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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Secondary Circulation loop on a combi
Can you have such a thing or is this one of Doctor Evil's fantasies?
If you can...how would you do it? TIA Mr F. |
#2
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Can you have such a thing or is this one of Doctor Evil's fantasies?
If you can...how would you do it? You'd do it the same as any secondary circulation loop. It doesn't really matter what the heating appliance is, provided there are no pressure reducing devices such as TRVs or air breaks (i.e. cold water cisterns) actually in the loop. These may be before the loop, however. However, not all combis would be suited to a secondary circulation loop. They work better on a storage based system as an instantaneous combi will cycle with much greater rapidity than a system boiler off a storage cylinder. Christian. |
#3
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Mr Fizzion wrote: Can you have such a thing or is this one of Doctor Evil's fantasies? Assuming youre referring to a secondary circulation loop on the hot water supply system, then; The combi fires on a draw off from the hot water outlets. The only way I could imagine installing a circulation loop would be to install a heat exchanger (tube-in-shell, preferably) on the secondary return and pipe the primary side of the HX as a zone on heating. You'd need the heating to operate 365 days. You could use an electric heater. There are also electric trace heating system for hws, which are installed under thermal insulation to minimize the heat loss from the pipes. These don't need a circulation loop. If you're doing that you'd be better off installing an unvented hot water storage cylinder ( which has got a heat exchanger & has got a large volume of water, so it won't discharge scalding water if the controls overshoot the set-point slightly). If you're doing that, you might as well scrap the combi and put in a conventional hot water storage system. You should realise that Drivel is a moron and his rantings should be treated accordingly. |
#4
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Mr Fizzion wrote:
Can you have such a thing or is this one of Doctor Evil's fantasies? It ought to work on "simple" combis so long as the manufacturer states it is ok for the "cold" inlet temp to much hotter than it usually would. You also need a combi that can operate on very low mains pressure (so that it will work correctly when the flow is being driven by the pump and not the mains). However you could potentially run into all sorts of difficulties with a modern combi that uses a more sophisticated control loop, or one that includes a small store of tempered water so as to give "instant" hot water. If you can...how would you do it? Timer, pipe stat, check valves, secondary circulation pump, loads of good insulation on the pipe run etc. You would then need to juggle stat temperatures carefully to get the operation you require without ending up in a deadlock state with the pipe stat demanding heat and the combi HW stat satisfied and hence inhibiting the burner (and the result that the boiler sits in HW mode for extended periods while the house gets cold). -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#5
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On Wed, 28 Sep 2005 13:43:02 +0100, Mr Fizzion wrote:
Can you have such a thing or is this one of Doctor Evil's fantasies? If you can...how would you do it? For me this is just plain nonsense. 1) I doubt very much whether any manufacture would permit the boiler to be used in this way. 2) The boiler is not designed to take luke warm let alone hot water as it's input. 3) All the while the 2ndry pump is going the boiler is in DHW mode. When does the house get heated? 4) The whole system would rely on the boiler shutting down because the primary is at or over its maximum temperature for DHW mode. This will only happen when the DHW temperature is very hot. Ergo the heat losses on the 2ndry loop will be huge. 5) Whilst the burner is shutdown the fan will still be going so that the primary will be losing heat at a rate comparable with the burner rating i.e. tens of kW. This is going straight out the flue! 6) The water bylaws forbid the permanent connection of the mains to a closed circuit. If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). -- Ed Sirett - Property maintainer and registered gas fitter. The FAQ for uk.diy is at http://www.diyfaq.org.uk Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html |
#6
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Ed Sirett wrote:
For me this is just plain nonsense. I would agree that the concept has serious flaws in many cases. 1) I doubt very much whether any manufacture would permit the boiler to be used in this way. 2) The boiler is not designed to take luke warm let alone hot water as it's input. Those two are likely to be show stoppers anyway... 3) All the while the 2ndry pump is going the boiler is in DHW mode. When does the house get heated? That is where the pipe stat and the timer comes in I suppose. Once the loop is up to temperature it kills the pump and allows it to return to heating mode. The big problem will be the heat capacity (or more the lack of it) of the pipework - it will get cold quickly. 4) The whole system would rely on the boiler shutting down because the primary is at or over its maximum temperature for DHW mode. This will only happen when the DHW temperature is very hot. Ergo the heat losses on the 2ndry loop will be huge. Where do most boilers sample the DHW output temperature. in the DHW flow on on the return of the primary for example? 5) Whilst the burner is shutdown the fan will still be going so that the primary will be losing heat at a rate comparable with the burner rating i.e. tens of kW. This is going straight out the flue! 6) The water bylaws forbid the permanent connection of the mains to a closed circuit. Circumventable with a doublecheck valve? If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Indeed ;-) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#7
