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Anybody created a pre-heat DHW cylinder
My solar PV system, produces a significant amount of unused electricity.
I have a Thermal store based heating system .... providing mains pressure DHW off one heat exchanger and underfloor heating from the other ... the water content of store being circulated around the boiler when heat demand is called. A consideration is to install a 2nd hot water cylinder, and use the excess PV power to feed an immersion heater .... creating a large store of heat. Any call for DHW will result in thye incoming cold mains being pre-heated by this store .... when store is depleted, the normal heat exchanger function within the Thermal store would maintain DHW supply, topped up if necessary by boiler. I did ask a few weeks back about just using Solar PV excess direct into Thermal store immersion, but as this is kept 'at temp' don't really see a way to easily do that. This pre-heat method would seem a suitable alternative ... and using the mass of the water as an energy store. |
Anybody created a pre-heat DHW cylinder
On 03/11/2015 18:03, rick wrote:
I did ask a few weeks back about just using Solar PV excess direct into Thermal store immersion, but as this is kept 'at temp' don't really see a way to easily do that. You need to reprogram it so the heat store isn't kept at full temp to make space for the solar energy, or fit a new immersion at a lower point so the solar energy can heat the bottom of the tank. You could export some of the energy so others benefit. |
Anybody created a pre-heat DHW cylinder
On 03/11/15 18:03, rick wrote:
My solar PV system, produces a significant amount of unused electricity. Dont worry, it wont last. Winter is nearly here. -- the biggest threat to humanity comes from socialism, which has utterly diverted our attention away from what really matters to our existential survival, to indulging in navel gazing and faux moral investigations into what the world ought to be, whilst we fail utterly to deal with what it actually is. |
Anybody created a pre-heat DHW cylinder
On Tuesday, 3 November 2015 18:04:02 UTC, rick wrote:
My solar PV system, produces a significant amount of unused electricity. I have a Thermal store based heating system .... providing mains pressure DHW off one heat exchanger and underfloor heating from the other ... the water content of store being circulated around the boiler when heat demand is called. A consideration is to install a 2nd hot water cylinder, and use the excess PV power to feed an immersion heater .... creating a large store of heat. Any call for DHW will result in thye incoming cold mains being pre-heated by this store .... when store is depleted, the normal heat exchanger function within the Thermal store would maintain DHW supply, topped up if necessary by boiler. I did ask a few weeks back about just using Solar PV excess direct into Thermal store immersion, but as this is kept 'at temp' don't really see a way to easily do that. This pre-heat method would seem a suitable alternative ... and using the mass of the water as an energy store. I haven't run the numbers but expect you'd be better off all round to feed the electric heat into the existing tank. The water wil go above set point, and not need other heat sources until the temp is back down again. NT |
Anybody created a pre-heat DHW cylinder
On Tuesday, 3 November 2015 18:04:02 UTC, rick wrote:
My solar PV system, produces a significant amount of unused electricity. I have a Thermal store based heating system .... providing mains pressure DHW off one heat exchanger and underfloor heating from the other ... the water content of store being circulated around the boiler when heat demand is called. A consideration is to install a 2nd hot water cylinder, and use the excess PV power to feed an immersion heater .... creating a large store of heat. Any call for DHW will result in thye incoming cold mains being pre-heated by this store .... when store is depleted, the normal heat exchanger function within the Thermal store would maintain DHW supply, topped up if necessary by boiler. I did ask a few weeks back about just using Solar PV excess direct into Thermal store immersion, but as this is kept 'at temp' don't really see a way to easily do that. This pre-heat method would seem a suitable alternative ... and using the mass of the water as an energy store. Not worth bothering about. There will be no heat when you need it most. Also heat leaks away from small heat stores before you can use it. Small thermal heat stores are a complete waste of space/money. |
Anybody created a pre-heat DHW cylinder
A typical sub 4kw domestic array will only be generating a few kwh units each day during the winter months so economically a pointless waste of time, money and effort. You will be better doing your cooking or washing during the daytime, maybe with a slow cooker and timer.
