How to check voltage on a 1746-OA16 card

[GHaulk]

I am having problems with some of our 1746-OA16 cards on a SLC 500 system. I am controlling solenoid valves with this card and they are 120VAC, 25 Watt each. That should put me at .20 amps per solenoid (just shy of the .25 amp rating for each point on the card).I keep having problems with some of the ppoints burning out. This being a Triac card, I am a little confused on how to check the voltage coming out to make sure the card is working properly. I can check for voltage at each point and I get no reading, even if a point is working. Can anyone tell me the proper way to check the point on this card with the volt meter?

 

[controlsdude]

digital cards usually have removable terminal blocks on the front of the card. Hopefully the oem gave you this option. Just power rack down remove the front terminal block, check your voltages coming in, look for frayed terminals, might be a short. go in field check for shorts.

Look at attachment for how this is disassembled.

since you have the term block in hand check for shorts in the field terms, ohm check with 120v off.

with power back on and isolated to which solv is causing short.
last thing to do is whichever solv is creating short, disconnect the solv at other end, make sure it is not bad wiring.

the current draw is .25a @60C and .5a @30C. Is it really that hot their(60C)?

Hope this helps, stay calm and keep a clear head, you should know what the problem is in a short time.

 

[jde777]

Are there any snubbers on the outputs? May want to add them. Also may want to fuse the outputs.

 

[controlsdude]

I just assumed that you had fused outputs but if your blowing the card then you probably dont. On the contrologix they have internal fuses on the card, I do not believe they had them on the slc500 digital io series. Hopefully your wiring output to these cards has a breaker on it, if not then you might want to put one in.

 

[GHaulk]

I understand everything all of you said and I have actually checked the resistance of the solenoids to see if they are good. My question actually was: If I need to check to see if the card itself is actually sending out voltage to the solenoid, how would I do that? I've tried it and I seem to get 0 volts even on solenoids that I know are working. By the way, I am checking from the terminal on the card to the neutral. Does this make any sense?

 

[SteveMeisel]

I had a problem exactly as yours. We were losing triac card outputs that were driving solenoids and a fuse was between them. I solved it by switching the triac card out with a relay card and the problem went away. You may want to give it a try.

Steve

 

[GHaulk]

I have thought about that. I have done just the opposite in the past where I had a heat controller I was switching very fast and very often and the relay cards were starting to fail so I switched to Triac. Fixed that problem. I may just change to relay cards since I'm not switching that often. I would still like to know how to check that voltage.
Thanks Steve

 

[controlsdude]

You need to force the output on to get 120vac out of the a particular output. Otherwise you need to let the machine cycle when it comes on from the front indicator on the card.

Is this what your saying?

you know how to force an output on through the program?

 

[controlsdude]

did you also take into consideration jde777 suggestion on snubbers or mov's to get rid of the spike that solenoid valves always introduce?

 

[controlsdude]

This is out of the AB pdf on SLC500 digital io

Surge Suppression
Most output modules have built-in surge suppression to reduce the
effects of high-voltage transients. However, we recommend that you
use an additional suppression device if an output module is being
used to control an inductive device such as:
• relays
• motor starters
• solenoids
• motors
Additional suppression is especially important if your inductive
device is in series with or parallel to a hard contact such as:
• pushbuttons
• selector switches
By adding a suppression device directly across the coil of an
inductive device, you will reduce the effects of voltage transients
caused by interrupting the current to that inductive device and
prolong the life of the switch contacts. The diagram below shows an
output module with a suppression device.

If you connect an SLC 500 controller triac output to control an
inductive load, we recommend that you use varistors to suppress
noise. Choose a varistor that is appropriate for the application. The
surge suppressors we recommend for triac outputs when switching
120V ac inductive loads are a Harris MOV, part number V220
MA2A, or an Allen-Bradley MOV, Catalog Number 599-K04 or
599-KA04, Series C or later.

 

[jde777]

You have to measure from neutral to the output. So where ever nuetral is in the cabinet to the output point should give you your 120vac when ON.