PLC for switching heating load?

[jones1467]

Hi, I am hoping that someone here can help.
I am looking for a means of switching a contactor for a 3 or 1.5kw immersion heater to be driven by a 4-20mv or maybe a 0-10v variable signal.
I am hoping to switch on my water heater during the day when my solar panel production reaches a set value
The idea is to switch the immersion on when the input signal reaches a predetermined value over a given time (to stop on/off switching) as well as switching off at a futher given value.
My solar inverter gives out a 4-20ma relative to 0-1500watts production. When the solar unit produces in excess of 750watts over maybe 4mins, i'd like it to switch on my immersion and of course switch off again when it see's below 600watts for again maybe 4mins.
My water is normally heated by an oil boiler but I would like to use this tyoe of system as I am not home during the day and would like to use the energy produced.

Any ideas? Micro PLC?

 

[endoftheworld]

Is there much call for this sort of thing? I've just prototyped a unit which could easily do this from a 4-20ma signal, and/or several other inputs and switch up to 4 240v devices depending on what software I chose to write.

We designed it for water pumping systems but could easily be adapted. Nice LCD display too, and BMS outputs.

Won't hit the market until late September though.

 

[RichJohnson]

I've read this request at least four or five times in this past year. Must be call.

 

[JimmyJamJerusalem]

You could defo use a PLC system but which one...?

 

[JimmyJamJerusalem]

Having a look around there are some Compact Logix ones that would defo do it but very expensive!!

 

[JimmyJamJerusalem]

Would probably be better (and cheaper) to use pulse width modulation

 

[JimmyJamJerusalem]

Would still need a PLC controller for that though....

 

[endoftheworld]

I already have the unit to do this, it's a commercial rainwater control panel. We design, build and program them. Dedicated hardware, not PLC, very compact. I just need to write new software for solar PV.

Maybe this is a product I should launch.