Adding a radiatior to a circuit that's already been extended

[Jamieg285]

Hi,

we're mid way through a conservatory build and we're at the point of disussing the raditor requirements.

We're planning on adding a long double rad and the nearest pipes are in the lounge.

The lounge rad is also a long double rad, and is last in the circuit. Feed is from 15mm, which is buried in the floor.

To complicate matters, there is already a tee off the feed/return of the lounge rad for a small single rad in the kitchen (direct opposite side of wall)

The current suggestion is that another tee is added to the kitchen side of the wall to feed the conservatory, meaning there will be 2 tees in close proximity.

I am concerned that this will cause flow problems somewhere in this circuit and one or more of the rads won't get hot enough.

The boiler will be able to cope, as we are getting a new one fitted, with 30% capacity over requirements.

I've read about reducing bore size to increase flow - assuming that this additional tee is OK, should we be reducing the new run to 10mm, or would 15mm still be OK?

Thanks in advance,

Jamie.

p.s. I know rads in a conservatory aren't the best idea, but you try convincing my wife, who is also funding all the work.

 

[Agile]

There is no point in reducing any pipe sizes.

On a standard system 15 mm can only cary about 3.5 kW. It sounds as if your system already has this heat output.

The best thing you can do is to add it in 15 mm and hope that by very careful rebalancing by an experienced person that then it will work reasonably well.

Strangely to me, many people in the trade seem to have considerable difficulty doing balancing.

Tony

 

[DeltaT]

There is no point in reducing any pipe sizes.

On a standard system 15 mm can only cary about 3.5 kW. It sounds as if your system already has this heat output.

The best thing you can do is to add it in 15 mm and hope that by very careful rebalancing by an experienced person that then it will work reasonably well.

Strangely to me, many people in the trade seem to have considerable difficulty doing balancing.

Tony

I hate to disagree Tony auld chum, but I think you find in most systems a 15mm pipe will carry a lot more than 3.5KW

11*C Delta T @ .3m/s = 2KW
11*C Delta T @ 1.5m/s = 10KW
20*C Delta T @ .3m/s = 3.63KW
20*C Delta T @ 1.5m/s = 18.1KW

 

[Agile]

I agree that it "can" if you up the flow rate.

But that would be very noisy at the extremes and in any case a "normal" pump would be insufficient particularly on an average sized system.

Tony

 

[PEDANTICVINDICTIVEMAN]

Sall gonna depend on how big the rads are innit, if they big burgers it aint gonna work very well, 3 rads at 9000btu's a peice = 18000 btu's, it's not gonna do it.

I rarely fanny around with balancing, if it all works and gets hot that does me, on a bungalow with the boiler in the middle of the property, 2 22mm flow and returns to each end of the bungalow with 10mm droppers to each rad, the TRV's balance out the smaller rooms for you with bedrooms TRV's set at no 2, always works a treat for me.

 

[vulcancontinental]

Each to their own.

I was surprised to read somebody recently writing in Gas installer that 15mm will take 6KW. He must have tinnitus and sell pumps and radiator valves.

You can get 20 KW through 15 if the pumps big enough but you wouldn't want to sit next to it.

I always used the rule of thumb 3KW 15mm - 16KW 22mm - 30KW 28mm and 22mm for both the cold feed and expansion with the pump on setting 1 and nobody in a house up to 4 bedroom will hear a thing, the pump will last for ever, no air in the rads and no cutting out the cold feed/exp pipework to clear the build-up of crud.

I know it's old fashioned but it's worked forever and that's a big plus for me.

As for balancing, it's not difficult but few bother and frankly it's so easy without any thermometer and a good quality valve.

just my sixpennyworth

 

[Agile]

That was a good rule of thumb for conventional boilers ( 11° delta T ) and probably what Dick Puller has used!

However, with condensing boilers and up to 20° differential then that can be increased a little with the pump on "2" and not much noise in a system.

Tony

 

[bengasman]

...I always used the rule of thumb 3KW 15mm - 16KW 22mm - 30KW 28mm and 22mm for both the cold feed and expansion with the pump on setting 1...I know it's old fashioned but it's worked forever and that's a big plus for me....

It may have worked back in the days, but things have changed.
15mm will easily do 10 kW, or in layman's terms: 10 metres of standard radiator, or 5 metres of double panel.

 

[Agile]

But thats only if the whole circuit is designed as a semi microbore and appropriately balanced.

The OP would have no flow at all in his rads if he kept a cylinder coil fed with 22 mm and no balancing valve.

Tony

 

[bengasman]

But thats only if the whole circuit is designed as a semi microbore and appropriately balanced.

The OP would have no flow at all in his rads if he kept a cylinder coil fed with 22 mm and no balancing valve.

Tony

Even with a 22 mm to each rad, there is no guarantee they all get hot if you install it wrong. If you start off with the idea that things might be done wrongly, you might as well not give any advice.

The basic question is: can you run 5 kW on 15 mm pipe with a new boiler?
The answer is: yes, that is no problem at all, provided that the installer actually knows what he is doing, and cares to do a decent job.

 

[vulcancontinental]

...I always used the rule of thumb 3KW 15mm - 16KW 22mm - 30KW 28mm and 22mm for both the cold feed and expansion with the pump on setting 1...I know it's old fashioned but it's worked forever and that's a big plus for me....

It may have worked back in the days, but things have changed.
15mm will easily do 10 kW, or in layman's terms: 10 metres of standard radiator, or 5 metres of double panel.

It works present day as well 20 years after fitting.

I acknowledge you're right (if the pipe lengths are not too long) but I also like to avoid the possibility of noise if the pipework and pump is secured in a stud wall airing cupoboard and when I do come across such systems and they've had much of a life there's often push-fit fittings and an isolating valve around the cold feed / open vent area indicating past problems.

Sealed systems of course are another matter.

I'm just an old dog with a memory watching the new tricks!

Like I said, each to his own; if it works for you, then it works!

 

[mickyg]

11*C Delta T @ .3m/s = 2KW
11*C Delta T @ 1.5m/s = 10KW
20*C Delta T @ .3m/s = 3.63KW
20*C Delta T @ 1.5m/s = 18.1KW

you been reading the ukcopperboards installation books as well then?

 

[D_Hailsham]

We're mid way through a conservatory build and we're at the point of discussing the radiator requirements.

I thought that heating systems in conservatories had to have independent time and temperature controls - see Building Regs Approved Document L1B.

How will you do this if you are just tapping off the existing heating circuit?

 

[DeltaT]

11*C Delta T @ .3m/s = 2KW
11*C Delta T @ 1.5m/s = 10KW
20*C Delta T @ .3m/s = 3.63KW
20*C Delta T @ 1.5m/s = 18.1KW

you been reading the ukcopperboards installation books as well then?

Is that it Micky??..............Is that all you've got to say on the subject???