15mm pipe run from central heating manifold query

[Donkey Table]

Hi Guys

Im aware the say you should keep 15mm runs supplying radiators to 12 metres. However if running one rad from a manifold, how much can I get away with?

Im not holding a gun to your head. One of my runs has to be just over 13 meters.

Thanks in advance.

Donkey.

 

[Ben-gee]

What size rad in terms of heat output?

 

[Donkey Table]

Hi Ben thanks for replying.

3567 Watts
12178 BTUs

Thats the only rad on the run.

 

[ShaunCorbs]

22mm as far as you can

 

[Donkey Table]

22mm as far as you can

I can get 22mm to the manifold no probs, its the single radiator circuit run from the maniford is 13 metres, across the house down the wall etc. I would like to stick with 15mm for that section. In addition that is the run to the rad, not combined return.

 

[ShaunCorbs]

I’m guessing it’s plastic then ?

 

[Donkey Table]

I’m guessing it’s plastic then ?

Yes Hep2 15mm barrier. Im trying to keep the manifolds away from the bedrooms. Hence the longer runs from the manifold to some of the rads. I have heard you get a click and woosh when they switch on. From the boiler to the manifold I can use 22 or 28 mm, thats not the issue at the moment. The pump will be by the boiler.

 

[John.g]

13M x 2 = 26M total, if you are happy with rad dT of 15C then flowrate required = 3.4LPM., head loss through 15mm piping ~ 1m, rad valves+radloss say another 0.8M, total of 1.8m say 2m loss, if 22mm pipe then piping loss ~ 0.1M, + radvalves&radloss of 0.8M = 0.9m say 1.0m total loss. theoretically may get away with it with a bit of rad balancing, others will soon inform.
water velocity through 15mm piping at 3.4LPM ~ 0.55m/sec?.

 

[Donkey Table]

13M x 2 = 26M total, if you are happy with rad dT of 15C then flowrate required = 3.4LPM., head loss through 15mm piping ~ 1m, rad valves+radloss say another 0.8M, total of 1.8m say 2m loss, if 22mm pipe then piping loss ~ 0.1M, + radvalves&radloss of 0.8M = 0.9m say 1.0m total loss. theoretically may get away with it with a bit of rad balancing, others will soon inform.
water velocity through 15mm piping at 3.4LPM ~ 0.55m/sec?.

 

[Donkey Table]

Bags of umpph at the manifold. I was thinking delta t of 20. It's a system boiler. I'm guessing as it's above 0.3 m/sec I won't get sludging.

 

[John.g]

If you are happy with 2681 watts, 75% of rad rated output which you will get with a boiler temp of 70C, rad dT 20C, then better again because of lower flow rate required of 1.92LPM.

 

[ShaunCorbs]

13M x 2 = 26M total, if you are happy with rad dT of 15C then flowrate required = 3.4LPM., head loss through 15mm piping ~ 1m, rad valves+radloss say another 0.8M, total of 1.8m say 2m loss, if 22mm pipe then piping loss ~ 0.1M, + radvalves&radloss of 0.8M = 0.9m say 1.0m total loss. theoretically may get away with it with a bit of rad balancing, others will soon inform.
water velocity through 15mm piping at 3.4LPM ~ 0.55m/sec?.

Did you account for it being plastic and an internal dia of 12mm ?

 

[John.g]

I used a ID OF 11.5mm Shaun based on measuring the ID of 1/2 ins (Irish).

 

[Donkey Table]

Did you account for it being plastic and an internal dia of 12mm ?

Errr no. I was relying on the rads being the only ones on the 15mm circuit.

 

[Donkey Table]

15mm Hep2 internal dia is 11.3 mm; copper is say 13.6. The area for 11.3 is 100 mm square, 12.5 is 145mm square. Emmiti recommend a max run of 10 meters (20 metre out and back) before you take a noticable reduction in radiator output.

16mm MLCP internat diameter is 12 mm.

In addition (info supplied by Wavin)
Hep2 barrier 22mm internal dia 17.7mm
Hep2 barrier 28mm internal diameter is 22.5mm

 

[Ben-gee]

12.5 gives 123 not 145; anyway you seem to really want to do it in 15mm so go ahead.

 

[Donkey Table]

12.5 gives 123 not 145; anyway you seem to really want to do it in 15mm so go ahead.

Ah sorry Ben I meant 13.6 internal diameter for copper 15mm giving 145 mm sq.

If I plan it correctly, I can use 15 mm. Im trying to make the instal as cost effective as possible. If I start using 22mm Hep2 the cost goes up quite alot, and the reels are smaller and the waste goes up. I dont want any joints in the run other than at the source and destination. I can get 100 metre reels of 15mm.

All the rooms have to be able to control their respective rads, they have thermostats in every room.

The house is 3500 square foot on 3 levels.

 

[ShaunCorbs]

20mm mlcp cheap enough

 

[Donkey Table]

20mm mlcp cheap enough

Ok Ill fez up to this, Im not equiped for MLCP, however today I have finally managed to get a plumber to take the job on and he uses MLCP so while he does the work it will be.. I can do copper or PB. I was suprised with MLCP, expecting thinner walls. The 16mm stuff has a 12mm internal diameter.