a little off topic, but i have a control relay question

i have a 1/4 rack of plc 5 that i would like to tinker with at home to control some lights and such. i'm not rewiring the whole house by any means, but just want to try some things. i'd like the output card to bring in a relay to enable a group of lights or an outlet (mainly for my porch lights and landscaping lighting). i'm having a hard time finding a relay that has only 1 contact on it and is rated for 15 or 20 amps. i don't need a relay with a bunch of contacts and its just bad practice to install a device that has a lower rating than breaker. any suggestions?

thanks

Have you tried McMaster-Carr?

http://www.mcmaster.com/

Type "relay" into the search engine and there are many. I saw some general purpose rated for 15 amp.

Good Luck.

or www.grainger.com
You can get octal or pin based relays with 2,3, or 4 sets of contacts. There are other options but the cost may be too prohibitive for your needs.

I missed the rating part, most relays are 5 or 10 amp but you can get SSR (solid state relays) that go up to over a 100A.
http://www.crydom.com/product/ssrindex.asp

Better to use a contactor for that load or an SSR. I have found that normal relays, although rated for 15 amps, are only rated that high for AC1. They are unable to quench the arc properly and burn out.
If you wish to continue on this path, Omron make one rated at 15 amps.
beerchug

The breakers are sized for the expected total aggragate load for the branch circuit.

Relays are often sized for the load on the relay contact.
For example if you are switching a 100 watt incendesent light, than a standard KH or KUP style relay, with 3 or 5 amp contacts, may due the trick for you. A larger relay with a 15 amp contact will likely have a large coil that may be hard on you PLC outputs due to arching from switching off the inductive load etc.

Check you loads, and your PLC output specifications. You may find that the PLC outputs may be able to handle the resistave loads of your lighting circuit without the extra relay.

Mike

thanks for the great info. i haven't worked with ssr's much so i really hadn't given them much thought. i will definately look into them more. those are some great links too. that crydom site is exactly what i was looking for, where i can enter what i need and have it show me what meets those requirements.

I hope you will not hardwire all those devices in parallel. If you bring them in an "Home-run" panel you can do this parallel wiring from the relay and you will also have the oportunity to change the logic later when your wife tells you her 254th opinion on how perfect it could be

So if you do it that way, best is to use 2 relays in parallel and use the normal of-the-shelf ones with 5 or 10 amp rating. This way if you blow a contact you can just replace it with what you have in stock.

And it will give you the chance to play around more at chrismass time.

Remember the fact that if you are asking for this special thing... it tell you that "special" is exactly what you don't want in your system. Use standard devices unless you really don't have a choice.

Solid state relay

Normally, plc output contact (In your's case ,relay output module better)2 amp. maximum .
for load 15 Amp or more size..Solid state relay or Contactor is a good choice..However,it depend on How offen you run load .
Should be aware the current when starting .. need to up size of
Solid state or contactor too.

Platootod

i ordered 3 ssr from mcmasters (7664K16) for only 10 bucks a pop i figured they're worth a go. i was expecting them to cost a bit more than that. this should get me going.

Well I just used 4 or 5 small relays
jumped of the primary.