whole house instantaneous water heating

BoatMad

This may have been covered before, I was looking on Screwfix.ie at a range of hot press mounted instant water heaters that can supply a standard shower and sink. ( typical 5-9kw ) I have very good mains pressure ( a bit too good sometimes !)
In my case I already have one shower with its own instant heater and Im removing my only bath and installing another shower. I have no need for a cylinder and dont actually heat any water in it.

I was thinking of removing my cylinder and plumbing the big instantaneous water heater into the hot water plumbing,( converting to unvented) this would supply the new shower, give me hand washing water in the kitchen sink ( dish and clothes on cold fill) and in fact I could even remove the existing shower based instantaneous shower. Theres only the two of us and I could interlock the two showers with flow switches so that both cant be active at once, if that was needed

It would also give me mains pressure hot water , which is an issue at present as I have high pressure mixer taps on the kitchen sink

has anyone tried this these types of units ?

Dtp1979

BoatMad wrote: »

This may have been covered before, I was looking on Screwfix.ie at a range of hot press mounted instant water heaters that can supply a standard shower and sink. ( typical 5-9kw ) I have very good mains pressure ( a bit too good sometimes !)
In my case I already have one shower with its own instant heater and Im removing my only bath and installing another shower. I have no need for a cylinder and dont actually heat any water in it.

I was thinking of removing my cylinder and plumbing the big instantaneous water heater into the hot water plumbing,( converting to unvented) this would supply the new shower, give me hand washing water in the kitchen sink ( dish and clothes on cold fill) and in fact I could even remove the existing shower based instantaneous shower. Theres only the two of us and I could interlock the two showers with flow switches so that both cant be active at once, if that was needed

It would also give me mains pressure hot water , which is an issue at present as I have high pressure mixer taps on the kitchen sink

has anyone tried this these types of units ?

Yes millions of people have. There's more commonly called combi boilers. They heat your house and supply unlimited hot water in the right conditions. Your house seems perfect for it. They can be gas or oil fired

BoatMad

Nope. I have a perfectly good boiler. I want to heat the water using a electric heater

Dtp1979

BoatMad wrote: »

Nope. I have a perfectly good boiler. I want to heat the water using a electric heater

Then just keep your cylinder and use the immersion 24/7

K.Flyer

I presume THIS is the type of thing that you are talking about, having looked at the website you mentioned. I have never seen one in use in Ireland, most likely because of the unreliable mains pressure.
However, if it does what it says on the tin I can see the attraction to it.
My only advise would be to ensure that it will be fitted in accordance with manufacturer's instructions and in accordance with your local council mains water regulations.

BoatMad

K.Flyer wrote: »

I presume THIS is the type of thing that you are talking about, having looked at the website you mentioned. I have never seen one in use in Ireland, most likely because of the unreliable mains pressure.
However, if it does what it says on the tin I can see the attraction to it.
My only advise would be to ensure that it will be fitted in accordance with manufacturer's instructions and in accordance with your local council mains water regulations.

Yes something like that. I have good constant pressure and I already use a pump-less instant shower to good effect.

What I'm trying to find put is if it does " what it says on the tin".

Dardania

That thing will pull 40A-45A. That's a lot of current. Be sure your electrical infrastructure is up to the job

Typical domestic supplies 12kVA are fused at 63A. Do you have any other loads of significance that might be on at same time as the water heater? Do you use a clothes dryer, older oven etc.?

BoatMad

Dardania wrote: »

That thing will pull 40A-45A. That's a lot of current. Be sure your electrical infrastructure is up to the job

Typical domestic supplies 12kVA are fused at 63A. Do you have any other loads of significance that might be on at same time as the water heater? Do you use a clothes dryer, older oven etc.?

Looking at 7 kW unit , no more , I've computed by system loads , I can handle the 7kw ok , possibility 9kw, but at that level I'd have to electrically interlock the heater to the overall system load. I could do that but it's a pain

All appliances are modern 2014-2015

Dardania

Sounds like you might scrape by with the loads so...one can never be sure

I went down a similar ish road to yourself - removed hot water cylinder (needed the space in a small house) and put electrically heated taps & shower in place, all fed from mains water pressure.

