Solar Diverting switch

sargan

On the Solic the Switching is checked every 1/50th of a second, so the maximum time to switch is that, no need for any threshold. Plus the switching is done at the zero cross over point avoids noise .... some units have an issue with noise - causing for example light flicker (switching harmonics)

Dave_Fowler

I've tried to find more details about the Solic 200. The manufacturer's specification sheet says it can be set to have a zero export power threshold in it's normal mode of operation (mode 2). It also says that it's response time to power variations is less than 5 seconds. One retailer also adds that it checks the loading 20 times a second but I've not been able to verify this on the manufacturer's technical specification datasheet http://www.solfex.co.uk/uploads/downloads/SOLiC-200-Installation-guide.pdf [@Sargen is there another manufacturer's datasheet which I've not discovered where you are getting your figures?]

A 5 second delay in completely reacting to changes in solar generation / household loading is not a problem. I've set my design to react in 2 seconds and can verify that the import meter has a much slower reaction time to changes in load - it appears to average the current over 4 or 5 seconds.

Early versions of some proportional immersion heater controllers did cause light flicker in exceptional circumstances. These were the ones which employed zero-crossing burst mode switching with a relatively low burst rate. Zero-crossing burst mode switching causes no Radio Frequency Interference (RFI) as all the current switching is done at the point on the mains cycle when no current is flowing.

Controllers which use phase angle control switching can cause RFI if there is insufficient filtering on the input and output cables. The current to the immersion is switched part way through each mains cycle. The RFI is caused by the large spikes of current. Harmonics of 50Hz can extend well into the radio frequency band.

I understand the newer proportional controllers use a high frequency switching signal to pulse width modulate the mains input. As this is done at a much higher frequency than the mains supply, filtering is much simpler.

Dave F

sargan

If you want more details of Solic 200 ... email them, owner emailed back same day ... and suggested a call ... very helpful.
My understanding is that the Solic switching takes place at zero point .... avoid switching mid cycle and avoiding interference.
It has no need of bulky filters.

Dave_Fowler

sargan wrote: »

If you want more details of Solic 200 ... email them, owner emailed back same day ... and suggested a call ... very helpful.
My understanding is that the Solic switching takes place at zero point .... avoid switching mid cycle and avoiding interference.
It has no need of bulky filters.

I suspect the Solic, like most proportional controllers, will use zero point burst mode switching, and will have a burst rate which is high enough to avoid the possibility of light flicker.

The better expensive ones use the high frequency pulse width modulation technique.

Dave F

sargan

Pretty sure it's not burst mode.

Dave_Fowler

sargan wrote: »

Pretty sure it's not burst mode.

If it isn't burst mode, I don't think it can be zero point switching.

Zero point switching means that the current is switched on at the beginning of a mains cycle and off again at the end of the same cycle or at the end of another later cycle. In proportional control burst mode the 'proportional' part of the control is the proportion of fully off cycles to fully on cycles.

Edit:-
One way to look at this is to consider grouping every say 100 cycles of mains. If one cycle of mains is 'off' and the other 99 'on' then there would be a reduction in power of 1%. 2 cycles 'off; and 98 'on' would be 2% reduction ... 97 cycles 'off' and 3 cycles 'on' would reduce the power by 97% etc.

If this grouping of 'on' and off' cycles is repeated every 100 cycles then power would be controlled proportionally.

If you do the mathematics, this simple 'zero point switching burst mode' means the bursts are repeated every 2 second (50 Hz mains and 100 cycles per burst). This low rate can cause light flickering. A more sophisticated method would be to use 'half cycle switching' - there are two zero points in every mains cycle - but there would have to be control to ensure the same number of positive and negative half cycles were removed. Another method would be to have variable length bursts where the number of cycles is reduced when 'half power' load is approached (50% on, 50% off); this type of control could reduce the burst length to say 10 cycles - 5 'on' and 5 'off'. 10 cycle bursts would then occur every 1/5 second.
End Edit

Dave F

sargan

The company confirmed that its switching causes no interference nice... and none seen so far.

There are multiple ways of controlling power - PWM for example, but I do not have full details of design.

I can confirm no filter capacitors or inductors... some switches have huge filter arrangements to try and remove harmonics. (So rules out phase angle)
Solic advise this approach not needed as their switching does not cause interference.

It only has one switching device so for sure is not PWM, maybe it is some modified form of Burst mode - but I have no detailed technical design information.
It does work, and no interference has been noted.

The owner is very happy to discuss if you want to know more.

I'm just pleased it works as described.

silverwhistle

I've an early generation iboost, so just a single feed used for my immersion tank. It cost me £210 at time of installation and this thread made me think about it. Seems I've saved 3112 units in the slightly under three years I've had it so my any acccounts I reckon it's paid itself back. The issue here being at what rate you cost out your fuel. It provides all my summer 7 months hot water, and along with my wood-burning stove means that my annual gas bill is £36, which last time I looked was less than any supplier charges for the standing charge (except my zero rated one..).

Whatever the switch you use I think diversion is worth it in a lot of cases.

sargan

agree with your final point fully.

sargan

For those contemplating what switch to buy ...

A week ago I put a post about Solar Switches, and explained my reasons for buying the Solic 200

Just read that one guy today attempted to make a warranty claim for a failed Immersun, and the manufacturer (Eco4), sent an email stating that as of 29th June 2016, the company had ceased trading.

Glad I didn't shell out the £350