scotslad Posted December 3, 2015 Report Share Posted December 3, 2015 Possibly a strange question for the plumbers and heating engineers. Tried googling it but not finding the info i'm after Is there such a thing as an Instantanous Water heater that can handle pre heated water going throu it? I have been told they need a cold water supply. But not sure they understood fully wot i was meaning I'm about to start renovating an old ruin and trying to figure out the heating system, was orginally looking at Boimass/RHI but so dear to install. Got plentiful supply of free timber and solar is not an option Now looking at a log burner and back boiler but looking for a way to heat water throu the summer without putting the fire on (esp in a modern insulated house) or it would be like a suana, plus i'm used to old cold houses. Going to install and electric shower for summer use so really only a bit of hot water for washing hands etc, Proably quite a tiny quantity really. Was thinking under sink Instantanous units would be cheaper than using the immersion coil to heat 3 or 400 ltrs of water. But could u plumb the units in (inline?) so the HW passes throu the element but element only comes on if water below the specified temp? That would probably be my preffered if possible as water will always be X temp no matter how hot the tank is. Or could u plumb the elemnet to the cold water pipe with some sort of thermastic value conectted to the hot line so if tank hot water is too cold the water heater would come on? Even thought i could have 2 hot water taps but would look funny or a manual valve to switch supplies from the 2 HW sources Ideas are definately outside the box thinking but might be wot i'm looking for if they work Cheers in advance Quote Link to comment Share on other sites More sharing options...
TR1 Posted December 3, 2015 Report Share Posted December 3, 2015 Have you thought about using a 3 way tap. Cold , hot tank and instantaneous supplies. Quote Link to comment Share on other sites More sharing options...
millrace Posted December 3, 2015 Report Share Posted December 3, 2015 you could build a set up using relays non return vales stats and a timer but really your just overthinking and overworking something and possibly underestimating the amount of hot water you may need and say you have kitchen utility bathroom and ensuite thats 4 heaters required,,,, costly but will be the easiest most realiable way of achieving what you want Quote Link to comment Share on other sites More sharing options...
scotslad Posted December 3, 2015 Author Report Share Posted December 3, 2015 TR! Never knew u even got a 3 way tap. I will have a look Cheers millrace, possibly ur right and i am under estimating how much i use. But even at the house i'm in the now i don't use an awful lot, prob only 2 basins a day if ur lucky, and most of that will be washing hands after work or dishes and thats without having a dishwasher either. In this new house will be sticking a dishwasher in so really just for washing my hands really, esp if sticking an electric shower in. Is it possible and worth looking into further? Sounds complicated with relays and non return values? but wee bit above my head Quite happy to buy 3/4 heaters (seem to be around the 100 mark but not entirely sure if suitable) if needed, compared to the money that i'll be saving by not putting a boimass boiler in it would still be a cheap way of guarantteeing hot water without sticking the fire on, which is my main concern with solely having a back boiler for heating/hotwater. Heating going to be UFH so doubt it will really be on for 8 months a year Quote Link to comment Share on other sites More sharing options...
Doc Holliday Posted December 3, 2015 Report Share Posted December 3, 2015 Blimey! You don't want much. That sounds a rather protracted way to heat water just to wash your hands. I have an electric instaneous water heater in my office for the sink and wash hand basin. I think it's a 3kw but it only heats the water by a set amount, say 12 degrees. So if your incoming supply was 8 degrees in the winter you'd only get 20 degrees out of the tap. You can make the water hotter by slowing down the flow. In theory you could probably work them inline but I'm not sure how well it would work as you will lose a certain amount of flow through the appliance. I'll find out the make and model of mine and speak to the manufacturer and let you know what they said. I'll wager there'll be howls of laughter initially. Quote Link to comment Share on other sites More sharing options...
millrace Posted December 3, 2015 Report Share Posted December 3, 2015 You'll find most heaters are mains driven easily overcome but using a pump but again hassle if trying to use hot system am I right in that your planning underfloor and by running it from a stove back boiler type unit? Quote Link to comment Share on other sites More sharing options...