the shower is I think 7.5kW or possibly 8.5kW - we don't have massive pressure (the thing occasionally shuts down due to low pressure from incoming supply) but when it is working, we have a relatively okay flow & temp. If you're thinking about moving the heat source away from the point of use, you would need to consider heat loss / dead leg in the pipework between, which leads me to suggest that the 9.5kW heater may be best to plan for rather than 7kW (unless of course you can access the pipework and ensure it's well insulated)

Strictly speaking local councils don't like people to connect directly to mains for appliances, and like to have everything bar the kitchen sink fed from 24 attic storage, with booster pumps if necessary. I say this in a do as I say rather than do as I do of course! But you should consider the impact of a water outage

Will your usage be significant? The cost comparison, including both OpEx & CapEx with a combi boiler would be interesting to do, bearing in mind a contemporary combi boiler may be able to condense more readily than a system boiler when heating the house, with weather compensation & reduced flow/return temps to radiators (as it doesn't have to worry about hitting min 65C/70C temp to satisfy water storage temp requirements...)

BoatMad

Tks

I read about oil fired condensing issues and I'm concerned there is too much smoke and mirrors.

Capital costs , around 200-250 euros for 7 kW. I'll do all plumbing myself , electrical feed is already there 10 sqmm

Not sure about 9kw. Leaves about 3kw, ( not factoring in power factor )

I have good continuous pressure , not worried about water outages, these are very rare these days , and remember I still have cold water tank , it's just the hot water clyinder I'm removing

Dardania

BoatMad wrote: »

Tks

I read about oil fired condensing issues and I'm concerned there is too much smoke and mirrors.

Capital costs , around 200-250 euros for 7 kW. I'll do all plumbing myself , electrical feed is already there 10 sqmm

Not sure about 9kw. Leaves about 3kw, ( not factoring in power factor )

I have good continuous pressure , not worried about water outages, these are very rare these days , and remember I still have cold water tank , it's just the hot water clyinder I'm removing

oil fired I tend to agree with you (both about smoke and mirrors, and how electricity would be attractive in comparison with) - I considered an oil boiler for a refurbishment project, and the combi boiler domestic hot water was done by an internal store, which seemed disingenuous.

Still: it's about half the cost to heat water with oil than electricity: http://www.seai.ie/Publications/Statistics_Publications/Fuel_Cost_Comparison/Domestic-Fuel-Cost-Comparisons.pdf so be aware of that if you're heavy hot water users.

Best of luck if you do it!

Wearb

There is nothing complicated or spurious about oil condensing boilers, as has been suggested by the last two posts. It is a tried and trusted technology. It is recommended by everyone who understands how it works. Can any of you outline a situation where a condensing oil boiler would not perform better than a standard efficiency oil boiler.

I am not writing this to have a go, but to correct the record for other readers of this thread.

Dardania

Wearb wrote: »

There is nothing complicated or spurious about oil condensing boilers, as has been suggested by the last two posts. It is a tried and trusted technology. It is recommended by everyone who understands how it works. Can any of you outline a situation where a condensing oil boiler would not perform better than a standard efficiency oil boiler.

I am not writing this to have a go, but to correct the record for other readers of this thread.

My point is RE how the combi boiler effect is achieved with combi oil boilers, through the use of an internal store. One still has an internal store of water, possibly on a separate time clock, with the requisite standing energy losses of same. So you can have instantaneous, but you may have energy losses due to the standing water heat loss in the oil combi boiler.

Additionally, with condensing oil boilers, it seems they don't modulate as one would expect with a gas boiler. See here: http://www.boards.ie/vbulletin/showpost.php?p=81673304&postcount=27
so weather compensation becomes less easy / less efficient - the overall system efficiency one can achieve is less than what you expect from a gas condensing boiler... it's fine if your demand is contant, but what happens if you have TRVs changing load requirement as they close down - does the boiler start getting into on/off control rather than throttling back?

please, by all means, set me straight for the sake of education. I find the concept of condensing boilers fascinating, particualrly how they operate in practice, but must confess that with oil, I see some asterixes which give me cause for pause

you want to compare against conventional oil boilers - they're obviously more efficient, but still not perfect when compared against other means of heating water (be that LPHW or DHW)

Wearb

Smoke and mirrors and asterixes! All very ambiguous put downs of the technology, that may leave readers doubting the value of having an oil condensing boiler.

