Want more water heated with electric.

[ericmark]

The immersion heater is pictured here, it seems it only heats the top of the tank, and if there is no sun on a day, I run out of hot water, but with the central heating I get enough hot water to last around 4 days, powered from an iboost+ can I heat more hot water?

And will that mean just thermostat change, or whole immersion heater change?

 

[Roddy Young]

The thermostat is set to about 30 degrees in your photo. Why not raise it to 50 degrees. Then you could mix with cold in your shower or bath - it would "go further" that way.

 

[fourtytwo]

The thermostat is set to about 30 degrees in your photo. Why not raise it to 50 degrees. Then you could mix with cold in your shower or bath - it would "go further" that way.

Absolutely I noticed that too.
I use solar to heat my hot water and the stat is set to 60C (kills bugs I believe).
30C sounds like a bio brewer, in fact my beer heater is about 25C the yeast loves it.

 

[ericmark]

It is an old photo, I have adjusted the temperature to be as hot as it can without tripping the reset. But the amount of hot water means a couple of dull days, and we run out of DHW.

 

[Johntheo5]

There's a few inherent problems with top mounted immersions/thermostats.
One is element length, if the cylinder has indirect heating (cylinder coil) then the element can't bee too long as it may foul the coil, another problem is the stat length, the stat length is often much shorter than the element length resulting in element not switching back in until a fair amount of hot water is drawn off. Even if the stat is the full length of the element then from say a fully heated cylinder to 65C then the stat will not switch in until probably ~ 25% of the HW has been drawn off as the stat is measuring the average water temperature, so a 200L cylinder with the element heating 180L may mean that it doesn't start reheating until another 40/45L is drawn off. You could install a destratification pump or a willis type external element but this brings its own challanges.
I would disconnect and pull out the stat (with power isolated) and measure it, for a start.

 

[fourtytwo]

It is an old photo, I have adjusted the temperature to be as hot as it can without tripping the reset. But the amount of hot water means a couple of dull days, and we run out of DHW.

I wonder what your solar system size is ? Your system gives priority to household loads such as freezers etc so potentially on a dull day your immersion is receiving almost nothing anyway ??

Mine is an overpanelled 1Kw inverter who's priority is water heating and we never run out in the summer but we do have to use the boiler in winter.

I understand the issue with element lengths and that is a problem but I find with the standard top mounted immersion there is a limit to how much water you can heat without dangerously overheating the top of the tank so without major plumbing alterations there is little we can do. I don't fancy the idea of a de-stratification pump although it would not have to run continuously, if I had a choice I would choose a tank with a low mounted horizontal heating element.

 

[ericmark]

As far as I can work out the TS-220 thermostat is 7" long, that is well short of where the top of the hot coil is, yes the Willis system would be ideal, but not sure I could find a plumber in Wales who could install it, in Ulster it would be easy, but people who say they are tick, are normally the reverse.

Solar is around 5 kW maximum, today 11 am exporting 1.3 kW in summer most days the battery fully charges, and we do export, which as it stands we don't get paid for it, so as it stands want to use the iboost+, I will admit once I get payment sorted out, the iboost+ is not the best option, using a simple timer and heating with off peak would be better, as in the main payment for solar is higher than the cost of off peak power.

We have used oil to heat the DHW but there is no tank thermostat, and more to the point, no easy way to get cables down two floors to where the boiler is, so would need some wireless solution. And noted the oil level this year is over half full, one previous years at that time it was below half full, so it seems oil use has gone down a lot by using electric instead, not a surprise, as a lot of 32 mm pipe work to heat between boiler and hot water cylinder.

Winter I can't stop the C Plan heating the DHW, there is no valve to allow the hot coil to be turned off. So immersion heater for summer only. The tank is maintained too hot in winter for the immersion to cut in. Designed that way, which is why @Roddy Young idea would not work, the water is over 65ºC and that I am told is OK for legionnaires to die.

But even in summer we can get 5 days in a run where the solar is not exported, and this means no DHW. The iboost+ does not help, at 3 kW the heater will cause some circulation within the tank, but at 500 watt, that will be a lot less.

