Immersion Heater - PV electricity

[madmurg]

I think that is why they are firing on the zero crossing so cutting out the interference

 

[Keith Walker]

Hi Keith,

Well done getting your system up and running and going to the trouble of launching the associated web site.
I had a quick look at the web site but couldn't see any details of the 3KW power controller, have you designed your own circuit or are you using a proprietary solution? That question also applies to mains filtering.

Regards
John

Hi John,

The 3kW power dimmer is now on my website. I'm not an electronics expert, so it's pick and mix from the internet. I wish I'd discovered this forum sooner

Cheers, Keith

 

[Trader9]

Hi Keith

I see a mention of the 3kW power dimmer being on your website, but I can't find a link or your website address. Could you please post it so I can have a look. I have been playing with a 3800W dimmer and would love to see what you have come up with.

Regards, Trader9

 

[Keith Walker]

Hi Keith

I see a mention of the 3kW power dimmer being on your website, but I can't find a link or your website address. Could you please post it so I can have a look. I have been playing with a 3800W dimmer and would love to see what you have come up with.

Regards, Trader9

Hi Trader9,

It's www.talkingsolar.co.uk

Cheers, Keith

 

[echase]

I think that is why they are firing on the zero crossing so cutting out the interference

Cuts out one sort of interference but replaces it with two others, one for zero crossing distortion and one for pulsing. Should be less overall but acceptability all depends on what regulations apply.

 

[thushar]

I can't bring myself to read all 35 pages to see if anyone has mentioned one of these but they do exactly what seems to be required;

Igloo Solar Energy PV & Thermal Panels & Heat Pumps Essex London Cambridgeshire kent hertfordshire sussex surrey berkshire south east south west & midlands

Not cheap but very effective.

Found this - > http://solarimmersionheaterswitch.co.uk

and Business Building Kits items in Fair Trade Hub Shop store on eBay!

Looks more cost effective & my test installation working perfectly good.

 

[peterjsoul]

I've been following this thread with great interest hoping to find a solution that works for me. Many thanks to pmcalli and inie meanie for their specific help and advice but I couldn't use their methods because I have been unable to obtain a crydom triac as they seem to be permanently out of stock. Instead I've tried out a Fotek SSR-25 (readily available and cheap) linked to a 3Kw immersion. Output is adjusted manually with a potentiometer. The next stage is to find a way to control it automatically - I'm thinking maybe arduino.

 

[inie meanie]

Hi
I think the fotek SSR-25 is just an on off relay not a variable power controller.

FOTEK-SSR-25DA Solid State Relay

 

[peterjsoul]

Hi
I think the fotek SSR-25 is just an on off relay not a variable power controller.

FOTEK-SSR-25DA Solid State Relay

I think you are right about the DA but I have a VA which is variable. I control it manually with a 470 ohm 2W potentiometer. I've tested it using a light bulb when it behaves like a light dimmer, with a kettle and with my immersion heater. I can check that it is using solar energy and not drawing from the grid by monitoring the grid meter using an optismart. This is working OK but I now need to work out how to control it automatically.

 

[runthangs]

I've come across a "3800W SCR Voltage Regulator Dimming Light Speed Control" on ebay that'd appear to achieve the same for a fraction of the price of, say, a site transformer - would such a device be sufficient for reducing a 3kw immersion energy usage down to half or lower?

 

[Trader9]

Hi Peter

I have that exact relay and I have a working prototype using an Arduino Uno microprocessor which measures the solar and the house load via two efergy current transformers. See OpenEnergyMonitor CT interface for more detail, but you only need four resisters and a capacitor. The Arduino does all the work and calculates both wattages.
I then use this information to drive one of those 5Vdc eight relay boards on ebay for about £10. On the relay contacts I have a resistance network tuned to give eight different resistances to the SSR-25 VA. The AC output voltages then control the load to the immersion heater.

It sounds like it would be quite lumpy, delivering 125W then 250W in 125W steps up to 1kW. But if you put the numbers into a spreadsheet I get 11kWh in summer and up to 4kWh on a good winters day.

If you are interested I would be happy to give you all the code (sketch) for the Arduino.

Regards, Trader9.

 

[Trader9]

Hi runthangs

I have some of those ebay dimmers and there is nothing wrong with them except the control circuit is a bit simple and they don't switch on until about 60Vac or more so you go from 0 to 3.125 amp which is a minimum of 187W the lowest start load you could use. You can improve the circuit with a few extra components, see page 89 fig 5.19 in a book by R.M. Marston called "110 thyristor projects" and you can then get down to 1-2Vac output.

I also have some of the SSR-25 VA that Peter mentioned and that is a far better bet as it goes down to low voltages and comes mounted on a better heat sink and all for only £9.99 from Hong Kong. Lower input current too.

See my note to Peter on how you could interface this to a Arduino.

Regards, Trader9

 

[runthangs]

187Vac is pretty much what im after, I want to avoid as much wiring/diy electronics as possible.

My controller ive written on LINUX in Perl/c/bash, and the controller switches power via the USB port that switches on a Mains plug. I run it on a NetBook sitting in the airing cupboard but will likely port it to a raspberry pi. It reads the live generation via Bluetooth from my pv inverter, and based on thresholds switches the USB voltage. Also sends emails, has a pause function for the Mrs (as I dont have a simple way to read electricity consumption yet and switch on the deltas). The NetBook runs on a schedule so suspends at set times.

 

[Trader9]

Hi runthangs

187Vac is way to high, as that is 1821Watts. You are never going to get that much spare solar on a regular basis, even in summer. What you need is a system that starts low, say 43.8 Vac for a 100W load and then increase as the solar increases. This is the only way you will get any power in the winter. It would be better to get 100W all day than 1821W for ten minutes.

I think if you do use an ebay 3800W dimmer, then I would increase the heat sink size and ensure good ventilation and don't put it in the immersion heater cupboard.

 

[peterjsoul]

Hi Trader9

That sounds perfect for what I am trying to achieve and is exactly along the lines I have been thinking about. It would be great if you could let me have the sketch and very helpful if you could provide a circuit diagram.

Regards

Peter