Home CH Plumbing Question

[Biggles]

Spurred on by my success with fitting my own CH on the boat, I am thinking about adding some more radiators to my house. On the boat I used 22mm for the flow and return and this exited to each radiator with less than a 200mm of 15mm.

 

At home I am going to have to run 3 separate "spurs" to the new radiators.

So my question is how close to the radiators would be recommended to take the 22mm. As this will have to be surface mounted I am thinking about the look of it.

 

Would 2m be to long to run the 15mm? The rest of the 22mm I can hide behind furniture.

 

Thanks

[nicknorman]

Spurred on by my success with fitting my own CH on the boat, I am thinking about adding some more radiators to my house. On the boat I used 22mm for the flow and return and this exited to each radiator with less than a 200mm of 15mm.

 

At home I am going to have to run 3 separate "spurs" to the new radiators.

So my question is how close to the radiators would be recommended to take the 22mm. As this will have to be surface mounted I am thinking about the look of it.

 

Would 2m be to long to run the 15mm? The rest of the 22mm I can hide behind furniture.

 

Thanks

 

Presuming this is a pumped system 15mm is totally adequate for a long run to one radiator. You could consider microbore pipe (10 mm, or 8mm if it's a small radiator) for the visible portion, 2m of that would be fine. You really don't need much flow of water through a particular radiator for it to work fine, presuming it isn't a huge one.

[Biggles]

Hello Nick

Yes its a pumped system. The longest run to a 300 x 1500 3 column (1400w) is where I would like to reduce to 15mm for the last 2m, however if 15mm would be OK too just how far can that be run from a 22mm flow and return?

The other radiators I can get 22mm almost up to the the last 1m or less

Edited February 24, 2015 by Biggles

[nicknorman]

Hello Nick

Yes its a pumped system. The longest run to a 300 x 1500 3 column (1400w) is where I would like to reduce to 15mm for the last 2m, however if 15mm would be OK too just how far can that me run from a 22mm flow and return?

The other radiators I can get 22mm almost up to the the last 1m or less

I am not a "professional" but personally I would run 15mm or less all the way from the manifold / T where the pipe work for that radiator comes from, to the radiator. You only need 22mm for the main part of the circuit which is feeding multiple radiators, or if it is a gravity system.

 

Bear in mind that biggest is not necessarily best. By using bigger pipes you increase the volume of water in the system which means it takes longer to heat up from cold, and the bigger diameter the pipe is, the more heat it loses (heat loss being to do with surface area). Insulation for 22mm pipes seems to be a lot pricier than for 15mm, not to mention the cost of the copper.

[Neil Smith]

I have used 15mm on the boats pumped system for everything including flow and return only 3 rads on the advice of my gas safe heating engineer.

 

Neil.

[smileypete]

Agree with Nick, though all the rads will almost certainly need re-balancing via the lockshield valves.

 

cheers, Pete.

~smpt~

Edited February 24, 2015 by smileypete

[BEngo]

15 mm is the way to go. Microbore is theoretically feasible and marginally cheaper, but it either has to be trunked or otherwise enclosed on any long visible runs because it is mind-bogglingly difficult to get the pipes straight enough to look good 15 mm does not suffer from this.....

 

Your CH pump may need to be speeded up or replaced as part of the re-balancing mentioned by smileypete as the extra pipe runs will increase the total head loss, but they are cheap and easy to swap out after a trial.

 

 

Don't forget some new corrosion inhibitor too.

 

N

[Biggles]

Thanks guys so far. So from what you say and all seem to agree that 15mm would be fine for the longest single run which is about 6m flow and return.

[nicknorman]

Thanks guys so far. So from what you say and all seem to agree that 15mm would be fine for the longest single run which is about 6m flow and return.

Yes.

[Boatingbiker]

On domestic system with pump you can use 15mm pipes for radiators either single or multiple radiators with a combined output of 3000 watts, if the total output is greater than 3000 watts then increase pipe size to 22mm. After extending the system you will need to re-balance all the radiators by use of the radiator valves. hope this helps

[Biggles]

Will this be the right thread to go into the female on a radiator?

