Radiator ratings confusion?!?

[TheLastMan]

I have calculated the heat loss from my living room and it is between 3,200 and 3,800 watts when the external temp is 0 degC and the internal required temperature is 21 degC.

However, all the radiators I have seen have ratings quoted as output (watts or btu) at a "Delta T" of 50. Now that would require an internal temperature of, say, 30 degC and an external temp of -20 deg C!!!
Or have I misunderstood?

What I want to know is what rating of radiator(s) would I need to keep my living room warm when the outside temperature is 0 degC.

Thanks for any help!

 

[spudkey]

the temp quoted is the difference between the radiator temp and the room temp eg boiler water temp 70 and room temp 20

 

[TheLastMan]

the temp quoted is the difference between the radiator temp and the room temp eg boiler water temp 70 and room temp 20

Thanks! That is very helpful - it makes some sense now

So what rating am I likely to need with a room heat-loss of 3,200 watts?
Presumably I would not want to have a radiator much hotter than 70 degC ( with three young kids)?

The space I have for a radiator is 2.0m x 0.8m. The highest rated radiator I have found is about 2600 watts at "Delta 50" and that was a 1.6m x 0.6m double panel / double fins. Would that be good enough or should I look for the biggest radiator I can find to fit the space?

Thanks for helping!

 

[D_Hailsham]

the temp quoted is the difference between the radiator temp and the room temp eg boiler water temp 70 and room temp 20

Thanks! That is very helpful - it makes some sense now

So what rating am I likely to need with a room heat-loss of 3,200 watts?
Presumably I would not want to have a radiator much hotter than 70 degC ( with three young kids)?

The space I have for a radiator is 2.0m x 0.8m. The highest rated radiator I have found is about 2600 watts at "Delta 50" and that was a 1.6m x 0.6m double panel / double fins. Would that be good enough or should I look for the biggest radiator I can find to fit the space?

Are you wanting a "designer rad" or a standard flat panel type? If you are only after a standard, have a look at the Stelrad Elite Range; they have rads which will provide your required output within the size constraints you gave.

Don't forget that the rad size is based on a "worst case" scenario - heating up the room from 0C to 21C. It will rarely be called upon to do this, particularly with global warming raising average winter temperatures. The water temperature will. also, rarely get up to 70C for the same reason as it will be modulated by the boiler.

Presumably you have used a heat loss calculator to determine the rad size, if so, it should have automatically compensated for the fact that you are using a delta of 49C (70-21) instead of the standard delta of 20C (70-20). If this is correct you just need to get a rad of the size specified by the calculator.

 

[Agile]

The space I have for a radiator is 2.0m x 0.8m.

The highest rated radiator I have found is about 2600 watts at "Delta 50" and that was a 1.6m x 0.6m double panel / double fins.

Thanks for helping!

I dont see how you can say that!

Obviously a radiator which is 2m long will have a higher heat output!

See what the heat output is with a 2000 x 600 DC.

There are probably some manufacturers who make 2000 x 700 or just possibly 2000 x 800 rads. Different manufacturers make different sizes although most now make them in multiples of 200 mm with the odd 100 in the smaller sizes.

The output only varies by a small amount between different manufacturers for the same size e.g. 2000 x 600 DC. More or less fins etc.

Tony

Tony

 

[TheLastMan]

Are you wanting a "designer rad" or a standard flat panel type?

"The boss" wants a designer rad. Once I have told her the cost, I think we are more likely to end up with something from the prettier end of the Stelrad range!

If you are only after a standard, have a look at the Stelrad Elite Range; they have rads which will provide your required output within the size constraints you gave.

Thanks for the tip.

Don't forget that the rad size is based on a "worst case" scenario - heating up the room from 0C to 21C. It will rarely be called upon to do this, particularly with global warming raising average winter temperatures. The water temperature will. also, rarely get up to 70C for the same reason as it will be modulated by the boiler.

If the water never reaches 70c then presumably the rad will not be performing to specification. Should I get a higher rated rad to compensate?

Presumably you have used a heat loss calculator to determine the rad size, if so, it should have automatically compensated for the fact that you are using a delta of 49C (70-21) instead of the standard delta of 20C (70-20). If this is correct you just need to get a rad of the size specified by the calculator.

The heat loss calculator was not that sophisticated. It was suggesting rads with ratings of 2600 after calculating a heat loss from the room of 3800. That is partly why I was confused.

 

[TheLastMan]

The space I have for a radiator is 2.0m x 0.8m.

The highest rated radiator I have found is about 2600 watts at "Delta 50" and that was a 1.6m x 0.6m double panel / double fins.

Thanks for helping!

I dont see how you can say that!

Because I've only looked at B&Q and The Radiator Company

Obviously a radiator which is 2m long will have a higher heat output!

That is common sense assuming the same design of radiator. From my limited search I did not find a 2m radiator.

See what the heat output is with a 2000 x 600 DC.

Now I know that such things are available I will do a wider search. The whole point of my post was I really did not know what I was looking for, so wanted some advice before wasting too much time driving round plumbers merchants or browsing the web.

There are probably some manufacturers who make 2000 x 700 or just possibly 2000 x 800 rads. Different manufacturers make different sizes although most now make them in multiples of 200 mm with the odd 100 in the smaller sizes.

2000 x 800 is the maximum we can accommodate. If we can get away with something smaller it would be better.

 

[D_Hailsham]

"The boss" wants a designer rad. Once I have told her the cost, I think we are more likely to end up with something from the prettier end of the Stelrad range!

Good luck keeping the boss happy

If the water never reaches 70c then presumably the rad will not be performing to specification. Should I get a higher rated rad to compensate?

NO! Just get a rad of the size provided by your calculator. The radiator only needs to give out 3kW, or whatever the spec says, when the outside temperature is 0C and you want the room at 21C. When the outside temp is 10.5 C the radiator only needs to give out 1.5kW (it's directly proportional to the temp difference) in such a case the water temp will not need to be as high as 70C, so the boiler controls will automatically lower the temperature.

A radiator is not like an electric fire, which gives out a fixed amount of heat. The output of a radiator depends on three factors: temperature of the water entering the rad; temp of water leaving the rad; temp of the air adjacent to the rad. All manufacturers specs are quoted for temperatures of: 75C, 65C and 20C. There are complicated formulae which can adjust the output for different temperatures; but you need not bother about that!

The heat loss calculator was not that sophisticated. It was suggesting rads with ratings of 2600 after calculating a heat loss from the room of 3800. That is partly why I was confused.

What calculator did you use? Some of the online ones are very basic!