Size of Radiators or sizing of radiators for a room

[Andy1946]

It is a good idea to have radiators far larger than the plumbers tell you to fit (I plan always to install about 4 times larger than the calculations suggest), you may ask why? Here are the reasons:-

1) Lower temperature needed in the hot water supply for the same room temperature an important point when small children are in the house and also more efficient for your boiler to work at a lower temperature.
2) Rooms heat up quicker when needed to be warm.
3) Less heat loss in the supply when the pipes are not quite so piping hot (all pipes should be fully insulated where you do not require heat anyway!)
4) Temperature is more stable in the rooms with a larger mass of water and if airing a room, losses are replaced quicker.

Good insulation of the house is a must for any house and should also be part of any renovations made.....

The extra size of Rad costs very little more generally and the overall functionality is fantastic.....

 

[Bon]

2) Rooms heat up quicker when needed to be warm.

Only if your boiler is 4 times the calculated size too, which renders.....

The extra size of Rad costs very little more generally and the overall functionality is fantastic.....

....untrue

 

[Andy1946]

You have not thought your reply out well. If your boiler is so short in power that it cannot supply enough water to heat up rads that are 4 x larger than what would normally be installed for that room, then the whole system is undersized for your whole house anyway.......you must freeze!!

You really have to approach this in a more scientific manner and assume that as the boiler can (and was sized for to) heat the whole house, but seldom the whole house at one and the same time, then it can heat say at least 1/2 of the house in a significant manner!!! Therefore one room cannot be a problem!!

I have been resizing my rads now for about 12 years and I can say that I have done it, it works and is a complete hit with my family.

It does EXACTLY what I said it did, no more no less......to prove me wrong, you will need to do the same in your house at least......

I can also say confidently, after reading your post, that you have NOT done it and are therefore only speaking from an error of thought in your own theory! Quite a difference in perspective I feel!!

Please feel free to offer further criticism but in a well thought and scientific manner, just shooting from the hip will not hit the target.....nor will I bother to reply further to bigoted inaccurate opinions from someone seemingly with a chip on his shoulder!!! It is just not needed here on such a great web site....

 

[thetman]

The heat output for a radiator is provided by the manufacturer for various mean water temperatures. If you want to run the system at a lower temp to avoid burns etc, you select the appropriate size of radiator based on the correction factor, just quadrupling the rad size is not going to achieve the same effect.

As for the boiler capacity, the boiler is capable of heating (x) amount of water through a temp difference of . If you have an unusually high amount of water in the system, the boiler mey not manage a high enough temp difference to enable the house to be heated under full load conditions.

 

[Andy1946]

As I have mentioned before, but maybe you missed it, if the boiler is undersized for the house (or is not correctly set up or needs an overhaul), you might have the problems you mentioned.

But if it is correctly sized or as I also recommended in another blog, ( no house should have less than 28 kw, no matter how small the house is, as you can get quite a large amount of piping hot water for a decent shower with such a boiler. I do not believe in paying for the storing of hot water, so we have no hot water storage tank!), the price difference is smal between the 18 and the 28KW boiler, but the comfort difference is huge, you will not get the problems that you "feel" that you might get.

I have over 12 years of positive experience using these over sized rads in my kitchen, bathroom, lounge and all the bedrooms (first with an old 18 KW Boiler and later when I replaced it some 8 years ago, with a modern 28KW version).....so I am not talking from a standpoint of inexperience or lack of practical experience, are you though?

I feel that I have put my money where my mouth is, are you willing to do the same? I seriously doubt it. But it would be great if you did as you would enjoy a comfort that you are completely missing at this time, or should I say, your whole family is missing this comfort!!!

I started doing it this when I found that although the water was still very hot WHEN LEAVING THE RADIATOR, the rooms still took too long to warm up!!! So even the old 18KW was capable of warming a room up much faster, but the area of radiator was simply too small when the room was cold, to make a FAST difference!!!

Now, the lounge for example is pleasantly warm within 5 minutes of turning up the stat, in fact I feel we save money in the longterm, as we now ONLY heat the room when we are in it, otherwise never......the house is well insulated as well and the "frost watch" function is always on, but it never gets that cold in the first place inside even in a hard winter!!

