Immersion Heater - PV electricity

[pauldreed]

Haha - those cheap power supplies, battery chargers etc you get from the likes of DealExtreme don't have any filter components in them.

That's probably why they are on DealExtreme!!

 

[inie meanie]

Haha - those cheap power supplies, battery chargers etc you get from the likes of DealExtreme don't have any filter components in them.

Well it must depend on their design.If they don't use a triac then they dont need any thing I suppose. Just a regulated output via a FET etc they won't have that problem.

 

[chriswarhurst]

Hello all,

New to this and picked up a google search thread - my company has developed a 240v low power immersion heater for domestic installation that incorporates 2 elements a 250w and 500w into one immersion heater. The idea is that it compliments your solar PV array and heats your water tank up slowly throughout the day. Starting at 250w, switching to 500w, then switching both on which gives you 750w then back to 500w then 250w later in the day. It works really well - we received the prototype last week and it works really well on its own connected to a simple timer. If you have developed a switching system tied to the inverter then I would be really interested in talking to you about it. contactable on [email protected]

 

[pauldreed]

Hello all,

New to this and picked up a google search thread - my company has developed a 240v low power immersion heater for domestic installation that incorporates 2 elements a 250w and 500w into one immersion heater. The idea is that it compliments your solar PV array and heats your water tank up slowly throughout the day. Starting at 250w, switching to 500w, then switching both on which gives you 750w then back to 500w then 250w later in the day. It works really well - we received the prototype last week and it works really well on its own connected to a simple timer. If you have developed a switching system tied to the inverter then I would be really interested in talking to you about it. contactable on [email protected]

Hi Chris, what length is the element(s)? and does it have a inbuilt thermostat?
... oh, and how much money!!

 

[chriswarhurst]

The immerser is made from Incoloy - 11” long with a standard 21/4 inch BSP thread. 240v TWIN element version 1 x 500w and 1 x 250w including two 7” stat pockets and two TSDR stats. If its a one off purchase its £110 + VAT if you are looking at bulk we can come down in price. Got to say the figures it producing so far are fantastic - effectively it is raising the water temperature high enough so that the boiler is currently switched off - and for free as the power it is drawing is within the output of the 3.8 Kw Solar Array. Watching the performance closely as we head into the winter months. Hope this helps

 

[suntrap]

Well it must depend on their design.If they don't use a triac then they dont need any thing I suppose. Just a regulated output via a FET etc they won't have that problem.

No, they are standard switch-mode designs (power supplies, not power controllers) which all need mains filtering. Their PCBs have positions for filtering components but these are all missing!

 

[suntrap]

it works really well on its own connected to a simple timer

Unfortunately, connecting it to a timer is a very inefficient way of maximising your use of solar power whilst minimising (or for most, preferably eliminating) your draw from the grid - the difference between output when the sun is shining and on a dull day is easily a factor of ten and a timer cannot predict this.

If you have developed a switching system tied to the inverter then I would be really interested in talking to you about it.

Read this thread and you will see that there are several such systems, one (sadly, only one) of which has had all its details published and made available on a royalty-free basis.

 

[pauldreed]

The immerser is made from Incoloy - 11” long with a standard 21/4 inch BSP thread. 240v TWIN element version 1 x 500w and 1 x 250w including two 7” stat pockets and two TSDR stats. If its a one off purchase its £110 + VAT if you are looking at bulk we can come down in price. Got to say the figures it producing so far are fantastic - effectively it is raising the water temperature high enough so that the boiler is currently switched off - and for free as the power it is drawing is within the output of the 3.8 Kw Solar Array. Watching the performance closely as we head into the winter months. Hope this helps

Chris, this sounds very much like an element designed for boats - not domestic hot water systems, and for the majority of this thread's readers would be unsuitable for the following reasons;
1) As suntrap has commented, using a timer is inefficient as on dull days, the power would be drawn from the grid, therefore a more complex switching solution should be sought.
2) Hot water rises to the top of the tank, therefore if top mounted (as is the norm) then this element would only heat the top 11", leaving the majority of the tank cold (would work OK if it could be bottom fitted).

 

[chriswarhurst]

Its an adaption of a standard immersion heater that uses two low power 240v immersers - we can do an 11 inch or 27 inch for larger tanks. The timer I agree is a crude mechanism balanced against a 3800 w Solar PV system. The array puts out 400w on the most cloudy rainy day so 250w from 0900 till 1500 hrs is background power consumption. The 500w element kicks in at 1130 till 1330 so still well within average power tolerances. You are right in that the switching mechanism is suboptimal but I disagree with the word inefficient it depends on the cost basis. A simple electronic timer costs £38. A bespoke emma unit is over £1000 so the cost benefit analysis over time against a viable use of the energy in heating hot water actually makes it very efficient.

As far as the tank is concerned - this is designed to sit in the top third horizontally so it only heats up the top 100 Ltrs or so. That means it is not wasted in trying to heat the whole tank up - something that it just does not have the power to do. 100 Ltrs of water is enough for average normal domestic use. Modern mains pressure systems have the immerser mounted horizontally in the top third of the tank. This system is not designed to sit vertically at the top of the tank as is common with older HW cylinders. Its not perfect but it is working and producing free hot water. Hope this is of use

 

[pauldreed]

...The array puts out 400w on the most cloudy rainy day..

Yes but how much power is being used in your home... fridge, freezer, etc, offset home consumption against your 400W, and there won't be a lot left for the immersion heater.

... but I disagree with the word inefficient...

IMO inefficient is an accurate description! if you put the washer on, boil the kettle, dishwasher etc. where does the power come from to power the immersion heater? The grid of course, which is kWh chargeable.

...A simple electronic timer costs £38. A bespoke emma unit is over £1000 ..

You havn't grasped the concept of this thread!
We are trying to develop cost effective control systems, albeit in different ways, which cost far less than £1,000 and nearer the £38 mark.