Converting one pipe to two pipe system

nicw_3

Hi, we live in a very cold old house and so spend a fortune trying to heat it in winter. We are having underfloor insulation put in and working on draught-proofing, but one problem is our inefficient heating system. Some of the radiators in the main rooms don't get very hot - when we had some work done last year, we were going to have a power flush done, but our plumber said that as it's a one pipe system there was no point, as it wouldn't actually flush the rads. As we're going to have the floors up anyway to do the insulation, we wondered whether this might be a good time to look at converting to a two-pipe system in hopes of improving the overall efficiency of the heating? Will this actually make much of a difference both in terms of actual heating and cost?

Doozergirl

What radiators do you have?  That's going to make the biggest difference and if you have an old one pipe system then it's possible that you have old, undersized single panel radiators as well. 

But yes, if you have the floors up then now is definitely the time to bite the bullet and reap the rewards!

nicw_3

@Doozergirl Yes, old single panel radiators, though some of them are quite big. We've got one vertical column radiator that we put in last year (and it's the worst one for heating up), and a couple of columns we were going to swap in but haven't got around to yet.

Doozergirl

You'll notice a massive difference if you change all of it. 

With the one pipe system, even if you flushed manually by taking the rads off and running water through them outside, you'd still experience an unbalanced system of some being hotter than others simply because of the heat loss as the water travels through all the rads in the house.

You will notice a difference changing rads to those with convector fins as they do a much better job of moving warmed air as well, meaning you don't need to stand next to the thing to feel the warmth.   

And it makes perfect sense to do the pipework for a more balanced and efficient system, plus none of it will be gunky if it's all new.  You will be really pleased with the result, I'm sure.  The other benefit being that your radiators won't need to take up as much room, either.  

FreeBear

And if you are replacing radiators & plumbing, take a look at the layout of the system. With a decent level of insulation and no cold draughts, there really isn't much need to bung radiators under the windows (in my opinion), especially if you have god quality double/triple glazed units.

If the radiators can be mounted on internal walls, minimise the length of pipes which will lead to fewer joints - Less risk of leaks, and cuts down on the amount of copper needed. Also worth considering fitting oversized radiators - This will allow for a lower water temperature (with a condensing boiler, it will run more efficiently). And should you fit a heat pump in the future, the radiators may not need changing.

Bendy_House

Definitely convert from one to two pipe (speaking as an owner of the former... :-(  )

Definitely look to over-size the rads if you replace them. Some might be reusable - that's your call.

The cooler you can run your system temp at, the more efficient it will be with a condensing boiler. Just as importantly - probably - is that it should also future-proof your CH system for use with more environmentally-sound energy units such as A&GSHPs.

UFH is ideal for both - it works with cooler water temps. (Not sure how this works out when the boiler also supplies 'hotter' rads, tho'?!)

The biggest difference is insulation. Followed by insulation. And then...

silvercar

We changed from a one pipe system to a 2 pipe. The big difference is that the rooms heat up much quicker. With a one heat system the radiator that is last on the run took ages to heat up and often, even when the heat reached that radiator (about half an hour sometimes) the radiator didn't get as hot.

nicw_3

Thanks everyone! Getting our heating guy round for a quote!

nicw_3

FreeBear said:

And if you are replacing radiators & plumbing, take a look at the layout of the system. With a decent level of insulation and no cold draughts, there really isn't much need to bung radiators under the windows (in my opinion), especially if you have god quality double/triple glazed units.

If the radiators can be mounted on internal walls, minimise the length of pipes which will lead to fewer joints - Less risk of leaks, and cuts down on the amount of copper needed. Also worth considering fitting oversized radiators - This will allow for a lower water temperature (with a condensing boiler, it will run more efficiently). And should you fit a heat pump in the future, the radiators may not need changing.

Just wanted to say thanks for this advice, I wouldn't necessarily have thought about changing the layout but there are a couple of spots where this definitely makes sense (not least to avoid pulling up our entire lounge floor to cross the room when the rad can just go on the other side!)

nicw_3

@Doozergirl @FreeBear @Bendy_House Thanks all for the great advice a few months ago. We have just finished the conversion - we were able to replace the worst of our single panel radiators with some nice columns, which are absolutely kicking out heat now. The kitchen has never been warm in the three years we've lived here, and the first day the new system was running in there it was actually sweltering. Took the advice on relocating a couple of rads and, I think, accidentally on oversizing a couple too.

Just finished the work yesterday so we'll see whether we're doing much in the way of cutting down costs, but in terms of actually heating the house, the conversion has definitely been a success - thanks so much for pointing us in the right direction!

FreeBear

nicw_3 said: Took the advice on relocating a couple of rads and, I think, accidentally on oversizing a couple too.

Oversizing the radiators is a good thing - It will allow you to run the heating at a lower flow temperature which will lead to a small saving on gas if you have a condensing boiler. It also puts you in a better position when the time comes to fit a heat pump.

Most of my radiators are 25-30% larger than they need to be, and by the time I've finished the thermal upgrades, more like 50% oversized. Just means the house heats up a bit quicker