scotslad Posted December 3, 2015 Author Report Share Posted December 3, 2015 Aye it does seem complicated. Never knew how much u take HW for granted when u have a combi boiler on town gas. Just turn the tap on and expect it to be there This house is out in sticks so if i have any additional back up boilers i then need gas/oil tanks etc, not long in getting up to 3 or 4K just for some hot water throu the summer. Lot of money. Would buy a lot of electricity even if i go down the more normal immersion heater route, but just seems crazy to heat whole tank when i will use very little Yes millrace, looking like a log burner/back boiler into a thermal store and UFH. The boimass boiler route would of been ideal but looking like 12-14K to install for a 120m2 2 bed house, plus around 3-500 to service a year, seem to be quite complicated too so can see problems further down the line. But far easier to regulate the tank temp and heat it throu summer without heating the house Ideally i would combine with a solar water unit but roof faces wrong direction and a lot of trees too so fairly shaded Quote Link to comment Share on other sites More sharing options...
LondonLuke Posted December 3, 2015 Report Share Posted December 3, 2015 http://www.plumbworld.co.uk/triton-t30i-hand-wash-unit-3kw-576-21962?utm_source=GoogleBase&utm_medium=GB&utm_campaign=GoogleBase&gclid=CMqTqPDbwMkCFSoOwwodo0AKFA Job jobbed Quote Link to comment Share on other sites More sharing options...
scotslad Posted December 3, 2015 Author Report Share Posted December 3, 2015 Aye it does seem complicated. Never knew how much u take HW for granted when u have a combi boiler on town gas. Just turn the tap on and expect it to be there This house is out in sticks so if i have any additional back up boilers i then need gas/oil tanks etc, not long in getting up to 3 or 4K just for some hot water throu the summer. Lot of money. Would buy a lot of electricity even if i go down the more normal immersion heater route, but just seems crazy to heat whole tank when i will use very little Yes millrace, looking like a log burner/back boiler into a thermal store and UFH. The boimass boiler route would of been ideal but looking like 12-14K to install for a 120m2 2 bed house, plus around 3-500 to service a year, seem to be quite complicated too so can see problems further down the line. But far easier to regulate the tank temp and heat it throu summer without heating the house Ideally i would combine with a solar water unit but roof faces wrong direction and a lot of trees too so fairly shaded If i could somehow plumb a unit in below each sink to work along side and just top up the water if needed would be ideal, possibly even if only a 12c rise would be enough if i kept the big water tank lukewarm, would prob stay that temp for quite a while in a well insulated tank Quote Link to comment Share on other sites More sharing options...
scotslad Posted December 3, 2015 Author Report Share Posted December 3, 2015 Cheers luke. Sorry to be stupid but can that unit run off the hot water pipe? with hot water coming in. I know it defeats the point in them a bit but really only be needed to provide a top up to water temp throu summer so i don't need the log burner on as much to keep the thermal store at HW temp all the time. Hope that makes sense, as it is quite a strange thing i'm asking i think Quote Link to comment Share on other sites More sharing options...
Winston72 Posted December 3, 2015 Report Share Posted December 3, 2015 I think what your after is something "SIMILAR" and i do mean that in the loosest terms, is the Ravenheat energy catcher, yes that goes on a combi for the hot water but, it pre heats the water before it enters the appliance Quote Link to comment Share on other sites More sharing options...
millrace Posted December 3, 2015 Report Share Posted December 3, 2015 (edited) Your going to struggle to heat buffer tank from stove not long enough burn time without constantly feeding i wouldn't even consider this, stove burn out in say 1 hr where as biomass unit averages 4 hr burn time and superheats the flu gas etc underfloor requires a lot of water/energy to heat,typically you run coil from buffer to hot water cylinder defo do your research on what your planning you ceem to be trying the impossible on the cheap.....won't work...... Edited December 3, 2015 by millrace Quote Link to comment Share on other sites More sharing options...
