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older/newer GCH radiator efficiency?
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 |
older/newer GCH radiator efficiency?
On Sunday, 14 June 2020 18:48:04 UTC+1, Duncan DiSaudelli wrote:
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. |
older/newer GCH radiator efficiency?
harry wrote:
Radiators do not have an efficiency. Newer ones claim higher "efficiency" by having lower water content. Unless the old ones look likely to spring a leak, I'd leave them ... |
older/newer GCH radiator efficiency?
On Sun, 14 Jun 20 17:43:05 UTC, Duncan DiSaudelli wrote:
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? 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. Might it be just as sensible to get the system (and thus the radiators) power-flushed? 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. -- Cheers Dave. |
older/newer GCH radiator efficiency?
On 14/06/2020 20:33, Dave Liquorice wrote:
On Sun, 14 Jun 20 17:43:05 UTC, Duncan DiSaudelli wrote: Excellent information; thanks for your help. I can see how to go about doing some calculations and measurements. |
older/newer GCH radiator efficiency?
On Sunday, 14 June 2020 18:48:04 UTC+1, Duncan DiSaudelli wrote:
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 All rads are 100% efficient. It's not as if some of the heat can be lost outdoors from the rad. NT |
older/newer GCH radiator efficiency?
On 14/06/2020 17:43, Duncan DiSaudelli wrote:
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 If the system has been treated with inhibitor through its life, then there is no reason for them to be that bad. there anything radically different about modern designs which would make them more efficient? 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) In other words, if they are still of sound construction, is there much point in replacing them? Not really, unless there are rooms that can't get to temperature etc. Might it be just as sensible to get the system (and thus the radiators) power-flushed? Or mains water flush yourself: http://wiki.diyfaq.org.uk/index.php/...ating_flushing -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
older/newer GCH radiator efficiency?
On 15/06/2020 01:04, John Rumm wrote:
On 14/06/2020 17:43, Duncan DiSaudelli wrote: Hello 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 |
older/newer GCH radiator efficiency?
On Sun, 14 Jun 20 22:18:14 UTC, Duncan DiSaudelli wrote:
Excellent information; thanks for your help. I can see how to go about doing some calculations and measurements. 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. -- Cheers Dave. |
older/newer GCH radiator efficiency?
Duncan DiSaudelli pretended :
In other words, if they are still of sound construction, is there much point in replacing them? No point at all. Might it be just as sensible to get the system (and thus the radiators) power-flushed? 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. |
older/newer GCH radiator efficiency?
Dave Liquorice pretended :
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. Which will not matter, if the thermal efficiency of the home has been improved - as seems likely, since the original rads were specced. |
older/newer GCH radiator efficiency?
Duncan DiSaudelli formulated on Monday :
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. 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. |
older/newer GCH radiator efficiency?
On 14/06/2020 17:43, Duncan DiSaudelli wrote:
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 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. |
older/newer GCH radiator efficiency?
In article ,
Duncan DiSaudelli wrote: 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? 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. -- *Toilet stolen from police station. Cops have nothing to go on. Dave Plowman London SW To e-mail, change noise into sound. |
older/newer GCH radiator efficiency?
In article ,
Harry Bloomfield wrote: Duncan DiSaudelli formulated on Monday : 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. 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. 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. -- *24 hours in a day ... 24 beers in a case ... coincidence? * Dave Plowman London SW To e-mail, change noise into sound. |
older/newer GCH radiator efficiency?
On 14/06/2020 20:33, Dave Liquorice wrote:
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... 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. -- Reentrant |
older/newer GCH radiator efficiency?
On Sunday, 14 June 2020 20:11:05 UTC+1, Andy Burns wrote:
harry wrote: Radiators do not have an efficiency. Newer ones claim higher "efficiency" by having lower water content. Unless the old ones look likely to spring a leak, I'd leave them ... Nothing to do with efficiency. There is no energy conversion. |
older/newer GCH radiator efficiency?
On Monday, 15 June 2020 01:04:32 UTC+1, John Rumm wrote:
On 14/06/2020 17:43, Duncan DiSaudelli wrote: 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 If the system has been treated with inhibitor through its life, then there is no reason for them to be that bad. there anything radically different about modern designs which would make them more efficient? 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) In other words, if they are still of sound construction, is there much point in replacing them? Not really, unless there are rooms that can't get to temperature etc. Might it be just as sensible to get the system (and thus the radiators) power-flushed? Or mains water flush yourself: http://wiki.diyfaq.org.uk/index.php/...ating_flushing 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. |
older/newer GCH radiator efficiency?