Yes there is always going to be losses with stored hot water, but that is no reason to cast doubt on the condensing technology. And to suggest (correctly) that modulation is better than non modulation, is not a reason to cast doubt on the technology either.
It IS ok to say that modulation will give you better efficiencies, but that doesn't mean that non modulating boilers are in anyway spurious.
I also agree with you re weather compensation, BUT yet again, it doesn't mean that condensing oil boilers are not better than standard efficiency ones.

Re the link posted; I think it goes a long way in explaining my point about condensing oil boilers.

Dardania

Wearb wrote: »

Smoke and mirrors and asterixes! All very ambiguous put downs of the technology, that may leave readers doubting the value of having an oil condensing boiler.

Yes there is always going to be losses with stored hot water, but that is no reason to cast doubt on the condensing technology. And to suggest (correctly) that modulation is better than non modulation, is not a reason to cast doubt on the technology either.
It IS ok to say that modulation will give you better efficiencies, but that doesn't mean that non modulating boilers are in anyway spurious.
I also agree with you re weather compensation, BUT yet again, it doesn't mean that condensing oil boilers are not better than standard efficiency ones.

Re the link posted; I think it goes a long way in explaining my point about condensing oil boilers.

That whole thread was very informative indeed...

I think the asterixes and spurious (you were the only one to use that word!) views around oil condensing boilers come about because gas boilers were more widely known for it prior to oil boilers. So everyone came with an expectation from the gas world, and applied to oil...

If you were to compare a condensing gas boiler with a condensing oil boiler, what would you recommend? Imagine the capital costs for both are the same (cost of oil boiler + tank = cost of gas boiler + BGE connection), and a home owner needed to just choose 1. And why would you make that recommendation?

Wearb

I never suggested that you used the word spurious, so that is just a red herring. However I am not going to ruin this thread by being pedantic about it.

If I were to make recommendations at today's prices, I would go with oil. However, if I were to go on historical prices, I would recommend mains gas. I would run a mile from bulk (tanker) gas. I have posed extensively on this topic before, so I will be brief.

People sometimes get too hung up on whether an oil boiler is condensing all the time or not. There are great efficiencies to be had from it either way. Good insulation and a properly designed system, will mean that there will be very little difference between gas and oil, excepting -of course- the difference in price per delivered Kw. (there being substantially less energy in a litre of gas, compared to oil)

Your previous link to an older thread, explains all of this very well. As was pointed out; the flue gas temperature tells the whole story.

Sleeper12

I hate to burst your bubble but if you are thinking that you will get hot mains pressure instantly you'll be very disappointed. Think of this instant heater as an electric shower (both are around 9kw). At 9kw you can only get around 3 to 5 litres per minute, just like the electric shower you have at the moment. It doesn't matter how powerful your mains pressure is, you have to slow it down for it to be heated up. 3 litres per minute in the winter is about half the pressure that you already have at your kitchen sink.
I'd look at a combi boiler or stick with the hot press cylinder.

hatchman

Is there any truth to what is stated on this site ? condensingboiler.org.uk sorry cant post the full web address !

Think this may have been discussed before. Just briefly read another thread on it.

BoatMad

Sleeper12 wrote: »

I hate to burst your bubble but if you are thinking that you will get hot mains pressure instantly you'll be very disappointed. Think of this instant heater as an electric shower (both are around 9kw). At 9kw you can only get around 3 to 5 litres per minute, just like the electric shower you have at the moment. It doesn't matter how powerful your mains pressure is, you have to slow it down for it to be heated up. 3 litres per minute in the winter is about half the pressure that you already have at your kitchen sink.
I'd look at a combi boiler or stick with the hot press cylinder.

Thanks for that

Well , I notice the 3kw units are stating 4-5 litres a minute. My current triton is better then that ( it's not pumped ) , if I could get its rate from my kitchen or bathroom sink , I d be happy. I have no need for any more hot water then hand washing or rinsing a few glasses. In fact we went through this last summer and never generated any sink hot water at all !

I'm just finished installing radio controlled networked TRVs connected to a raspberry pi , so I'll wait and see how that's pans out. The ecomonics of hanging boiler seem very dodgy , with a considerable break even period.

Worst case I'll go for super insulated water store and night rate and remove my existing tritons be use a whole house water pump on the hot water

Dardania

Wearb wrote: »

I never suggested that you used the word spurious, so that is just a red herring. However I am not going to ruin this thread by being pedantic about it.

If I were to make recommendations at today's prices, I would go with oil. However, if I were to go on historical prices, I would recommend mains gas. I would run a mile from bulk (tanker) gas. I have posed extensively on this topic before, so I will be brief.