LondonLuke Posted December 3, 2015 Report Share Posted December 3, 2015 (edited) Cheers luke. Sorry to be stupid but can that unit run off the hot water pipe? with hot water coming in. I know it defeats the point in them a bit but really only be needed to provide a top up to water temp throu summer so i don't need the log burner on as much to keep the thermal store at HW temp all the time. Hope that makes sense, as it is quite a strange thing i'm asking i think To be honest it was more of a tongue in cheek suggestion - it's an answer to the problem but I doubt it is the answer. It was more the image of having a £30 water heater on the wall of a brand newly refurbished house. Edited December 3, 2015 by LondonLuke Quote Link to comment Share on other sites More sharing options...
39TDS Posted December 3, 2015 Report Share Posted December 3, 2015 I have got two "instant" water heaters, one is like the one in Luke's link and one is more like a small immersion heater and actually holds a few litres of water. The one in Luke's link is a waste of time. Yes you can just about rinse your hands with it but that is it and I definitely wouldn't fit another ever again. You would regret it if you did I promise you that. The other is more useful and you can just about get a third of a bucket of hot water out of it before you have to stop and let it catch up. No doubt you are supposed to only run cold into it but I can't see why hot would bother it. It isn't a pressurised system though, just gravity. My house runs entirely on wood fuel as far as DHW and central heating goes. I have an ordinary immersion tank in the airing cupboard that the fire heats up. I don't have the immersion on though. A fire in summer will heat the water enough to last a few days, that will include showers as long as you don't use too much and don't expect scalding water. There are usually cool evenings in the summer when a fire doesn't cook the whole house and cold showers are quite welcome when it is roasting hot weather anyway. Seems odd to go for a full wood heating system and then fit an electric shower. ps. it would be a whole lot easier to boil a kettle than use one of the heaters in that link. As I said, I have one so I do know. (as i think Luke did too) Quote Link to comment Share on other sites More sharing options...
scotslad Posted December 4, 2015 Author Report Share Posted December 4, 2015 (edited) Thats why i'm looking at under the sink solutions that also feed of the same pipes if possible and to save putting an extra tap in. I know with combi boilers u can't run pre heated water into them and all the instant heaters mention cold mains and not pre heated, (looked into adding a log burner to my existing combi a few years ago when i built my garage) but there obviously designed where there is not hot water. Dunno about wanting the impossible millrace and quite happy to pay for it, was happy to pay for boimass but just think not as good as made out and far too complicated esp with servicing costs. Can see there being a bit going wrong in future, esp compared to a simple back boiler and ur only really getting an extra 10-15% effecientcy for all the bells and whistles If u have the fire on 1st thing while i make piece and walk dogs etc and load it well up u could get 2hrs then and then again when u come in at nite. The plumber didnae think it would be a problem (but he's away for a long wknd this wknd) and just had my brain wave/**** at work today. Its just how i get hot water in summer that concerns me. As long as the system works happy to pay for it, but at same time i have thought about the kettle option too, but u dinae want to have to do that in a modern renovated house.(when i say renovated its complete new roof and walls stripped back to masonry so not just a lick of paint) Thats why i thought these things might be a solution but only occasionally had to use 1,hence my question Cheers winsto i will have a look at the Ravenheat system Cheers tds, is urs a well insulated house? Where i live the now isn't great insulation wise but still only got temp on central heating at 14 for hotest so used to cool/cold houses. Worried i'll cook with all the insulation that i'm going to have to put in Edited December 4, 2015 by scotslad Quote Link to comment Share on other sites More sharing options...
scotslad Posted December 4, 2015 Author Report Share Posted December 4, 2015 (edited) Basically If i plumbed a 7,10 or 13kw instant heater onto the hot main below a sink. Would hot water flow as normal throu the element if the incoming temp was ok (when fire on and tank hot), and would instant heater only turn on if the incoming temp was below normal (if tank was cooling between fires) Had a look on the ravenhead system, its slightly different to wot i'm wanting Edited December 4, 2015 by scotslad Quote Link to comment Share on other sites More sharing options...
