How to wire a 120VAC square D latching relay

Can you provide a schematic diagram? Square D/Schneider's website shows only a photo of the relay. Downloadable PDFs are only of certifications -- not of much use to the designer!

I couldn't find any schematics either but i do have the relay in front of me. The base is an 11 pin base where only 9 pins are utilized. Pin "A" is the Com pin where the neutral goes. Pin "B" is the "Latch" and they use pin "8" as the reset.Diodes connect from Pin "B" to pin "8". Its a DPDT relay ( double pole double throw). First pole is on pin "7" with pin "4" as NO and pin "1" as NC. the second pole is on pin "9" with pin "6" as NO and pin "3" as NC. I hope this helps...

Here's the relay schematic:

The diagram is on page 30 in this document.

That's a nice link provided thanks!

My guess is that you momentarily apply 120 VAC to Pin B to latch the relay, and momentarily apply 120 VAC to Pin 8 to reset it. The internal latching mechanism operates on (pulsating) DC and so SQD has conveniently included rectifier diodes so that you don't have to supply the DC yourself. The resistor is required probably because it takes less juice to reset the relay (0.8 VA) than to latch it (2.0 VA).

Take care not to touch the unused (latch or reset) pin when applying power to the other pin. The unused pin will be "live" (pulsating DC) so long as power is applied to its counterpart.

Thanks! I'll give it a try and see how it works

Hello Guest

Below is a diagram for what you are trying to do using (1) timer & 4 cheaper relays.

If you have any questions please reply.

Hope this helps.

Jeff

A simple way is to energize a relay coil when the circuit goes into alarm. Utilize this relay's normally closed contact in the alarm line, which will keep the circuit open until de-energized. AKA "lock-out relay". This requires no electronics.

Actually, once you have lactheed the relay into alarm. Most lacthing relays can be reset manually. So you don't have to provide an electrically controlled reset if the technician is trained how to reset the relay.

Your latching relay would probably look more like the below. The above would work for a standard relay. You could use another set of contacts on the realy to inhibit start or whatever until the alarm is worked out as well.

Hi JOSHYB

Europium's posts to how your latching relay operates are correct!

In your original post you said: most alarms on the systems i work with self reset once the right conditions are met.

Are you just trying to correct an oversite in the current system(s) to make it/them safer or just to allow your technician time to assess the alarm cause?

Are you going to use a seperate relay for each possible alarm 'type' to try to pin-point the 'area/system part' that caused the alarm or just latch a general alarm circuit to prevent the operator(s) from restarting the system until the technician arrives?

This is just curiosity on my part as there may be alternate solutions to your problem.

joshyb; i belive there is a magnet in you relay that holds it closed when plused with the operating voltage, the (alarm) & released when pulsed the reset, reversing the magnatic field of the relay coil. perry