On 14/06/2020 20:33, Dave Liquorice wrote:
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. 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 |
older/newer GCH radiator efficiency?
On Mon, 15 Jun 2020 14:42:15 +0100, Dave Plowman (News) wrote:
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. 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. -- Peter. The gods will stay away whilst religions hold sway |
older/newer GCH radiator efficiency?
On Monday, 15 June 2020 14:50:45 UTC+1, Dave Plowman (News) wrote:
In article , Duncan DiSaudelli wrote: 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? You'd have to state what you mean by efficiency. In the 'scientific' meaning that would be energy in versus useful energy out. useful energy out over energy in is the definition. And since the only things they do is produce heat, they are very close to 100% efficient. no, they are 100% efficient. But many use it to mean working well for the job in hand. Only you can answer that. If he could he wouldn't have asked Modern rads may produce more heat for a given size. typically yes, due to fins on the rear and sometimes dual panels. But won't save anything in running costs. they do when it keeps a boiler in condensing mode for longer. If the heat from the rad is reasonably even over its entire surface, power flushing won't help. right If it is partially blocked it will have cool(er) spots on it. Yup. And if it's working fine it often has a cooler area too. If it has a cooler area AND it's not putting enough heat out is it time to suspect a problem. NT |
older/newer GCH radiator efficiency?
On Monday, 15 June 2020 21:11:07 UTC+1, PeterC wrote:
On Mon, 15 Jun 2020 14:42:15 +0100, Dave Plowman (News) wrote: 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. 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. That would be true if all water out of the rad were at room temp. It isn't, so the rad's energy input = flow rate x (inlet temp rise - outlet temp rise) x SHC of water. 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. A rad is 100% efficient because there is nowhere for any waste energy to go. Thus energy input & energy output are actually the same thing for a rad. NT 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. |
older/newer GCH radiator efficiency?
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older/newer GCH radiator efficiency?
harry wrote:
Andy Burns wrote: harry wrote: Radiators do not have an efficiency. Newer ones claim higher "efficiency" by having lower water content. Unless the old ones look likely to spring a leak, I'd leave them ... Nothing to do with efficiency. There is no energy conversion. Hence the scare quotes. |
older/newer GCH radiator efficiency?
On 15/06/2020 18:33, harry wrote:
On Monday, 15 June 2020 01:04:32 UTC+1, John Rumm wrote: On 14/06/2020 17:43, Duncan DiSaudelli wrote: 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 If the system has been treated with inhibitor through its life, then there is no reason for them to be that bad. there anything radically different about modern designs which would make them more efficient? 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) In other words, if they are still of sound construction, is there much point in replacing them? Not really, unless there are rooms that can't get to temperature etc. Might it be just as sensible to get the system (and thus the radiators) power-flushed? Or mains water flush yourself: http://wiki.diyfaq.org.uk/index.php/...ating_flushing Efficiency is defined as a ratio between useful energy output divided by useful energy output. And as was previously explained, of not much real relevance to a radiator. 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. Fair enough with a boiler, but not the topic under discussion. A radiator does not need to extract the maximum energy from the primary water on each pass. Since it gets to have multiple subsequent attempts, and any heat left in the water is either lost into the fabric of the house, or deducted from that that the boiler needs to replace. Neither of which are bad outcomes usually. With a modern boiler, there is merit to the the total heating load of the rads presenting enough load to the boiler, for a significant part of the heating season, to keep return temperatures low enough for maximum condensing heat recovery. However this is not really a new consideration since even with old non condensing fixed output boilers, inadequate load could result in short cycling, which also lowered fuel efficiency. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
older/newer GCH radiator efficiency?
On Sun, 14 Jun 2020 20:33:41 +0100 (BST), in uk.d-i-y "Dave Liquorice" wrote:
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 Radiator balancing houldn't be hit and miss... http://www.diyfaq.org.uk/plumbing/rad-balance.html 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. Phil Addison |
older/newer GCH radiator efficiency?
