Are new radiators more efficient?

I read this

“You may think all radiators are born equal, but you'd be wrong. ... In fact, modern radiators can be up to 50% more efficient than their year 2000 counterparts”

And I’m thinking, the boiler is creating the same amount of heat, is there any actual difference?

my rads are Id guess 30 years old, should I change….even just to get rid of sludge

If you want to receive proper replies, I suggest you change your signature, this is not a political site

I had a complete new system installed last summer - boiler, rads and all pipework.
The previous system was probably 40 years old.

When the first cold weather arrived, I thought there was a problem as the radiators weren't getting hot - strange thing is, the house was still nice and warm.

When the old system was running, you'd burn your hand on them but now the boiler flow is set to 60C and I guess the radiators run about 55C. So yes, they are indeed a great deal more efficient.

Alan 483256 said:

I had a complete new system installed last summer - boiler, rads and all pipework.
The previous system was probably 40 years old.

When the first cold weather arrived, I thought there was a problem as the radiators weren't getting hot - strange thing is, the house was still nice and warm.

When the old system was running, you'd burn your hand on them but now the boiler flow is set to 60C and I guess the radiators run about 55C. So yes, they are indeed a great deal more efficient.

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30 years of painting them doesnt help

Notch7 said:

I read this

“You may think all radiators are born equal, but you'd be wrong. ... In fact, modern radiators can be up to 50% more efficient than their year 2000 counterparts”

And I’m thinking, the boiler is creating the same amount of heat, is there any actual difference?

my rads are Id guess 30 years old, should I change….even just to get rid of sludge

Click to expand...

It depends what you mean by efficiency. Modern rads might be better in terms of heat output per m2 rad area (at a given water temperature) but changing to them won't save you any gas. If heat isn't dissipated by the rads it goes back to the boiler, it doesn't disappear. If you change to rads with higher kW/m2 the water temperature can be lower for a given heat output, which could give more condensation, hence slightly better overall efficiency, but that's all.

fixitflav said:

It depends what you mean by efficiency. Modern rads might be better in terms of heat output per m2 rad area (at a given water temperature) but changing to them won't save you any gas. If heat isn't dissipated by the rads it goes back to the boiler, it doesn't disappear. If you change to rads with higher kW/m2 the water temperature can be lower for a given heat output, which could give more condensation, hence slightly better overall efficiency, but that's all.

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Exactly!
Talking about the 'efficiency' of a radiator doesn't really make sense.
Electric radiators are a simpler example to consider - they are all virtually 100% efficient; though they have different sizes, power outputs and they differ in the ways they heat the room - radiative, convective, aided with a fan etc.
Having appropriately sized rads for the space, comparing system efficiencies, comparing unit costs for different sources of energy and calculating the energy savings gained, over the cost of a new install, are probably more useful conversations to have!

ianmcd said:

If you want to receive proper replies, I suggest you change your signature, this is not a political site

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It’s a joke, I thought it appropriate as it has a connection to DIY. If you thinks it’s partisan, I apologise

RandomGrinch said:

Exactly!
Talking about the 'efficiency' of a radiator doesn't really make sense.
Electric radiators are a simpler example to consider - they are all virtually 100% efficient; though they have different sizes, power outputs and they differ in the ways they heat the room - radiative, convective, aided with a fan etc.
Having appropriately sized rads for the space, comparing system efficiencies, comparing unit costs for different sources of energy and calculating the energy savings gained, over the cost of a new install, are probably more useful conversations to have!

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Many thanks, that makes a lot of sense.

My reason for the thread was because I’ve been thinking of getting the rads changed and when googling, I’ve come across these claims radiators are now more efficient - which makes no sense to me.

New rads seem to have enclosed ends and grill so I guess they may connect more efficiently, I wondered if they could heat a room faster.

Im sure the system must be full of sludge so maybe changing to new rads would improve flow etc.