So unless you are willing to "bite the bullet" and "put your money where your mouth is", why not back off and forget the whole thing? Leave the blog for people who are genuinely interested in learning something new and useful......instead of arguing from a position of ignorance over the matter?

Actions speak louder than words, you are hereby cordially invited to visit my house in Germany to see for yourself the way things really work. A cheap flight is around 100 pounds return from the UK, I will pay half provided you come on this blog and tell the REAL truth afterwards. What do you say to that?

 

[Andy1946]

As I have mentioned before, but maybe you missed it, if the boiler in your house is undersized for the house (or is not correctly set up or needs an overhaul), I agree, you might have the problems you mentioned.

But if it is correctly sized or as I also recommended in another blog, ( no house should have less than 28 kw, no matter how small the house is, as you can get quite a large amount of piping hot water for a decent shower with such a boiler.

I do not believe in paying for the storing of hot water, so we have no hot water storage tank!), the price difference was very small between the 18 and the 28KW boiler, but the comfort difference is huge, I do not get the problems that you "feel" that you might get in such a situation.

I have over 12 years of positive experience using these over sized rads in my kitchen, bathroom, lounge and all the bedrooms (first with an old 18 KW Boiler and later when I replaced it some 8 years ago, with a modern 28KW version).....so I am not talking from a standpoint of inexperience or lack of practical experience, are you though?

I actually only started with the lounge that was very cold all the time and gradually extended over the whole house as we redecorated, not all at once!!!

I feel that I have really put my money where my mouth is, but are you willing to do the same? I seriously doubt it. But it would be great if you did as you would enjoy a comfort that you are completely missing at this time, or should I say, your whole family is missing this comfort!!!

I started doing it this when I found that although the water was still very hot WHEN LEAVING THE RADIATOR, the rooms still took too long to warm up!!! So even the old 18KW was capable of warming a room up much faster, but the area of radiator was simply too small when the room was cold, to make a FAST difference!!!

Now, the lounge for example is pleasantly warm within 5 minutes of turning up the stat, in fact I feel we save money in the longterm, as we now ONLY heat the room when we are in it, otherwise never......the house is well insulated as well and the "frost watch" function is always on, but it never gets that cold in the first place inside even in a hard winter!!

So unless you are willing to "bite the bullet" and "put your money where your mouth is", why not back off and forget the whole thing? Simply ignore me and go read something else or write something that we can read? Just leave this blog for people who are genuinely interested in learning something new and useful......instead of arguing from a position of ignorance over the matter?

Actions speak louder than words, you are hereby cordially invited to visit my house in Germany to see for yourself the way things really work. A cheap flight is around 100 pounds return from the UK, I will pay half provided you come on this blog and tell the REAL truth afterwards. What do you say to that?

I have just re-read your last post and I get the impression that you are possibly a plumber and fixed on the tables of room sizes etc. that plumbers use and are unwilling to even think of an experiment. I have met this attitude before on BOTH side of the English Channel!!!

The x4 that I use was originally just a test and it proved to do exactly what I wanted it to do, so I did not "play" with the values anymore! It would have been expensive and costly to start buying even more radiators of various sizes just to see if I was at the "perfect point" so to say.....it was simply not worth it......

I would guess that more is better than too little and once you are beyond the optimum point, even bigger rads do not make much difference. Maybe 3 x might have achieved what I wanted, I would not argue the point in the slightest, but my value works for me.....

Having done all rooms except the hallway, I can only say it has exceeded all my hopes and expectations and my boiler seems to cope really well!! But it is a German made high pressure boiler, perhaps that is part of the secret.....who knows?

Have a great "rest of" the weekend!

 

[Bon]

2) Rooms heat up quicker when needed to be warm.

The use of a plural forced my less-superior brain to think you meant more than one room (as is normally the case when reading a plural).

Just so I get this right, you're saying that people should install 4 times the surface area of heat emitter than a calc would suggest? You must not like having much wall space then.

You are correct in that I do not possess anywhere near your majestic figure of 12 years experience, however I'm sure that there are people out there who have 4 times your recommended experience to qualify a person's opinion as being correct over that of others (see what I did there?) and still disagree with you.