People sometimes get too hung up on whether an oil boiler is condensing all the time or not. There are great efficiencies to be had from it either way. Good insulation and a properly designed system, will mean that there will be very little difference between gas and oil, excepting -of course- the difference in price per delivered Kw. (there being substantially less energy in a litre of gas, compared to oil)

Your previous link to an older thread, explains all of this very well. As was pointed out; the flue gas temperature tells the whole story.

To tell the truth you've not convinced me on the merits of oil vs natural gas. I did ask why you would make your recommendation.
I think we'll both stay entrenched in our views, but rest assured when the situation arises that oil could suit (no nearby mains gas supply) I'll bear it in mind!

hatchman wrote: »

Is there any truth to what is stated on this site ? condensingboiler.org.uk sorry cant post the full web address !

Think this may have been discussed before. Just briefly read another thread on it.

Elements of it seem correct - the dry & wet heat exchange bits are beyond my knowledge - but what it does make clear is that your flow & return temps have to be correct to get condensing working. Which goes back to the radiator sizing versus the heat loss of the room.

BoatMad wrote: »

Thanks for that

Well , I notice the 3kw units are stating 4-5 litres a minute. My current triton is better then that ( it's not pumped ) , if I could get its rate from my kitchen or bathroom sink , I d be happy. I have no need for any more hot water then hand washing or rinsing a few glasses. In fact we went through this last summer and never generated any sink hot water at all !

I'm just finished installing radio controlled networked TRVs connected to a raspberry pi , so I'll wait and see how that's pans out. The ecomonics of hanging boiler seem very dodgy , with a considerable break even period.

Worst case I'll go for super insulated water store and night rate and remove my existing tritons be use a whole house water pump on the hot water

If you're contemplating super insulated water store, with pumped supply from it, why not heat the water using the oil boiler? Circa ~80% of the night rate cost per kWh, and can reheat during the day if you want evening showers etc. - if you can get wireless zone valve in to control?

The pump is a PITA of course, but one can get unvented DHW cylinders for mains connection (and of course appropriate safety devices, as pressurised water + 65C turns to steam if released to ambient pressure in a hurry)

John T Carroll

BoatMad wrote: »

Thanks for that

Well , I notice the 3kw units are stating 4-5 litres a minute. My current triton is better then that ( it's not pumped ) , if I could get its rate from my kitchen or bathroom sink , I d be happy. I have no need for any more hot water then hand washing or rinsing a few glasses. In fact we went through this last summer and never generated any sink hot water at all !

I'm just finished installing radio controlled networked TRVs connected to a raspberry pi , so I'll wait and see how that's pans out. The ecomonics of hanging boiler seem very dodgy , with a considerable break even period.

Worst case I'll go for super insulated water store and night rate and remove my existing tritons be use a whole house water pump on the hot water

In the winter, the mains supply water temperature can be down to 6C, if you assume say a required shower/hand wash temperature of 45C then you will get a (instantaneous) flowrate of 0.37 LPM/KW, so 3Kw will give you 1.1 LPM, 7 Kw will give you 2.6 LPM which is a very poor showering flowrate especially if you have an existing 9.5 kw electric shower which gives 3.5 LPM, just barely aqequate in the winter. The mains or pumped has nothing to do with the actual heating of the water, you would use a pumped shower if the mains pressure is too low to give you the required flowrate reliably.

BoatMad

John T Carroll wrote: »

In the winter, the mains supply water temperature can be down to 6C, if you assume say a required shower/hand wash temperature of 45C then you will get a (instantaneous) flowrate of 0.37 LPM/KW, so 3Kw will give you 1.1 LPM, 7 Kw will give you 2.6 LPM which is a very poor showering flowrate especially if you have an existing 9.5 kw electric shower which gives 3.5 LPM, just barely aqequate in the winter. The mains or pumped has nothing to do with the actual heating of the water, you would use a pumped shower if the mains pressure is too low to give you the required flowrate reliably.

My current unpumped instant shower unit produces sufficent flow, even in winter. If I could duplicate that at all the water outlets in the house I'd be happy. That's my goal.

