Replacing Radiators and Keeping Boiler

paperclap

Hi all,

We're currently renovating our house, and are looking to replace some of our old (probably original) radiators, and add a new one in. The four that we're looking to replace are single panel with no convectors, so not fantastic at letting off heat.

Boiler and System
We have a Potterton Profile 40e boiler, which I believe is somewhere between 8-12 KW output. It was installed around 25 years ago. We've a conventional system, with a hot water cylinder in the airing cupboard and a cold water tank in the loft space (we're in a bungalow). Admittedly, not the most efficient boiler compared to newer combi boilers... but we're a little of the mindset of "if it ain't broken, don't fix it" — unless we're given a good reason to otherwise! Additionally, we're not yet looking to renovate our kitchen and bathroom, so don't really want to mess with the current set up of the boiler location and airing cupboard, etc.

Central Heating Pipework
With the above in mind, we're not looking to replace all our pipework either (though, we are relocating one pipe to a corner of a room). Our central heating pipework is 15mm copper throughout.

Radiators
Kitchen — No radiator — Would like to add a small one
Bathroom — Towel radiator — Keeping
Hallway — Single panel / no convector — Replace
Bedroom 1 — Single panel / no convector — Replace
Bedroom 2 — Single panel / no convector — Replace
Living Room — Single panel / no convector — Replace
Conservatory — Double panel / single convector — Keeping

So, I suppose the question is: can we replace the above four radiators (and add one, in the kitchen), and have our boiler and system be okay with that?

Thank you in advance.

Jeepers_Creepers

Hi Laurence.

12kW is not a huge amount, but should heat most 2-3 bed homes, and yours is 2-bad? As you say, if it's working - and they are pretty basic beasts with relatively little to go wrong - then nurse it along until you are ready (or need) to replace it.

The single panel rads - do they not give out much heat because (a) they are single panel non-convector rads or (b) because they just don't get very hot?

Anyhoo, to replace them with 'larger' rads makes complete sense, both now and for the future. For 'now', they might give you the extra warmth you require, and for the future they will allow you to run the new boiler at a lower water temp = more efficiently. So, when you upsize these rads, don't just give yourself an extra couple of hundred watts to improve your current situation, but go a bit further so that'll they still give you the heat you require without them getting as hot.

Your current boiler will probably be chugging out CH water at around 80oC? Ie, the rads will be very 'ouch' if you touch them. You'll really want your new boiler to be doing this at at least 10oC lower so it's in solid condensing mode most of the time.

When you say your pipework is all 15mm copper, I presume you mean the pipes to each rad, and not the pipe flowing and returning to the boiler? These should be 22mm.

To cut to your question; yes, you can fit larger rads now, and the worst possible outcome will be that they don't provide any extra heat! Ie, if your boiler is currently running flat-out and has nothing left in reserve (which I doubt), then it ain't going to magic up extra output for your 'larger' rads. I doubt this will be the case - I suspect you will get more heat out as the boiler will have some reserve - but you will in any case have future-proofed your setup.

FAR more importantly, tho', is to take this opportunity to improve the insulation of your home. If your floors are T&G, then draught-proof them at the very least, and add insulation under them if it's easy to do so. Add internal insulation to all your exterior walls (or cavity or exterior following advice), and tons of the stuff in your loft.

Jeepers_Creepers

And please fit a magnetic filter to the return pipe to your boiler, and chuck in doses of system cleaner - start cleaning yer pipes out now so they will be sorted for whenever you do replace the boiler   One will be fitted then anyway, but the sooner the better.

paperclap

Hey again Jeepers_Creepers

That's correct, we're in a 2-bed.

All of the radiators get hot (no cold spots, trapped air, etc). I guess they simply don't give off much heat because they're single panel / no convector. That said, our double panel / single convector radiator in the conservatory doesn't seem to get warm at the bottom — hopefully not sludge sitting there?!

Correct, all the pipework to the radiators are 15mm, and the flow and return pipes coming out of the boiler are 22mm.

As you probably already know (from my other thread ), we have cavity wall insulation, fibreglass insulation between the joists, and polystyrene insulation between our rafters (though, may be removed sooner or later!). But, no insulation in the floor — solid concrete. We've laminate throughout, which doesn't help give a "warm" feeling at all

We've also got double-glazed windows throughout... but a few blown, so imagine some of the seals are gone. Probably a few minor draughts here and there too (could do with some caulking along the seams).

A magnetic filter to the return pipe? I'm new to central heating, so I'll have to give that a Google!

paperclap

Sorry, my mistake — have just checked the conservatory radiator... and it is actually a double fin, not single fan.

We've got the heating on right now. It seems the bottom is getting hot! Though, not as hot as the top. Guess heat rises, so the may be normal?

theoretica

If you are having that sort of work done I expect it would add very little to the job take the conservatory radiator off and flush it out if it does have sludge.

Jeepers_Creepers

laurencewhymark said:

Hey again Jeepers_Creepers

That's correct, we're in a 2-bed.

All of the radiators get hot (no cold spots, trapped air, etc). I guess they simply don't give off much heat because they're single panel / no convector. That said, our double panel / single convector radiator in the conservatory doesn't seem to get warm at the bottom — hopefully not sludge sitting there?!