As for labelling my views as "bigoted" then I think you're being a tad harsh. If anyone is displaying the traits of a person so set in his own ways and reluctant to entertain the views of others then I feel it is you my friend.

Oh and by the way, this is a forum, not a blog. Blogs are for people who feel the urge to publicise their every thought without giving a truly public chance for people to reply. A forum does just that so you might want to prepare for your ideas to be criticised.

 

[Andy1946]

You wrote:-

Q.The use of a plural forced my less-superior brain to think you meant more than one room (as is normally the case when reading a plural).

A.I did mean more than one room, as I have done this in most of the house with no problems attached. Thats why I used the plural in the first place, why you did not follow that I cannot fathom, it was written fairly simply I thought!

The trick is that it is highly unlikely that all or even half of the rooms will all start demanding hot water at the same time......!!! Even if they did, I am sure my boiler would handle it well.....

I do use remote radio operated thermostats with a mini controller that takes into account the speed at which the room warms up and shuts off earlier to achieve exactly the temp required with little or no overshoot or wasted heat!!!

My heating/hot water bills are now less that €600 (Euro not Pounds) a year. Which is exceedingly low for a house of 135 Sq Meters here in Germany, where fuel is very expensive generally.....

You also wrote:-
Q.Just so I get this right, you're saying that people should install 4 times the surface area of heat emitter than a calc would suggest? You must not like having much wall space then.

A. I was suggesting it only as a thought, with my experiences thrown in, but I know 4 x works for me, maybe 3 x would have done well enough too, I was not about to waste money "fiddling about" to get the sizes exactly right. Nor am I a laboratory with money for such testing....Mine just worked and worked exactly as I wanted it to!!! I did not have any "space" problems installing to around 4 x....some might have problems in this area.....

My thoughts were to alert people to the fact that there are some good "spinoffs" from such a move as the extra costs are actually minimal in the cost of a heating system as a whole, and it would actually appear to save money as certain rooms are now only heated when required, not before. I even have one room where my daughter has her Lizard, that is kept warm the whole time through the winter, once the Lizard is gone, we shall save some more money!!!

For me, 4x was not that much of a problem as I used only double rads with the extra finning in the middle, I have not a clue what they are called in English (or even German for that matter!! They are ordered as "DK" here!).

They are of course as high as will fit in with the room's decor (under the window ledges 60CM except in the kitchen where it is under the seating and only 30 CM high!)) and approximately twice as long as "normal", so they overlap the width of the window a little each side in my case (except the Kitchen as otherwise stated).....but the effective surface area is still about 4 x the calculated sizes. But no one in all the years has actually noticed that they are in fact oversize for a room of this volume, it just all looks quite normal.

Using single core rads would have made the size effect more noticeable of course......but actually it would have cost more as single core for the extra area works out not only far larger, but also more expensive then....

Also, I add special reflective foam to the wall behind the rad to make sure that heat is not put into the walls at all as far as possible......so aiding efficiency.....

I hope these last answers have managed to spur your further interest in trying out such a fix, maybe in your case only 2x will achieve the required functionality! I was not interested in experimenting further personally or financially once I found that my arbitrary 4 x worked....

In such blogs, I personally feel that calling into question the efficacy of "fix" like this after someone has personal and positive experience over 12 years, when you yourself have (I would guess at any rate) not ever tried this out at all, let alone over such a long period of time, you come over as a little bit rude.

You certainly do not have to agree with me or even reply to any of my blogs and posts, & normal "questions" are of course fully in order from anyone, but to go to such lengths of scathing questioning about the viability from your only at best "theoretical point of view" is simply "DOWNRIGHT BAD MANNERS!!!" in my book......

But if you do not understand why I wrote that last sentence or the thoughts behind it, that at least would explain everything to me in that area....."one is what one is".

An old German saying that springs to mind at this time is that "one cannot spring over one's own shadow!" If an explanation is needed, just ask, I will assist, the translation has already been done of course!

