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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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Why are expansion vessels so expensive, more than the heater they're needed for?
We're considering a small under-sink unvented water heater for our
kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? -- Chris Green · |
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#2
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
Chris Green wrote:
We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? I'd have thought that you could find a potable water EV for less than that? How is 1.7m of pipe supposed to replace this function? Is it a dead leg full of air perhaps. |
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#3
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On Sun, 04 Feb 2018 12:24:16 +0000, Chris Green wrote:
We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...water-control- pack-87783101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? Perhaps another expansion vessel? https://www.mrcentralheating.co.uk/water-storage/expansion-vessels is my first hit. Looks as though you could fit for about £37. We had one added to the incoming mains for our combi because the manual said it was needed. AFAICR it was much simpler - integrated unit which fixed into the cold supply. Cheers Dave R -- AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64 --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
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#4
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 04/02/2018 12:24, Chris Green wrote:
We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? You need less than that if you use 22mm pipe. The pack includes PRV do you need one? |
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#5
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Why are expansion vessels so expensive, more than the heater they're needed for?
Bob Minchin wrote:
https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? I'd have thought that you could find a potable water EV for less than that? Possibly but I've not seen [m]any much cheaper. How is 1.7m of pipe supposed to replace this function? Is it a dead leg full of air perhaps. No, it's apparently simply the ductility of that much copper that allows for expansion of the water in the unvented heater. -- Chris Green · |
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#6
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Why are expansion vessels so expensive, more than the heater they're needed for?
David wrote:
On Sun, 04 Feb 2018 12:24:16 +0000, Chris Green wrote: However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...water-control- pack-87783101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? Perhaps another expansion vessel? https://www.mrcentralheating.co.uk/water-storage/expansion-vessels is my first hit. Looks as though you could fit for about £37. I don't think they're really intended for small unvented heaters, their capacity is as much (if not more) than the heater. Apart from anything else there's not really space for something that big, it'll be tight enough getting the heater in there. -- Chris Green · |
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#7
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 04/02/2018 12:44, Bob Minchin wrote:
Chris Green wrote: We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer).Â* The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater!Â* That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel.Â* 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? I'd have thought that you could find a potable water EV for less than that? How is 1.7m of pipe supposed to replace this function? Is it a dead leg full of air perhaps. Its there to stop the water in the tank reaching a tap when it expands. This is because the heated water may contain bacteria or other stuff that shouldn't get out of a cold water tap. If the run it too short you put a one way valve to stop the water going back and then you need an expansion vessel to take up the expansion. With a long pipe you just let the expanded water go back along the pipe as it won't reach another outlet. BTW these water heaters aren't designed to deliver potable water so you don't need a potable water expansion tank, the check valve prevent none potable water from the heater getting back to a tap. |
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#8
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 04/02/2018 12:57, Chris Green wrote:
Bob Minchin wrote: https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? I'd have thought that you could find a potable water EV for less than that? Possibly but I've not seen [m]any much cheaper. How is 1.7m of pipe supposed to replace this function? Is it a dead leg full of air perhaps. No, it's apparently simply the ductility of that much copper that allows for expansion of the water in the unvented heater. Incorrect, see my other post. |
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#9
Posted to uk.d-i-y
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Why are expansion vessels so expensive, more than the heater they're needed for?
Chris Green wrote:
Bob Minchin wrote: https://www.fastlec.co.uk/87-783101-...ntrol-pack-877 83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? I'd have thought that you could find a potable water EV for less than that? Possibly but I've not seen [m]any much cheaper. How is 1.7m of pipe supposed to replace this function? Is it a dead leg full of air perhaps. No, it's apparently simply the ductility of that much copper that allows for expansion of the water in the unvented heater. Without prejudice to whether it is true, I think you mean elasticity, not ductility, the latter being irreversible. -- Roger Hayter |
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#10
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Why are expansion vessels so expensive, more than the heater they're needed for?