BoatMad

John T Carroll wrote: »

In the winter, the mains supply water temperature can be down to 6C, if you assume say a required shower/hand wash temperature of 45C then you will get a (instantaneous) flowrate of 0.37 LPM/KW, so 3Kw will give you 1.1 LPM, 7 Kw will give you 2.6 LPM which is a very poor showering flowrate especially if you have an existing 9.5 kw electric shower which gives 3.5 LPM, just barely aqequate in the winter. The mains or pumped has nothing to do with the actual heating of the water, you would use a pumped shower if the mains pressure is too low to give you the required flowrate reliably.

My current unpumped instant shower unit produces sufficient flow, even in winter. If I could duplicate that at all the water outlets in the house I'd be happy. That's my goal.

BoatMad

If you're contemplating super insulated water store, with pumped supply from it, why not heat the water using the oil boiler? Circa ~80% of the night rate cost per kWh, and can reheat during the day if you want evening showers etc. - if you can get wireless zone valve in to control?

The pump is a PITA of course, but one can get unvented DHW cylinders for mains connection (and of course appropriate safety devices, as pressurised water + 65C turns to steam if released to ambient pressure in a hurry)

Yes I've looked at unvented pressurised DHW systems. The cost and payback period are significantly greater then adding a single instant heater.

There are many solutions , I'm looking for the combination of lowest cost per given functionality( arnt we all I hear u say )

John T Carroll

BoatMad wrote: »

My current unpumped instant shower unit produces sufficient flow, even in winter. If I could duplicate that at all the water outlets in the house I'd be happy. That's my goal.

Fair enough, the 9.5 Kw (or equivalent power to your existing Triton ) unit (link in some other post) would seem to fit the bill for you. This unit would need to have electric/electronic temperature control because you might only need a trickle of hot water to wash your hands or whatever whereas 9.5 kw will give a minimum flowrate of say 3.5 LPM, I assume that it has temperature control but I would certainly ask them a few questions before investing.

Dardania

BoatMad wrote: »

Yes I've looked at unvented pressurised DHW systems. The cost and payback period are significantly greater then adding a single instant heater.

There are many solutions , I'm looking for the combination of lowest cost per given functionality( arnt we all I hear u say )

John T Carroll wrote: »

Fair enough, the 9.5 Kw (or equivalent power to your existing Triton ) unit (link in some other post) would seem to fit the bill for you. This unit would need to have electric/electronic temperature control because you might only need a trickle of hot water to wash your hands or whatever whereas 9.5 kw will give a minimum flowrate of say 3.5 LPM, I assume that it has temperature control but I would certainly ask them a few questions before investing.

What about heat lost in the pipework?

John T Carroll

Dardania wrote: »

What about heat lost in the pipework?

Obviously a factor but once up to temperature then flowrates would be as calculated. First thing in the morning, I have measured 3 litre "waste" before kitchen sink is up to full temperature of say 60C (from upstairs hot water cylinder). If then frequent use is made of tap then not much run off to get up to temperature. Of course the unit could be located downstairs. On my recommendation recently, a relative who just needs hand wash facility downstairs installed a 5 litre undersink heater which does the job fine for her. There are various manufacturers of sink (3 Kw) mounted units but as there is a lot of switching going on with them, I thought they may be a bit troublesome so didn't recommend that, has anyone any info on these?.

BoatMad

John T Carroll wrote: »

Fair enough, the 9.5 Kw (or equivalent power to your existing Triton ) unit (link in some other post) would seem to fit the bill for you. This unit would need to have electric/electronic temperature control because you might only need a trickle of hot water to wash your hands or whatever whereas 9.5 kw will give a minimum flowrate of say 3.5 LPM, I assume that it has temperature control but I would certainly ask them a few questions before investing.

indeed I have sent an email to the manufacturers just doing that

BoatMad

John T Carroll wrote: »

Fair enough, the 9.5 Kw (or equivalent power to your existing Triton ) unit (link in some other post) would seem to fit the bill for you. This unit would need to have electric/electronic temperature control because you might only need a trickle of hot water to wash your hands or whatever whereas 9.5 kw will give a minimum flowrate of say 3.5 LPM, I assume that it has temperature control but I would certainly ask them a few questions before investing.

What I would really like is to divert the 9.5kw capable cable and feed all the hot water from a 9,5Kw unit mounted in the hot press. This would include the existing triton which would be decommissioned. It would also then provide hot water to the two washing basins in the two bathrooms, and the downstairs guest shower and kitchen sink , in effect the whole house

None of these systems are needed in parallel , even if they were to be turned on together I presume either the flow rate would fall or the temperature would fall, either being acceptable and cured by shouting !