 

[Bon]

 

[Sandy Beech]

Forgive me asking but is the 12 years quoted experience gained whilst installing central heating systems in hundreds of houses on a professional basis or 12 years personal experience in your own house or houses?

If the former I may choose to listen but if not I may prefer to listen to the professionals whose opinions I have learned to trust.

 

[Balenza]

No need to oversize the rads to the spec you state.

Haven't you ever heard of weather compensation ?.
I doubt it.

you come over as a little bit rude

.

And you're coming over as a complete ****

 

[Andy1946]

Own house experience only with regard to rad sizes. It could be that only 3 x or even 2 x would achieve a close or similar result, who knows? I only tested 4 x....

I do all my own work (Carpentry, electrical, Water, Central heating, chimney work, Sat dish installs [Wave Frontier!! The hardest of all to install] and computer networks, PCs and the like).

The only part I do not do is with regard to the gas connection to the central heating and our garden gas tank(that I also was allowed to do in the UK in the 70's), which is not allowed in Germany, it must be a qualified plumber.

When we had the gas tank first installed, I insisted on a 2nd reducer near the house, against the wishes of the installer!!! 10 years later the codes were changed to making it a requirement (to me it is common sense only!) and I was the ONLY person in this area of Germany (according to the TÜV Guy for our area) that did not need to make such a change as I already had it!!! Boy was the TÜV Guy surprised and VERY complimentary!!!

 

[sooey]

I do all my own work

Name's not Jack is it?

 

[Andy1946]

Weather compensation is needed, but if the rads are undersized, the only effect is that the water must be made incredibly hot to achieve the required room temperatures.

Having to heat the water to 80°C or more makes the rads dangerous to both children, pets and adults alike......(having a leak, which luckily we have never experienced, must be very different when it is almost boiling water going everywhere!).

Having a larger rad area allows the room to be heated quickly without the use of excessively high water/rad temps which also shorten the life of the boiler and brings some boilers (mine included) out of their most efficient working temperature range.

Fuel usage is also important, as is insulation of all pipes where heat is not required to be brought.....insulating the wall behind a rad, helps too....

The water we circulate is at about 50°C on average, but on a warm day it drops to about 45°C, you cannot hold your hand on a rad for long I do agree, but there is little or no risk of scalding....its only uncomfortable to do.

What few people seem to understand is that the requirement is to have a particular temperature achieved and held in say a particular room, that the amount of BTUs required to do that is a constant assuming a specific outside temperature.

Having more or less radiator area ONLY changes the TIME to achieve that level (assuming a constant water temperature as well) and the size of fluctuations when airing or opening a door, which are smaller with a larger heating capacity.

NOTHING ELSE MATTERS....the minimal extra (theoretical) heating costs to achieve that are more than off set when you do not need to pre-heat rooms before using them!!! Plus the comfort that is also available....

I do realize that it may not be easy for everyone to understand the whole subject and many wrongly feel that having larger rads means using more heat energy or needing a larger boiler, it does not mean this at all provided that the boiler was correctly sized for the house or even a bit larger in the first place.....in this case "Bigger is better" for efficiency!

Think about this:- having X BTUS amount of heat energy in 50 liters of water instead of 25 liters of water just means that the 50 liters are half as hot as the 25!!!! The energy level is still exactly the same!!!!

So also is the heating bill you might think, but not having to heat the water up so hot means that the efficiency of the boiler is less important and also the losses while transporting the water are less.....ergo, it costs slightly less to get the same number of BTUs in a larger body of water at a lower temp!!

My local Heating Engineer (a good friend) says that it could theoretically mean that I save 10% on gas bills because the central heating water does not need to get that hot.

He has measured the exhaust temperatures and they are way down..... but he has not studied us exactly and I would advise you to take such comments, without full evidence, with a large helping of salt. But our heating bills are seemingly relatively low I do agree, lower gas usage than for 20 years (but more cost as the gas price is more than 4 x higher 52 cents a liter recently against 20 Pfennig or 10 cents a liter!)...

We used to have really tough winters here in central Germany, down to -15 to 20°C at night. The last 2 years have been relatively mild, but we are ready if another tough one comes along....

 

[Whitespirit66]

WHATEVER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!