Holding circuit - DIY safe start question

[CalypsoCowboy]

Can someone look over my idea for a holding circuit / DIY safe start circuit and give me some feed back. This is for a 120v rig.

The power switch is a 2-way maintained switch with NO contact. The element and pumps are 2-way maintained switch with a NO and NC contact. The NO driving the element/pump, the NC side is connected to the holding circuit. So when the element or pump is on, the NC is open.

So in theory, when I switch on the power switch, closing the contact, the relay will only close if both the element and pump are off and the NC is closed. If either are on, and the NC side is open, it won't turn on the relay.

Once all the circuits are powered, to turn off the power, I just open the power switch.

My only concern is the power switch will most likely be a 10amps. This should be fine for starting, as the only load will be the relay as the pumps and element will be off.

When the circuit is powered I will be running a 2000w element, will I have any problems with 20a running through a 10amp switch if I'm not trying to break the circuit? I think I would be okay as long as I don't try and break the circuit.

My only concern would be when I am running the element. If I try to turn off the entire panel without turning off the element first, I'm switching 20amps which isn't good. If I turn off the element via my element switch (not pictured) then I'm only breaking the relay current which should be minimal and fine.

Does this all make sense?

-Josh

 

[vindee]

If the pump and element get power through the N.O. contacts of there respective switches, what exactly is the relay contact powering.
Not really getting what your trying to do here.

 

[vindee]

A better alternative would be to use two separate relays. Have your main power switch feed power to two momentary 3-position switches with 1 N.O. and 1 N.C. contact on each switch.
The N.C. contact would be your seal circuit (or holding circuit) for the relay.
When you turn your main switch off both relays would drop out. Turning the main switch back on would require each switch to be rotated to the on position to pull the relays back in.

 

[CalypsoCowboy]

This would be the main power for the panel. The element, pumps, pid would all be fed further into the circuit.

The hope was to have something simplish that would prevent the panel from being powered if the element or pump switches were in the on position.

The other thought for power switch placement is after the junction of the loopback wire and just before the coil on the relay.

 

[orangehero]

The main switch needs to be rated to at least 120V/20A.

 

[P-J]

This would be the main power for the panel. The element, pumps, pid would all be fed further into the circuit.

The hope was to have something simplish that would prevent the panel from being powered if the element or pump switches were in the on position.

The other thought for power switch placement is after the junction of the loopback wire and just before the coil on the relay.

I took on the challenge of planning out your idea of a safe start interlock. With that said I redesigned one of my recent drawings and implemented Safe Start within it. Switches 1 through 5 are all interlocked.

Hopefully it might help in the design and plan for your setup.

As always - click on the image to see and save a full scale diagram that is printable on Tabloid paper (11" x 17").





Edit: Another thought for you. I spent a little time modifying your initial diagram to provide a circuit that will work. The power on switch only carries the current used to energize the relay.

Hope it helps.

P-J

 

[CalypsoCowboy]

PJ, thanks for the information.