Contactors: ? About Wiring

[flyer81]

Available through my local electrical supply was a contactor #EC402120. This is a 120v contactor. My goal is to switch two ballasts on via a single timer. The contactor has two poles marked L1/L2 and T1/T2.

My question is whether I should hook one load and one neutral up through this single contactor or I could use it to control two load wires the same way i would hook up a breaker: The neutrals and grounds are hooked up to a bus, and the load is hooked up through a breaker/contactor.

Or should I use one contactor for each pair of load and neutral wires?

 

[rives]

If you are running 120v to your ballast, then you would only switch the hot wire with the contactor, or both hot wires if you are running separate circuits.

The electrical code forbids switching neutrals.

 

[McKush]

a wise man, wink, wink, ^^^^, once sent me this link : http://www.automationdirect.com/adc/Shopping/Catalog/Relays_-z-_Timers/Electro-Mechanical_Relays/Power_Relays,_Open-Style,_40A_%28AD-PR40_Series%29/AD-PR40-2C-120A


if your relay is similar then you can power two separate circuits with one 120v connection.

I use one relay to power two hot lines for a 240v fixture, but you can use one relay to power two 120v circuits just as easily. Sounds to me that is what you would like to do.

 

[The Meadows]

I got two 30 - 40 amp dpdt contactors off amazon for $5.00 each plus $5.00 each second day shipping. So, for $20, I got two big contactors shipped using second day air. $40 for one seems a bit high.


http://www.amazon.com/gp/offer-listing/B001KGSJ74/ref=dp_olp_new_mbc?ie=UTF8&condition=new

 

[rives]

Good find, not sure where you got the $40 figure though? McKush's link has a 40a power relay for $20. It is DPDT, so it includes a set of normally closed contacts and can be used for things like a flip. Power relays are normally much more heavy duty than definite purpose contactors, which are usually built as cheaply as possible for the air conditioning industry.

 

[flyer81]

I ended up with contactors out of a desire to pay cash and buy local. My local electrical supply house only had contactors, no relays. I was mildly shocked .


With a relay it looks like you can see the structure and understand what was going on. With the contactor... its all inside of a black box. Just wanted to be sure.

Right now I have a small box built with 4 wires going on. 2 -3 prong male plugs and 2 females. The loads are wired in through the contactor. Just waiting on the timer to be shipped.

My idea was to have the male plugs plugged into wall sockets on two different circuits and the female plugs would run to the ballasts . The timer would then control the power to the ballasts on/off.

Ive wired up entire circuits, subpanels, new outlets etc. This is my first time playing with relays/contactors. Next step: building my own controller with PLCs/Arduino.

 

[rives]

Power relays are more of an industrial item, whereas the dp contactors are used extensively in HVAC, so that might explain your local sourcing. The relays have replaceable components (contacts, coil) and the contactors are cheap enough that they are normally just swapped out rather than rebuilt. Either one should work just fine for your purposes - I prefer the relays because their flexibility allows me to stock one part for whatever gadgets I can dream up.

 

[McKush]

For lurkers and stumblers... here is a good link where a heavy duty DPDT (similar to the one in my link above) are used in a single ballast flip/flop circuit.

https://www.icmag.com/ic/showthread.php?p=3856938&highlight=flip+flop+relay#post3856938


at $19.50 they are a very versatile component.

My only comment is to use a proper metal enclosure for your project. Be safe. You don't want sloppy work creating shorts between connections or wires forcing a connection always on or always off. Wires in/out of your box need to be secured with grommets or clips, etc... solder connectors on to the wires. don't provide an opportunity for a frayed hot wire to short to ground. Protect the ones you love and the ones you don't love.

sermon over

 

[flyer81]

My only comment is to use a proper metal enclosure for your project. Be safe. You don't want sloppy work creating shorts between connections or wires forcing a connection always on or always off. Wires in/out of your box need to be secured with grommets or clips, etc... solder connectors on to the wires. don't provide an opportunity for a frayed hot wire to short to ground. Protect the ones you love and the ones you don't love.

Definitely worth repeating.