Pipework for new CH System

[CHarr]

I'm planning my new CH installation. The house is being extended and the original 1960s DIY single-pipe system has been completely removed, and I'm starting again with a combi-boiler and two-pipe (22mm) feed & return with room stat & TVRs (except in hall with room stat).

I have never used it before (!) but was going to use 22mm PB-1 Barrier pipework for the main pipework, using polyplumb reducing tees to run 15mm pipe (PB-1 underfloor & 15mm copper above floor) to individual rads. I need 11 radiators, and hope to be able to run single lengths of pipework (no joins) between each rad to simplify installation and minimize possibilities of leaks or need for maintenance.

Does this sound sensible and are polypipe's products suitable & reliable for this application?

 

[Dan Robinson]

If starting from scratch, why not use an underfloor manifold and 10mm pipe and just run from the central point of each rad with zero joins?

It is not a simpler system, but if leaks under the floor are your main concern it works well.

Also allows you to better control the rooms. And if you reeeaallly wanted to zone each room.

Although with a combi, and decent insulation levels weather comp would be easier providing the household doesn't have too many taste heating wise.

 

[CHarr]

If starting from scratch, why not use an underfloor manifold and 10mm pipe and just run from the central point of each rad with zero joins?

A very different view, here: http://community.screwfix.com/thread/87094?start=0&tstart=0

I'd assumed that with a 'radial' system, I'd end up with a greater length of pipework in total. By running the main circuit along hall & landing from front to back, I can have fairly short 'branches' to the rads, and several can be directly fed from the main 22mm pipe runs. I'm not too concerned about the prospect of leaks (assuming polyplumb fittings actually work!), but do want to minimise the joist notching and so on.

Out of interest (well, to me, anyway), I've calculated 118m3 floor area, and a 10.5 kW total requirement. I'm amazed at how small the requirements are for some of the rooms (I'm struggling to think that a 500w fan heater would EVER get my main bedroom warm, for example, on a frosty morning). The boiler will be 28/30kW, so if I generously specify individual rads, I'm hoping that the house can heat up quickly from cold, before TVRs start shutting down.

 

[Dan Robinson]

Over sizing rads is never a bad thing. Means you can run the boiler at much lower temperatures - mine is hobbled to 55 degrees for heating, but is compensated so that it only gets that hot when it is .... time to check ..... OK not what i remembered...

Currently it will hit 55 when it is 3 degrees above freezing. Although to be fair I will be playing with the settings over the next 6 months or so.

 

[Dan Robinson]

A very different view, here: http://community.screwfix.com/thread/87094?start=0&tstart=0

Let them have their view. I have this system in my house and it works fine.

 

[CHarr]

Any views on using 22mm PB-1 barrier pipe & polyplumb reducing tees to 15mm to individual rads?

 

[Dan Robinson]

It is perfectly acceptable as long as the installation guidelines of the pipe and fittings is followed.

Remember this stuff gets incredibly droopy when heated. Lots and lots of clips will be needed.

Lubricate very joint before pushing the fittings on.