On 14 Jun 2020 at 18:43:05 BST, "Duncan DiSaudelli" wrote:
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 FWIW, I was in a similar situation a few years back. I had a new combi fitted, and I was persuaded to keep the original rads by the plumber - something along the lines of 'they just work, they don't make them like they used to'. He power flushed the system and it did, indeed, work. However: * There was no way the system could get the house up to a reasonable temperature, even after I'd put in insulation and draft proofed. The house is/was double glazed, but as a Victorian terrace, difficult to apply thorough insulation. * It would take some hours to heat up. They were almost all long, tall (but low profile) rads. I think the plumber's reasoning was that the system must have been designed properly in the first place, and the new boiler certainly wouldn't do any harm. * The system was noisy and still pretty sludged up. The magnetic filter would have needed endless cleaning had I been bothered, and when I drained the system to fix a leak the water was filthy. * The enamel/paint was peeling on most of them - not a major concern, but it didn't do the decor any favours. So I've ended up replacing most of them with new finned radiators, overspeccing by about 20%. I mains water flushed, and reverse flushed, for pretty much a whole day until it ran clear. I could redesign the system to fit decor and comfort - some rooms now have 2 smaller rads for example. I've also routed pipes away from the floor and behind skirting - much neater. This didn't need new rads of course. The main issue with resiting was finding decent wall - some are on stud partition. And routing the pipes was sometimes a challenge. Newer designs won't be more efficient in an energy consumption sense, but will heat up and, depending on the design, pump out heat more quickly. And if appearance matters, they might look better. Very pleased now with the way it works. If I had my time again I'd have done it all at the outset. But obviously milages vary . . . -- Cheers, Rob |
older/newer GCH radiator efficiency?
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older/newer GCH radiator efficiency?
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older/newer GCH radiator efficiency?
In article ,
wrote: And since the only things they do is produce heat, they are very close to 100% efficient. no, they are 100% efficient. Nothing is ever 100% efficient. A rad will make a tiny amount of noise due to the water circulating. That noise is unwanted use of energy. -- *A fool and his money can throw one hell of a party. Dave Plowman London SW To e-mail, change noise into sound. |
older/newer GCH radiator efficiency?
On Tue, 16 Jun 2020 02:10:48 +0100, Phil Addison wrote:
They are good though and makes balancing much less hit and miss as Radiator balancing houldn't be hit and miss... http://www.diyfaq.org.uk/plumbing/rad-balance.html Tried that. The system is highly complex ie not just a pair of pipes that goes from one rad to the next. There are rads on long spurs, with different lenghts/bends for the pipes, spurs with rads connected overlapping and rad acroos the main pair. It makes the system very sensitive to adjustments. Less than 1/8 turn of a valve can completely stop (or start) the flow through that rad or any of the others. Then you have the settling time after an adjustment if you're traying to get an even temp drop across all rads. Thermal imaging camera allows you to see how much flow is (or isn't!) going through a rad by the size of the rising hot water column from the inlet. This also responds very quickly to any changes. -- Cheers Dave. |
older/newer GCH radiator efficiency?
On Tue, 16 Jun 2020 08:55:10 +0100, PeterC wrote:
Looking at it another way, I'd consider a radiator which took water in at 70 degrees and passed it out at 65 degrees to be less efficient than one which passes it out at 55 degrees. The second done is doing a much better job at putting the energy where it's wanted. Is that efficiency or is it effectivness? Effectiveness, but the real world gets in the way. A rad designed to output x BTU with temps of 80 C flow and 70 C return and 20 C room temp will have have an associated water flow rate. If you want 80 C in and 55 C out, you have to reduce the amount of water flowing through the rad to give it a chance to transfer the heat to the room. Which will be also be at a slower rate than the 80/70 situation due to the rad to room temp difference being lower (75 C v 67.5 C average rad temp). The amount of heat transferred to the room is only related to the surface area of the rad (fixed) and the temperature difference between the rad and room. A rad running at a lower average temp than the design is going to be undersized, fullstop. No amount of messing about with flow/return temps either by boiler settings or water flow rate are are going to affect that. -- Cheers Dave. |
older/newer GCH radiator efficiency?
