Immersion Heater - PV electricity

[inie meanie]

Seems a shame that the burst fire is a problem because when we have the power you don't need the lights on!

 

[Worcester]

I'm not sure that burst fire is a problem - it's phase angle that does havock with harmonics and EMF.

I'm still waiting for @echase to point me to the regulations / guidance note.. and to explain how / why the Solar 24 is different...

I know that there are already over 2000 Immersuns installed, and I am not aware of any complaints.

Certainly we see no flickering, and running an oscilloscope on the power supply nor do we notice anything untoward...

 

[Gavin A]

I know that there are already over 2000 Immersuns installed, and I am not aware of any complaints.

really?

we've got one install where the flicker is pretty serious, and immersun said they were aware of problems in a small percentage of cases IIRC, though I might have got that wrong, it presumably must be up to dozens by now.

The regs are these ones, which they confirm they meet, but I'm not entirely convinced they do. Even if they technically do, then the flicker from the units is definitely unacceptable in situations where the local grid network as large volt swings / high impedance - this one's in the countryside at the end of quite a long single phase line.

BS EN 61000-6-1 Electromagnetic compatibility (EMC). Generic standards. Immunity for residential, commercial and light-industrial environments 2007BS EN 61000-6-3 Electromagnetic compatibility (EMC). Generic standards. Emission standard for residential, commercial and light-industrial environments 2007

The issue can be resolved for the customer by using LED lights or CFLs in place of halogens / incandescants, but that doesn't solve the issue for the neighbours.

We've backtracked a lot on installing these units, and won't do it where there's a risk of high volt swings. It's a right pain in the arse as we were about to offer them to all our existing customer base, but couldn't risk it after seeing how bad it was for these customers.

 

[Gavin A]

ah, hold on they're different regulations, it's BS EN 61000-3-3:2008 and EN 61000-3-11 that are the regulations in question.

this diagram explains why the Immersun can't meet those regulations, as it shouldn't be able to cause a volt swing each time it cuts in of more than just under 0.3% or around 0.7V, but the location we had it at I measured around a 2V drop from switching on a 3kW load, so effectively every time the burst fire kicks in on each cycle it's causing around a 2V drop on that cycle.

Presumably this is why dishwashers and washing machines are restricted to around a 1kW element.

EN 61000-3-3 is now mandatory under the EMC Directive for all equipment that consumes up to 16A/phase from the public 230V supply. Test laboratories use an instrument called a ‘flickermeter’ to measure to this standard. EN 61000-3-3 limits the emissions of voltage fluctuations and flicker

Design for EMC Part 6: ESD, dips and dropouts, etc.

http://www.reo.co.uk/files/handbook_en_61000-3-3_and_en_61000-3-11.pdf

I've been meaning to get back to 4-Eco about this tbh.

 

[suntrap]

Thanks - that's really interesting. Just one point though: elements in dishwashers etc are not limited to 1kW (my dishwasher element's the best part of 3kW [though it is old]; washing machine about 2kW; oven in total >3kW but interestingly it staggers the switching of its elements). However, they are not controlled by burst firing so they will only cause intermittent flickering as they switch on and off infrequently, rather than constant flickering by being switched several times a second.

 

[Gavin A]

Thanks - that's really interesting. Just one point though: elements in dishwashers etc are not limited to 1kW (my dishwasher element's the best part of 3kW [though it is old]; washing machine about 2kW; oven in total >3kW but interestingly it staggers the switching of its elements). However, they are not controlled by burst firing so they will only cause intermittent flickering as they switch on and off infrequently, rather than constant flickering by being switched several times a second.

I think it's the newer models that have smaller elements, and use the burst fire just to keep them topped up with heat, probably as they use so much less water and lower temps... not my field though, but I have stuck power meters on a few in the past to see what they're drawing.

 

[suntrap]

Oh I see - so they have smaller elements in order that they can use burst firing? With solar panels, good reason to get a new dishwasher!

 

[Worcester]

Hi GavinA,

Thanks for the detail, it must be down to some of the characteristics of the individual installation, as I say we have had no reported problems at all. Reading the documents you posted, I wouldn't be suprised if some of the supplies don't meet those specications!

 

[inie meanie]

Thanks Gavin A for the information. So where does this leave us? I have a burst fire model and a phase angle unit running, both work really well. Has anybody come up with suitable filtering for the phase angle cutting? I have used commercial two stage units , but I don't have any specific equipment to test if it is below the regulation amount of interference.

 

[TechyTim]

Hi guys,
Just had a look at latest comments on ths thread as I have now more or less dropped out of Controller market (4 left in stock if anyone interested) but this latest batch confirm my comments 6 months ago that no-one will be able to legally market a cheap proportional control due to harmonics, etc.
Hence why I was marketing the SolarHeat which was simple fixed switching but not the most efficient.
Did echase manage to get his design commercially developed?