Greetings Mulderm,
you’ll eventually get this problem fixed ... but the fact that you’re asking these particular questions indicates that you might not really understand some of the SAFETY! aspects of using the triac type modules ... so to try to save you (and other readers) some unnecessary grief, here’s a reprint of another post ...
A scary story -
A technician needs to work on a motor starter - nothing fancy - just a plain-old everyday three-pole contactor with a 120 VAC coil. And incidentally, the coil is controlled by a solid-state triac-type AC output module on a PLC system. So the technician makes durn sure that the 480 VAC, 3-phase line power is disconnected - and locked-out and tagged-out - and checks with his meter to make sure that the juice is really off. Good - so much for the high voltage stuff.
Now the 120 volt AC coil voltage can be easily controlled by the PLC - so the technician just forces the proper output off - and confirms that the coil drops out. Yes, indeed - the LED for the coil’s output is off. And a meter test across the coil terminals indicates that there is less than 1 VAC showing up there. Well, that’s probably just a “false” kind of reading - maybe coupling in from nearby wiring. Anyway, less than 1 volt isn’t going to hurt anything. So now it’s OK to climb in amongst the wiring and fix the contactor - right?
What’s wrong with this picture?
The contactor coil is “loading” the circuit - and “draining off” the leakage current - and so the meter reading looks acceptably low. But a SERIOUS problem shows up once the wiring to the coil has been disconnected. Then there will be NO load on the output circuit - and the voltage will “float” up to its applied voltage level - 120 VAC. Now ... if the technician just happens to brush against that coil feed wire ... this could get very ugly. Especially if the technician happens to be wet with sweat and making good contact with something grounded.
The fact is - to the technician’s skin - that trickle of “leakage” current is going to feel just like a 120 VAC live wire - EVEN THOUGH THE PLC OUTPUT IS OFF! Now some people will say: “Well, that’s going to be a very low current signal - not enough to really hurt you.” Yeah - maybe so. The shock might not hurt you - but it can sure make you hurt yourself.
finally ... if you decide to mount a “dropping” resistor in parallel with the load to fix your problem, make sure that it is mounted safely ... basic idea: when the output eventually turns ON, then the resistor has line voltage applied - and it becomes a small heater ... depending on its resistance value, etc. it can get hot enough to melt wiring insulation and damage other components ...
