installing a 2 zone central heating system

[dontknowitall]

I don't think you can go OTT with a 22mm heating circuit and 15mm individually to/from most or all radiators. It will probably last for much longer than a microbore system and put up with more neglect.

 

[Tinno]

hi dontknowitall, thx for the advice...so theres no need to rip out some of the 22m and swap it for 15mm to feed several rads in order to keep the velocity above the min requirement (what ever that is in plastic piping - same as copper?).


Obviously, i'm putting the heating myself, its a big job in terms of labour and i want to get it right first time. I want a system that is efficient and lasts a long time. I think the advice that i am getting from this forum is going a long way to making sure that happens, so thx to everyone who has contributed, especially doitmyself. Anymore info and advice would be great.

 

[dontknowitall]

I don't know it it's you or me muddled up here.

The heating circuit will be the 22mm flow from and continuing in 22mm return to the boiler.

Off this circuit you will tee in 15mm from flow of heating circuit to flow end of radiator and 15mm return from radiator to heating circuit return.

 

[Tinno]

yes, exactly....22mm running close to radiators then tee'ing off ith 15mm to the radiator. I'm just thinking that i may have gone too close to the rads with the 22mm. For example, i have a rad that is about 0.4kw, the 22mm goes close to this, i then tee off using 15mm, total length of 15mm being aprox 5.2m (incl flow and return). I'm thinking is the piping too big for such a small rad to get the flow of the water running at the minimum velocity??

 

[dontknowitall]

That's one of the reasons for fitting lockshield valves so you can regulate the flow of the water through the radiator.

What you're doing sounds fine.

 

[stevetheplumber]

Just looking at your sizing of pipes and yes it does look a bit ott generally you can get the last 2 rads of the 22 in 15 unless they are massive so at the 3 from last your branch of twice in 15 one to that rad and 15 to next with 15 tees to the next
dont get to hung up on velocities generaly for domestic work its done by eye and you have no control over the pump with most combis

 

[Tinno]

ok thx stevetheplumber. Anybody know what is the max distance a 15mm pipe can go from the main 22mm piping to a radiator? can it go on for ever, for example if i had a rad say located 10m away from the 22mm pipe is it ok to run 20m of 15mm pipe (flow + return) without any detrimental effect? I have been working on the principle of getting the 22mm pipe as close to the rads as possible so that the 15mm is not too long.

 

[dontknowitall]

10m is fine for a 15mm pipe. I did a run of around 14m metres using 10mm pipe and (apart from an air lock) it works fine too (on a sealed system).

To be fair Tinno, someone would have picked up a potential problem for you by now if you were doing things wrong! The written word is fine in all those books, but there's nothing like the real life version to prove the books wrong (...or right!)

Just go for it!!

 

[doitmyself]

That's one of the reasons for fitting lockshield valves so you can regulate the flow of the water through the radiator.

But it's easier to reduce the flow if the rad is fed from the correct sized pipe as the pipe itself acts as a flow reducer.