39TDS Posted December 4, 2015 Report Share Posted December 4, 2015 It would work fine if it was a non pressurised system. No doubt there are ways to make it work on a pressurised system. They do not restrict the flow in any way and there is nothing to measure the incoming temperature. It is actually quite a good idea if you really are only using a small amount of water. No my house is not well insulated. Quote Link to comment Share on other sites More sharing options...
39TDS Posted December 4, 2015 Report Share Posted December 4, 2015 If you are so worried about the heat in the house and wood is free, why not just open the windows? Quote Link to comment Share on other sites More sharing options...
secretagentmole Posted December 4, 2015 Report Share Posted December 4, 2015 (edited) OK is it me or are people missing a trick here? The OP only wants to run the instantaneous hot water heater in summer when the solid fuel heating is not running. Instantaneous water heater runs on electricity. When hot water supplied from solid fuel, turn electricity to water heater off. When not burning solid fuel in summer, turn back on. The device will not be used when water is heated, water will merely be flowing through it! Simple! Edited December 4, 2015 by secretagentmole Quote Link to comment Share on other sites More sharing options...
rjimmer Posted December 4, 2015 Report Share Posted December 4, 2015 I think the 'instant' heaters rely on the water pressure drop, when you open the tap, to turn them on, so mains pressure is needed. Hot/warm water stored in a tank/cylinder would only be under pressure from the header tank that might not even be in the roof. Some sort of thermostat-controlled heater should be available if it can be switched on/off automatically. Quote Link to comment Share on other sites More sharing options...
Twistedsanity Posted December 4, 2015 Report Share Posted December 4, 2015 Thought about this? http://www.ebay.co.uk/itm/Ecocent-air-source-heat-pump-DHW-250-ltr-Black-top-/321816945262?hash=item4aedc8e26e:g:qeQAAOSwBLlU2Mu- Quote Link to comment Share on other sites More sharing options...
scotslad Posted December 4, 2015 Author Report Share Posted December 4, 2015 OK is it me or are people missing a trick here? The OP only wants to run the instantaneous hot water heater in summer when the solid fuel heating is not running. Instantaneous water heater runs on electricity. When hot water supplied from solid fuel, turn electricity to water heater off. When not burning solid fuel in summer, turn back on. The device will not be used when water is heated, water will merely be flowing through it! Simple! Aye i think ur are not far away, i wasn't sure if u could actually run water throu it when it was turned off or run pre heated water throu it in case i damaged it. Quote Link to comment Share on other sites More sharing options...
scotslad Posted December 4, 2015 Author Report Share Posted December 4, 2015 (edited) I think the 'instant' heaters rely on the water pressure drop, when you open the tap, to turn them on, so mains pressure is needed. Hot/warm water stored in a tank/cylinder would only be under pressure from the header tank that might not even be in the roof. Some sort of thermostat-controlled heater should be available if it can be switched on/off automatically. Cheers rjimmer, ur right tank will not be in the roof but just raised up so cieling hieght really. Think i may be on the right track now but just need to do some more research and speak to some of the makers etc to see wot they're saying. The house is on a private water supply anyway and while it does seem to have a bit of pressure not entirely sure it is mains, so i will ahve to look into that part. Cheers TDS, aye had thought of opening the windows the problem with that is MIDGES Little ********, bought a box full of midge jackets last year bloory things are every where. Better than it was thou as dropped a lot of trees so gets far more breeze than it used to That's probably wot i'll do but it would be quite handy if HW was always toasty even if tank temp drops down a bit say to 40c, mean u might only need fire on once a week or so Cheers twisted, Is that not an air source heat pump? Not really convinced there a good thing and have looked into them a bit, think they really struggle to do DHW and use a lot of eleccy to heat it. But to be fair might be more economic in summer. Will have a bit more of a dig about, cheers for all the help so far. Think i'm getting there Edited December 4, 2015 by scotslad Quote Link to comment Share on other sites More sharing options...
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