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Anybody created a pre-heat DHW cylinder
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Anybody created a pre-heat DHW cylinder
On 03/11/2015 18:25, dennis@home wrote:
On 03/11/2015 18:03, rick wrote: I did ask a few weeks back about just using Solar PV excess direct into Thermal store immersion, but as this is kept 'at temp' don't really see a way to easily do that. You need to reprogram it so the heat store isn't kept at full temp to make space for the solar energy, or fit a new immersion at a lower point so the solar energy can heat the bottom of the tank. You could export some of the energy so others benefit. reprogram what ? ......... there is a simple standard thermostat ... set to 60 degrees. I could set it to 450 and immersion stat to 60 but then tank would not get warm enough when there is no PV power |
Anybody created a pre-heat DHW cylinder
On 03/11/2015 19:18, The Natural Philosopher wrote:
On 03/11/15 18:03, rick wrote: My solar PV system, produces a significant amount of unused electricity. Dont worry, it wont last. Winter is nearly here. today is a particularly damp, grey & gloomy day ... just looked it produced 2.2kWh today |
Anybody created a pre-heat DHW cylinder
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Anybody created a pre-heat DHW cylinder
On 04/11/2015 17:13, Alan Braggins wrote:
I've considered doing something similar. My thermal store is two cylinders in parallel, with both DHW and UFH being heated by them. But the remaining failed old Nu-Heat UFH is being replaced by radiators How did your Nu-Heat fail ? ............ mine is Nu-Heat and runs really well. Although I went wit the pex system not their earlier triple pipe rubber system. |
Anybody created a pre-heat DHW cylinder
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Anybody created a pre-heat DHW cylinder
On Wednesday, 4 November 2015 18:02:40 UTC, rick wrote:
On 03/11/2015 19:18, The Natural Philosopher wrote: On 03/11/15 18:03, rick wrote: My solar PV system, produces a significant amount of unused electricity. Dont worry, it wont last. Winter is nearly here. today is a particularly damp, grey & gloomy day ... just looked it produced 2.2kWh today Yep . Both of mine did 2.1 each. |
Anybody created a pre-heat DHW cylinder
On Wednesday, 4 November 2015 17:13:53 UTC, Alan Braggins wrote:
In article , wrote: A typical sub 4kw domestic array will only be generating a few kwh units each day during the winter months He could be planning it now to use next summer. Tch. You don't need any heat in Summer |
Anybody created a pre-heat DHW cylinder
On 04/11/2015 17:59, rick wrote:
On 03/11/2015 18:25, dennis@home wrote: On 03/11/2015 18:03, rick wrote: I did ask a few weeks back about just using Solar PV excess direct into Thermal store immersion, but as this is kept 'at temp' don't really see a way to easily do that. You need to reprogram it so the heat store isn't kept at full temp to make space for the solar energy, or fit a new immersion at a lower point so the solar energy can heat the bottom of the tank. You could export some of the energy so others benefit. reprogram what ? ......... there is a simple standard thermostat ... set to 60 degrees. I could set it to 450 and immersion stat to 60 but then tank would not get warm enough when there is no PV power No timer so you can use solar during the day and switch in other sources when its going dark? |
Anybody created a pre-heat DHW cylinder
On 04/11/2015 18:04, rick wrote:
On 03/11/2015 22:47, wrote: I haven't run the numbers but expect you'd be better off all round to feed the electric heat into the existing tank. The water wil go above set point, and not need other heat sources until the temp is back down again. NT Can't do that ... max temp I can have store get to is 60 degree ....... any higher and you risk damage to underfloor heating pipes. They should have a mixing valve to prevent the floors getting too hot. |
Anybody created a pre-heat DHW cylinder
On Wednesday, 4 November 2015 18:04:32 UTC, rick wrote:
On 03/11/2015 22:47, nt wrote: I haven't run the numbers but expect you'd be better off all round to feed the electric heat into the existing tank. The water wil go above set point, and not need other heat sources until the temp is back down again. Can't do that ... max temp I can have store get to is 60 degree ....... any higher and you risk damage to underfloor heating pipes. If your ufh runs off a bottom coil you can normally heat the water above it to over 60. Otherwise as you say it's a preheat tank. But a preheat tank brings a few issues: 1. water staying in the unsafe temp zone - ok for most things but not ideal for showers 2. Lots more area for heat loss, but in fairness a foot or 2 of insulation is pretty cheap. 3. Upfront costs that arent there with feeding the power into the main HW cyl. NT |