Dardania

John T Carroll wrote: »

Obviously a factor but once up to temperature then flowrates would be as calculated. First thing in the morning, I have measured 3 litre "waste" before kitchen sink is up to full temperature of say 60C (from upstairs hot water cylinder). If then frequent use is made of tap then not much run off to get up to temperature. Of course the unit could be located downstairs. On my recommendation recently, a relative who just needs hand wash facility downstairs installed a 5 litre undersink heater which does the job fine for her. There are various manufacturers of sink (3 Kw) mounted units but as there is a lot of switching going on with them, I thought they may be a bit troublesome so didn't recommend that, has anyone any info on these?.

Fitted them a few months ago - noted comments on the thread that recommended them to me:

http://www.boards.ie/vbulletin/showpost.php?p=96072616&postcount=28

THis type: http://www.watersave.ie/product/eht10-electric-hot-water-tap/

John T Carroll

BoatMad wrote: »

What I would really like is to divert the 9.5kw capable cable and feed all the hot water from a 9,5Kw unit mounted in the hot press. This would include the existing triton which would be decommissioned. It would also then provide hot water to the two washing basins in the two bathrooms, and the downstairs guest shower and kitchen sink , in effect the whole house

None of these systems are needed in parallel , even if they were to be turned on together I presume either the flow rate would fall or the temperature would fall, either being acceptable and cured by shouting !

Thats fine but my only concern would still be if you only wanted say a hot water flowtate of say 0.5 LPM, how does the heater cater for this?, in an electric shower if one reduces the flowrate too much, a safety stat will open and close so you will get hot water one minute and cold water the next, obviously on the shower you just adjust the flowrate to avoid this happening but this would be very inconvenient/wasteful on a kitchen tap.

John T Carroll

Dardania wrote: »

Fitted them a few months ago - noted comments on the thread that recommended them to me:

http://www.boards.ie/vbulletin/showpost.php?p=96072616&postcount=28

THis type: http://www.watersave.ie/product/eht10-electric-hot-water-tap/

Thanks for that, its interesting the 8 to 10 sec delay in getting hot water but if you think about it its almost exactly a "mini" electric shower where one also has to wait around 10 secs for hot water.

BoatMad

John T Carroll wrote: »

Thats fine but my only concern would still be if you only wanted say a hot water flowtate of say 0.5 LPM, how does the heater cater for this?, in an electric shower if one reduces the flowrate too much, a safety stat will open and close so you will get hot water one minute and cold water the next, obviously on the shower you just adjust the flowrate to avoid this happening but this would be very inconvenient/wasteful on a kitchen tap.

can the thermostat in the heater not modulate to match the flow rate ?

John T Carroll

BoatMad wrote: »

can the thermostat in the heater not modulate to match the flow rate ?

Hopefully yes but its not as simple as storage tank temperature control as this is simply a electro/mechanical on/off device (thermostat) with a hysteresis of around 5C. The tankless heater control would have to switching on/off every few secs to maintain the required temperature and would probably be electronic in nature.

John T Carroll

BoatMad wrote: »

can the thermostat in the heater not modulate to match the flow rate ?

Just found another bit of info re that heater. Theres is no thermostat, just a overtemp stat that must be reset at the panel. It has 3 power settings, High, Medium and Low. It also has a minimum flow switch which interrupts the power if the flowrate is too low. All in all a bit inflexible in my opinion, but would/should certainly work when correctly set up.

BoatMad

John T Carroll wrote: »

Just found another bit of info re that heater. Theres is no thermostat, just a overtemp stat that must be reset at the panel. It has 3 power settings, High, Medium and Low. It also has a minimum flow switch which interrupts the power if the flowrate is too low. All in all a bit inflexible in my opinion, but would/should certainly work when correctly set up.

that wont work with thermostatic mixers so , thats no good for me

John T Carroll

BoatMad wrote: »

that wont work with thermostatic mixers so , thats no good for me

The storage route is probably the best route as you suggested yourself, night rate electricity + well insulated cylinder if you are intent on going down the electric road.

BoatMad

John T Carroll wrote: »

The storage route is probably the best route as you suggested yourself, night rate electricity + well insulated cylinder if you are intent on going down the electric road.

yes confined by the manufacturer , not a solution , will have to investigate a unvented mains pressure hot water system