Relay current rating vs. upstream circuit bkr rating

[ThatGuy]

I have a circuit that is controlling a couple of alarm lights in an industrial facility. These lights are connected to a couple of sensors, and I am placing a couple of relays in the circuit in series to perform the logic I need ("AND" logic) to control the lights. These are LED-style Unimar lights which draw about 0.12 amps each, and the relays controlling the lights are ice-cube relays, with a contact rating of 5A. The breaker supplying the circuit is a 20A 120V breaker. Do the relay contacts need to be rated for 20A, or just the rating of the lights themselves?

I'm having trouble loading a picture into this, so a rough diagram with ASCII characters is here:
RELAY CONTACTS @5A
20A CB CR-1 CR-2 LED Lights 0.12A Each
----o^o--------------||-------||------------------------O----
| |--------O----
|
| CR-1
|-----[sensor]------------------------------O----
|
| CR-2
|-----[sensor]------------------------------O----

 

[ThatGuy]

Apologies

Apologies

I apologize for the diagram; the forum removed the spaces that made the diagram make sense. You can see the main line is a 20A CB in series with two relay contacts and the indicator light.

 

[StephenSDH]

Everything in the circuit needs to be rated for the OCPD. Just add a 5A Din Rail breaker or fuse to protect your relays. Should cost 5-20 bucks. Probably cheaper then up sizing your relays to contactors.

If you want "AND" Logic for the sensors you need to put them in parallel.

Steve

 

[ThatGuy]

Thanks for the response. Would that just need to be one of the supplemental CB's, like the older Allen-Bradley 1492-CB? Or does it need to be thermal-magnetic, like the UL489 style?

I think you are thinking of OR logic by saying they need to be in parallel.

 

[StephenSDH]

I think you are thinking of OR logic by saying they need to be in parallel.

Yeah your right. I wasn't thinking straight. As far as the supplementals go, I can't give you advice.

Here is a SquareD UL489 Mini Circuit Breaker or you can just use a fuse.

http://www.schneider-electric.us/pr...i-9-system-ul-489-miniature-circuit-breakers/

 

[jim dungar]

If the circuit wiring leaves the enclosure that contains the OCPD, then a supplementary device can not be used, it must be a UL489 one.

And Square D makes a rail mounted version of their QO breakers, QOUxxx

 

[don_resqcapt19]

Why do the relay contacts have to be rated the same as the OCPD that protects the circuit? Switches don't have to be...they only have to be rated for the connected load.