Anybody created a pre-heat DHW cylinder
On 04/11/2015 19:48, dennis@home wrote:
On 04/11/2015 18:04, rick wrote: On 03/11/2015 22:47, wrote: I haven't run the numbers but expect you'd be better off all round to feed the electric heat into the existing tank. The water wil go above set point, and not need other heat sources until the temp is back down again. NT Can't do that ... max temp I can have store get to is 60 degree ....... any higher and you risk damage to underfloor heating pipes. They should have a mixing valve to prevent the floors getting too hot. No the design has a mixing valve on the DHW take off, but the main feeds off for the UFH loop is not via a mixing valve ... the main tank stat prevents it going over 60 degree. |
Anybody created a pre-heat DHW cylinder
On 04/11/2015 21:35, rick wrote:
On 04/11/2015 19:48, dennis@home wrote: On 04/11/2015 18:04, rick wrote: On 03/11/2015 22:47, wrote: I haven't run the numbers but expect you'd be better off all round to feed the electric heat into the existing tank. The water wil go above set point, and not need other heat sources until the temp is back down again. NT Can't do that ... max temp I can have store get to is 60 degree ....... any higher and you risk damage to underfloor heating pipes. They should have a mixing valve to prevent the floors getting too hot. No the design has a mixing valve on the DHW take off, but the main feeds off for the UFH loop is not via a mixing valve ... the main tank stat prevents it going over 60 degree. 60c is too high for underfloor heating IMO. If someone collapsed on a floor that could get that hot they could die. If it had a mixer then that would limit the temperature and allow more heat to be stored by allowing a higher temp in the thermal store. |
Anybody created a pre-heat DHW cylinder
On Tue, 3 Nov 2015 18:03:55 +0000, rick
wrote: This pre-heat method would seem a suitable alternative ... and using the mass of the water as an energy store. I had a similar installation many years ago but using solar water as the pre-heating. The solar tubes warmed a heavily insulated cylinder in the attic. Incoming mains water went first to the solar cylinder and then to the second cylinder heated by a gas boiler. It was interesting to play with but didn't achieve much. In the summer it provided most of the hot water, in the winter sod all. |
Anybody created a pre-heat DHW cylinder
On Wednesday, 4 November 2015 21:35:08 UTC, rick wrote:
On 04/11/2015 19:48, dennis@home wrote: On 04/11/2015 18:04, rick wrote: On 03/11/2015 22:47, nt wrote: I haven't run the numbers but expect you'd be better off all round to feed the electric heat into the existing tank. The water wil go above set point, and not need other heat sources until the temp is back down again. Can't do that ... max temp I can have store get to is 60 degree ........ any higher and you risk damage to underfloor heating pipes. They should have a mixing valve to prevent the floors getting too hot. No the design has a mixing valve on the DHW take off, but the main feeds off for the UFH loop is not via a mixing valve ... the main tank stat prevents it going over 60 degree. This extra electricity comes at times of high sun output, ie when ufh is not usually being used. So in principle you could add a stat that stops the ufh pump coming on when the cyl is too hot for it. Then you get the benefit of your extra leccy without a bunch of extra costs. NT |
Anybody created a pre-heat DHW cylinder
On Wed, 4 Nov 2015 21:35:01 +0000, rick wrote:
Can't do that ... max temp I can have store get to is 60 degree any higher and you risk damage to underfloor heating pipes. They should have a mixing valve to prevent the floors getting too hot. No the design has a mixing valve on the DHW take off, but the main feeds off for the UFH loop is not via a mixing valve ... the main tank stat prevents it going over 60 degree. Strikes me as bad design then. Can't you fit a mixing valve between the flow and return of the floor loop such that the pump circulates via the valve when the temp approaches 60 C. -- Cheers Dave. |
Anybody created a pre-heat DHW cylinder
On Wednesday, 4 November 2015 22:43:06 UTC, Dave Liquorice wrote:
On Wed, 4 Nov 2015 21:35:01 +0000, rick wrote: Can't do that ... max temp I can have store get to is 60 degree any higher and you risk damage to underfloor heating pipes. They should have a mixing valve to prevent the floors getting too hot. No the design has a mixing valve on the DHW take off, but the main feeds off for the UFH loop is not via a mixing valve ... the main tank stat prevents it going over 60 degree. Strikes me as bad design then. Can't you fit a mixing valve between the flow and return of the floor loop such that the pump circulates via the valve when the temp approaches 60 C. 60 seems unusually high for ufh NT |
Anybody created a pre-heat DHW cylinder