 

http://www.screwfix.com/p/yorkshire-tectite-sprint-male-elbow-15mm-x/54976

 

Ta

[nicknorman]

Normally you would put a lockshield valve at one end of the radiator (for balancing) and a TRV or at least an on/ off valve at the other end. Is there a specific reason why you want to plumb straight into the radiator, seems rather unusual.

[Biggles]

Yes Nick. I have no room for the lockshield to come straight out (Wall in the way) so need to turn the corner and put the lockshield directly under the rad.

[nicknorman]

Yes Nick. I have no room for the lockshield to come straight out (Wall in the way) so need to turn the corner and put the lockshield directly under the rad.

Fair enough. Yes it's the right thread size (1/2" bsp). The only problem might be that there is only one correct position for the exit (straight down, presumably) and that might not coincide with the fitting being tight enough, with a further turn being unachievable. I guess it depends on the degree of taper on the thread and maybe you can "adjust" it by varying the amount of thread tape.

[Biggles]

Is there a better way of turning a 90 exiting a radiator for getting a lockshield on?

[nicknorman]

You could fit a straight radiator tail (1/2" x 15mm) and then fit a seperate 90 deg bend once the tail was in tight, something like this for the tail: http://www.ebay.co.uk/itm/2-X-MYSON-CHROME-RADIATOR-VALVE-TAIL-/141582171929?pt=LH_DefaultDomain_3&hash=item20f6f47f19

 

But I don't know how much room you actually have, this would probably take up a bit more room than your solution.

[Biggles]

My solution is not elegant but its the only way I can see to do it.

[nicknorman]

My solution is not elegant but its the only way I can see to do it.

It'll probably be OK, I just thought I would mention the issue with being able to tighten the fitting only until it is pointing down. But there is a fairly long, mild taper so it will probably be OK. Don't forget to use thread tape because the seal is within the threads, not on any mating surfaces.

[Neil Smith]

On tapered threads you can use swan liquid ptfe paste, brilliant stuff it stays flexi and never leaks also smear around olives and threads on rads and all comp fittings, but on parallel threads use 20 turns of ptfe tape.

 

Neil.

[smileypete]

Is there a better way of turning a 90 exiting a radiator for getting a lockshield on?

 

There's corner lockshield valves around, usually chrome as intended for towel radiators, so not cheap, and not all have a 1/2" BSP taper end.

 

The screwfix part is a non demountable push fit, and may have a parallel thread. Might be able to get a compression version with taper thread from the likes of Ebay, would still need a valve for balancing elsewhere.

 

Usually the taper threads on rads need 12-14 turns of the normal PTFE tape, should be able to then get the valve at the required angle.

 

cheers, Pete.

~smpt~

Edited February 24, 2015 by smileypete

[nicknorman]

The screwfix part is a non demountable push fit, and may have a parallel thread.

 

My general feeling is that parts like that that have a flange are parallel, with the seal intended to be made against the flange, whilst those without any sort of flange but just thread that stops, are tapered. If not, then how else can you get such a fitting to seal? Surely not just by adding masses of tape?

[Neil Smith]

Yes 20 turns on parallel thread will seal it without a washer/ring or anything.

 

Neil.

[Bod]

Yes 20 turns on parallel thread will seal it without a washer/ring or anything.

 

Neil.

 

Must be a devil to start.

 

Bod

[smileypete]

My general feeling is that parts like that that have a flange are parallel, with the seal intended to be made against the flange, whilst those without any sort of flange but just thread that stops, are tapered. If not, then how else can you get such a fitting to seal? Surely not just by adding masses of tape?

 

Agree but from a quick glance it didn't look very tapered, so never say never.

 

Dealing best with unusual situations is part of what separates good tradesmen from the rest.

 

cheers, Pete.

~smpt~

[nicknorman]

Yes 20 turns on parallel thread will seal it without a washer/ring or anything.

Neil.

That sounds like such a bodge to me!