Automatic immersion heater

[Nickhlx]

 

 

The problem with the old radiator is that once you turn the cylinder OFF because it's getting too hot, the radiator itself will boil and burst, or shoot all it's contents out of the PRV assuming you have one. Then you have to go through the rigmarole of refilling it with water to use it again.

 

And in winter, freezing becomes a problem at night, so adding antifreeze means it it has to be indirect. Which introduces a load more issues to cope with!

 

At least with PV all you are dealing with is wires.

 

....which is why you would use the cylinder stat to open the (dump or three way) valve to allow the excess heat either to go to rads inside the boat (in winter) or a small rad or even a loop of pipe to take the edge off the high water temp in the collector - I bet it would be rare to see the collector water reach boiling point if ever in the UK with a black rad as the collector - it would need to be insulated really well ( so don't insulate it really well !)

 

Nick

[Nickhlx]

I think ideally what we would like is:-

 

A Dedicated controller that senses when the batteries are charged say 14.4v & less than 4A (settable) Which diverts any excess power to the immersion while holding the batteries at float at say 13.8V. It should be adaptive so that it reduces power to the immersion when the sun goes in or down and increases it as the power from the panels rises automatically. I expect that the immersion heater would probably be 12v 500w to keep the cable size reasonable. Best to stay away from 240V ac as the panels dont make it and the heater doesn't need it.

 

I think this would probably be a specially designed product not something cobbled together.

 

Top Cat

 

I have been using the "Intelligent Immersion - I2 " for a couple of years on the house system - http://www.intelligent-immersion.co.uk/ - works proportionally and brilliantly when it detects surplus power in excess of a few 10's of watts trying to escape from the house onto the grid, and when the immersion is up to temp, the cylinder stat diverts the excess to a convector heater in the day room in Autumn / Winter, so saving the need to heat that room at those times of year. They now do an I3 which has added remote Wi-Fi control / viewing, which could be useful to see what's happening on the boat from home... and its British, the guys are very helpful and based in Hampshire !

 

Nick

Edited July 18, 2015 by Nickhlx

[davidb]

Better link here

 

http://www.intelligent-immersion.co.uk

 

That looks a good price. Cheers David

[Nickhlx]

I am in discussions with them at the moment to upgrade my I2 to manage 7.5 kWp -

 

( Am I missing something ? - the link seems identical to me)

 

Nick

[Top cat]

Thanks Nick, I will look them up.

 

Edit, Done that it looks like a better, cheaper gizmo than the one I got, oh well you can't win them all and im still getting free hot water.

 

T C

Edited July 20, 2015 by Top cat

[Robbo]

Better link here

 

http://www.intelligent-immersion.co.uk

 

That looks a good price. Cheers David

 

Don't think that will work with a boat setup as it looks like it monitors what goes back to the grid by using a clip on sensor and then uses that to determine what power the immersion should use.

[mattcyp]

In reply to the oringial post, I've got a similar setup, I think (1.1kw of solar and a a heft charge controller).

 

I have one of these mounted in the engine room with an LDR mounted on the roof next to one of the solar pannels (so on 10m of wire). The output of the little 12v device I linked to then switches a solid state AC relay which turns on or off a 500w 230v immersion heater.

 

It works pretty well - as the sun goes in and out it turns it on and off, and will turn it off each evening when it gets dimmer. The immersin heater uses about 45a, leaving a good 15a to go to the batteries. My only concerns are that I don't feel relaxed about leaving this sort of device on when I'm not on the boat (its all a bit homemade), and it can be tricky if some pannels get shaded but the LDR isn't. However, all in all it does a great job and it's never accidently drained my battereis by more than 10ah or so (at 12v).

 

Ask away if you've any other questions - I'm quite happy to post some pictures too.

 

Matt

 

edited for spelling

Edited July 21, 2015 by mattcyp