operate 120v motor with .5 amp relay

[treas]

I have a 120v cube relay but do not know how to wire it to control a motor thru a fire alarm relay. The fire alarm relay can only handle .5 amp. When the fire alarm goes off the relay will open and should drop power to the motor operated doors. I burned up the first relay using it as a switch

 

[waross]

You need a contactor to control the motor. A relay is typically used for logic and control. A contactor is used to energise a load such as a motor or heaters. There is a lot of overlap between contactors and relays at the smaller sizes.
I have found that refrigeration contactors are cheap and dependable. Use the cube relay to energise the contactor and use the contactor to control the motor.
yours

 

[treas]

My terminology may be wrong. The cube relay that I have has a contactor and two sets of N/O and N/C relays that change state when 120V is applied. I don't know how to wire this to make the power drop to release the doors. Thanks

 

[treas]

The cube relay that I have has a coil. Is this also called a contactor?

 

[Skogsgurra]

A contactor is very similar to a relay. Only built for higher power.

Gunnar Englund

http://www.gke.org

 

[itsmoked]

treas; can you sketch what you are trying to do. I can see your terminology is very confused and we will all be talking in circles. If you can provide a sketch then we can skip the terminology.

Draw it in something that you can produce a jpeg file from then you can post it in here. See how to post in this FAQ: faq238-1161

You can even draw it on paper with dark ink and take a photo of it. Just make sure it isn't too big a file when you have it in jpeg form.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[GTstartup]

You say:
The cube relay that I have has a contactor....

I think you mean:

The cube relay that I have has a contact(s)

You say:

.....and two sets of N/O and N/C relays that change state when 120V is applied

I think you Mean:

and two sets of N/O and N/C contacts that change state when 120V is applied

Seems like this door motor should already have an operating contactor. You just need to wire the fire relay N/C contacts in series with the device (relay, pusbutton etc.) that may energize the existing contactor. This will prevent operation of the door when the fire relay is energized.

 

[waross]

Hi GTstartup
I took the use of "contactor" to mean the coil but only the OP knows for sure.
I think it's time for treas to call an electrician or a fire alarm tech.
respectfully

 

[GTstartup]

Warcross,

Yep. Roger that

 

[treas]

 

[machmech]

Hello treas

I'm just curious I was a volunteer Firefighter and wonder if your attempting to open doors when your pager goes off? If so have you considered the doors opening for every pager test?
I thought about this concept only to realize I did not want to go and close the doors for a test.

Sincerely, Chuck

 

[jraef]

Semantics, semantics, semantics.

Contacts are the switching components of relays and contactors. Contacts have ratings based upon their ability to switch different types of loads. Motors are difficult loads to switch, so the contacts must be capable of that type of duty or they will not last long. The contacts in the fire alarm are NOT rated for switching any appreciable motor load, so they must switch another device on and off, and that 2nd tier device would be the motor controller, be it a relay or contactor.

A contactor is just a name given for a relay with heavier duty contacts specifically designed for motor or other difficult load switching. That isn't to say that relay contacts are not motor rated, some are, but that is not their primary design criteria. Relays are typically designed so as to switch very fast and with low power consumption, contactors are not.

Heavy duty itself is a relative term. The relay in the picture IS a heavier duty device compared to the .5A contacts in the fire alarm relay. The relay appears to be an Idec RH2, with contacts that are indeed motor rated for 1/3HP at 240VAC, or 1/6HP at 115VAC. If your motor is that size or below, you can use this relay to switch the motor on and off, you will not need another "contactor". If the motor is larger than that, then don't bother with this relay, go buy a contactor.

Now as to the wiring, you did not post any details on the motor, it will make a difference.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[Skogsgurra]

Sorry to spoil the fun.

Treas, I think that you need to talk to a certified electrician about this. We should have stopped you after your first question. This is the kind of work that should NOT be done by someone who doesn't even know the basics. It can easily get nasty and dangerous. I do not think that anyone in here would like that.

Keith: I didn't realize that it was so easy to publish pictures. Thanks for the detailed directions in your FAQ. Much needed - much appreciated!

Gunnar Englund

http://www.gke.org

 

[treas]

Thank you to those that had helpful comments. I was able to bypass the the .5 amp relay by wiring the 120v thru the pilot relay shown, and still allowing the fire alarm signal to initiate the closing of the doors. Thanks again.