Maybe I should apologize because I did not give enough information in the beginning:
The purpose of this circuit is to switch the UPS inverter of when my 220V camping fridge does not demand power (when thermostat is OFF). The reason is that while the inverter is not supplying power to any device it still draws power from the 12V battery. The inverter is switched on and off by two push buttons. If you push the ON button it closes the push button momentary and the inverter switches on. If you push the OFF button The OFF push button closes momentary and switches the inverter off.
My 12V circuit is therefore just mimicking the two ON OFF push buttons on the inverter. And I can still use the buttons on the inverter if I would like.
I hope this helps

 

That was what I was thinking you wanted. Does the thermostat actually control the 220 directly? Or does it control power through some other circuitry? I just can't imagine a thermostatic switch handling all that power.

 

Said this in post #13

It would seem the TS wants the fridge to continue working via the inverter when a power failure occurs. But the TS doesn't want the inverter working {edit "working" to "running"} when the fridge is not demanding cooling. So how do we switch the inverter on with the t-stat? I believe that is the appropriate question.

 

We often fall victim to the temptation to provide answers on "mere scraps of information".

You are right I will try and give more info

 

That was what I was thinking you wanted. Does the thermostat actually control the 220 directly? Or does it control power through some other circuitry? I just can't imagine a thermostatic switch handling all that power.

OK now I see what I didn't think about , I have not opened the fridge yet, but I am sure there will be a relay inside that the thermostat powers. I will have to think about that part of the circuit again an change the drawing

 

Said this in post #13

Some more info that this idiot did not give you. I am not using the inverter as a UPS. When I am at a camping sit where there is
electricity, I switch the toggle to Utility. When I am at a camping place with no power or while driving, I switch the toggle to the 12V side. The fridge is in my home built camping trailor.

 

more info that this idiot did not give you.

If you're an idiot - then so am I. I think most (if not all) of us miss details from time to time.

So it's as I was thinking - you want to run your fridge from either campsite power, home power OR battery power. Obviously campsite and home site power is one and the same. So we're switching between battery and mains. To reiterate, you want the inverter to run ONLY when the fridge needs power. So you're switching the inverter on and off from the t-stat. To do that depends on the electronics inside. Chances are it IS a relay. Nevertheless, the solution should be the same.

 

If you're an idiot - then so am I. I think most (if not all) of us miss details from time to time.

So it's as I was thinking - you want to run your fridge from either campsite power, home power OR battery power. Obviously campsite and home site power is one and the same. So we're switching between battery and mains. To reiterate, you want the inverter to run ONLY when the fridge needs power. So you're switching the inverter on and off from the t-stat. To do that depends on the electronics inside. Chances are it IS a relay. Nevertheless, the solution should be the same.

Would you agree with this one? I already tested the 12v part, when i put 12v on relay 1 the inverter starts and when i remove the 12v the inverter stops.

 

That depends on how your inverter works. IF the two buttons (ON and OFF) are momentary then I have to re-think my approach. But if the inverter can be set to the ON position and you control the battery power to the inverter (working on a drawing now) the approach would be different.

 

If you're an idiot - then so am I. I think most (if not all) of us miss details from time to time.

So it's as I was thinking - you want to run your fridge from either campsite power, home power OR battery power. Obviously campsite and home site power is one and the same. So we're switching between battery and mains. To reiterate, you want the inverter to run ONLY when the fridge needs power. So you're switching the inverter on and off from the t-stat. To do that depends on the electronics inside. Chances are it IS a relay. Nevertheless, the solution should be the same.

That depends on how your inverter works. IF the two buttons (ON and OFF) are momentary then I have to re-think my approach. But if the inverter can be set to the ON position and you control the battery power to the inverter (working on a drawing now) the approach would be different.

The buttons are momentary. The battery is connected to the inverter permanently, when you switch the inverter on, it starts inverting 12v to 220v. When you switch it off it stops. When I get home, I plug the Inverter's mains cable into 220v utility power and it charges the battery. Of course then the fridge is unplugged from the 220v output of the inverter. I should actually use a inverter only, but I got the UPS for an excellent price and it's very handy because we often have load shedding in South Africa and then I use it as a UPS at home for my computer and printer.
It also has an excellent built in battery charger.

 

AH! Battery charger! I didn't think of that.

Anyway, here's what I came up with - using an inverter, not a UPS:

Maybe from here someone can make suggestions. But I don't think it's going to be that easy. But hey! I'm an idiot too.

[edit] And this is assuming the T-Stat doesn't need 220 V to work.

 

Actually, it may be easy enough to add a relay to act as the push to start button. When the T-Stat opens, power is lost and the inverter shuts off. Won't matter if the relay stays on all that time. Just use a very low current draw type relay and it will have negligible affects on the battery.

 

Actually, it may be easy enough to add a relay to act as the push to start button. When the T-Stat opens, power is lost and the inverter shuts off. Won't matter if the relay stays on all that time. Just use a very low current draw type relay and it will have negligible affects on the battery.

Thank you for all your insights, I have to go now, will look at it tonight and let you know.

 

Here's my last input. Notice the relay above the Inverter: (should mention the switch (SW1) is a 4PDT switch)