Hello
Our house has some single and double radiators, probably 1980s vintage, fed from a conventional gas fired boiler.
Except for the fact that they might be full of rust and sludge etc., is there anything radically different about modern designs which would make them more efficient?
In other words, if they are still of sound construction, is there much point in replacing them?
Might it be just as sensible to get the system (and thus the radiators) power-flushed?
DDS
Radiators do not have an efficiency. To find if they are full of sludge, run your hand over them and see if there's any cold spots. (Invariably at the bottom.) As long as they keep the place warm and aren't leaking leave them alone.
You might consider thermostatic valve. If already fitted,make sure they're working.
Newer ones claim higher "efficiency" by having lower water content. Unless the old ones look likely to spring a leak, I'd leave them ...
They'll have less thermal output for a given water temperature. Old systems with conventional boilers were designed such that the radiators gave enough heat with water temps of 70+ C and a 10 C drop.
New systems with condensing boilers require the return to be about 55 C for maximmum boiler efficency. This means the flow is only 65 C and if you have old radiators they won't push out enough heat.
This is why modern radiators tend to be double panel with fins on both panels. Just to get the heat transfer from the cooler water.
Hard to tell. Feeling the centre top and bottom of each rad might indicate ones sludged up. Bits of black insulation tape an IR thermometer at a consistent distance will put some numbers on things. Once up to temp and stabilsed the bottom will be cooler but it ought to be even along the length, not cooler in the middle
Or get a thermal imaging camera, that really shows up sludged radiators. They don't come cheap for something with a reasonable resolution and screen size. The Fluke PTi120 is 120 x 90 pixels and comes in at around £650 + VAT.
They are good though and makes balancing much less hit and miss as you can see how much hot water is entering the rad by the size of the column rising from the inlet. Particulary if you have a complex system with rads fed from T'd flow/return sections or rads on long convulted pipe work.
Excellent information; thanks for your help. I can see how to go about doing some calculations and measurements.
All rads are 100% efficient. It's not as if some of the heat can be lost outdoors from the rad.
NT
If the system has been treated with inhibitor through its life, then there is no reason for them to be that bad.
How do you define efficiency though? If the current ones can get all the rooms to the desired temperature in a reasonable period of time on the colder days, then there is nothing much to be gained from higher output ones.
There is some argument that higher output rads can gain a bit more condensing efficiency from a modern boiler, but probably not worth ripping and replacing just for that.
(you would get a better return on investment adding weather compensation if the boiler supports it, so that the boiler can select flow temperatures appropriate to the weather, and running more efficient lower flow temperatures much of the time. That also makes for better comfort and less system noise)
Not really, unless there are rooms that can't get to temperature etc.
Or mains water flush yourself:
Excellent advice too - thanks all for your help. I'm now well enough armed to talk to our plumbers when they come to quote over the next few weeks.
DDS
Wouldn't go that far, to many variables for numbers to be of much use other than perhaps those from an IR thermometer along the bottom of a rad to seee if it's cool in the middle.
As others have said if the system works and keeps the place warm on a cold windy winters day, don't fix it.
Duncan DiSaudelli pretended :
No point at all.
If there is sludge in your system, then it needs to be thoroughly flushed out. Modern boilers have much smaller water passages which are easily choked up with sludge, so flush and add a magnetic filter in the boiler return pipe, plus check the filter often over the first few months.
My own rads are mid-1980's, now over sized because I have improved the house heat loss over the years, but I have taken careful care of the system with inhibiters.
I had a new boiler fitted 15 months ago, so took the opportunity to fully drain the system and decide whether it might need a flush, based on the water which came out. It was perfectly clear, so pointless flushing.
At the same time, I had a magnetic filter fitted, which I have checked for debris several times - I needn't have bothered, there was almost none at all. I also fitted TRV's all round, as these are now a requirement, plus a modern control system and a newer type 3-port - its an open vented system, my choice.
Dave Liquorice pretended :
Which will not matter, if the thermal efficiency of the home has been improved - as seems likely, since the original rads were specced.
Duncan DiSaudelli formulated on Monday :
Some bolier installers insist on a proper power flush, when fitting a new boiler. Power flushing can form a large part of the cost of a new boiler.
Higher output radiators of a similar size might be worth fitting if: Some rooms struggle to reach temperature when its very cold, or You want to heat a room faster ( useful if you are out most of the day or have a room with occasional occupancy)
You might also consider whether a radiator with smaller dimensions but similar output would be beneficial to you room layout.
You'd have to state what you mean by efficiency. In the 'scientific' meaning that would be energy in versus useful energy out. And since the only things they do is produce heat, they are very close to 100% efficient.
But many use it to mean working well for the job in hand. Only you can answer that. Modern rads may produce more heat for a given size. But won't save anything in running costs.
If the heat from the rad is reasonably even over its entire surface, power flushing won't help. If it is partially blocked it will have cool(er) spots on it.
Quite - a nice little earner for them.
Mate with a long standing BG service contract was forced to have one - and pay for it - when a rad stopped working. Didn't sort the faulty valve.
There's an example of this on Charlie DIYte's recent Youtube video on servicing a Magnaclean. The FLIR camera reveals a cold spot in a rad due to sludge buildup which an agitator clears away.
Nothing to do with efficiency. There is no energy conversion.
Efficiency is defined as a ratio between useful energy output divided by useful energy output.
Eg a gas boiler with 90% efficiency means that 90% of the chemical enrgy in the gas is converted to heated hot water output.
10% is wasted.
A radiator with a higher rated output will result in a lower return temperature - which will make the boiler more efficient.
So although a new bigger radiator and the old one will have the same
100% efficiency, the _system_ efficiency may well be better with a bigger one.Probably not enough to pay for it though!
We swapped two of ours out - one wasn't keeping the room warm (it's now a study, not a bedroom) and the other leaked.
Andy
Yes - there are two ways of looking at this: the energy in is all that in the water above ambient temperature so, on that basis the efficiency is low. the 'real world' efficiency is 100% simply because the energy out is governed by the radiator itself and the ambient conditions, i.e. the rad. 'takes' what it puts out. Any inefficiencie are from losses in the circulatory system if the energy is going to a space where it's not wanted. A former GF's place had the downstairs CH pipes under the suspended floor and airbricks in the walls - half a gale at times and no insulation on the pipes. Given the length of the runs there must have been a hell of a loss.
CH is unusual in that the output and losses are almost all from external factors.
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