Roger Hayter wrote:
Chris Green wrote: Bob Minchin wrote: https://www.fastlec.co.uk/87-783101-...ntrol-pack-877 83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? I'd have thought that you could find a potable water EV for less than that? Possibly but I've not seen [m]any much cheaper. How is 1.7m of pipe supposed to replace this function? Is it a dead leg full of air perhaps. No, it's apparently simply the ductility of that much copper that allows for expansion of the water in the unvented heater. Without prejudice to whether it is true, I think you mean elasticity, not ductility, the latter being irreversible. True, I knew it was the wrong word! :-) -- Chris Green · |
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#11
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Why are expansion vessels so expensive, more than the heater they're needed for?
dennis@home wrote:
On 04/02/2018 12:44, Bob Minchin wrote: Chris Green wrote: We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer).Â* The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater!Â* That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel.Â* 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? I'd have thought that you could find a potable water EV for less than that? How is 1.7m of pipe supposed to replace this function? Is it a dead leg full of air perhaps. Its there to stop the water in the tank reaching a tap when it expands. This is because the heated water may contain bacteria or other stuff that shouldn't get out of a cold water tap. If the run it too short you put a one way valve to stop the water going back and then you need an expansion vessel to take up the expansion. With a long pipe you just let the expanded water go back along the pipe as it won't reach another outlet. BTW these water heaters aren't designed to deliver potable water so you don't need a potable water expansion tank, the check valve prevent none potable water from the heater getting back to a tap. Ah, now that's a more sensible explanation than my original one (which came from the installation instructions for one of these). Thank you. -- Chris Green · |
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#12
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Why are expansion vessels so expensive, more than the heater they're needed for?
dennis@home wrote:
On 04/02/2018 12:24, Chris Green wrote: We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? You need less than that if you use 22mm pipe. That's a point, two 15/22mm couplings would be simple enough. The pack includes PRV do you need one? No, it's one of the reasons the Redring model above makes sense as it's rated for rather higher water pressure than most. -- Chris Green · |
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#13
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
dennis@home wrote:
BTW these water heaters aren't designed to deliver potable water so you don't need a potable water expansion tank, the check valve prevent none potable water from the heater getting back to a tap. Ah! I had assumed is was one of these fancy hot and cold and boiling water taps that you can make tea from. In that case it does not have to be a potable EV just one made from stainless steel but they might end up being one and the same. A heating/solar thermal type EV needs inhibitor to stop it rusting. |
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#15
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 04/02/2018 16:55, Brian Gaff wrote:
I guess its also not going to work that well on mains pressure either though. Never did get this expansion vessel idea on such systems, Water is unique in expanding when cold and when hot! Brian Yes, it's at its most dense at 4 degC - and expands above that *and* below that - more so when it turns to ice. -- Cheers, Roger ____________ Please reply to Newsgroup. Whilst email address is valid, it is seldom checked. |
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#16
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 04/02/2018 12:24, Chris Green wrote:
We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? My Quooker doesn't have an expansion vessel. It has a combined check valve, which stops hot water going back into the cold mains, and a PRV which spills a small amount of water into the drain when expansion takes place. Can't you do something similar? Should work, provided the heater can stand a bit more pressure than the PRV is set to. -- Cheers, Roger ____________ Please reply to Newsgroup. Whilst email address is valid, it is seldom checked. |
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#17
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 04/02/2018 12:24, Chris Green wrote:
We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? 1.7m of pipe doesn't seem much to take up the expansion. Perhaps one of these could have the same effect? http://www.wickes.co.uk/Sioux-Chief-...3-4in/p/143499 |
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#18
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 04/02/2018 19:51, Roger Mills wrote:
On 04/02/2018 12:24, Chris Green wrote: We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? My Quooker doesn't have an expansion vessel. It has a combined check valve, which stops hot water going back into the cold mains, and a PRV which spills a small amount of water into the drain when expansion takes place. Can't you do something similar? Should work, provided the heater can stand a bit more pressure than the PRV is set to. Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. -- Cheers, Roger ____________ Please reply to Newsgroup. Whilst email address is valid, it is seldom checked. |
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#19
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Why are expansion vessels so expensive, more than the heater they're needed for?
In message , Roger Mills
writes On 04/02/2018 19:51, Roger Mills wrote: On 04/02/2018 12:24, Chris Green wrote: We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...ontrol-pack-87 783101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? My Quooker doesn't have an expansion vessel. It has a combined check valve, which stops hot water going back into the cold mains, and a PRV which spills a small amount of water into the drain when expansion takes place. Can't you do something similar? Should work, provided the heater can stand a bit more pressure than the PRV is set to. Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. Any particular reason you can't supply it from the hot feed? There has to be more than 1.7m of pipe there. -- Tim Lamb |
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#20
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 04/02/2018 20:29, Fredxx wrote:
On 04/02/2018 12:24, Chris Green wrote: We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer).Â* The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...83101-cwp.html costs *more* than the water heater!Â* That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel.Â* 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? 1.7m of pipe doesn't seem much to take up the expansion. Perhaps one of these could have the same effect? http://www.wickes.co.uk/Sioux-Chief-...3-4in/p/143499 You need something that will hold about 300ml to ensure the water expanding from the heaters tank doesn't reach a potable water outlet. I doubt the arrester holds anywhere near that. No expansion vessel will work unless a check valve is also fitted. Just under 1m of 22mm pipe will do. Or 0.5m of 28 mm pipe if my maths is correct. |
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#21
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Why are expansion vessels so expensive, more than the heater they're needed for?