On 16/06/2020 12:32, Dave Liquorice wrote:
On Tue, 16 Jun 2020 08:55:10 +0100, PeterC wrote: Looking at it another way, I'd consider a radiator which took water in at 70 degrees and passed it out at 65 degrees to be less efficient than one which passes it out at 55 degrees. The second done is doing a much better job at putting the energy where it's wanted. Is that efficiency or is it effectivness? Effectiveness, but the real world gets in the way. A rad designed to output x BTU with temps of 80 C flow and 70 C return and 20 C room temp will have have an associated water flow rate. If you want 80 C in and 55 C out, you have to reduce the amount of water flowing through the rad to give it a chance to transfer the heat to the room. Which will be also be at a slower rate than the 80/70 situation due to the rad to room temp difference being lower (75 C v 67.5 C average rad temp). The amount of heat transferred to the room is only related to the surface area of the rad (fixed) and the temperature difference between the rad and room. A rad running at a lower average temp than the design is going to be undersized, fullstop. No amount of messing about with flow/return temps either by boiler settings or water flow rate are are going to affect that. If the new boiler ever arrives here I'm planning on putting fans under the radiators in some rooms until redecoration allows new (and sometimes relocated) radiators. I couldn't find evidence of how to quantify the effect but a trial with 3 x 100mm PC case fans (under-run at 9V) seemed to have some benefit. -- Robin reply-to address is (intended to be) valid |
older/newer GCH radiator efficiency?
On Tue, 16 Jun 2020 11:26:47 +0100, Dave Plowman (News) wrote:
In article , wrote: And since the only things they do is produce heat, they are very close to 100% efficient. no, they are 100% efficient. Nothing is ever 100% efficient. A rad will make a tiny amount of noise due to the water circulating. That noise is unwanted use of energy. If the noise doen't escape from the room it'll end up as heat. You can tell that happens as a noisy CH system at night makes one all hot and bathered ;-) -- Peter. The gods will stay away whilst religions hold sway |
older/newer GCH radiator efficiency?
On Tue, 16 Jun 2020 11:58:23 +0100 (BST), in uk.d-i-y "Dave Liquorice" wrote:
On Tue, 16 Jun 2020 02:10:48 +0100, Phil Addison wrote: They are good though and makes balancing much less hit and miss as Radiator balancing houldn't be hit and miss... http://www.diyfaq.org.uk/plumbing/rad-balance.html Tried that. The system is highly complex ie not just a pair of pipes that goes from one rad to the next. There are rads on long spurs, with different lenghts/bends for the pipes, spurs with rads connected overlapping and rad acroos the main pair. It makes the system very sensitive to adjustments. Less than 1/8 turn of a valve can completely stop (or start) the flow through that rad or any of the others. I don't see how that invalidates the procedure, surely it should work for any layout (well, at least a domestic layout with one boiler and one pump? The procedure boils down to opening all the hand and balance valves wide-open, then progressively turning down the 'too-hot' balance valves. You don't necessarily want the same temperature drop across each, that's only true if all the rads are the exact perfect thermal size for the room, but you do want them all to be capable of reaching full temperature right across each radiator - no cool outlets. But note that in some cases this will be impossible due to bad design of the pipework - or maybe sludge. I had a case where the largest rad in the house was furthest from the boiler but was fed by a long length of 10mm tube. Calcs proved there was no way the pump could generate enough head to feed that rad, and the answer was to re-pipe it in 15mm. I had a LOT of trouble convincing the plumbing contractor to do that! Then you have the settling time after an adjustment if you're traying to get an even temp drop across all rads. Indeed, the lag can be a pain. Thermal imaging camera allows you to see how much flow is (or isn't!) going through a rad by the size of the rising hot water column from the inlet. This also responds very quickly to any changes. I haven't had the chance to use an IR camera, and can see it would be helpful to see the immediate effect of a small turn of the valve, but I emphasise that you don't want full flow in all the rads. Any oversized rads need less than full flow, and any close to the boiler need throttling back to increase their flow resistance so as not to bypass (steal) the flow from the furthest. A common misconception is that increasing flow-resistance will make a radiator cooler. Not necessarily: for a rad already getting as much heat as it can dissipate, closing its valve a bit just makes the pump increase its pressure so that rads further away get more flow. Phil Addison |
older/newer GCH radiator efficiency?