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"Aidan" wrote in message oups.com... Mr Fizzion wrote: Can you have such a thing or is this one of Doctor Evil's fantasies? Assuming youre referring to a secondary circulation loop on the hot water supply system, then; The combi fires on a draw off from the hot water outlets. The only way I could imagine installing a circulation loop would be to install a heat exchanger (tube-in-shell, preferably) on the secondary return Boy are you confused. |
#8
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"John Rumm" wrote in message ... Mr Fizzion wrote: Can you have such a thing or is this one of Doctor Evil's fantasies? It ought to work on "simple" combis so long as the manufacturer states it is ok for the "cold" inlet temp to much hotter than it usually would. You also need a combi that can operate on very low mains pressure (so that it will work correctly when the flow is being driven by the pump and not the mains). However you could potentially run into all sorts of difficulties with a modern combi that uses a more sophisticated control loop, or one that includes a small store of tempered water so as to give "instant" hot water. What difficulties might these be? Or did you make that up? If you can...how would you do it? Timer, pipe stat, check valves, secondary circulation pump, Can be booster pump to achieve the pressure to operate the combi. http://www.heatweb.com/products/pumps/homebooster.html Plumb Center also sell them. You also need a time clock to switch off during the night. loads of good insulation on the pipe run etc. You would then need to juggle stat temperatures carefully to get the operation you require without ending up in a deadlock state with the pipe stat demanding heat and the combi HW stat satisfied and hence inhibiting the burner (and the result that the boiler sits in HW mode for extended periods while the house gets cold). Set the pipe stat to 40C |
#9
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2) The boiler is not designed to take luke warm let alone hot water as
it's input. But I suspect most boilers would cope for the minute or two operation period. That is where the pipe stat and the timer comes in I suppose. Once the loop is up to temperature it kills the pump and allows it to return to heating mode. The big problem will be the heat capacity (or more the lack of it) of the pipework - it will get cold quickly. It only needs to be on for about one minute to heat the loop. Then the loop will stay hot for many minutes with a high hysterysis thermostat satisfied. Obviously any secondary circulation system would have to be very well insulated. This applies to all types. It will still cycle the boiler much more than a storage based system, though. However, I don't see this as a show stopper, just a disadvantage. 6) The water bylaws forbid the permanent connection of the mains to a closed circuit. I can't see how this applies to secondary circulation loops. They aren't really closed loops. If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Indeed ;-) Whilst I'm no fan of permanently on secondary circulation loops in most cases due to energy efficiency reasons, I can see the benefit of a manually operated (i.e. 2 minute timed) system in a domestic property, as it would be very effective at water conservation. A manually operated system would also actually save energy, as the reheated water will start at a higher temperature than fresh mains. Christian. |
#10
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"Ed Sirett" wrote in message news On Wed, 28 Sep 2005 13:43:02 +0100, Mr Fizzion wrote: Can you have such a thing or is this one of Doctor Evil's fantasies? If you can...how would you do it? For me this is just plain nonsense. On what does he base this wild claim on....we shall see.... 1) I doubt very much whether any manufacture would permit the boiler to be used in this way. The boiler is not being monkied about with. 2) The boiler is not designed to take luke warm let alone hot water as it's input. Some are and most are really. See makers. Many accept very hot water from solar preheated water. Eco-Hometec for e.g. The cold inlet to most combi's is just a pipe to a plate heat exchanger and a flow switch. Nothing there to say 40C water will screw the system up. 3) All the while the 2ndry pump is going the boiler is in DHW mode. When does the house get heated? You really can't figure this out can you. A highly insulated loop from the outlet to the inlet with pipe stat set to 40C means that the loop will be warm within a minute or so and then be switched off, amd stay off for a long time. There are keep warm boilers around. The same thing but extended to outside the boiler casing. 4) The whole system would rely on the boiler shutting down because the primary is at or over its maximum temperature for DHW mode. What are you on about? This will only happen when the DHW temperature is very hot. Ergo the heat losses on the 2ndry loop will be huge. Again. What are you on about? 