Tim Lamb wrote:
In message , Roger Mills writes On 04/02/2018 19:51, Roger Mills wrote: On 04/02/2018 12:24, Chris Green wrote: We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on. It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient. Our water pressure is within the MS6 specification so we don't need a pressure reducing valve. However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:- https://www.fastlec.co.uk/87-783101-...ontrol-pack-87 783101-cwp.html costs *more* than the water heater! That's really ridiculous. I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75! Is this a sensible idea? My Quooker doesn't have an expansion vessel. It has a combined check valve, which stops hot water going back into the cold mains, and a PRV which spills a small amount of water into the drain when expansion takes place. Can't you do something similar? Should work, provided the heater can stand a bit more pressure than the PRV is set to. Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. Any particular reason you can't supply it from the hot feed? There has to be more than 1.7m of pipe there. That's a point, removes the back feed issues as well, the hot water isn't potable. -- Chris Green · |
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#22
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Why are expansion vessels so expensive, more than the heater they're needed for?
Chris Green wrote:
Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. Any particular reason you can't supply it from the hot feed? There has to be more than 1.7m of pipe there. That's a point, removes the back feed issues as well, the hot water isn't potable. To expand on this, can anyone see any reason at all why I can't put an unvented water heater in the *hot* feed to the sink? It would solve virtually all problems in one go (at least the rules on how you plumb it problems):- The hot feed is low pressure, we have a conventional old-fashioned header tank fed hot water cylinder No back feed issues as it's non-potable water anyway Minimum length of pipe to take-off is easy to fulfil (even though it's irrelevant) It sounds a funny way to do things but it would actually work quite well, if we happened to want a *lot* of hot water then we'd eventually get hot feed from the cylinder. There will be a bit of heat loss from the pipes when we draw off small amounts but I don't see that as being a big issue. What the 'local' heater will do for us is give immediate hot water and stop the waste of water. -- Chris Green · |
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#23
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Why are expansion vessels so expensive, more than the heater they're needed for?
In message , Chris Green
writes Tim Lamb wrote: My Quooker doesn't have an expansion vessel. It has a combined check valve, which stops hot water going back into the cold mains, and a PRV which spills a small amount of water into the drain when expansion takes place. Can't you do something similar? Should work, provided the heater can stand a bit more pressure than the PRV is set to. Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. Any particular reason you can't supply it from the hot feed? There has to be more than 1.7m of pipe there. That's a point, removes the back feed issues as well, the hot water isn't potable. The other possible upside is that the hot water supply is likely to be from a water softener which may reduce scaling in the undersink heater. -- Tim Lamb |
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#24
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 05/02/2018 09:41, Chris Green wrote:
Chris Green wrote: Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. Any particular reason you can't supply it from the hot feed? There has to be more than 1.7m of pipe there. That's a point, removes the back feed issues as well, the hot water isn't potable. To expand on this, can anyone see any reason at all why I can't put an unvented water heater in the *hot* feed to the sink? It would solve virtually all problems in one go (at least the rules on how you plumb it problems):- The hot feed is low pressure, we have a conventional old-fashioned header tank fed hot water cylinder No back feed issues as it's non-potable water anyway Minimum length of pipe to take-off is easy to fulfil (even though it's irrelevant) It sounds a funny way to do things but it would actually work quite well, if we happened to want a *lot* of hot water then we'd eventually get hot feed from the cylinder. There will be a bit of heat loss from the pipes when we draw off small amounts but I don't see that as being a big issue. What the 'local' heater will do for us is give immediate hot water and stop the waste of water. Unless there is a minimum flow rate specified I would think it would be OK. You wouldn't want to leave the heater off for long though as you would want to kill any bacteria that may have got there from the header tank that wasn't killed in the hot water tank. 60C should kill most things so see what the stat can be set to on the heater. 60C is quite hot for a tap if there are kids or forgetful adults about. |
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#25
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Why are expansion vessels so expensive, more than the heater they're needed for?
