I'm presently running my entire house off my solar setup, with the main loads such as geysers and pumps running during the day, using available PV, and then running the house on batteries through the night. My oven is presently only connected to the mains, as it is mostly only used after sunset for dinner. I haven't connected it to my batteries as it would very quickly kill them.

I have excess solar during the day, so it would help reduce costs to run the oven from the solar setup, should the oven be used during the day (weekends, public holidays etc). In order to do this, I was thinking of using a 30A relay / contactor which has both a NC and NO set of inputs and outputs. I would wire it such that the mains would run through normally closed and the inverter supply through the normally open. I could then use a Sonoff to switch the relay / contactor, depending on available PV, time of day etc. 

Has anyone done something similar to this? If so, which relay / contactor did you use? Any other thoughts on this?

I was considering using the following:

https://www.stepbuildingsupplies.co.za/products/2no-2nc-control-relay-240vac-coil

Edited June 30, 20214 yr by Schnavel

I use this relay with 2NO for my geyser and Stove/oven. When the grid is available, the relay energizes and and keep the geyser and stove On. Imediately when I loose the grid i.e loadshedding, the relay switch off and opens the supply to my geyser and stove. That way, the wife or anyone can not use the stove, oven or geyser during loadshedding. Straight forward and no Sonoff needed in my case 

 

https://www.hager.ie/products-e-catalogue/energy-distribution/modular-devices/relays-contactors/contactors/esc240s/85950.htm

Yeah, that would work, but not for my application, hence why I am thinking of having a relay with 1x NC and 1x NO.

The Sonoff would then switch the relay / contactor, based on available PV, time of day, battery SoC etc.

You would probably need 2x NC and 2x NO contacts as you most likely would need to switch the Neutral as well...

 

4 minutes ago, GreenMan said:

You would probably need 2x NC and 2x NO contacts as you most likely would need to switch the Neutral as well...

 

Valid point! I would definitely need to switch the neutrals as well as the lives.

Then the one in the link I originally specified should work (2x NO and 2x NC).

I had a quick look and I think that the unit you suggested is a control relay and cannot handle the high current that a oven would require.  

2 hours ago, GreenMan said:

I had a quick look and I think that the unit you suggested is a control relay and cannot handle the high current that a oven would require.  

Thanks - I have checked and that specific unit can only handle 10A.

Looking around for a relay / contactor which can handle 30A, is proving to be rather expensive - project may not be worth it.

Have a look at this for a awesome solution for a DIY ATS switch which work fine as your oven and pump load diverter between PV/Inverter and grid. Obviously you would not need the over/under voltage protection relay. 

You could use the Sonoff that you suggested earlier to provide the signal to switch the load between power as supplied by the PV INVERTER shown in the circuit. 

TheBackShed.com - Forum

At first glance the schematics may appear a tad daunting but it does work ! I suggest that you first take a look at the circuit for switched Live inputs in order to familiarize  yourself with the logic. Then once you are clear with the logic then you can get to grips with the one with switched Neutrals. The timers are there to allow delays between switching from grid to solar and vice versa.  I would say that if you are dealing with a purely resistive load you could possibly do away with the timers however you said you have pumps so I would use the timers...

I've been thinking how to manage this as well. As another option, if you went the home automation route would this work? 

https://www.voltex.co.za/product/cbi-astute-smart-isolator-4x4-30a/

It's 30A but I think the norm is a 45A on the stove? 

12 hours ago, Robbo said:

I've been thinking how to manage this as well. As another option, if you went the home automation route would this work? 

https://www.voltex.co.za/product/cbi-astute-smart-isolator-4x4-30a/

It's 30A but I think the norm is a 45A on the stove? 

It would depend on whether your stove and oven are both electric, then 30A may be an issue. My unit is a gas top, with an electric oven, so 30A is more than sufficient,

12 hours ago, Robbo said:

I've been thinking how to manage this as well. As another option, if you went the home automation route would this work? 

https://www.voltex.co.za/product/cbi-astute-smart-isolator-4x4-30a/

It's 30A but I think the norm is a 45A on the stove? 

These are nice units - I do have some already. However they will only switch power on and off from 1x source. Schnavel wants to switch the oven/pump between solar/inverter/battery and Utility and hence why you need the safe switching capability that the ATS will provide.