Immersion heater regulator

[glbell]

Hi,

Is there such a thing as an immersion heater regulator.
I have no electrical experience but here is the question.

Usual topic of diverting PC electricity to hot water.

Instead of changing the 3kw element to a 1kw as most do can you have a regulator (something like a dimmer switch) where you can put the immerser on when you are producing 1kw say WITHOUT then using 2kw off the grid (as would happen) this is acheived through regulating the power to the element - is that possible.

this means when you have 3kw you can use it to quickly heat the water but when you only have 1kw it just takes longer.

At present we are wasting time switching on and off (aint sustainable) so its either a 1kw element or some sort of regulator.

Any thoughts please

 

[telectrix]

why not use a timer?

 

[Gary K]

Do a search for immersion heater, you will find loads of threads on the subject

 

[madmurg]

Check out this page
Solar Energy Management | OpenEnergyMonitor

 

[fredfred2]

Instead of changing the 3kw element to a 1kw as most do can you have a regulator (something like a dimmer switch) where you can put the immerser on when you are producing 1kw say WITHOUT then using 2kw off the grid (as would happen) this is acheived through regulating the power to the element - is that possible.

Any thoughts please

Yeah I think this thing works exactly like you describe, but I don't know who makes or sells it. I'm looking for the same thing.
-fred

 

[Worcester]

Check out this thread: http://www.electriciansforums.net/s...ral-heating-linked-monitoring.html#post551986

 

[ian]

You could try one of these, just installed one, seems to be working ok, EMMA SP15 installed & saving money within an hour « Coolpower Products Blog

Ian

 

[pww]

Before going ahead with any of this consider:
How much are you REALLY going to save each year? A 4kw, south facing system is maybe going to produce £400 worth of exportable electricity a year at 3.2p per unit. This export price is actually very similar to the unit price of the gas you would in theory be replacing via solar. Given that you are probably going to use say 50% of the solar electricity elsewhere anyway (a good assumption since anyone considering adding immersion usage is going to maximise use throughout the house anyway), you are left with at most maybe £100 worth of usable electricity to power said immersion. I understand that units such as Emma - which regulate the immersion current avoiding inadvertant grid energy use - cost at least £1000, plus fitting etc. Now one must assume also a lifespan similar to an inverter, perhaps 10/15 years.
To my mind you would only just about save enough in gas costs to pay for the unit before it needed replacing. Perhaps my thinking is flawed. Certainly if you could fit such a system for say £200 it makes much more sense, but the systems I've seen at those prices appear to be too simple and liable to actually cost you in inadvertant grid use.

 

[Scobo]

I've just bought one of these ... 3 kW Immersion Heater Power Reducer - Convert 3 kW Heater - 1.5 kW - Solar Power | eBay
Our immersion uses 2.5kw so this will reduce the power to about 1.2kw.
Im also going to fit a cheap timer switch to have the immersion come on for a few hours in the afternoon when we generate the most power.
Sure, it's not fully automatic and will not be totally free on really cloudy days but the parts will cost less than £70.

 

[pww]

I've just bought one of these ... 3 kW Immersion Heater Power Reducer - Convert 3 kW Heater - 1.5 kW - Solar Power | eBay
Our immersion uses 2.5kw so this will reduce the power to about 1.2kw.
Im also going to fit a cheap timer switch to have the immersion come on for a few hours in the afternoon when we generate the most power.
Sure, it's not fully automatic and will not be totally free on really cloudy days but the parts will cost less than £70.

You have a 2.88kw system in scotland, peaking at ?2.5kw for a couple of months. Average output more like 1.6kw. 0.6kw background electricity usage leaving 1kw spare. Sorry but it just doesn't make sense to use even a derated to 1.2kw immersion system in this set up. You will end up replacing heating water from gas at 3p unit to grid electric (more often than not) at 13/14p per unit (and heating less water less efficiently as well).

 

[Scobo]

You have a 2.88kw system in scotland, peaking at ?2.5kw for a couple of months. Average output more like 1.6kw. 0.6kw background electricity usage leaving 1kw spare. Sorry but it just doesn't make sense to use even a derated to 1.2kw immersion system in this set up. You will end up replacing heating water from gas at 3p unit to grid electric (more often than not) at 13/14p per unit (and heating less water less efficiently as well).