Correct, all the pipework to the radiators are 15mm, and the flow and return pipes coming out of the boiler are 22mm.

As you probably already know (from my other thread ), we have cavity wall insulation, fibreglass insulation between the joists, and polystyrene insulation between our rafters (though, may be removed sooner or later!). But, no insulation in the floor — solid concrete. We've laminate throughout, which doesn't help give a "warm" feeling at all

We've also got double-glazed windows throughout... but a few blown, so imagine some of the seals are gone. Probably a few minor draughts here and there too (could do with some caulking along the seams).

A magnetic filter to the return pipe? I'm new to central heating, so I'll have to give that a Google!

D'oh! Sorry, missed that it was the same Laurence :-)

If all your current rads are 'hot', then good chance the larger ones will pull more heat out of the water and get more into the room (12kW should be enough). More importantly, when you do replace your boiler, the water will be cooler, and you will certainly want it to be so for the extra energy savings. So, as long as they ain't intrusively big, then don't shirk on the sizing up - double panel with one or two fins for the sitting room, for example.

The connie rad - is it properly hot at the top, as hot as the other rads? If 'yes', then good chance it is sludge along the bottom. If 'no', then it might just be at the end of the circuit or tee'd off an existing rad, so is just not getting as much flow as the others.

Your old boiler is basic in design (part of the reason it lasts a long time...). It's essentially a heating container with a fire under it. It can cope with a slow build-up of sludge without too much consequence, tho' it will affect to some degree how well it gets heat from the flame. The new boiler, however, will have much narrower waterways, especially if you go 'combi' type, and this will not thank you at all for giving it any sludge (as I've learned to my cost).

So, fitting a mag filter now, and adding the right long-term chemicals, will likely improve what you have already, and will certainly better prepare the system for the new boiler whenever that happens. 

Solid floor? No draughts then! If you are replacing the flooring, add a low-density fibreboard layer - 8mm if you can - butted up tightly together, and then your new covering. It'll make a world of difference.

'Blown' D-G units remain thermally efficient - it's mainly just a cosmetic issue.

paperclap

Don't be silly, no worries at all

Regarding the conservatory radiator, it is hot at the top, yes. And now you mention it, it is tee'd off of the living room / back bedroom radiator pipes.

When we come to relocate the pipework in the back bedroom, we'll of course have to drain (and refill) the system then. However, as we're plastering (or relining) the walls (and of course, walls behind the radiators), do you think it would be worth trying to do everything in one go (relocate pipes, replace radiators and adjust those pipes, add in new radiator in kitchen)... to prevent having to drain and refill the system several times? Bit of an awkward one really, as I'd expected to replace the radiators as one of the later tasks!

Will certainly look into a magnetic filter.

Will look into adding fibreboard too! Though, skeptical we can, as we'll need to meet the depth of the current kitchen and bathroom tiles and flooring

Jeepers_Creepers

Unless you have a 'proper' powerflush - where (usually) hot water and chemicals are pumped around your system and the 'stuff' is collected by large mag filters is carried out, then hardened sludge ain't going to move with just some draining-downs. You could do it by adding strong chemicals, running it for 2 weeks, and then draining it all down (and a couple of flushing refills), or you could take a more long-term approach by adding 'long term' chemicals - ones you can leave in for months, some indefinitely - and then 'slowly' collect the s*** using the mag filter - that saves carrying out drain-downs until it's needed.

A mag filter should be a standard fitment to all CH systems. In fact I think you'll find it's a warranty condition for a new boiler. So all I'm suggesting is, the sooner you can add one, the sooner it'll start getting to work.

You can then leave the pipe changes and replacement rads until the walls are lined.

Once the system is drained down for the rads being moved, take the opportunity to have the connie rad (which I presume you are keeping?) removed too and hosed out. You can then replace it.

The fibreboard is only 8mm thick, although you can also get thinner ones. Don't underestimate how effective even a thin layer can be - just imagine a cold bare floor and you sit on it... Now place a sheet of 6mm LDF under yer bum - aaaahhhh, the difference.

What floor covering will you ultimately have - 'solid' or carpet?

FreeBear

laurencewhymark said: Radiators
Kitchen — No radiator — Would like to add a small one

Have a look at kickstrip (or plinth) heaters - You can get ones that plumb in to the CH system, or purely electric, or a combination of the two. They take up zero space in the kitchen, so if wall space is limited, a big plus. Down side is cost, need to be wired in to the mains (new switch/socket required), and base units may need to be pulled out to put the plumbing in.

I have one in my kitchen, and despite the downsides, would fit another without a second thought.

Jeepers_Creepers

laurencewhymark said:

Sorry, my mistake — have just checked the conservatory radiator... and it is actually a double fin, not single fan.

We've got the heating on right now. It seems the bottom is getting hot! Though, not as hot as the top. Guess heat rises, so the may be normal?

Just seen this. Fair chance your system is not quite balanced - ie the other rads are getting a much better flow than the connie rad, and that's why it's slightly cooler at the bottom - just not enough hot flow.

When a rad fills with sludge, it tends to form a pyramid in the middle-bottom, and this area will usually be obviously 'cold' and won't heat up.

You can always try turning off the rad the connie is extended from (and other rads too if needed), to force more flow through it - see if it becomes fully hot then.