5) Whilst the burner is shutdown the fan will still be going so that the primary will be losing heat at a rate comparable with the burner rating i.e. tens of kW. This is going straight out the flue! More confusion. 6) The water bylaws forbid the permanent connection of the mains to a closed circuit. Not so. Thermal store are done this way. Here are The DPS Heat bank makers giving advice on uk.d-i-y on how to connect up a heat bank using "exactly" this method. http://tinyurl.com/cfet8 If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). What tripe. The basin and washroom may be way off from the combi, so looping the DHW makes sense. In fact a secondary circulation loop saves a hell of a lot of water and gives instant DHW at the taps, which is a great convenience. Have a look at the one box AVC Heatmaster for a system in your view is not grown up. ...and you are a professional? Struth. |
#11
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"John Rumm" wrote in message ... Ed Sirett wrote: For me this is just plain nonsense. I would agree that the concept has serious flaws in many cases. What serious flaws might these be? 1) I doubt very much whether any manufacture would permit the boiler to be used in this way. 2) The boiler is not designed to take luke warm let alone hot water as it's input. Those two are likely to be show stoppers anyway... Any evidence of this? Or just making it up again. 3) All the while the 2ndry pump is going the boiler is in DHW mode. When does the house get heated? That is where the pipe stat and the timer comes in I suppose. Once the loop is up to temperature it kills the pump and allows it to return to heating mode. The big problem will be the heat capacity (or more the lack of it) of the pipework - it will get cold quickly. Not it heavily lagged. 4) The whole system would rely on the boiler shutting down because the primary is at or over its maximum temperature for DHW mode. This will only happen when the DHW temperature is very hot. Ergo the heat losses on the 2ndry loop will be huge. Where do most boilers sample the DHW output temperature. in the DHW flow on on the return of the primary for example? DHW outlet 5) Whilst the burner is shutdown the fan will still be going so that the primary will be losing heat at a rate comparable with the burner rating i.e. tens of kW. This is going straight out the flue! 6) The water bylaws forbid the permanent connection of the mains to a closed circuit. Circumventable with a doublecheck valve? A rank DIYer and confused professional agreeing with each other. My, oh, my! If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Indeed ;-) A rank DIYer and confused professional agreeing with each other. My, oh, my! The professional should stick to Vaillants. |
#12
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"Christian McArdle" wrote in message . net... 2) The boiler is not designed to take luke warm let alone hot water as it's input. But I suspect most boilers would cope for the minute or two operation period. That is where the pipe stat and the timer comes in I suppose. Once the loop is up to temperature it kills the pump and allows it to return to heating mode. The big problem will be the heat capacity (or more the lack of it) of the pipework - it will get cold quickly. It only needs to be on for about one minute to heat the loop. Then the loop will stay hot for many minutes with a high hysterysis thermostat satisfied. Obviously any secondary circulation system would have to be very well insulated. This applies to all types. It will still cycle the boiler much more than a storage based system, On what do you base this article of faith? though. However, I don't see this as a show stopper, just a disadvantage. 6) The water bylaws forbid the permanent connection of the mains to a closed circuit. I can't see how this applies to secondary circulation loops. They aren't really closed loops. Yep, you are right. If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Indeed ;-) Whilst I'm no fan of permanently on secondary circulation loops in most cases due to energy efficiency reasons, 6 of 1/2 dozen of the other. You save a hell of a lot in water wastage which on a meter you pay for. Then the convenience. Most people who use the front door toilet (cloakroom) very rarely wash their hands in hot water, because of the long lag. I can see the benefit of a manually operated (i.e. 2 minute timed) system in a domestic property, as it would be very effective at water conservation. A manually operated system would also actually save energy, as the reheated water will start at a higher temperature than fresh mains. I have seen a pump on the DHW draw-off pipe activated by a flow switch. This pumps out water from a cylinder pronto reducing the lag |
#13
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It will still cycle the boiler much more than a storage based system,
On what do you base this article of faith? It is based on the fact that a storage based solution will be able to perform a considerable amount of secondary loop heating service before this activates the vessel thermostat, allowing the boiler to perform a slightly longer more efficient burn. With an instantaneous combi, the combi must fire every time the secondary loop pump activates, and in the worst case, if the loop circulation is slow, it might even be below the modulation threshold, so it might even have to cycle to maintain primary temperature, although careful design can eliminate this. Therefore, even in a best case scenario, the instantaneous combi fires every time the loop thermostat calls for heat, whilst the storage based system could service for hours without boiler assistance, with sufficient capacity and thermostat hysterysis/double thermostat. Christian. |