I called a plumber to change the thermostat or immersion heater, and he asked for a picture of the immersion heater, so I assume the picture shown when I started the post would tell plumbers if a longer thermostat could be fitted.

 

[Johntheo5]

The thermostat is in a (dry) pocket, all thats required is to isolate the power remove the wires from the stat, pull it up and out, measure it, then get a bit of stiff wire and push it down into the pocket until it bottoms out, measure this. What size cylinder have you got?, a 7 ins stat is normally only used in a top mounted dual element immersion with a sink/bath switch, and it switches the neutral.

 

[fourtytwo]

Solar is around 5 kW maximum, today 11 am exporting 1.3 kW in summer most days the battery fully charges

Ohh so you are charging batteries as well!!
My guess is the priority scheme for the solar energy is something like this
1/ Charge batteries
2/ Service household loads
3/ iBoost (hot water)
4/ Export

So it seems to me your hot water is too far down the list to get any useful power except on very sunny days.
In our household of just two people it requires 3-5Kwh to cover usage and maintain the tank at 65C

Does the iBoost have a display of power delivered (to the heater) ?

 

[ericmark]

The iboost+ display shows either off, amount of power being used seems to start at around 100 watt, up to full 3 kW, and satisfied i.e. the thermostat has opened. However inside the airing cupboard so not some thing one watches all the time. It has a CT coil on the DNO meter tails, and has a selection of settings as to at what point it starts to heat water, think set at 200 watt, so once export hits 200 watt it start to heat the water.

The batteries are after house hold loads most of the day, from 1 am to 5 am they will charge from the off peak, the reason for the 200 watt setting on iboost+ is so the batteries are charged before the iboost+ cuts in. Today is typical in summer the dip in SOC (state of charge of battery) after 5 am until the sun comes out, and DHW is heated with no problems, but a day like this and the water is simply not heated, the battery was only fully charged with the off peak supply, there was no export on that day, so the DHW was not heated. Had to go back to May for this example when the battery not fully charged by solar, so not too often in Autumn and Spring, Summer rare, and Winter central heating running, so Spring and Autumn is only time.

Before the Smart meter and over night charging of the battery, it did happen more, the off peak charging means we start with fully charged battery so even on a poor day as shown, it was 10 pm before we started to use electric at peak rate.

 

[fourtytwo]

Very interesting graphs, it's a shame the tank temperature is missing, are you able to add that ?
At the end of the day you have chosen a battery to absorb most of your surplus power so the only way I can see that there is more surplus to also heat your water is to add more panels (assuming the inverter can cope) as your present system is undersized to do both.
Here is my system on a mid-May day, note it takes till 1pm to fully heat the water!

 

[ericmark]

Yours is also interesting, my iboost+ does not connect to internet, so can't record performance. As far as I am aware, you are today required to have a battery to be allowed to be paid for export, the problem is the rules are changing, when I commissioned it to be fitted, one did not require a smart meter to be paid for export, by time fitted you did.

To be frank the iboost+ was a mistake, today one is paid more for export during the day, to what one pays for the off peak power. But the tariffs seem to be changing week by week. With British Gas I have to pay £75 to leave until April 2025, the off peak tariff I am on is called an EV tariff, but I don't have an EV unless you count my e-bike and mobility scooter, it is for 5 hours, and is far cheaper than the tariff called economy 7 which as one may guess is for 7 hours.

My solar panel info does not exactly match the smart meter info, I will guess due to a number of factors, from the server for solar being in China, to the time in summer, some things are showing UTC others DST so even the smart meter stuff phone app seems to be UTC but meter and in home display show DST so to be sure I start charging battery at 1 am. If I look at today, it shows max usage at 23:30, but time at moment is 22:51. And it shows nothing for early hours, but the solar software shows the normal charging of battery. It says I have used 13p worth of power today 0.22 kWh which does not add up. My tariffs are 8.95p and 31.31p.

