laying new rad pipes,how many zones

d o'c

I have to lay pipes soon for rads in new build.
going with pex pipe, ground floor hot press. Was planning 2 heat zones, 1st floor/ ground floor

Ideally I'd like 1 heating loop for 1st floor....but..
My 1st floor has some rooms where the floor steps downs (approx 300mm)
If I run pipework from ground floor Hot press i cannot maintain a level/steady climb to all rads,
I can for several, then it must route downward for a few rooms, then back up again.

I'm thinking this will cause airlock issues?, and will lead to problems when trying to drain.


If I split the 1st floor into 2 zones, I can get a steady rise in pipework by heading 2 ways once I get through the gnd floor ceiling.
However the heat load won't be an even split, 1 supply/return will be doing 3-4 rads the other will be to 7-8.
Will an uneven split give problems, will the water tend to flow more to the shorter loop.?

Outkast_IRE

Stick with the upstairs downstairs system , and make it a sealed pressurised system this will ensure airlocks arent a issue . And for the rads that are down the steps just ensure you put in a drainoff down there on one of the pipes feeding the rads.
You usually have a third zone for just the cylinder .
If your making it a sealed pressurised system you need an expanison vessel , a fill loop and a saftey valve are fitted.

Carlow52

4 zones IMO
2 upstairs : high level and low level
one down stairs and the HW

d o'c

Yes I'm going with a pressurized sealed system.

Just done some room heating calcs ,and 25Kw required gnd floor alone.
Is this asking too much from a 3/4 pex pipe on 1 zone.

On gnd floor I'll be clipping the pipes to the floor insulation, then covering with screed

What is best used to cover the pipes before I pour the screed, to stop the pipes contracting,and to stop loosing too much to the screed