#14
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"Christian McArdle" wrote in message . net... It will still cycle the boiler much more than a storage based system, On what do you base this article of faith? It is based on the fact that a storage based solution will be able to perform a considerable amount of secondary loop heating service before this activates the vessel thermostat, allowing the boiler to perform a slightly longer more efficient burn. With an instantaneous combi, the combi must fire every time the secondary loop pump activates, and in the worst case, if the loop circulation is slow, it might even be below the modulation threshold, so it might even have to cycle to maintain primary temperature, although careful design can eliminate this. Therefore, even in a best case scenario, the instantaneous combi fires every time the loop thermostat calls for heat, whilst the storage based system could service for hours without boiler assistance, with sufficient capacity and thermostat hysterysis/double thermostat. A secondary circulation loop is well, a secondary circulation loop. Whether there is a large cylinder on the loop or an instant water heat makes no difference. The loop will cool no quicker on any of them. You could have a few small DHW vessels on the loop, in series, like under sink units, have a pressure vessel too. So when you draw off small volumes of water at the local point, the combi does not kick in as there will be no flow through the boiler until the pressure has dropped - avoids nuisance firing. There could be a thermostat on each small vessel to fire the combi to replenish the vessel of DHW. A Dutch/Belgian company did somthing similar to this - distributed storage giving instant water at the taps. The total volume of all the vessels is enough to fill a bath. |
#15
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Doctor Drivel wrote: You could have a few small DHW vessels snip. Thanks for clarifying that for us all, Dr. Drivel, I'm sure that's all crystal clear now. Is it just me, or can anyone else detect the tiniest soupcon of utter ********? |
#16
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On Thu, 29 Sep 2005 00:21:22 +0100, Ed Sirett
wrote: 2) The boiler is not designed to take luke warm let alone hot water as it's input. One would hope the boiler can handle lukewarm water at least for a couple of minutes. My loft sometimes reaches 50 celsius in the summer and there will be a few litres of water in the pipe at possibly over 20 celsius. If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Having hot water in less than a second is a luxury rather than a necessity. If it were easily possible with my new combi I would do it. Since it seems not to be I shall be content with waiting 30 seconds! Mr F. |
#17
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"Aidan" through a wall of brainache wrote in message oups.com... Doctor Drivel wrote: You could have a few small DHW vessels snip. Thanks for clarifying that for us all, Dr. Drivel, I'm sure that's all crystal clear now. To normal people it would be....but.... Is it just me, It is you for sure. or can anyone else detect the tiniest soupcon of utter ********? Those with brains can't detect any at all, so precluding you. Sad but true. |
#18
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"Mr Fizzion" wrote in message ... On Thu, 29 Sep 2005 00:21:22 +0100, Ed Sirett wrote: 2) The boiler is not designed to take luke warm let alone hot water as it's input. One would hope the boiler can handle lukewarm water at least for a couple of minutes. My loft sometimes reaches 50 celsius in the summer and there will be a few litres of water in the pipe at possibly over 20 celsius. More like 30 to 35C My mains temperature is 19C right now If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Having hot water in less than a second is a luxury rather than a necessity. If it were easily possible with my new combi I would do it. Since it seems not to be I shall be content with waiting 30 seconds! It does save on water too. |
#19
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If a house needs a secondary loop it also needs a grown up heating system
that will include a stored HW of some type (vented, unvented or thermal store). Having hot water in less than a second is a luxury rather than a necessity. If it were easily possible with my new combi I would do it. Since it seems not to be I shall be content with waiting 30 seconds! Actually, there is some environmental benefit as well as a convenience one, due to the reduced wastage of water. I would suggest that a secondary loop that has a boost button that you can press before have a bath, or before sitting on the toilet (so it is ready when you finish) means that energy is actually saved as well as water. However, a secondary loop constantly on connected to a combi is likely to be somewhat wasteful of energy. Christian. |
#20
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"Doctor Drivel" wrote:
