Long thin "radiator"

[Nick Atty]

I want to add an additional radiator to a loft converted to a bedroom. I think the radiator fitted is just about adequate for the room, but: a) SHMBO likes her bedrooms about 10 degrees hotter than I do b) the radiator (which is on the only vertical wall in the room) is behind where we have the bed-head, so it's hard for the air to get out, and the bed tends to push up against it, boiling my head in the night.

Along one side of the room is a suitable surface for putting a long, thin, radiator - it's about 4 metres long but only about 20cm wide. I've got easy access to the heating pipes at either or both ends of it.

From my canal boat experiences, I know about "finrad" - a copper tube with thin metal squares attached to it, which is very efficient but looks nasty, cuts you if you brush against it, and collects more dust than a dyson.

A prolonged google has only turned up some "designer" radiators, but at

400quid a metre, this is more than I really want to spend - by at least one order of magnitude.

Currently my thoughts are running to a loop of chrome tube, on chrome stand-offs, so I end up with about an 8 metre run, with feed at return at the same end. But the joints are going to have to be compression and will look a bit nasty with 6 inline couplers as well as the elbows at the end.

How much heat is this likely to give out? Will 22mm tube work better than 15mm (greater surface area)? Can anyone think of anything better at a sensible price? Or any improvements to the idea?

[Jeff]

How about a kick panel heater set into the wall, have a look on the Myson site

Regards Jeff

[fred]

In article , Nick Atty writes

Here's a heat loss table:

'd need to have 4x15mm pipes to get 500W from the sort of span you are talking.

An alternative might be to make up some flat panels in metal to act as heat spreaders with the pipes behind in close (conductive) thermal contact. Then you might then be able to get about a kW.

As to the fittings I'd be inclined to strip back the chrome at the ends and use solder fittings, then use a sleeve made of larger diameter chrome pipe to cover the joint, split & reformed if necessary.

[Andy Hall]

Are we talking about degrees Celsius or the deprecated Fahrenheit?

You've used metric everywhere else, so I assume Celsius, but 10 degC seems like a lot.

Before you do anything, you will need to calculate the actual heat loss. You can use the Barlo program to do this, or drop me a mail and I'll send you the Myson one.

You need to take account of surfaces, insulation and air changes. There can be huge differences resulting from these, and unless you do the sums reasonably well, you run the risk of being hugely out. Also, don't forget to take account of the intended temperature drop of the radiator. For a conventional boiler this is 82 degrees in and 70 out. Less for a condensing boiler. Radiator data sheets work on the basis of higher temperatures so for th 82/70 situation, you need to derate using a factor of 0.9

Myson, Stelrad and Barlo make skirting radiators that would fit your dimensions. There are conventional ones as low as 30cm.

If you make your own and only use tube with no fins, I think it is highly unlikely that you will get enough surface area to release the heat that you will need. 22mm is going to be better, but I suspect when you do the sums, you will find that the results are still way out

- my guess would be by at least an order of magnitude.

[John Stumbles]

If you look at the output of chromed towel radiators and guesstimate the amount of chromed tube they comprise compared to what you're proposing I think you'll just get a few 100 Watts - not enough. I assume by '20cm wide' you mean high, and that it's where the sloping roof meets the wall. Could you lose a little space and put a low conventional rad a little way out from this point?

/ / / / || 200 | || 300mm high rad mm | || ------------

If you don't mind it looking a bit odd you could mount a taller rad on the slope

/ / // / // / // / // 200 | // mm |// ------------

Or rip up the floor and install UFH!

[Lurch]

On Sun, 13 Mar 2005 11:35:08 +0000, Nick Atty strung together this:

Something along the lines of what I thought, but galv of up to 2" diameter and painted. You may get away with using 28mm copper for ease of availability as 2" galv would require someone to manufacture the joints for you, a commercial heating engineer.

Don't know how to do a size calculation for a length of pipe, however, for 8 meters I would imagine 22mm would suffice but if SWMBO likes it hot in the bedroom then 28mm could be a safe bet. (Although, you may have m isunderstood her request and you may get better results with a firemans uniform)?

[Nick Atty]

More a figure of speech than anything. She certainly likes bedrooms at warm living room temperatures.

