Twist timer activated transfer switch?

[motskyroonmatick]

Power--120v AC from solar inverter.

Purpose- Transfer power for normally on circuits to one dedicated 20amp circuit for length of time the timer is set for.

Theory of operation- Normal mode of operation 4 outlets powered. Twist timer switch engaged transfers power to a single 20 amp outlet. When the timer switch shuts off by reaching 0 the power is returned to the normally powered 4 outlets.

Practical application- Remove non critical power to Bar to support high power use(welding) and have power return automatically to the bar with out having to remember to throw switches or breakers.

What are your experiences with this sort of thing?

I'd like to build it from off the shelf components and incorporate it in to our single leg 120VAC power distribution box which I will be scratch building.

[BBadger]

I think I understand what you want, like one of those nice spring-wound mechanical timers that turns on an output. That part is easy and off-the shelf. Making that timer also shut off power to the other circuit when operating is the more exotic functionality. There are a couple ways it could be accomplished, but I couldn't find something directly off-the-shelf.

A DC circuit could be built that that controls two solid state relays (SSR), one for each set of outputs. The circuit would be driven by the timer that provides a connection to a signal voltage when counting down. That could be the timer above. That signal would then use a circuit (such as a logic inverter) to produce an inverted second signal. Each respective signal would control a normally open (NO) SSR. Alternatively, you could avoid the inversion circuitry and just use a normally closed solid state relay; however, those are usually far more expensive and uncommon.

This would not be a difficult circuit to fabricate. It would, however, involving electronics such as a DC power source, some resistors, a logic inverter gate, and connecting to some SSRs (e.g. this). It'd probably reside on a breadboard or something like that, or protoboard. The benefit of such a system is that it wouldn't be a mechanical switch on the actual power routing, and probably last longer and not generate sparks. It'd also be relatively low power. The cons: having to build a separate control circuit.

Alternatively, there are electromagnetic coil-based relays that have NC/NO connectors on them, but will use more power. It would probably be relatively easy to hook up: the timer would be wired to AC input, and energize the relay's coil when counting down. The relay would then switch states, connecting or disconnecting power to your outputs, hopefully without too much spark. It'd probably make a satisfying sound as well. The entire system could run off of AC without extra circuitry. The cons of such a system is that the contacts may spark when switched, and the coil uses power when energized.

Finally, the only off-the-shelf timer that allows switching power exclusively between outputs isn't quite a countdown timer. It's a 24hr timer by Intermatic, specifically the model T105 1NC/1NO DPST switch. That device is more like a time switch, as it has a full clock and you set when you want it to turn on or off. While it might work by setting the time to turn off after the current time, it's not all that intuitive or even quick to set. So I don't know if this a useful solution.

[Popeye]

Paragon makes different mechanical timers the might work for you. They will handle the current you want and are often used for defrost applications in commercial freezers.
Popeye

[Token]

Y’all know a spring wound SPDT timer from any big box store will do the trick, right?

The magic is in the DT - Double Throw.

They make ‘em in 15 minutes to 24 hours.

20A too.

Less than $50 at any big box store.



That one is on clearance for like $12 …

https://m.supplyworks.com/#/sku/406342/ ... 0196-a512h

[BBadger]

Y’all know a spring wound SPDT timer from any big box store will do the trick, right?

The magic is in the DT - Double Throw.

^ This is the solution.

[motskyroonmatick]

Y’all know a spring wound SPDT timer from any big box store will do the trick, right?

The magic is in the DT - Double Throw.

They make ‘em in 15 minutes to 24 hours.

20A too.

Less than $50 at any big box store.



That one is on clearance for like $12 …

https://m.supplyworks.com/#/sku/406342/ ... 0196-a512h

Holly Crap!!!! That's a super elegant solution. I was thinking I would have to adapt a transfer switch or make up something with contactors. Thanks! I will look in to those!

Thank you everyone who responded.