You could have a few small DHW vessels on the loop, in series, like under sink units, have a pressure vessel too. So when you draw off small volumes of water at the local point, the combi does not kick in as there will be no flow through the boiler until the pressure has dropped - avoids nuisance firing. All combi firing unless it is in a high velocity trajectory towards the sun is a waste of time There could be a thermostat on each small vessel to fire the combi to replenish the vessel of DHW. A Dutch/Belgian company did somthing similar to this - distributed storage giving instant water at the taps. You've been eating them funny mushrooms again haven't you? The total volume of all the vessels is enough to fill a bath. Yes of course it is. Get back to that counter Dribble. Copper sales are going through the roof but a few more sales won't go amiss. -- |
#21
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"Doctor Drivel" wrote:
My mains temperature is 19C right now That's the output from the combi you fool. It does save on water too. No it doesn't, you have much to learn and so little time before you get locked up again. -- |
#22
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"Christian McArdle" wrote in message . net... If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Having hot water in less than a second is a luxury rather than a necessity. If it were easily possible with my new combi I would do it. Since it seems not to be I shall be content with waiting 30 seconds! Actually, there is some environmental benefit as well as a convenience one, due to the reduced wastage of water. I would suggest that a secondary loop that has a boost button that you can press before have a bath, or before sitting on the toilet (so it is ready when you finish) means that energy is actually saved as well as water. However, a secondary loop constantly on connected to a combi is likely to be somewhat wasteful of energy. Have a flow switch on the lines to the toilets. When a flush the pump comes on. Or have an infra red sensor in the kitchen too. When occupied the pump runs. People in the kitchen tend to use water. Still have pipe stat when it reaches 40-45C. Using a pipe stat in a well insuated loop would mean the pump would not cycle too often anyhow. |
#23
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"Matt" the resident space cadet wrote in message ... "Doctor Drivel" wrote: You could have a few small DHW vessels on the loop, in series, like under sink units, have a pressure vessel too. So when you draw off small volumes of water at the local point, the combi does not kick in as there will be no flow through the boiler until the pressure has dropped - avoids nuisance firing. All combi firing unless it is in a high velocity trajectory towards the sun is a waste of time Our space cadet is into the sun again. I wonder how much that Treki uniform cost him. |
#24
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"Matt" our resident space cadet wrote in message ... "Doctor Drivel" wrote: My mains temperature is 19C right now That's the output from the combi you fool. Must an intergalactical combi. It does save on water too. No it doesn't, ...confusion has set in. |
#25
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"Christian McArdle" wrote in message . net... If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Having hot water in less than a second is a luxury rather than a necessity. If it were easily possible with my new combi I would do it. Since it seems not to be I shall be content with waiting 30 seconds! Actually, there is some environmental benefit as well as a convenience one, due to the reduced wastage of water. If using a mains pressure system having hot water within 1 second at the tap mean that kettles can be filled with hot water reducing electricity consumption quite a bit. It pays for itself in more ways than one. |
#26
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"Doctor Drivel" wrote:
"Christian McArdle" wrote in message .net... If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Having hot water in less than a second is a luxury rather than a necessity. If it were easily possible with my new combi I would do it. Since it seems not to be I shall be content with waiting 30 seconds! Actually, there is some environmental benefit as well as a convenience one, due to the reduced wastage of water. If using a mains pressure system having hot water within 1 second at the tap mean that kettles can be filled with hot water reducing electricity consumption quite a bit. It pays for itself in more ways than one. But the figures simply don't stack up and you can't prove it "pays for itself" True but sad. -- |
#27
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"Matt" from where the clouds are blue and birds say cuckoo wrote in message ... "Doctor Drivel" wrote: "Christian McArdle" wrote in message .net... If a house needs a secondary loop it also needs a grown up heating system that will include a stored HW of some type (vented, unvented or thermal store). Having hot water in less than a second is a luxury rather than a necessity. If it were easily possible with my new combi I would do it. Since it seems not to be I shall be content with waiting 30 seconds! Actually, there is some environmental benefit as well as a convenience one, due to the reduced wastage of water. If using a mains pressure system having hot water within 1 second at the tap mean that kettles can be filled with hot water reducing electricity consumption quite a bit. It pays for itself in more ways than one. But Yes, but. Me thinks Matt is not really Matt. Me thinks he is an old poster from here. |
#28
Posted to uk.d-i-y
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Secondary Circulation loop on a combi
Recent research that in UK households with combis kitchen water use is 2.5 higher than other systems. (18L vs 7.2L per person per day).