dennis@home wrote:
On 05/02/2018 09:41, Chris Green wrote: To expand on this, can anyone see any reason at all why I can't put an unvented water heater in the *hot* feed to the sink? It would solve virtually all problems in one go (at least the rules on how you plumb it problems):- The hot feed is low pressure, we have a conventional old-fashioned header tank fed hot water cylinder No back feed issues as it's non-potable water anyway Minimum length of pipe to take-off is easy to fulfil (even though it's irrelevant) It sounds a funny way to do things but it would actually work quite well, if we happened to want a *lot* of hot water then we'd eventually get hot feed from the cylinder. There will be a bit of heat loss from the pipes when we draw off small amounts but I don't see that as being a big issue. What the 'local' heater will do for us is give immediate hot water and stop the waste of water. Unless there is a minimum flow rate specified I would think it would be OK. I've not seen any minumum flow rates or pressures specified. You wouldn't want to leave the heater off for long though as you would want to kill any bacteria that may have got there from the header tank that wasn't killed in the hot water tank. 60C should kill most things so see what the stat can be set to on the heater. 60C is quite hot for a tap if there are kids or forgetful adults about. It'll be on all the time and we will have the water quite hot (most have a maximum of 70 or 75), it's never for handwashing or such, just kitchen type things. -- Chris Green · |
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#26
Posted to uk.d-i-y
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 05/02/2018 09:41, Chris Green wrote:
Chris Green wrote: Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. Any particular reason you can't supply it from the hot feed? There has to be more than 1.7m of pipe there. That's a point, removes the back feed issues as well, the hot water isn't potable. To expand on this, can anyone see any reason at all why I can't put an unvented water heater in the *hot* feed to the sink? It would solve virtually all problems in one go (at least the rules on how you plumb it problems):- The hot feed is low pressure, we have a conventional old-fashioned header tank fed hot water cylinder No back feed issues as it's non-potable water anyway Minimum length of pipe to take-off is easy to fulfil (even though it's irrelevant) It sounds a funny way to do things but it would actually work quite well, if we happened to want a *lot* of hot water then we'd eventually get hot feed from the cylinder. There will be a bit of heat loss from the pipes when we draw off small amounts but I don't see that as being a big issue. What the 'local' heater will do for us is give immediate hot water and stop the waste of water. That is what I have done. It works well and I have instant hot water at a temperature of my choice. |
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#27
Posted to uk.d-i-y
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Why are expansion vessels so expensive, more than the heater they're needed for?
Chris Green wrote:
Chris Green wrote: Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. Any particular reason you can't supply it from the hot feed? There has to be more than 1.7m of pipe there. That's a point, removes the back feed issues as well, the hot water isn't potable. To expand on this, can anyone see any reason at all why I can't put an unvented water heater in the *hot* feed to the sink? It would solve virtually all problems in one go (at least the rules on how you plumb it problems):- The hot feed is low pressure, we have a conventional old-fashioned header tank fed hot water cylinder No back feed issues as it's non-potable water anyway Minimum length of pipe to take-off is easy to fulfil (even though it's irrelevant) It sounds a funny way to do things but it would actually work quite well, if we happened to want a *lot* of hot water then we'd eventually get hot feed from the cylinder. There will be a bit of heat loss from the pipes when we draw off small amounts but I don't see that as being a big issue. What the 'local' heater will do for us is give immediate hot water and stop the waste of water. It will give you the convenience of immediate hot water, but I don't think it will reduce any waste. When you draw off hot water your new heater will fill up with cold water from the pipe, and the pipe will still be filled with hot water from the main tank, which will then cool down unused. -- Roger Hayter |
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#28
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On 05/02/2018 11:59, Roger Hayter wrote:
It will give you the convenience of immediate hot water, but I don't think it will reduce any waste. When you draw off hot water your new heater will fill up with cold water from the pipe, and the pipe will still be filled with hot water from the main tank, which will then cool down unused. It probably won't save any energy, but it will prevent you throwing *water* away, waiting for the tap to run hot. Could be significant if the water is metered - and more environmentally friendly even if it's not. -- Cheers, Roger ____________ Please reply to Newsgroup. Whilst email address is valid, it is seldom checked. |
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#29
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Why are expansion vessels so expensive, more than the heaterthey're needed for?
