davidinhull
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| posted on 27/5/16 at 06:23 PM |
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Solar powered immersion heater
Hi
Hoping someone on here has a better grasp of electricity than me!
I have solar panels, and an optimmersion which monitors the power produced by the panels and the use in the house
If there is an excess of power produced, it can divert that power to the immersion (immersion on its own circuit, so only allowed the power the
optimmersion diverts to it)
This means it can receive regularly changing power up to 3kw/hr but it does vary all the time with weather and usage in the rest of the house, so at
times may be only getting a few hundred watts
Would this cause problems for the immersion heater?
I ask, as 2 have failed after a year of use each, so before I buy another, was wanting to find any particular type that would be better suited
I rang a manufacturer of immersion heaters, but they refused to believe that the immersion would do anything other than draw 3kw/h
Does that make sense?
Thanks in advance
David
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hizzi
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| posted on 27/5/16 at 09:21 PM |
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i presume the immersion is standard and not something special for the solar system? standard immersions are cheap as chips these days, more often its
the stat rather than the whole unit. also is it a copper cylinder or stainless or even bare steel. some have sacrificial anodes that require changing,
if the anode is away it will corrode the immersion and you get water coming out the stat hole or sometime a major bang as it shorts into the water
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coyoteboy
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| posted on 28/5/16 at 04:07 AM |
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Depends how the controller does the power delivery. I'm guessing it uses something like phase chopping (a bit like pwm) to effectively alter the
rms voltage the heater sees. These can create big voltage steps as the chop occurs and in a wire wound type of device I guess it may set up sharp
thermally induced vibrations but I would have thought the mass of the wire enough to absorb and average that out. I've seen big problems with
unsupported 32awg nichrome heater wire operating at about 90% of melting point, with a chopper, but I'm guessing an immersion isn't that
delicate.
Tried another brand with different construction?
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hkp57
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| posted on 28/5/16 at 06:05 AM |
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I have a similar setup and had no burnt out heaters, my water tank has two immersion heaters, one at the bottom and one at the top. The Solar
controller is connected to the top one so it does not try and heat the entire tank just the usable layer at the top basically a pre heat for the
Biomass boiler to top of when we have it on.
We use the Solar - iBoost controller
http://www.marlec.co.uk/product/solar-iboost/
[Edited on 28/5/16 by hkp57]
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davidinhull
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| posted on 28/5/16 at 07:09 AM |
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Thanks people
Looks like the solar I-boost is very similar, but I can only power one immersion - good to hear at least one person has no problem with a similar set
up and standard immersion
The tank is copper, and I have a backer anti-corrosive immersion suitable for hard water (as I have)
No idea how the optimersion regulates the power!
The first immersion that gave up had been in the house since before we bought it, so I put its failure down to age, and didn't worry, the second
after only a year is concerning me more!
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big-vee-twin
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| posted on 28/5/16 at 10:39 AM |
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Check your water quality main thing that causes them to fail is the hardness of water.
You can get stainless steel elements designed to work in hard water areas.
I had 2 go in 18 months and it was water quality that caused it, the deposits cause hot spots.
Just noticed your in Hull, water there is hard and aggressive I have done a lot of work around Hull and we always specify water softeners because of
the problems, worth a check.
[Edited on 28/5/16 by big-vee-twin]
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
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davidinhull
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| posted on 28/5/16 at 01:22 PM |
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The water quality is a good point, I was jumping to the conclusion that it was the solar power variability causing the problem, as it has happened
since installing the panels. However the immersion was never used before they were fitted (gas hot water primarily, the immersion could be used if the
boiler packed up) so it could be the considerably greater time heating in the hard water
David
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02GF74
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| posted on 30/5/16 at 11:00 AM |
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quote:
Originally posted by davidinhull
I rang a manufacturer of immersion heaters, but they refused to believe that the immersion would do anything other than draw 3kw/h
the power drawn will depend on the voltage, so if connected to UK mains 240 VAC, that is correct. If supply exceeds that, then it will draw more.
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davidinhull
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| posted on 30/5/16 at 11:37 AM |
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So now I'm back to being confused!
I vaguely understand we have a set resistance in the element, 240v supply , so power is fixed (ohms law?)
However the optimersion (or little magic box - as I have no idea how it works) definitely moniters the power generated, the power used by true test of
the house, and only diverts the difference to the immersion
Looking at the output from the solar panels, and the readings for the rest of the house, I'm quite confident this actually happens
So the immersion may be only drawing 2kw
Perhaps the optimersion changes the voltage?
http://www.rexelenergysolutions.co.uk/product/2500556982/Wattson-Optimmersion-Controller
Maybe the link will clarify?
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davidinhull
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| posted on 4/6/16 at 10:47 AM |
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No laughing at the back please
I have swapped the immersion fit a titanium coated one to deal with the hard water. I was expecting the old one to be covered in lime scale, but was
basically clean.
I did however discover the overheat switch on the old one tripped, so that would be my problem!!!
Should have looked at the basics first - doh -you stupid boy
Still, if it goes again I'll know where to look
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