There's clever !

[Harry Bloomfield]

 

[ericmark]

I think the iboost+ can have two immersion heaters connected to it, and it does heat top first then bottom, but I think in the main there are no change over contacts on British immersion heaters, so it does not heat up as he describes.

In the main the two immersion heaters have bottom connected to off-peak, and top to peak supply, and the bottom one is set to a higher temp to the top one, so in the main the top one will not run, it will only run when you have used all off-peak water.

In the beginning the idea was only heat whole tank for a bath, what was before we insulated the tank so well.

But other than with the iboost+ I do not think we heat the water as he shows. And the iboost+ uses DC and a varying amount of power, so although my immersion heater may be rated at 3 kW, I may only be using 200 watt to heat the water, it only uses excess solar power, and is only a gain if you don't get payment for exported power, as in the main off-peak is lower cost to export payment, so better to simply heat the DHW with off-peak, and then export the solar power.

I would have to read the iboost+ instructions again, I do know two 3 kW immersion heaters only ever use 3 kW not 6 kW but not really looked as to how it decides which to heat when.

But if you really want to see a clever method, then look at the Willis system, with the immersion outside of the main tank, and heating the tank from top down, not bottom up, but in main land UK seems we are too "tick" to work out how to do that. Seems they do use it with solar, but I would not install it in Wales, as to find a plumber who knows how to install it, would be hard.

 

[Harry Bloomfield]

I think the iboost+ can have two immersion heaters connected to it, and it does heat top first then bottom, but I think in the main there are no change over contacts on British immersion heaters, so it does not heat up as he describes.

Domestic electrics, was never something I was involved with, so I had no idea whether it might be used in the UK.

But if you really want to see a clever method, then look at the Willis system, with the immersion outside of the main tank, and heating the tank from top down, not bottom up, but in main land UK seems we are too "tick" to work out how to do that. Seems they do use it with solar, but I would not install it in Wales, as to find a plumber who knows how to install it, would be hard.

If I had a use for one, then I would be inclined to DIY install.

 

[ericmark]

The Willis system means time = amount of DHW, the longer it runs, the more you have, so having a time clock for the immersion heater then makes a lot of sense, however I would want to visit Ulster again, and talk to people who use the system, as never talked to anyone with it fitted.

The tank I have only has one immersion heater, I can't see the gains with a second immersion heater will be worth the expense. The picture shows how wired.

Dual Immersion Heater Operation
The Solar iBoost+ automatically detects when two immersion heaters are connected.
As hot water is drawn from the upper part of the tank, it is important the heaters are connected as shown so that the Solar iBoost+ can automatically give heating priority to the top heater.
Excess generation is diverted to the top heater until temperature is reached and the heater thermostat opens. Solar iBoost+ then automatically switches to the lower heater to continue to divert excess generation until the lower heater is also satisfied and ‘Water Tank HOT’ is displayed.
When diverting to the lower heater, the Solar iBoost+ will periodically (every 15 minutes)
switch to the top heater and the cycle of heating begins again. This maintains the temperature in the upper part of the tank.
An indication of the current heater being supplied is shown on the ‘Heating by Solar’ display.
This operating mode is the same whether diverting excess generation or in boost function.

Not quite the same as the USA system, but it does the basic same thing.

However, other than iBoost+ and Willis, the original idea of two immersion heaters was bath/Sink, so you only heated the top of the tank if not going to have a bath, at that time lagging was rather poor, latter when the Economy 7 arrived, we started using bottom for off-peak, and top for peak, and if off-peak set warmer than peak, the upper immersion would only work if you were likely to run out of hot water anyway.

But control methods did change over the years, as we lost the white meter and other methods of switching between off-peak and peak were used, and this included methods to ensure both not switched on together. The problem was as the methods to control off-peak changed, the timers also changed, and there have been problems when wrong timers used.

I was rather surprised, I had been told for years, gas is cheaper than electric, and I know my daughter has a hot coil and an immersion heater, and the hot coil was set to higher temperature to immersion heater, so as long as boiler running, the immersion heater did nothing, to save money she turned the gas temperature sender down, and this in turn caused the electric to run, and a high bill.

So in this house, the electric was considered as a back-up, only to be used, if short of oil. Until, that is, when solar fitted, before solar by experiment we found running the boiler 4 times a week, with ½ hour slots (although only ran for 20 minutes) gave us enough hot water in the summer, we have a C Plan and 20 kW oil boiler, so around 25 kWh per week. When iboost+ fitted went to heating with the immersion heater, OK only top of tank heated, but only used for handwashing. And the iboost+ logs how much energy used today, yesterday, and over the last week, total for week between 2.5 kWh and 3 kWh, and our oil use went really down.

So at least with my house, using electric cheaper than oil, but not the case with my daughter, I must ask her about it, at the time, grand children were little babies, now both in University, only seems like last year.

 

[Harry Bloomfield]

Not quite the same as the USA system, but it does the basic same thing.

The clever part of the USA system, is that it is completely automatic. It heats just the top part with the upper element quite quickly, providing a small amount of water at the top, at temperature first - then go on to heat the bulk of the water, once that is at temperature. I'm always impressed, by ridiculously simple ideas, which solve issues. I wonder why we never see that, in the UK?

 

[ericmark]

I wonder why we never see that, in the UK?

Have you used stored domestic hot water for a shower? I have in mother old house, she had a power shower, so it used a lot of water, and a standard 40 gallon cylinder, which never ran out, so why bother with two immersion heaters? This was the traditional UK immersion heater, 1950's the idea was only heating the top cost less. And with so little insulation that was correct.

My brother-in-law had this system

it shows a single tank, but in reality there were two, likely 100 gallons each, and to take the weight, the floor was far heftier than normal, so OK as a new build, but not some thing which could be added latter.

However the whole idea is to have a tank to bring together many forms of heating, the DHW passes through the hot coil, not taken from the tank, so it is at cold water pressure, without pressuring the tank, as if pressurised then needs annual test. So his wood burner, LPG, solar panels, and mains electric could all heat the house and provide DHW.

He had daughters in Germany, and could turn down heating before visiting them, then turn it back up at the air port when he landed, and house toasty warm when he got home, all from the solar, storing energy as hot water far better than batteries. But down side is house has to be designed from word go to do that, can't add it latter.

But his tank was way over size, with no hot coils, if we had no gas or oil heating in the UK, we would likely have off-peak, so looking for a different design, his design was not really suited to his off-peak supply.

 

[Harry Bloomfield]

Have you used stored domestic hot water for a shower?

At home, no. We have a 9.5Kw electric shower, and our immersion heater, is only there for emergency use, should the gas boiler fail.

It wasn't even connected until recently, because I had diverted its supply cable, to other uses. Recently, when Octopus offered an irregular hours worth of free power, I decided to reconnect it, so it could be made use of, during that free hour.

 

[ericmark]

We have two options with twin immersion heaters extra water or use of off-peak, unless there are room constraints, if we want more capacity we would normally fit a larger tank, he does not seem to have a problem with room so why not simply use a bigger tank. A larger tank would mean he has more ability to store energy, I have been considering a longer immersion heater, to store more energy.