replacing radiator with slightly wider one (one pipe system )

[hughesie68]

Hi there,

I want to replace a radiator in my hallway with a slightly wider one . Its a single pipe system in a solid floor , so what i was thinking of doing was cutting the existing tails and using a couple of elbows and short lengths of pipe
to widen the existing tails to accommodate wider radiator.

____I____I___ to I__ __I
_____I_____I_______

Would the radiator still drawn the hot water up into it??

Or is it quite easy to dig screed to expose pipe work and replace with compression fixings and new widened section of pipe work.

Hope this all makes sense

 

[hughesie68]

Sorry my drawing went wrong
should be like this


____I_____I____ to

I_ _I
__I___I___





See if that works

 

[standard8]

What sort of size difference are you talking millimetres or meters?

all the best,

James

 

[Dotty]

Sorry Hughsie, welcome to the forum by the way, I keep looking at your pic and can't think straight. Cos all I can think of now is Space Invaders!

 

[hughesie68]

200mm approx

 

[hughesie68]

Ha Ha , looks more like space invaders than what im trying to get across

 

[Dotty]

200mm approx

100mm each end?

 

[Dotty]

I wouldn't advise burying compression fittings in screed.

 

[hughesie68]

Not made it very clear but basically pipes will come out of the single pipe ; left pipe will come up , left then up again , right pipe will come up , right then up ,to accommodate 200mm wider rad .
Phew

 

[hughesie68]

Yes 100mm each end

 

[standard8]

My, very, humble opinion is try it into the existing connections first, if you can mount the rad a bit higher and bend the risers to give you the 100mm you need each end I think this would help. It would ease the flow of water quite a bit if you could avoid elbows and pull, say, to 45Deg instead. More if you have to but anything less than a straight 90Deg is better. If this then doesn't work go for the nuclear option of digging up the floor. If you end up having to do this do not use compression fittings, they are much more prone to leaking at a later date, use solder fittings and don't forget to wrap them to stop the screed attacking the copper.

I hope this helps, don't be afraid to argue or question cos it is only an opinoin after all!!

all the best

James

 

[hughesie68]

Just thought it would look neater if the tails came up out of floor with the elbows and new pipe work kept as close to the underside of radiator as possible , but was unsure if the water would still draw up into the radiator .
Thanks for the compression fitting / screed tips .

Matt

 

[standard8]

To be honest Matt, it may work with elbows, I regularly work on old one pipe systems and it never ceases to amaze me what it will circulate around. I do take your point, it would look a lot neater tucked up against the rad. Maybe use my previous theory, try it and see, if it don't work swear and try the next option?

James

 

[hughesie68]

Thanks for your help James . I was just going to do it this weekend , it was only when i read on another site about the tails needing to be as short as possible that got me thinking could i be setting myself up for problems .I am now begining to wonder whether i should even bother putting a larger rad in , its just quite a cold hallway and i thought it may help The Valves do need replacing although the rad that is there is a modern double convector.

 

[standard8]

Matt, just a point. You have got the rad with top connection one end and bottom connection the other? I'm sorry I can never remember which is flow and which is return, I think the top connection is flow and bottom return. This will help a lot, also be aware that there are specialist TRV's for one pipe systems, they have a bigger opening through the valve. hardly anyone every uses them, except my company of course!! Danfoss do then in there commercial range and again they do make a difference.

Good luck with it and if you need any more advice shout

all the best.

 

[hughesie68]

Radiator is bottom connection both sides , also the rads that have been replaced in the rest of the house (all bar kitchen and hall ) , by an old plumbing friend have trvs but i dont think they are specially for one pipe systems , but i dont know, they are Altech??Does this mean they are neeing to be replaced ? What if i have these trvs fully open and just use the room stat , will that be more effective ?
Once again , thanks for your help

Matt

 

[hughesie68]

Radiator is bottom connection both sides , also the rads that have been replaced in the rest of the house (all bar kitchen and hall ) , by an old plumbing friend have trvs but i dont think they are specially for one pipe systems , but i dont know, they are Altech??Does this mean they are neeing to be replaced ? What if i have these trvs fully open and just use the room stat , will that be more effective ?
Once again , thanks for your help

Matt

 

[standard8]

Matt, as I say it's not a wrong or right thing just a best option thing. Like a lot of this type of work you will often get away with a not perfect fix but it's worth knowing the best option in case you have trouble.

If your other rads are working brilliant if it works don't fix it but if your coming up against problems, i.e. rads not circulating it might be worth looking at.

It is possible that your pal has re-piped the new rads too two pipe of the existing carcass but obviously with the pipework in the screed this is a bit more of a pain the the proverbial. Don't thank me feels like I'm complicating things for you now!!

 

[hughesie68]

The only rad re piped was the one in conservatory ( hottest in the house ) all the others are single pipe still , they are ok although they are much hotter at the top than the bottom , maybe this is down to the trv's or just the fact that its a one pipe system .

 

[standard8]

Hotter at the top I would say does point to poor circulation through the rad's, others on here may want to correct me on this. It could be related to the TRV's maybe try the one pipe special on the rad your going to replace and you can compare.

The big thing that one pipe systems suffer from is that as you go round the circuit, away from the boiler, the temperature of the rad's will get lower and lower. It's a fact of the design, because each rad will drop the primary water temperature as it passes through it, then on to the next one which drops the flow temperature a bit more and so on.

That's why no one fits one pipe any more, but as I said we still service a lot of them, in church's, monasteries stalely homes etc. All big places without the money to change it. But they do work.

 

[AWheating]

one pipe systems work well, pipe the rad up as suggested with a couple of elbows at the bottom and it will work. most one pipe systems can be balanced so all rads work well.

as regards the rad hot at the bottom this is normally caused by air or corrosion(less likely), as heat rises the only reason the top of the rad should be cooler than the bottom is something is stoping the water/heat circulate like air.

 

[hughesie68]

Rads are warm at top and cool at the bottom , not the other way round unfortunately .
Also when i replace the hall radiator , should i not put a trv on as the hall is where the room stat is .

 

[hughesie68]

Also , the rad in the bathroom which is the only one that has not been replaced upstairs and has not got a trv is absolutely piping hot all over . Plumber said he could not balance system properly as two of the rads downstairs have not been replaced yet and the valves on them are old and seized up so this probably is not helping .These old rads are in two different rooms right next to each other , one is the hall rad which i have spoken about , the other is in the kitchen so may as well replace that while system is drained down .