Correct sized rads for new extension

[donmaico]

Hello. I worked out the total size and with the existing small kitchen area which is being incorporated into the 8 x4 mtr block, it totals approx. 40mtrs sq. Its all very well insulated and has three large glass areas(bifold doors, window and roof lantern totalling about 12mtrs sqr ,the glass being of the required spec) .
The plumber has fitted what i would describe as rather inadequate looking rads , one 600x 800 double panel double convector and one single panel single convector 450x 1200 mm.He reckoned it would be enough because of the insulation and the fact that modern rads are "very efficient" Now I have done a calculation using online tools and it would seem a room this size would need about 14k+ BTU heat emission to warm it sufficiently whilst what I have had fitted would only reach about half that amount ,7k. Because one is fitted under a window i am restricted by height to about 500mm max.As far as I can see i have one of two ways to go , either a 2000 double convector, double panel rad ,which just about adds with the other existing one to the req 14k ,or I buy a triple convector 1600mm rad.Either way the cost would seem to be about £340
Could someone please advise me on this? thanks

 

[bengasman]

See what happens this winter before you start changing things; hardly necessary to heat a conservatory to 21C any way.
One thing is for sure: the claim that radiator efficiency has gone up, is total nonsense.

 

[gasafengineer]

You could say radiator efficiency has increased with regard to the changes imposed on emmiter output rating in accordance with British & europeon standards , unless the 'plumber' failed to use any form of correction factor when sizing heat output in refference to emmiter mean surface temperature then a 15/20% increase in heat load output could possibly be the case here.

 

[bengasman]

You could say radiator efficiency has increased with regard to the changes imposed on emmiter output rating ....

Radiator efficiency has not changed one single percent; bar a tiny bit of IR, 100% of what goes in, comes out.

 

[gasafengineer]

100% of what goes in, comes out.

You may want to think a little on this , heat output rate regarding radiation will differ considerably in relation to a single panel versus a double panel.

 

[bengasman]

You may want to think a little on this , heat output rate regarding radiation will differ considerably in relation to a single panel versus a double panel.

Heat output rate has nothing to do with efficiency.

 

[gasafengineer]

 

[monoxide62]

Radiator efficiency means diddly squat , bit like comparing it to a 48" wide screen telly , dependant on where your sitting will dictate screen size.

I think we should refer to it as emmiter efficiency as opposed to radiator efficiency (70/30).

 

[bengasman]

...I think we should refer to it as emmiter efficiency as opposed to radiator efficiency (70/30).

Completely lost me on that one. 30/70???
I'm not sure what amount of heat input gets converted in ( IR ) light, but I'm pretty sure it is less than 1%, and most certainly not 30%.
As less than 1% is negligible, I call it 100% efficient. Has been like that for as long as there have been rads in their current form.

 

[monoxide62]

...I think we should refer to it as emmiter efficiency as opposed to radiator efficiency (70/30).

Completely lost me on that one. 30/70???
I'm not sure what amount of heat input gets converted in ( IR ) light, but I'm pretty sure it is less than 1%, and most certainly not 30%.
As less than 1% is negligible, I call it 100% efficient. Has been like that for as long as there have been rads in their current form.

The term radiators is a little misleading as the majority of heat is transmitted through convection (70%) rather than radiation (30%) , a double panel convector will emitt less heat than a single panel of equivilant output rating , this is due to radiation of rear panel 'not seeing' the room , so we could argue not all 'emitters' are 100% efficient , the other issues here are manufactures quote output ratings for bare steel , once these emitters are painted as much as 20% heat is lost due to lower emissivity , unless of course they are coated with clear varnish... or is it the other way round? never could remember.

 

[bengasman]

You mean efficacious, not efficient.

The efficacy ( per m2 or ft2 of occupied wallspace ) of radiators has gone up dramatically since the flat single panel rads from the sixites? fifties? forties?

In a modern ( insulated ) house, one little 0.5 m2 double panel, double convector can often be enough to heat up a room of about 30m2 or 300 ft2 in old money. To do the same room with the old flat models, you'd probaly need at least a 3 metre/10 ft long monster of maximum available height.

Efficiency of both types is exactly the same though, virtually complete i.e. ~100%.

 

[monoxide62]

You mean efficacious, not efficient.

, oh the confusion , was it not you that mentioned 'radiator efficiency'?

 

[bengasman]

Nope, no chance.
I've found a very easy way to remember what is what.
Efficiency of an Eyesore to heat a house is much higher than a Bermuda.
Efficacy of a Bermuda to keep a house warm in winter is much higher than that of an Eyesore for the simpe reason that an old working boiler works better than knackered Eyesore.

 

[monoxide62]

Radiator efficiency has not changed one single percent; bar a tiny bit of IR, 100% of what goes in, comes out.

Certainly NOT the case when using double panel convectors , even worse when using triple panel convectors.

 

[bengasman]

Radiator efficiency has not changed one single percent; bar a tiny bit of IR, 100% of what goes in, comes out.

Certainly NOT the case when using double panel convectors , even worse when using triple panel convectors.

If the heat goes in, but not out, where does it go?
Law of nature states:
No energy is created, no energy is lost. ( leave out nuclear for the moment )
Therefore: 100W heat energy in = 80W heat energy out + 20W in the form of????
It ain't light; you would see it. No sound; you'd hear it. No movement; you'd lose the radiator. Leccie and magnetic energy are out too. So what form does the 20W take?