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Anybody created a pre-heat DHW cylinder
On 04/11/2015 22:19, dennis@home wrote:
60c is too high for underfloor heating IMO. If someone collapsed on a floor that could get that hot they could die. If it had a mixer then that would limit the temperature and allow more heat to be stored by allowing a higher temp in the thermal store. Agree ... but floor will never get to 60 ... each room has its own zone with digital set back temperature control. The max temp of water in cylinder is 60 .... there is heat exchanger coil, with 28mm feeds to manifolds ... then individual zones .... so too many losses to get as high as 60. It probably would be nice to have a mixer on heating loop, wasn't in the design ... I could retrofit. Need to check if tank is happy being run hotter - problem will be Nu-Heat state design temp of cylinder in 60 .... they will be unlikely to confirm it can be run hotter - I will ask. Without some statement that tank can be run higher my risk would be too high to just 'chance it' |
Anybody created a pre-heat DHW cylinder
On 05/11/2015 09:18, Dave Liquorice wrote:
Only quoting the OP and that's the maximum to avoid damage. What ever, to me not having some regulation of the UFH loop temperature independant of the store temp isn't right. Limiting the store to 60 C reduces the amount of energy it can store by about 30%. And a store with a 60 C max must struggle to provide a decent quantity of DHW unless the OP has that mixer valve set to the pathtically low "safe" 43 C. Ours is set at 53 C or there abouts, hot as in you can put your hand in it but don't want to keep it there for more than a few tens of seconds hot. The store middle temperature is normally about 70 to 80 C, top can get to 90+ if I miss judge the weather and get a good burn going in the stove without the heating coming on enough. It can deliver a bath of DHW at 53 C and 15 to 20l/min before it starts to run out heat. The regulation is done by the stat keeping tank at 60 ........ you may deem that not enough but seems to work fine. Stat is fitted in lower 1/3 of store. There is never any shortage of ho****er ... this is set to 53 deg ... and runs at full mains pressure ... on 22mm pipes. You can run it full flow to fill a bath and still running hot when bath is full. Nu-Heat advise the high efficiency cross flow heat exchanger (rather than a coil)allows this. Flow is from mains pressure of 3.5bar at 25L/min .. and has never once run out of ho****er when in use. |
Anybody created a pre-heat DHW cylinder
In article , rick wrote:
On 04/11/2015 17:13, Alan Braggins wrote: I've considered doing something similar. My thermal store is two cylinders in parallel, with both DHW and UFH being heated by them. But the remaining failed old Nu-Heat UFH is being replaced by radiators How did your Nu-Heat fail ? ............ mine is Nu-Heat and runs really well. Although I went wit the pex system not their earlier triple pipe rubber system. Mine was the earlier double rubber pipe system. (Which apparently they sold briefly after the triple, but before moving to PEX.) Failures of the double and triple systems seem to be similar, and common. Mostly it's perished near the manifolds, one zone leaked somewhere I couldn't find it, and one zone (the last failure) isn't leaking, but the rubber is gunked up and hardly any water circulates. Possibly because, although it's had inhibitor in it, it's been repeatedly refilled because of all the leaks. |
Anybody created a pre-heat DHW cylinder
In article , harry wrote:
On Wednesday, 4 November 2015 17:13:53 UTC, Alan Braggins wrote: In article , wrote: A typical sub 4kw domestic array will only be generating a few kwh units each day during the winter months He could be planning it now to use next summer. Tch. You don't need any heat in Summer Some of us like to wash in hot water in the summer, even when the heating is off. Also, not all of the summer is warm enough to swim comfortably in my swimming pool without heating. (It used to be better, but more of it is shaded by trees now.) |
Anybody created a pre-heat DHW cylinder
On Thursday, 5 November 2015 14:22:15 UTC, rick wrote:
On 04/11/2015 22:31, nt wrote: This extra electricity comes at times of high sun output, ie when ufh is not usually being used. So in principle you could add a stat that stops the ufh pump coming on when the cyl is too hot for it. Then you get the benefit of your extra leccy without a bunch of extra costs. Assume you mean a manual switch in summer turning off boiler and enabling immersion .. with it's stat set higher .,.... an idea. that's totally different to what I suggested :) In order to draw off hot water you need to run a de-stratification pump I'm not seeing why. It's not normally how things work I presume your pump is drawn the wrong way round on that pdf. NT ....... existing pump does this and cycles primary (thru boiler) .. not an issue in winter when this extra heat goes into the building fabric. If I were to turn off control system, the de-stratification pump & zone valve (initiated by flow switch) would not work. I would need to install a shunt pump & one way valve .. operated by flow switch. This pic shows what I have .. and where shunt would go. The system is pressurised - left out expansion chambers and much of the other kit for clarity. http://www.4shared.com/office/XP0ObB...al_store_.html |