On Monday, 5 February 2018 12:18:13 UTC, Roger Mills wrote:
On 05/02/2018 11:59, Roger Hayter wrote: It will give you the convenience of immediate hot water, but I don't think it will reduce any waste. When you draw off hot water your new heater will fill up with cold water from the pipe, and the pipe will still be filled with hot water from the main tank, which will then cool down unused. It probably won't save any energy, but it will prevent you throwing *water* away, waiting for the tap to run hot. Could be significant if the water is metered - and more environmentally friendly even if it's not. and will save money if the DHW if heated by gas or immersion on E7 NT |
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#30
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Why are expansion vessels so expensive, more than the heater they're needed for?
Roger Hayter wrote:
Chris Green wrote: Chris Green wrote: Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. Any particular reason you can't supply it from the hot feed? There has to be more than 1.7m of pipe there. That's a point, removes the back feed issues as well, the hot water isn't potable. To expand on this, can anyone see any reason at all why I can't put an unvented water heater in the *hot* feed to the sink? It would solve virtually all problems in one go (at least the rules on how you plumb it problems):- The hot feed is low pressure, we have a conventional old-fashioned header tank fed hot water cylinder No back feed issues as it's non-potable water anyway Minimum length of pipe to take-off is easy to fulfil (even though it's irrelevant) It sounds a funny way to do things but it would actually work quite well, if we happened to want a *lot* of hot water then we'd eventually get hot feed from the cylinder. There will be a bit of heat loss from the pipes when we draw off small amounts but I don't see that as being a big issue. What the 'local' heater will do for us is give immediate hot water and stop the waste of water. It will give you the convenience of immediate hot water, but I don't think it will reduce any waste. When you draw off hot water your new heater will fill up with cold water from the pipe, and the pipe will still be filled with hot water from the main tank, which will then cool down unused. It will save a huge amount of water. We had to draw many litres of water before we got hot through, it was a good sink full if not more so maybe 20 or 30 litres. So, if we use, say, 5 litres of hot water to do some washing up we will heat that 5 litres of water twice. It's still *way* less than the 20 or 30 we'd have needed previously and saves a lot of water too. So, yes, it's not as good as it could be maybe but it's a whole lot better than it was and also much more convenient. -- Chris Green · |
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#31
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Why are expansion vessels so expensive, more than the heater they're needed for?
Roger Mills wrote:
On 05/02/2018 11:59, Roger Hayter wrote: It will give you the convenience of immediate hot water, but I don't think it will reduce any waste. When you draw off hot water your new heater will fill up with cold water from the pipe, and the pipe will still be filled with hot water from the main tank, which will then cool down unused. It probably won't save any energy, but it will prevent you throwing *water* away, waiting for the tap to run hot. Could be significant if the water is metered - and more environmentally friendly even if it's not. Exactly! ... and (as I explain in my response above) I think it will save quite a lot of water heating energy. -- Chris Green · |
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#32
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Why are expansion vessels so expensive, more than the heater they're needed for?
In message , Chris Green
writes Roger Hayter wrote: Chris Green wrote: Chris Green wrote: Just to clarify, I'm using PRV here to refer to a pressure *relief* valve, not a pressure *reducing* valve. Any particular reason you can't supply it from the hot feed? There has to be more than 1.7m of pipe there. That's a point, removes the back feed issues as well, the hot water isn't potable. To expand on this, can anyone see any reason at all why I can't put an unvented water heater in the *hot* feed to the sink? It would solve virtually all problems in one go (at least the rules on how you plumb it problems):- The hot feed is low pressure, we have a conventional old-fashioned header tank fed hot water cylinder No back feed issues as it's non-potable water anyway Minimum length of pipe to take-off is easy to fulfil (even though it's irrelevant) It sounds a funny way to do things but it would actually work quite well, if we happened to want a *lot* of hot water then we'd eventually get hot feed from the cylinder. There will be a bit of heat loss from the pipes when we draw off small amounts but I don't see that as being a big issue. What the 'local' heater will do for us is give immediate hot water and stop the waste of water. It will give you the convenience of immediate hot water, but I don't think it will reduce any waste. When you draw off hot water your new heater will fill up with cold water from the pipe, and the pipe will still be filled with hot water from the main tank, which will then cool down unused. It will save a huge amount of water. We had to draw many litres of water before we got hot through, it was a good sink full if not more so maybe 20 or 30 litres. So, if we use, say, 5 litres of hot water to do some washing up we will heat that 5 litres of water twice. It's still *way* less than the 20 or 30 we'd have needed previously and saves a lot of water too. So, yes, it's not as good as it could be maybe but it's a whole lot better than it was and also much more convenient. Also.. mains water may be 10 deg. C whereas your hot pipe is not going to cool below room temperatu-) -- Tim Lamb |
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