carry 2.5 kw so make sure all four rads wont struggle.e.g 4x1kw rads =
 
I would plumb the 10mm finals to 22mm. Branching off 10mm could cause problems later
 
usually with 10mm, rule of thumb is it will carry 2.5 kw so make sure all four rads wont struggle.e.g 4x1kw rads =

If there was a rule of thumb the it would all depend on the length of the thumb!

The only rule of thumb that I am aware of is that 15 mm will supply about 3.5 kW but that assumes the length of 15 mm is about 3m there and back.

Tony
 
You seem to be planning to do something that no heating expert would ever approve.

Only you know just why you think that you can do something that no professional would ever do.

Is it that you think that you know better than any professional or is it just that you cannot see that we do it in a particular way for a good reason?

Tony

:eek:

Isn't that the whole point of a forum, so that non-professionals can ask questions about the projects they are planning. By asking questions, where did he imply that he knows 'better than any professional'?

Why the lecture. Very strange!
 
He told us what he was going to do.

He told us that he also knows how its usually done ( by professionals ).

He then asked if he was likely to get any problems doing it differently.

He was told that he was likely to have problems.

Tony
 
If I take the 22mm pipe as close as I can, am I likely to have any problems if I then connect four radiators on one 10mm microbore sub-circuit ?

Sorry, but a question mark at the end of the sentence means its a question. He's not telling anyone anything.
 
If there was a rule of thumb the it would all depend on the length of the thumb!

The only rule of thumb that I am aware of is that 15 mm will supply about 3.5 kW but that assumes the length of 15 mm is about 3m there and back.

Tony


actually its somthing like 2.5kw for 10mm 7kw for 15mm and 14kw for 22mml.
 
Pipe length (total flow and return) and fitting have to be factored in as well
 

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