New combi boiler to fit, pipe work size confirmation & manifold question

[larneylee]

Hi,

I have bought a new house which has not central heating as the previous owners just used oil filled radiators once their combi boiler fitted in 2011 got condemned. The old combi boiler is upstairs in the bathroom and my plan is to fit our new Baxi 33HE downstairs just off the kitchen. The house is a 3 bedroom upstairs downstairs. Many years I helped a friend plumb in a house of the same size with 15mm speed fit and he has subsequently had 10 years problem free central heating.

I just want to confirm for myself that it is still okay to use 15mm pipe work to all of my house to all of my radiators? 9 radiators in total. I would be taking 22mm flow and return off the boiler for the first 1m then I was considering using or making a manifold on the flow side and a manifold on the return side, for easy connections. The simple manifold will either be 22mm or 28mm reduced to the 15mm pipe runs to the rads.

Can anyone with more relevant knowledge supply and further details? I am not bothered about the science of water just want to know the mechanics of the plan is sound and acceptable?

I look forward to your help, thoughts and perhaps any suggestions.

 

[mrStat]

So yes, I have seen several houses with centralised manifolds for the heating rads where every rad has a dedicated flow and return to the manifold by the boiler... Nothing wrong with it, just remember that it is a huge waste of pipe, you'd be better off supplying each floor in 22 at least and splitting the floors. Why anyone would want to try and run x18 pipes to a singular point is beyond me, most joists could not handle the notches and you'd end up weakening the floors.

But yes, theoretically you can... I just wouldn't do it in my home. We have x3 zone valves, x1 for each floor and x1 for the hot water. Our downstairs is on a 22mm drop and our upstairs loops out in 22mm with the rads each coming off in 15mm.

Just remember you will need to balance this lot as well. This will be best done at the manifold.

 

[cdbe]

I've done mine like this. I have a heating zone on each floor supplied by 22mm from each valve then manifold from a central point (the old airing cupboard in the case of upstairs). In the picture the three flow pipes are at the front with the three returns hiding behind - only two in use at the moment hence top pipe capped off. The 10mm pipes are for the 2 bathroom towel rails fed off the primary hot water circuit. The downstairs zone is a similar set-up in the cupboard under the stairs. It all works perfectly, there are no inaccessible joins - because we have laminate flooring everywhere. I imagine you could get away with 10mm to most radiators if you wanted - a lot of the manifolds seem to be 22 to 10's.