And the most likely reason pointed out is time for HW to arrive). So secondary loop of any sort would seem to help alleviate this waste. -- For full context, visit https://www.homeownershub.com/uk-diy...bi-197063-.htm |
#29
Posted to uk.d-i-y
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Secondary Circulation loop on a combi
12L per person per day of waster water with combi on average.
Immense time savings (3s vs 30s). People can buy combi for 2000 or for 700, Implementing this loop would make 700 boiler surpass 2000 one with convenience at fraction of a cost. -- For full context, visit https://www.homeownershub.com/uk-diy...bi-197063-.htm |
#30
Posted to uk.d-i-y
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Secondary Circulation loop on a combi
There is many ways to regulate the frequency I reckon e.g. hysteresis, timer).
Nevertheless, adding some buffer close to the outlets could greatly help with cycling - e.g. couple of litres of pipe storage. -- For full context, visit https://www.homeownershub.com/uk-diy...bi-197063-.htm |
#31
Posted to uk.d-i-y
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Secondary Circulation loop on a combi
In article direct.com,
mafj wrote: Recent research that in UK households with combis kitchen water use is 2.5 higher than other systems. (18L vs 7.2L per person per day). And the most likely reason pointed out is time for HW to arrive). So secondary loop of any sort would seem to help alleviate this waste. Not sure circulating water within a potable supply is either allowed or a good idea. And just when were we short of water in the UK? -- *Haunted French pancakes give me the crepes.* Dave Plowman London SW To e-mail, change noise into sound. |
#32
Posted to uk.d-i-y
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Secondary Circulation loop on a combi
On 23/10/2020 16:14, Dave Plowman (News) wrote:
In article direct.com, mafj wrote: Recent research that in UK households with combis kitchen water use is 2.5 higher than other systems. (18L vs 7.2L per person per day). And the most likely reason pointed out is time for HW to arrive). So secondary loop of any sort would seem to help alleviate this waste. Not sure circulating water within a potable supply is either allowed or a good idea. And just when were we short of water in the UK? More expensive combis have a setting that keeps firing the burners occasionally to keep the primary circuit hot. This allows faster hot water performance but uses more gas. |
#33
Posted to uk.d-i-y
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Secondary Circulation loop on a combi
On 23/10/2020 16:14, Dave Plowman (News) wrote:
In article direct.com, mafj wrote: Recent research that in UK households with combis kitchen water use is 2.5 higher than other systems. (18L vs 7.2L per person per day). And the most likely reason pointed out is time for HW to arrive). So secondary loop of any sort would seem to help alleviate this waste. Not sure circulating water within a potable supply is either allowed or a good idea. And just when were we short of water in the UK? DHW circulation is standard in larger buildings, without it there would be huge water wastage as people wait for hot water to reach the taps. I control mine with a pipe stat and a timer. |
#34
Posted to uk.d-i-y
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Secondary Circulation loop on a combi
In article ,
wrote: On 23/10/2020 16:14, Dave Plowman (News) wrote: In article direct.com, mafj wrote: Recent research that in UK households with combis kitchen water use is 2.5 higher than other systems. (18L vs 7.2L per person per day). And the most likely reason pointed out is time for HW to arrive). So secondary loop of any sort would seem to help alleviate this waste. Not sure circulating water within a potable supply is either allowed or a good idea. And just when were we short of water in the UK? DHW circulation is standard in larger buildings, without it there would be huge water wastage as people wait for hot water to reach the taps. I control mine with a pipe stat and a timer. But that will be from a storage system. A combi is connected to mains water. -- *Why don't sheep shrink when it rains? Dave Plowman London SW To e-mail, change noise into sound. |
