Home-automation to control fan heater based on solar PV output?

celerity

Cheers Z, helpful post as always.
re: your first suggestion, I've pretty much done this - I already have all the monitoring equipment to show when I have spare energy, and a fan heater that makes a difference. I even have the data uploading to the web every 5 mins, which wasn't trivial .

So, it's controlling the power to the heater I'm struggling with at the moment.
Someone did point me to http://www.phidgets.com/products.php?category=9&product_id=1014_2, which is an interesting starting point.

re: your inverter wiring idea, that is completely novel to me.
I think I have an SB2500HF. I had no idea some models had programmable relays on them, that is very cool.

/\dam

zeupater

celerity wrote: »

Cheers Z, helpful post as always.
re: your first suggestion, I've pretty much done this - I already have all the monitoring equipment to show when I have spare energy, and a fan heater that makes a difference. I even have the data uploading to the web every 5 mins, which wasn't trivial .

So, it's controlling the power to the heater I'm struggling with at the moment.
Someone did point me to http://www.phidgets.com/products.php?category=9&product_id=1014_2, which is an interesting starting point.

re: your inverter wiring idea, that is completely novel to me.
I think I have an SB2500HF. I had no idea some models had programmable relays on them, that is very cool.

/\dam

Hi

The problem with a fan heater is that the load will be too high and would be off and therefore providing no benefit more often than not. With a lower load (400W) you will be able to make use of much lower irradiation, with the possibility of switching between the 400W & 600W circuits, or both together, as the conditions allow (now theres a nice little application for some automated relays and a little logic to replace switches ).

Just looked at the spec for the SB2500HF .... looks like the multifunction relay is optional on that model .... (http://www.sma.de/en/products/solar-inverters/sunny-boy/sunny-boy-2000hf-2500hf-3000hf.html)

HTH
Z

celerity

Sorry, I'm talking rubbish about my inverter model, it is an SB4000TL, otherwise I wouldn't have seen outputs of 4200W+.
I can't see anything about a relay output in the manual though?

I see your point about a lower powered electric oil rad, cheers.

/\dam

Cardew

Get a (Large) variable voltage transformer connected to an oil filled Rad and let Ohm's Law be your friend.

penrhyn

Very satisfying winding up a Variac!

celerity

@ Cardew and penrhyn: way over my head I'm afraid

Cardew

celerity wrote: »

@ Cardew and penrhyn: way over my head I'm afraid

Not really the place to get into electrical theory - however;)

An electrical heater in UK is designed to work on a nominal 240 volts. At that voltage a 2kW heater will draw(use), unsurprisingly!, 2,000 watts.

The mains voltage in UK can vary from say 230volts to 250volts and the output of a simple electrical heater will draw(use) more or less watts depending on that voltage.

A variable transformer is an electrical device that can be connected to the 240v mains and have a voltage output that is variable. As the voltage decreases so does the power drawn by the heater.

These variable transformers are often called Variac.

Anyway forget the above! You can buy very cheaply some halogen heaters like this:

http://www.cnmonline.co.uk/Igenix-1600W-Halogen-Heater-With-Remote-Control-And-Timer-pr-36233.html

This has four 400watt heating elements that you can switch on and off with a remote.

zeupater

celerity wrote: »

Sorry, I'm talking rubbish about my inverter model, it is an SB4000TL, otherwise I wouldn't have seen outputs of 4200W+.
I can't see anything about a relay output in the manual though?

I see your point about a lower powered electric oil rad, cheers.

/\dam

Hi

Re: "I can't see anything about a relay output in the manual though?" ....
Info as requested ..... .... (http://files.sma.de/dl/5692/ZusatzFunktNG-TEN105011.pdf)

HTH
Z

thenudeone

Thinking about it a different way, how about:
1) An external light-sensing switch designed to turn outside lights on at night £10 like this http://www.tlc-direct.co.uk/Products/TLPEC1000.html
2) powering a 12V transformer £10 like this http://www.maplin.co.uk/12vdc-0.5a-power-supply-with-2.1mm-tip-513515
2) Wired to a relay with two-way switch contacts to reverse the action (i.e. to switch a device ON when it's light outside) £2 possibly like this http://www.maplin.co.uk/ultra-miniature-high-power-mains-relay-218688

Left to its own devices, such a device would leave the load (a heater) switched on from dawn to dusk which is no good. It needs to switch on only when the daylight is very bright (i.e. when solar PV generation is at its maximum)
To achieve this, place 1) inside a small enclosure allowing light in through an aperture, the size of which can be varied (at least initially) to reduce the light hitting the sensor, so that it does not power the load until it is very bright. The exact amount of light required would need to be discovered by trial and error.

One of these might be a safer alternative (less direct mains wiring) http://www.reuk.co.uk/Switch-Mains-Powered-Appliances-Safely.htm

One of these in a box would do the same thing but it only powers 600w so you would still need a relay unless the heater can draw only 600W with selectable elements http://www.livefoods.co.uk/product_info.php/habistat-sun-switch-day-p-493

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