Plumbing - Central heating extension and rising main query

[Fireball40k]

I am about to begin plumbing an extension and could do with a bit of advice on two points:

1) The existing central heating is an 8/10mm microbore system running to all radiators from a single manifold, which is fed from the boiler by 22mm pipe. I have replaced and re-sited the boiler (W/Bosch Greenstar 42i combi) and wish to add the following in addition to the existing microbore manifold via a new 22mm loop:
a) A downstairs under floor heating manifold
b) An upstairs under floor heating manifold
c) A towel radiator
d) A standard radiator
I intend to feed the two new radiators using 15mm spurs leading from the 22mm main loop.
My concern is with mixing all of these different types of elements on a single 22mm CH loop and some of them not getting the flow that they need - particulary the microbore manifold as it will be the last item in the loop - any thoughts?
Also, I intend to make the 15mm spurs to one of the radiators roughly 3-4 metres long in order to keep the main 22mm loop as short as possible - does anyone foresee any problems with this?

2) My second point relates to the rising main. I have installed a new 25mm MDPE main pipe and would like some advice on when to slim it down to 15mm. I want to get as good a head of pressure into the boiler (and the various kitchen/bathroom taps) as possible, so would it be best to use a 25mm to 22mm stop cock and then run 22mm as close as possible to the boiler and the kitchen/bathrooms before converting down to 15mm for the last stretch? - or is this not the done thing?

Your advice would be most welcome

Many thanks in advance

Steve

 

[Agile]

As long as the system is properly balanced you will not have any problems.

However, I am not sure that you have the required skill to integrate underfloor heating. Do you realise each UFH loop has to have its own pump and blending valve and seperate timing control???

The mains supply should be taken to the boiler in 22 mm and the cold water take off at that point in 15 mm. Thats the way to get the optimum performance but few plumbers would do it that way commercially and would probably try to talk you out of doing it that way even if you said you would pay the extra.

Tony

 

[Fireball40k]

Thanks Tony,

I do understand about the separate loops, pumps, valves and controls for the UFH, but can you give any tips on achieving the proper balancing of the various items connected to the 22mm loop?

Regarding the rising main query, is it worth feeding 22mm pipe the ten metres or so before it reaches the bathrooms and kitchen area, where I would then split it down to 15mm to feed the various taps?

Cheers

Steve

 

[Softus]

However, I am not sure that you have the required skill to integrate underfloor heating.

Fortunately, that knowledge is easy to obtain from a combination of this web site and the u/f heating kit supplier's instructions.

The mains supply should be taken to the boiler in 22 mm and the cold water take off at that point in 15 mm. Thats the way to get the optimum performance but few plumbers would do it that way commercially and would probably try to talk you out of doing it that way even if you said you would pay the extra.

Few plumbers are so insecure that they have to invent industry statistics in a forlorn attempt to make themselves look good.

 

[Agile]

Thanks Tony,

Regarding the rising main query, is it worth feeding 22mm pipe the ten metres or so before it reaches the bathrooms and kitchen area, where I would then split it down to 15mm to feed the various taps?

Cheers

Steve

I am not quite sure what you are asking.

I have told you what needs to be in 22 mm for the cold.

ALL hot water needs to be in 15 mm. In efficiency terms its better to use a little volume of pipe as possible but thats not always easy to achieve in which case two feeds in 15 mm from the boiler are OK.

Tony