Immersion Heater - PV electricity

[pauldreed]

I have solar panels fitted which generate up to 3.3kw, but most days it's 1 to 2KW.

I want to heat my water with that power, and have sourced a 1kw immmersion heater element (it was designed for boats!) with a suitable 2 1/4" BSP thread, but it is only 11" long.

If I mount this at the top of my water cylinder, would it eventually heat all of the water in the tank - or just the top 12" or so? (hot water rises).

I anticipate that the element would be solar powered for 5-6 hours, and if necessary the water temp could be topped up later via the gas boiler.

 

[antimatter]

This may help you sir

200W 12V Immersion Heater - Heating

 

[pauldreed]

This mat help you sir

200W 12V Immersion Heater - Heating

Thanks, but the supply is 240VAC and I would need a 1kw element to heat the water in the time allowed (whilst the sun is shining!)

 

[spud1]

A 1kw 12" element would struggle, I imagine, to heat a full sized cylinder of water when mounted into the top. Your best bet is to change the cylinder for the type that has 2 immersion heaters in the side (dual cylinder) and power the the lower of the two from you PV panels. this I think would heat the vast maj of the volume of a well insulated cylinder over the period you mentioned. You can get retrofit immersion heater kits that you can drill into the side of an existing cylinder to add for example an off peak immersion heater. But by the sounds of it you have an indirect cylinder that has a boiler heated coil within, and this would hinder the fitting of one of these. Hope that helps.

 

[pauldreed]

A 1kw 12" element would struggle, I imagine, to heat a full sized cylinder of water when mounted into the top. Your best bet is to change the cylinder for the type that has 2 immersion heaters in the side (dual cylinder) and power the the lower of the two from you PV panels. this I think would heat the vast maj of the volume of a well insulated cylinder over the period you mentioned. You can get retrofit immersion heater kits that you can drill into the side of an existing cylinder to add for example an off peak immersion heater. But by the sounds of it you have an indirect cylinder that has a boiler heated coil within, and this would hinder the fitting of one of these. Hope that helps.

Thanks, I have found a company today that would be prepared to manafacture an element to whatever specification I need, for about £60 so I may go with that idea.

 

[spud1]

Good good.

 

[robsparky1975]

dont forget to drain the water out before you drill it lol

 

[daniel hill]

will your inverter allow you to do this i no that the sunny boys that i have fitted in the past dont as they need a constant supply to them as yet i havent come across one that does as it is a major safety feature on them as if the supply fails or working on the grid they would still be a supply from your inverter on a line they think is dead

 

[pauldreed]

will your inverter allow you to do this i no that the sunny boys that i have fitted in the past dont as they need a constant supply to them as yet i havent come across one that does as it is a major safety feature on them as if the supply fails or working on the grid they would still be a supply from your inverter on a line they think is dead

I do not intend to interfere with the invertor or interupt the grid supply to it. The immersion element would be powered from the ring main (which on a bright day is supplied by the panels).

 

[Millerman]

Hi folks, just a quick update on this subject. I have designed a unit that will monitor the power produced by the solar system (FIT) and compare it with the household usage and will switch certain appliances on an off as required.

For example the solar panel is producing 2000w and the household is not using all of the power, so the surplus feeds back into the grid. This unit will switch the immersion heater on,(1Kw Heater).
If the householder switches the kettle on for example the immersion will switch it's self off. when the kettle has boiled the immersion will switch its' self back on, providing there is still enough power produced from the solar panels.

andyb09 at btinternet dot com

 

[pauldreed]

Hi folks, just a quick update on this subject. I have designed a unit that will monitor the power produced by the solar system (FIT) and compare it with the household usage and will switch certain appliances on an off as required.

For example the solar panel is producing 2000w and the household is not using all of the power, so the surplus feeds back into the grid. This unit will switch the immersion heater on,(1Kw Heater).
If the householder switches the kettle on for example the immersion will switch it's self off. when the kettle has boiled the immersion will switch its' self back on, providing there is still enough power produced from the solar panels.

andyb09 at btinternet dot com

Me too!
And it's installed and working now, but it's only heated a total of about 4kwh over the past 3 weeks due to cloudy weather & snow on PV panels.
I am hopeful that it will pay-off as the sun gets stronger.

 

[moush]

Hello,

I would be very interested in knowing which company supplied the immersion heater with lower rating, and also about your design to automatically switch power at the most efficient time.

I have a similar set up and have been wanting to do something similar.

Thanks and regards,
Stephen.

 

[pauldreed]

Hello,

I would be very interested in knowing which company supplied the immersion heater with lower rating, and also about your design to automatically switch power at the most efficient time.

I have a similar set up and have been wanting to do something similar.

Thanks and regards,
Stephen.

The firm which supplied the immersion heater was Howden-Electroheating who made the unit to my specification - costs about £65.
I designed the unit at component level to ensure that it only activates the immersion heater when the solar panels are generating enough power to support the load.
It was a steep learning curve!
But can now (even in January) start to reap the benefits.

 

[moush]

Thanks for the prompt reply.
Will post again to describe what I install.

 

[inie meanie]

I have been looking at a unit to just that but it is SO expensive. I have 3.8 kw pv and would like to spill the excess to the immersion heater. Any chance of some info on how you are doing it?
Thanks

 

[pauldreed]

I have been looking at a unit to just that but it is SO expensive. I have 3.8 kw pv and would like to spill the excess to the immersion heater. Any chance of some info on how you are doing it?
Thanks

I measure:
A) The power generated by the solar panels
B) The power used by the ring main
* deduct B from A (plus a further 1KW - to accomodate the power used by the immersion heater)
* and if the result is positive, then a relay switches on the immersion heater - if it is less, then it is switched off.

This is achieved by a circuit built from components sourced from Maplins and Ebay, a bit of fiddly soldering, and a lot of patience!

 

[inie meanie]

I measure:
A) The power generated by the solar panels
B) The power used by the ring main
* deduct B from A (plus a further 1KW - to accomodate the power used by the immersion heater)
* and if the result is positive, then a relay switches on the immersion heater - if it is less, then it is switched off.

This is achieved by a circuit built from components sourced from Maplins and Ebay, a bit of fiddly soldering, and a lot of patience!

That sounds great, exactly what I want to acheive. Any chance of a bit more information or pictures? Many thanks.

 

[pauldreed]

That sounds great, exactly what I want to acheive. Any chance of a bit more information or pictures? Many thanks.

I don't think pictures would help, because the unit is contained within a '2 gang mains surface box/blanking plate', so the photo would just be a small white box. It's the circuitry inside the box which makes the decisions.
I am contemplating marketing the device, so I'm a little reluctant to release the full circuit diagram at this time, but the operating principle I posted above is basically how it works.
I can't wait for some decent sunshine now, but even today, the unit switched 2kwh to the immersion heater, not enough to fully heat the store of water, but hey, it all helps!

 

[inie meanie]

HI
I understand that. You may have a problem as there is a device on the market which might be copyright protected, it is called EMMA. It costs about £1500. I was just wanting to make some thing for my self with no interest in selling on. Hey but well done on making it work.

 

[mac1]

Hi can you tell me more about your device