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Secondary Circulation loop on a combi
On 23/10/2020 18:46, Dave Plowman (News) wrote:
In article , wrote: On 23/10/2020 16:14, Dave Plowman (News) wrote: In article direct.com, mafj wrote: Recent research that in UK households with combis kitchen water use is 2.5 higher than other systems. (18L vs 7.2L per person per day). And the most likely reason pointed out is time for HW to arrive). So secondary loop of any sort would seem to help alleviate this waste. Not sure circulating water within a potable supply is either allowed or a good idea. And just when were we short of water in the UK? DHW circulation is standard in larger buildings, without it there would be huge water wastage as people wait for hot water to reach the taps. I control mine with a pipe stat and a timer. But that will be from a storage system. A combi is connected to mains water. True, I was responding to your comment and didn't spot that the subject was about combi boilers. |
#36
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Secondary Circulation loop on a combi
In article ,
wrote: On 23/10/2020 18:46, Dave Plowman (News) wrote: In article , wrote: On 23/10/2020 16:14, Dave Plowman (News) wrote: In article direct.com, mafj wrote: Recent research that in UK households with combis kitchen water use is 2.5 higher than other systems. (18L vs 7.2L per person per day). And the most likely reason pointed out is time for HW to arrive). So secondary loop of any sort would seem to help alleviate this waste. Not sure circulating water within a potable supply is either allowed or a good idea. And just when were we short of water in the UK? DHW circulation is standard in larger buildings, without it there would be huge water wastage as people wait for hot water to reach the taps. I control mine with a pipe stat and a timer. But that will be from a storage system. A combi is connected to mains water. True, I was responding to your comment and didn't spot that the subject was about combi boilers. Didn't potable water give you a clue? You can circulate a stored system in a house to give quicker hot from a tap. Whether it is worth it in cash terms, I doubt it. -- *The older you get, the better you realize you were. Dave Plowman London SW To e-mail, change noise into sound. |
#37
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Secondary Circulation loop on a combi
On 24/10/2020 11:14, Dave Plowman (News) wrote:
In article , wrote: On 23/10/2020 18:46, Dave Plowman (News) wrote: In article , wrote: On 23/10/2020 16:14, Dave Plowman (News) wrote: In article direct.com, mafj wrote: Recent research that in UK households with combis kitchen water use is 2.5 higher than other systems. (18L vs 7.2L per person per day). And the most likely reason pointed out is time for HW to arrive). So secondary loop of any sort would seem to help alleviate this waste. Not sure circulating water within a potable supply is either allowed or a good idea. And just when were we short of water in the UK? DHW circulation is standard in larger buildings, without it there would be huge water wastage as people wait for hot water to reach the taps. I control mine with a pipe stat and a timer. But that will be from a storage system. A combi is connected to mains water. True, I was responding to your comment and didn't spot that the subject was about combi boilers. Didn't potable water give you a clue? You can circulate a stored system in a house to give quicker hot from a tap. Whether it is worth it in cash terms, I doubt it. Errr ... my hot water is potable, is on a circulation loop, and is based on a 300 litre unvented cylinder. Search for potable dhw circulation pump for more info. I agree that it's probably not financially worthwhile to have a circulation loop, but in a large house (or hotel) it's a convenience that's worth paying for. My boiler and DHW cylinder are in a plant room (the old coal store) with quite long runs to the furthest bedroom and bathroom; when the circulation pump is off it can take a very long time to get hot water out of the tap or shower. |
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