On Monday, 15 June 2020 22:30:48 UTC+1, Robin wrote:
On 15/06/2020 21:55, tabbypurr wrote: On Monday, 15 June 2020 21:11:07 UTC+1, PeterC wrote: On Mon, 15 Jun 2020 14:42:15 +0100, Dave Plowman (News) wrote: 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. 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. That would be true if all water out of the rad were at room temp. It isn't, so the rad's energy input = flow rate x (inlet temp rise - outlet temp rise) x SHC of water. 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. A rad is 100% efficient because there is nowhere for any waste energy to go. Thus energy input & energy output are actually the same thing for a rad. That's conservation of energy. no, it's an explanation of radiator efficiency. Efficiency involves the concept of usefulness - as in the traditional definition "the ratio of the useful work performed by a machine to the total energy expended". Yep. And it's 100% for all rads as already explained On that it's entirely reasonable to consider how a radiator in a CH system affects the ratio of the energy released where it's wanted to the total energy expended (i.e. including all the energy released where it's not - e.g. in the boiler, pump, and pipes under suspended floors). It's completely reasonable. But it's not radiator efficiency, it's something else. Looking at it another way, I'd consider a radiator which took water in at 70 degrees and passed it out at 65 degrees to be less efficient than one which passes it out at 55 degrees. You'd be wrong then. The second done is doing a much better job at putting the energy where it's wanted. NT |
older/newer GCH radiator efficiency?
On Tuesday, 16 June 2020 09:28:35 UTC+1, Robin wrote:
On 16/06/2020 08:55, PeterC wrote: On Mon, 15 Jun 2020 22:30:39 +0100, Robin wrote: On 15/06/2020 21:55, tabbypurr wrote: On Monday, 15 June 2020 21:11:07 UTC+1, PeterC wrote: On Mon, 15 Jun 2020 14:42:15 +0100, Dave Plowman (News) wrote: 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. 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. That would be true if all water out of the rad were at room temp. It isn't, so the rad's energy input = flow rate x (inlet temp rise - outlet temp rise) x SHC of water. 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. A rad is 100% efficient because there is nowhere for any waste energy to go. Thus energy input & energy output are actually the same thing for a rad. That's conservation of energy. Efficiency involves the concept of usefulness - as in the traditional definition "the ratio of the useful work performed by a machine to the total energy expended". On that it's entirely reasonable to consider how a radiator in a CH system affects the ratio of the energy released where it's wanted to the total energy expended (i.e. including all the energy released where it's not - e.g. in the boiler, pump, and pipes under suspended floors). Looking at it another way, I'd consider a radiator which took water in at 70 degrees and passed it out at 65 degrees to be less efficient than one which passes it out at 55 degrees. The second done is doing a much better job at putting the energy where it's wanted. Is that efficiency or is it effectivness? It's a fair cop that I conflated the 2. My mitigation is that I was trying to stop the post growing even longer. Slightly longer 2nd attempt: The second radiator is more effective (assuming it's a good thing to have at least the option of warming the room faster) probably, though I don't know what 'second one' you refer to and (very probably) also more efficient no. in that the CH system delivers heat to the room more efficiently. no. You are still not grasping what radiator efficiency is. NT |
older/newer GCH radiator efficiency?
On Tuesday, 16 June 2020 11:27:22 UTC+1, Dave Plowman (News) wrote:
In article , tabbypurr wrote: And since the only things they do is produce heat, they are very close to 100% efficient. no, they are 100% efficient. Nothing is ever 100% efficient. incorrect. Another example is an electric convector heater. A rad will make a tiny amount of noise due to the water circulating. That noise is unwanted use of energy. Sometimes. Gravity flow systems make no water noise when kept below boiling point. Very well specced & designed systems in mild weather make no detectable noise. Systems that do produce noise, as most do, can expend at most millwatts on noise versus kilowatts on heat. That's in the region of a million to one, making no detectable difference to even a nonideal system. I question the blame of that laying with the radiators rather than the pump, but even if you decided it's all the rads' fault you'd still get a figure of 99.9999%. NT |
older/newer GCH radiator efficiency?
On Tuesday, 16 June 2020 11:58:27 UTC+1, Dave Liquorice wrote:
On Tue, 16 Jun 2020 02:10:48 +0100, Phil Addison wrote: They are good though and makes balancing much less hit and miss as Radiator balancing houldn't be hit and miss... http://www.diyfaq.org.uk/plumbing/rad-balance.html Tried that. The system is highly complex ie not just a pair of pipes that goes from one rad to the next. There are rads on long spurs, with different lenghts/bends for the pipes, spurs with rads connected overlapping and rad acroos the main pair. It makes the system very sensitive to adjustments. Less than 1/8 turn of a valve can completely stop (or start) the flow through that rad or any of the others. Then you have the settling time after an adjustment if you're traying to get an even temp drop across all rads. Thermal imaging camera allows you to see how much flow is (or isn't!) going through a rad by the size of the rising hot water column from the inlet. This also responds very quickly to any changes. Ah, reality. I hope you didn't copy Steptoe's heating system :) Though IIRC that was single pipe. NT |
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