Immersun/Sola Controla and harmonic distortion...

[Energetic]

Right here goes, have a feeling this might rumble on for a bit.

My business partner has just been speaking to a company building power management systems which will incorporate an immersion controller.

They are of the opinion that the Immersun and its similar competitors will be outlawed by the DNO's at some point in the future due to Harmonic Distortion in the grid caused by interruption of the AC waveforms.

Discuss...

 

[whinmoor]

Another one bites the dust...?

I think they will be difficult to outlaw. Heating water using electricity has happened for decades and this is simply an extension of that using solar technology.

I'm sure it won't be long until some Chinese company takes an Immersun apart and starts selling something very similar for £100. The research / reverse engineering is probably happening at this very moment in a lab near Shanghai.

A guy on the main forum has wired one in himself in a couple of hours so clearly a competent DIY'er can do it so DNOs or accreditation bodies can't threaten to strike off professional electricians who install these devices.

 

[BruceB]

Fitted an immersun yesterday with a Wattson already in place.
Everything was connected correctly and the immersun was working, but the Wattson was going all over the place in terms of net power measured.
It seemed to be reading +1kW to -1kW seconds apart when the immersun and pv were both relatively stable.
If the immersun works by using a triac to clip the ac waveform or similar, then I suspect the waveforms are really confusing the Wattson.
I suggested we let it 'settle down' for a few days, but I doubt it will!

 

[Worcester]

I know where they are comming from, and in this PARTICULAR case I believe that they've got it wrong wrt the ImmerSUN.....

There are two ways to control the power proportionally -
1) Burst fire - you want 20% you allow one cycle out of 5, 40 % cycles, 2 cycles out of five, and make sure you switch on / off at the zero corssing point.
OR
2) Phae angle where for 20% you allow 1/4 of each cycle through (as in a 1/4 of the area under the sine wave, so in this case 1/4 of the cycle) etc.

Burst fire using zero crossing point doesn't produce harmonics, phase angle does. In that case you need to put a special harmonics fi;ter in to stop the harmonics going 'upstream', in fact it is a requirement to do so if you use phase angle.

The ImmerSUN uses burst fire so doesn't produce the harmonics.

So you business partner's contacts is right - some of the systems out there use phase angle and don't include the required filter, and wrong because they obviously haven't done their research to see how individual systems are programmed (or perhaps more likely they were just trying to put the frightners on him to protect their market place )

 

[yellowvanman]

The ImmerSUN uses burst fire so doesn't produce the harmonics.

As I understand it the resolution of the immersun is 30W (ish) (1%), in which case do they control the power over 100 cycles?

 

[BruceB]

Whilst burst fire does not produce the harmonics/distortions related to cutting of the current at a non-zero point, it does produce harmonics.

An easy way to see this is to consider what is happening when say the immersun is firing one cycle in 5 (ie at 20% power). The fundamental frequency of the ac waveform through the immersion heater is no longer 50Hz it is 10Hz, with all the appropriate harmonics to form the one cycle in 5 waveform. It is a non-trivial problem to filter these harmonics out looking upstream if you want to be able to operate at variable power levels.

 

[Worcester]

They control it over how many cycles are nescessary.... for instance for 20% you wouldnt switch it on for 20 cycles out of 100, you do it one out of 5, similary for 75% you don't do it 75 cycles out of 100 (that would actually trigger an import register), you do it 3 out of 4. It's all about undertsanding also how metering and indiviudal meters work.

 

[Energetic]

I was under the impression that phase angle control as in lighting dimmers was random in application and therefore has an averaging effect over the whole network, effectively cancelling each other out.

 

[Worcester]

Maybe, in this case though we're switching up to 3kW + if they are daisy chained.

 

[Gavin A]

you're all making my brain hurt.

 

[Worcester]

yeah well Energetic started it :17:

 

[dansk]

you're all making my brain hurt.

lol, thats just i was thinking till i read your post, nice one.

 

[Gavin A]

unfortunately, I think I can actually understand the discussion, and I can see that there could well be a problem in the offing here.

I'd be wary about installing it anywhere that there's sound equipment installed, particularly professional level PAs / music studios, as stuff like this can get picked up in the amplifiers IME.

which is a bit concerning given that I'd just installed one in a church with a fair amount of amplification kit in place.

Worse case I can see it showing up as a low level clicking sound every time the burst fire thing kicks in. I know on festival sites etc we'd never allow stuff like water heaters etc to be installed on the same supply as the PA systems, as they'd cause a click through the PA when they switched on and off, and from what's being said on this thread it sounds as if the burst fire is effectively cutting the immersion in and out several times a second, which I'd think would cause at least a low level buzzing sound to be audible (for those who notice these sort of things).

I did about 10 years working on festivals, club nights etc. btw, including a fair amount of the technical side of things.

 

[Energetic]

OK so i think we're in agreement that there will be harmonic effects from both systems. The question is will there ever be enough of these fitted to cause problems with the DNO's?

Do we need to get an agreement from the manufacturers that the customers can return them if they get a letter from the DNO ordering disconnection? Should we inform customers that there is a potential for this to happen however remote?

 

[BruceB]

We are talking here about switching loads of a few kW. Whilst I think there will possibly be local harmonic effects, I doubt these will be significant beyond say a local transformer because of the self inductance of the cables and transformers. You will get the averaging effect across the network already mentioned. Also the Immersuns are CE marked so have to comply with the EMC Directive. Overall, I would be surprised if there is a long term issue for DNOs

The most significant effects might be to old fashioned audio amplifiers and distribution as Gavin mentioned. Modern digital circuits are likely to be fairly immune.

- - - Updated - - -

We are talking here about switching loads of a few kW. Whilst I think there will possibly be local harmonic effects, I doubt these will be significant beyond say a local transformer because of the self inductance of the cables and transformers. You will get the averaging effect across the network already mentioned. Also the Immersuns are CE marked so have to comply with the EMC Directive. Overall, I would be surprised if there is a long term issue for DNOs

The most significant effects might be to old fashioned audio amplifiers and distribution as Gavin mentioned. Modern digital circuits are likely to be fairly immune.