My main problem is the time of turning on a tap, to getting hot water, my wife will say there is no hot water, and I will run off some more water and it gets hot, closest tap to cylinder at full bore, takes 20 seconds to start to get warm, 30 seconds to be at temperature wanted to wash hands, but one we don't tend to turn on tap full bore, and after going to loo, one has washed hands in less than 20 seconds, in the back kitchen, we get ½ a bowl of water before we get hot water, front kitchen even more.

There is no lagging on the pipes, and only way to reach them is drop the ceiling, for the central heating pipes in winter, hardly matters, any heat is warming house, be it from radiators or pipes, but summer running the boiler every other day, it runs for 20 minutes before the return water temperature from the hot coil turns it off. The water in tank was not really hot, more heat went into the house than went into the water, we have noted using far less oil now, and water warmer than using CH on a timed run of 30 minutes 4 times a week.

Winter the water is far too hot, but no way to turn it off, only option is turn down boiler temperature which means rooms get too cold, but last house has an instant gas boiler for domestic hot water, that also would fill half a bowl before hot water got to the taps. I was called a Main 7 after over 30 years service one of the two boilers sprung a leak and needed replacing so swapped for a combi boiler but sold house without ever using it, son who bought it, says it is expensive to run, he has no tanks, so can't heat with solar with out huge expense, and father-in-law identical house kept the tanks and fitted solar water heating and it was a complete failure, solar electric work far better to solar water.

 

[fourtytwo]

Hmm so much in there it's hard to comment but one thing struck me straight away and that's where you say you have to have a battery to get paid for export ? First I have heard it, maybe silver tongued salesman selling you a battery lols

I am not impressed by your tariffs, mine is 20.2p flat and I don't have to pay the amortization on an expensive short life battery so I am not sure you are gaining much there. TBH I have a great antipathy to storing large amounts of Kwh in a semi-explosive device anywhere near my house so I would never consider it anyway.

How you use hot water in your house has a lot to do with energy saving awareness, as you say there is a considerable loss every time you run the hot tap from cold, not just in energy but also in water. We try to minimize the times of use and I also managed to insulate some of the hot water pipe runs in the coldest (in winter) parts of the house.

 

[ericmark]

It may not be law, but if the energy companies say new customers to be paid for export need to have a smart meter and battery, than that is what you need, a very small battery 3.2 kWh, but it ticks the boxes.

As to tariff yes want to move, but if I do before April 2025 then I have a £75 penalty clause.

The (in winter) does not seem to make sense, in summer yes, heat in the house in summer is not what I want, in winter it does not matter if heat comes from central heating or DHW pipes, any heat not from CH will mean the TRV's will cause the CH not to heat that part of the house as much, so swings and roundabouts, I have said before in winter the tungsten bulb saves energy, not money as electric costs more than oil, but energy yes, as the inferred output means we can have the room set to a lower temperature and still feel warm, before the demise of the tungsten bulb, CH set at 18ºC all day, after set 18ºC in daylight hours while we were active, and 20ºC at night while less active.

However it seems the politicians want us to spend more money, it helps the economy, however the spend was short lived, as LED lights last longer.

On reflection, or maybe because of this thread where I started to look back on how many times the battery was not fully charged, I realise that water is being heated, again a political issue, for years the standard washing machine was hot and cold fill, but energy ratings resulted in it being hard to comply with a hot fill, all so often the hot water system was used, but not enough hot water used for the hot water to actually reach the machine. However it did draw water from the hot system so pipes were hot for other water use. But think the idea is to get us to use more electricity, so the French government can make more money from the British, as the electric is part nationalised but not our government but French government.

But all I wanted to know was if looking at picture some one could tell me if I could fit a longer thermostat rather than having to empty the airing cupboard and remove the old one and measure with a bit of wire, it seems the answer is no, so it is empty the airing cupboard to find out.

 

[denso13]

But all I wanted to know was if looking at picture some one could tell me if I could fit a longer thermostat rather than having to empty the airing cupboard and remove the old one and measure with a bit of wire, it seems the answer is no, so it is empty the airing cupboard to find out.

It's a two minute job, you were close enough to take a photo, no need to empty the cupboard.