I'll have another look for those.

Thanks - if your gut feeling is that much I suspect I don't need the program!

[Nick Atty]

Yes - actually the surfase is along the purlin; sloping roof above this, and storage cupboards below. Standing it out is an interesting idea - I'll have to do some measurements. Thanks

[Nick Atty]

That's another good idea I hadn't come up with. You can hire dies for putting threads on large diameter pipes can't you?

[John Stumbles]

Short (as in height) column rads (like the traditional cast-iron ones you used to have in schools etc but current 'designer' manufacture) aren't _too_ expensive - I think 1 metre by about 300mm high by 3 column (about 150mm deep) was about £150 in B&Q when I looked recently.

[John Rumm]

Imagine that in a nice bit of trunking and you basically have a skirting radiator:

[Nick Atty]

googling on "skirting radiator" and could find nothing but houses fitte with them for sale, and "find the cheapest radiators at...".

[Lurch]

On Sun, 13 Mar 2005 14:27:18 +0000, Nick Atty strung together this:

I would assume so, I live across the road from a commercial heating engineer so have never needed to hire one! You can get hand operated ratchet dies or huge electric ones, a hand one is reasonably easy to use on 1 1/2" and smaller.

[Andy Hall]

You can get floor brackets for these types of radiator as well.

Personally, I think I'd go for this approach and use a standard sized radiator - at least you know what you're getting. It would be very dispiriting to put a lot of work into a tube affair, only to find it inadequate.

All of this in an attic room, pretty much does imply a sealed boiler system, although I did one like this once (carefully) with an open vented tank and under 1m of head.

[Andy Hall]

Do bear in mind that any of these enclosures reduce the heat output compared with the native rating. For a conventional radiator in a cabinet with air gaps and grille front, it can be as much as 30%.

All of this, plus the derating to 90% for water temperature, need to be included when sizing. However, if you can have long runs, then it should work.

[Nick Atty]

Oddly no. This was the attic of the single story part of the house - the header tank is in the loft of the two storey part.

It's a 1930s telephone exchange, that was initially converted into a bungalow with some upstairs space; this included putting a single storey extension on but with a proper roof. We reordered upstairs into a more sensible set of rooms, and converted the "walk in loft" into another bedroom.

[Nick Atty]

Of course, all this is for an additional radiator. I'm not planning to remove the exisitng one, rather I was thinking of setting its TRV to a lower level than the new one. So when the system first come on both run at first to get up to temperature, but overnight only the new one will run to keep the room up to temperature (this is the room with the thermostat for the upstairs zone in).

Many thanks to all for your thoughts. I see I can get 30cm high radiators from stelrad at up to 3m long (the high output version of which is 3Kw - a lot more than my pipework suggestion would even have delivered). So seeing if I can mount one of those on slightly longer brackets is my current thinking. Truely several heads are better than one.

[bigcat]

longer

I imagine a much neater result can be got by snaking microbore under the floorboards as simple ufh. Fit service valve to keep the flow rate down so temp doesnt get too high; would that work?

I was originally going to sugges that adding a small silent low rev fan can substantially improve a rad's output, but it looks like you've got it all worked out.

NT

[Nick Atty]

Well if we'd thought of it, we'd have had UFH put in. But we didn't.

And all the strengthening that went in to change this from being only a ceiling to being also a floor would get in the way.

I dunno. That's a very nice idea indeed.

With a temperature operated switch on inlet to the rad, it would only come on when needed.

I might try rigging something up as an experiment to try it. Even if I used a small spare computer fan and it made a bit of noise, it would be a good proof of concept.

If it worked, it would be cheaper and easier than my other plans.

[bigcat]

didn't.

I dont know what structure youev got there, but with the usual wood joist adffair it would mean lifting all the boards and notching or drilling the joists. Not half as easy as a fan.

Miles easier, no need to put a 2nd rad in at all.

The key to making fans silent is to get them down to around 1000rpm. You can do that with puter fans by wiring 2 in series on 12v, or else feeding them all on 6v. Of course lower speed equals less air movement per fan.

I'd try 4 puter fans per standard rad, along the base fanning upwards, and work from there.

Power consumption is so small that a thermostat, although ideal, can always wait till things get warmer.

NT