Anybody created a pre-heat DHW cylinder
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Anybody created a pre-heat DHW cylinder
On 04/11/2015 21:35, rick wrote:
On 04/11/2015 19:48, dennis@home wrote: On 04/11/2015 18:04, rick wrote: On 03/11/2015 22:47, wrote: I haven't run the numbers but expect you'd be better off all round to feed the electric heat into the existing tank. The water wil go above set point, and not need other heat sources until the temp is back down again. NT Can't do that ... max temp I can have store get to is 60 degree ....... any higher and you risk damage to underfloor heating pipes. They should have a mixing valve to prevent the floors getting too hot. No the design has a mixing valve on the DHW take off, but the main feeds off for the UFH loop is not via a mixing valve ... the main tank stat prevents it going over 60 degree. They normally use tall cylinders for these applications so that you can rely on stratification to deliver lower temperatures to the UFH using lower tappings on the cylinder. That does not stop you having the upper section hotter than the UFH temperature. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Anybody created a pre-heat DHW cylinder
On 05/11/2015 14:10, rick wrote:
On 05/11/2015 09:18, Dave Liquorice wrote: Only quoting the OP and that's the maximum to avoid damage. What ever, to me not having some regulation of the UFH loop temperature independant of the store temp isn't right. Limiting the store to 60 C reduces the amount of energy it can store by about 30%. And a store with a 60 C max must struggle to provide a decent quantity of DHW unless the OP has that mixer valve set to the pathtically low "safe" 43 C. Ours is set at 53 C or there abouts, hot as in you can put your hand in it but don't want to keep it there for more than a few tens of seconds hot. The store middle temperature is normally about 70 to 80 C, top can get to 90+ if I miss judge the weather and get a good burn going in the stove without the heating coming on enough. It can deliver a bath of DHW at 53 C and 15 to 20l/min before it starts to run out heat. The regulation is done by the stat keeping tank at 60 ........ you may deem that not enough but seems to work fine. Stat is fitted in lower 1/3 of store. That in itself means the upper section of the store will be able to reach a much higher temperature. There is never any shortage of ho****er ... this is set to 53 deg ... and runs at full mains pressure ... on 22mm pipes. You can run it full flow to fill a bath and still running hot when bath is full. Nu-Heat advise the high efficiency cross flow heat exchanger (rather than a coil)allows this. You have shown it as a coil in the diagram... normally there would be a circulation pump to drive the primary of the DHW HE - that solves the problem of cold pockets forming in the cylinder - the opt is pumped to the inlet of the PHE primary, and the return from it go back into a lower tapping on the cylinder. Like: http://wiki.diyfaq.org.uk/index.php/...Bank-Water.gif (that shows a vented store, but the same principle can apply for unvented) Flow is from mains pressure of 3.5bar at 25L/min .. and has never once run out of ho****er when in use. As long as you have adequate volume of water stored, and the PHE has enough transfer rate, you should be fine. (you will need to shift around 80kW to keep pace with a flow rate of 25 lpm) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Anybody created a pre-heat DHW cylinder
On Thursday, 5 November 2015 20:19:43 UTC, rick wrote:
On 05/11/2015 17:38, nt wrote: In order to draw off hot water you need to run a de-stratification pump I'm not seeing why. It's not normally how things work I presume your pump is drawn the wrong way round on that pdf. The baffle in the middle of the store for one reason. The other reason I know of is that the DHW take off is from a crossflow plate heat exchanger, to keep up continuous high flow rate of hot water, then need to stir the tank or it quickly would form a cold 'pocket' around itself and flow would cool down I'm not seeing how any of that adds up. A crossflow PHE must be external, and will run hot from the top, returning it to the bottom. The pumping inherent in that prevents cold pockets. To get best boiler efficiency & provide a cooler zone for ufh the boiler hot should enter the top of the cylinder. NT |
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