Apologies for the most boring STW thread ever.

I’m idly toying with the idea of replacing the ancient radiators in this more ancient house.

The feed is, I’m told, a “one-pipe system”. Is that going to cause compatibility issues?

Looking at Screwfix, they come in at about 20 quid, which is doable. I’m baffled by all the choice though, single / double / double plus; what’s “double plus”?

They’ll be fed by a back boiler that’s 30 years old if it’s a day. Is there anything I need to consider here; is there some sort of capacity I can’t exceed, ie should I replace like-with-like or can I uprate them with impunity?

I’m assuming that the existing rads are some sort of Imperial measurements. Is there any sort of ‘best practice’ I need to be aware of to convert them, any specific fittings I should be looking for?

Anything else I need to know?

Cheers all.

Apologies for the most boring STW thread ever.

There have been worse

I’m idly toying with the idea of replacing the ancient radiators in this more ancient house.

See at leats you set the scene and a context

The feed is, I’m told, a “one-pipe system”. Is that going to cause compatibility issues?

No – it means it has hot water than runs in a continoue loop from the hot part to all the rads [ modern ones have a hot feed and a cold feed]
If this was really the case then you would not need radiator valves andif you turn one off the system will pressurise – are you sure this is the case – only known it with open fire fed systems

Looking at Screwfix, they come in at about 20 quid, which is doable. I’m baffled by all the choice though, single / double / double plus; what’s “double plus”?

Single is one sheet of radiator steel
Double is a double
Double plus is marketting – I dont know b=never heard of it tbh

They’ll be fed by a back boiler that’s 30 years old if it’s a day. Is there anything I need to consider here; is there some sort of capacity I can’t exceed, ie should I replace like-with-like or can I uprate them with impunity?

I would assume th eperson who fitted the sytem matched the rads to the system – you may be able to work out how many Kw of heat you have and alter which rooms have what output

I’m assuming that the existing rads are some sort of Imperial measurements.

Should still be the same though we use mm rather than BSP to define it

Is there any sort of ‘best practice’ I need to be aware of to convert them, any specific fittings I should be looking for?

Depends on what is there tbh but flushing the system would be a very good idea

If you want to mai me I am in Ossy on sat so I can nip over and give you my pearls of wisdom face to face and pressurise you to ride rivvy on sunday

Anything else I need to know?

Probably – its a messy job to do and involves dropping all the water out so tbh i would rather do it in Summer thna in winter as it is imperative you get oit back up and running asap.

Probably – its a messy job to do and involves dropping all the water out so tbh i would rather do it in Summer thna in winter as it is imperative you get oit back up and running asap.

wheres you sense of fun! Why not have you’re whole jury-rigged, cowboy-fitted system condemned by Corgi on christmas eve, and live without it until mid January when everything from the gas meter up is ripped out and replaced. In the middle of that have the water main in your street replaced so that you’ve no water, hot or cold. Then have the water company stick a JCB through the electricity mains as well. Thats what I did and I’m much the better man for it!

@maccruiskeen – 😆

Okey.. let’s clarify a few things.

One pipe system – Water flows around each rad in turn before heading back through the boiler for reheating. Therefore rads at the end of the system will be significantly cooler.

Two pipe system. Water enters rad, then flows into second circuit back to boiler – not via other rads. Hot water can therefore get to all rads more evenly.. but system must be balanced to ensure water doesn’t go “path of least resistance” and just go through one.

Rads have a power output- measured in Watts, or BTU’s and the boiler should be capable of powering the total rad wattage if you want to maintain the target radiator temp. If your boiler is underpowered for the size of house, no increase in radiator size will work as you’ll just end up with cooler, but larger rads.

Single / Double / Double plus
This is the number of panels the rad has – double ones are twice (ish) as powerful for a given size, but are of course fatter. The plus bit will be a metal fin system between the panels. Increases output without making them bigger.

If the rads are old and corroded, then measure the distance between the valves and choose something that’s as close as possible as a replacement. You’ll therefore have minimal pipe alterations to do. Replacing valves is recommended too to give better control!

Jeff

If this was really the case then you would not need radiator valves andif you turn one off the system will pressurise – are you sure this is the case – only known it with open fire fed systems

Yeah. The ‘one pipe’ doesn’t go in the rad and out the other side; rather, there’s a T at each side and the pipe continues under the rad in parallel with it.

If you want to mai me I am in Ossy on sat so I can nip over and give you my pearls of wisdom face to face and pressurise you to ride rivvy on sunday

Are you really? I’d suggest a pint at the very least, but unfortunately I’m going to be away all weekend.

Probably – its a messy job to do and involves dropping all the water out so tbh i would rather do it in Summer thna in winter as it is imperative you get oit back up and running asap.

Well, it’s kinda been prompted by the fact it was all drained a week or two back due to a leaking pipe. So I know, mostly, how to do it now at least.

the boiler should be capable of powering the total rad wattage

How do I find that out? Will it be stamped on the boiler or something?

If the rads are old and corroded, then measure the distance between the valves and choose something that’s as close as possible as a replacement. You’ll therefore have minimal pipe alterations to do. Replacing valves is recommended too to give better control!

Ah, I assumed they’d come with new valves. Hm, more expense. Ho hum.

Oh, mind you, they’re only about three quid. That’s not too bad.

Boiler should say the power output somewhere so you can work out your max

Make sure it is the output to the water you have and not how much the boiler uses – if its 30 years old ther ewill be a big difference between the two

I am there Monday if that helps but it will need to be about 7 ish

I won’t be back; could possibly send photos tho?

HIJACK – sorry 😳

I was also framing a rad question for those in the know on STWDIY.

My hall measures L 8x W 1.5x H 4m with the 4m representing the bit housing the stair and upper landing. Current have one old single-panelled rad about 80cm by 90cm which is just too small to do the job.

Boiler is less than 10yrs old.
Do I have to work out the output of all the rads and subtract this from the boiler output to find what “spare” capacity I have, therby determining how big a rad I can fit in the hall?

Probably – its a messy job to do and involves dropping all the water out so tbh i would rather do it in Summer thna in winter as it is imperative you get oit back up and running asap.

Wise words.

Also be aware that the range of sizes generally available has dropped considerably. I think they are in 10cm increments now, but that could just have been the suppliers I went to. If true you will need to be careful whether you go bigger or smaller than the existing. With old pipework the last thing you want to do is start bending it *too* much. A 10 minute job can quickly turn into a pretty major disaster scene. Really. Trust me.

A rough way to work out the size of radiators is 20 watts per cubic metre, so for your hall 8×1.5x4m it would equate to a 960w radiator (ish). If its a older house with poor insulation, leaky windows or doors I would increase it 30 watts.

Not of any help at all really, but I did all the calcuations at home last year to find out why siome rooms never get warm – it turned out that some of those are a little underpowered on the rad front. But the cost of replacing them plus the fact that the boiler was struggling anyway (and had just been rebuilt after a near-terminal failure) put me off changing them. We had a log burner instead which is a lot more fun.

I quite enjoyed in a really sad way working out all the thermal things though. It made me feel like I had a proper job.

Don’t spend money on new rads without changing your one pipe system.

Water does not flow round each rad in turn on a one pipe system. It flows round a loop, usually circulates round the radiator with gravity.

Hm.

Part of the issue is, the rads are all starting to decay. I’ve got a couple with weeping bleed valves, which I’ve jury-rigged.

Replacing the pipe feed is almost certainly going to be prohibitively expensive.