Actually, if you check our output on PVoutput you'll see our system has been peaking at between 2 to 2.7kw since March and were only using around 200 watts when we're out during the week.
In any case, it's not so much about the financial saving for us as being able to switch off our boiler to save on wear & tear during the spring/summer.

 

[petex2416]

I have been watching this and the other threads regarding using solar pv and immersions with interest. As a company we seriously looked into offering such a system to our customers, using a unit that varied the voltage going to the immersion dependent on the output of the solar pv - the only way we could see of guaranteeing that any water heated was being done so for free. But by the time we worked out the cost of installing (factoring in any additional plumbing etc) and the actual savings per year (about £60) it just was not a viable proposition. By the time you had paid back the initial cost, the unit would probably have needed replacing. An unscrupulous salesman could probably have spun it into an attractive addon, but that was not for us.
Simple truth is that gas remains so much cheaper than electricity that taking the risk of using an immersion via a simple system, and ending up heating water electrically at 4 times the gas unit price makes little sense.
If however you do not have gas then the figures might well stack up better...

 

[Worcester]

Yep, however we are on oil. Every summer we switch it off and use the immersion heater anyway, so a control of this sort makes absolute sense, i.e. to control the immersion when excess is available, and then if nescessarily boost with paid electrcity at the end of the day (we pay 9.2p/kWh inc VAT for our leccy)

 

[FB.]

Before going ahead with any of this consider:
How much are you REALLY going to save each year? A 4kw, south facing system is maybe going to produce £400 worth of exportable electricity a year at 3.2p per unit. This export price is actually very similar to the unit price of the gas you would in theory be replacing via solar. Given that you are probably going to use say 50% of the solar electricity elsewhere anyway (a good assumption since anyone considering adding immersion usage is going to maximise use throughout the house anyway), you are left with at most maybe £100 worth of usable electricity to power said immersion. I understand that units such as Emma - which regulate the immersion current avoiding inadvertant grid energy use - cost at least £1000, plus fitting etc. Now one must assume also a lifespan similar to an inverter, perhaps 10/15 years.
To my mind you would only just about save enough in gas costs to pay for the unit before it needed replacing. Perhaps my thinking is flawed. Certainly if you could fit such a system for say £200 it makes much more sense, but the systems I've seen at those prices appear to be too simple and liable to actually cost you in inadvertant grid use.

While I generally agree with your comment, I thought that:

1.
Due to thermal losses (into the air in the boiler cupboard and into the atmosphere from hot exhaust gases) I thought that rather than about three-fold difference in price for the same amount of usable heat from electric v gas, I thought it was in the 1.7x range. So spend 12p on electric or 7p on gas, for the same amount of usable heat.

2.
The boiler and central heating pump also require a few hundred watts of electric power (plus wear-and-tear).

3.
My boiler (fitted by previous owners) is under-sized for my house. It has to run non-stop in winter to keep the house at 21'C and we often have to resort to backup heating and it is unlikely that the boiler would be able to heat the hot water while already struggling to heat the house. The poor boiler has to work so hard already that it occasionally shuts down from overheating due to running at maximum for hours on end in order to keep the house vaguely warm (and that's even if I've just bled the radiators). A lot of people complain that their central heating isn't up to the job too.
To fit a new boiler would cost ££££, as would fitting additional stand-alone gas heating. Depending what comes of the RHI, I might consider other heating options to replace the undersized boiler.

 

[TechyTim]

As explained in other posts on the main Solar PV thread, although cost of gas is usually 3p to 4p, the cost of heat to the hot water is much higher as the losses in pipework and boiler cycling are significant when heating hot water only.
From my days in Britsh Gas R&D, I estimate actual cost is closer to 7p with a 60% overall efficiency and annual saving in region of £50 to £100.
I am marketing the SolarHeat controller which doesn't try to vary the output but simply switches on the immersion when the output exceeds 2.5kW, and even allowing for a small amount of import can give worthwhile savings.