1. If the system is full of sludge, cleansing it will restore original performance.
2. Radiator efficiency:
2a. New radiators are no more efficient than old. Layers of paint may make a radiator slower to feel warm, but won't affect the amount of heat given out.
2b. Aluminium radiators are no more efficient than steel ones.
2c. The purpose of a radiator is to lose heat from hot water to a space. Some may lose heat quicker than others, but the same amount of heat is lost.

Notch7 said:

I’ve come across these claims radiators are now more efficient - which makes no sense to me.

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Yes, I'm afraid it may be down to some marketing tripe - but I'm willing to hear arguments otherwise!

Notch7 said:

New rads seem to have enclosed ends and grill so I guess they may connect more efficiently, I wondered if they could heat a room faster.

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Again, yes modern designs of radiators have features such as 'tube in tube', etc. that can promote convection, whilst using less water, so the design can heat the room quicker. In this case, the radiator is more efficient at dissapting the energy provided, into the environment; the energy expended by the system would be the same.

And for example, if we're talking about the 'efficiency' of heating a room, then I can instantly make the radiator 20% more efficient!
I am about to change a towel rail - the Chrome version is 797 BTU, the Grey version is 1005!

Notch7 said:

Im sure the system must be full of sludge so maybe changing to new rads would improve flow etc

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If you would like new rads, and you are suffering from poor performance, go for it!
But you won't gain any 'efficiency' savings by simply replacing the rads - and they will cost you money - a system cleanse could be the most 'cost effective' solution!

I see 'efficiency' as the wrong word, as clearly all heat energy in must come out as heat energy there can be no loses.

However I have been looking at the speed at which a radiator can heat a room. I looked at these having had a proper Myson fan assisted radiator and it worked well, the whole idea seemed good, so as an experiment I used a small fan and the thermostat normally used to brew beer to see if it helped.

However with a modulating boiler with lock shield valve and TRV head the experiment was a failure, sensor was on return, so the fan would only run if return water still warm, and the fan would switch off/on on a regular basis as to run the fan it needed more water through the radiator, the old Myson had no lock shield valve, and was used with a no modulating boiler, where hot water returning to boiler did not matter.

I have come to realise central heating is not as easy as it seems, back in around 1980 I fitted my first, at that time no TRV's and I found I had not allowed for the amount of heat which will peculate up from lower floor to upper floor. Up stairs too hot and down stairs too cool. The house before that had hot air central heating, blowing air around the room means whole room at same temperature, including at that time next to the single glazed picture windows so it increased the loses. But second house with double glazing fan assisted radiator worked well.

With a gas boiler the cooler the return water likely the more efficient the boiler runs, not sure with an oil boiler? In theory this house should cost more to heat than last one, as larger, and detached, where last one was a semi-detached, and double glazing is older, plus two sets of patio doors, but in fact the oil costs less than we paid for gas.

I have a fault I know, pump on return and pump hot before all radiators are hot, but pipe work hidden so don't know why. But since not a modulating boiler it still works.

ericmark said:

clearly all heat energy in must come out as heat energy there can be no loses.

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One could say that if the water leaving the radiator is still hot ( hotter than the air in the room ) then the radiator was not efficient at transferring heat from the water to the air in the room

bernardgreen said:

One could say that if the water leaving the radiator is still hot ( hotter than the air in the room ) then the radiator was not efficient at transferring heat from the water to the air in the room

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On that basis all rads are "inefficient", the water leaving the radiator is always hotter than the air in the room, unless the rad is very large (infinitely large in theory).

fixitflav said:

On that basis all rads are "inefficient", the water leaving the radiator is always hotter than the air in the room, unless the rad is very large (infinitely large in theory).

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Yes, and then we start talking about 'black body' radiation and 'perfect' radiators

Whatever you want to call it, there's no doubt that my new rads are "better" than the old.

The old ones had to be scorching before the rooms were comfortable, the new ones are just a bit more than 'pleasantly warm' for the same result.