Mechanical Contactor Relay and Light Circuits

Many control systems work on 24 volts. Some use DC and some use AC depending on what type of control system. In any case, however, 17v is an indicator of a damaged drive circuit or transformer. If the EMS guys can't figure it out, I believe I would have some qualified person troubleshoot and repair and then have him look around for other issues. Issues like this tend to attract other trouble.

well indeed, besides that ems system is pretty old... however, isn't it weird that eventhough the relays are receiving that voltage the contactors, the mechanical contactors are getting 120v and still one of them is not working? how do you actually troubleshoot a contactor, a mechanical contactor ( big relay)? or fix it? and how do you troubleshoot a relay working with a low coil voltage?

I think you know what it is--But you are saying it wrong--The contactors are not in series, but in parallel. If they were in series, any contactor would fail and there would be no light on any circuit--Series is AND and parallel is OR.---This AND this AND this AND this, you get lights(series).

2 power supplies and 4 contactors, and 1/8 of your lights out.

Are both power supplies common to good light circuits?

Is the bad lighting circuit on it's own contactor or does it share one with lights that work?

If 4 contactors means two circuits per contactor and you are missing only one, I would suspect a set of contacts in one, and not the entire contactor.

Take measurements on BOTH the control voltage(coil) and the line voltage--

120V on all line side of contactors? If no find out why. If yes--Pull the contactors in(make sure they all pull in) If they all don't go to the next paragraph, If they do--check for 120V on all load side of contactors? If no, measure and find the bad contacts. Check your neutrals-Are the neutrals switched with the contactors?

24V power supplies, are they 24V? If not, you may have a bad power supply. Measure. If they do have 24V, make sure you have it all the way to the controller--Then make sure you have it out of the controller to the coil. If there is a voltage drop through the controller, from 24V in to the output, then there could be your problem.

You measured 17V. Is it AC or DC? Did you measure to ground? If it is DC--Did you measure back to common, or ground?

I really appreciate your answer sir, when I said 120v in the contactors, I'm talking about the coil voltage, the one that opens or closes the contactor. I know that contactor, one part of it at least, the upper side is openned and it wont close even with that voltage present. Line 1,2,3,4,5,6 have 120v and terminals 1,2,3,4,5,6 have no voltage at all, so yes that pretty much means that the contactor isnt working properly, I want to know possible whys. The other big question I have is, I know those relays I have in a different big j box next to my panel activate the contactors, the mechanical contactors, i made the difference theere. Now my relays work with 24V AC, they are only getting 17V AC and this comes directly from the controller. However my relays dont seem to be wrong, just one of the terminals in one of the relays is giving me 40V, could that be caused by the insufficient volts in the coil? And if so, why do I still have 120V in all the coils of my contactors?

Contactors usually buzz loudly when they are about to go . This is usually caused by the windings in the coils going open and acting in an off/on state. Or the mechanical draw bar inside the contactor has simply worn to the point that it is kinking as it moves . If you have a contactor that is not moving at all , it usually means the coil winding has opened and there is no " pull in " of the draw bar and switching terminals . You can meter the coil terminals but if the seperation in the coils winding is very small you will get a false reading on your meter . To simplify testing ; disconnect all power to the system , disconnect coil feed terminals and then supply 115V. A.C. ( if this is your coil voltage ) to the coil terminals . If the contactor does not respond you have a bad coil in the contactor . If it buzzez , you have a going bad contactor. If it works repeatedly you have a controller that is not providing sufficient voltage to the coil.

Hope this helps .

Okay. 24V relays passing 120V to the contactor coils---Correct?

You have 40V--Find the voltage drop--Is it 120V enetring the 24V relay contacts? If not go "upstream" until you find 120V. If not--are they ice cube relays and have you replaced it? Still get the 120V to 40V drop--check the relay base, sometimes the sockets erode.

The 17V AC--Is it 17V on all the 24V relays? If so I would concentrate on the 120V to 40V drop for now. Check all the outputs from the controller and are they all 17V? Is there one that is different?

You do have contactors that are working in this system? I am still confused with what you have.

indeed its very confusing, there are 17v ac coming from all the terminals in the ems systen, and the relays call for 24v, but all the coil voltages in the contactors, which come from the relays are 120v

It sounds to me as if you have a faulty contactor coil. Check it out with an ohm meter the reading should be virtually a dead short. ie same reading you will get if you read from probe to probe on the meter. Just replace the faulty coil or if the contactor is obsolete model replace the whole thing. Stop worrying about the rest of the system if the relays are working and the other three contactors are opening and closing ok then it is fine. Just fix the faulty contactor and remember the rules if it works dont F*** with it!

Lets start with what we know:
The rest of the systrem is working correctly. Therefore the problem is specific to your one relay.

There is a small pilot or control relay that is activated by the 24v source, and this in turn is controling your 120v coil on your lighting relay.

Genrally if there is a problem with the control it is that 24v pilot relay.

Now it gets tricky:

Is the lighting contactor normally open or normally closed? This will effect how the lighting is controlled.

Is the problem you are describing a fault on the EMS system or are you trying to bypass the EMS control?

Energy management is set up and approved by the ownership and the parameters of the operation are usually spelled out in contract to the installer. The installer has no legal right to change the parameters of the program unless he recieves written orders to do so by the owner.

Your transformer is failing or overloaded due to several possibilities. 1. The VA rating is undersized. 2. One (or more) of the contactor coils is shorted or grounding. 3. There is a short in the control wiring. 4. The primary supply to the control transformer is low.5. One (or more) of the contactors is mechanically defective; this sometimes causes the magnetic plunger to overheat-pulling down the entire network. 6. The wire length is too long. Troubleshoot by resistance check of each contactor coil and also do a ground fault check. Determine what the voltage output of the control transformer is, unloaded. Contact the manufacturer of the contactors and find out what the VA load is; the transformer should be sized for the total load plus wire loss with (I recommend) a 50 % safety factor.

After reading recent comments, I agree the general concensus is you re-state more accurately, no offense. Better yet take a series of accurate measurements at each coil.

There is usually a mechanical means of operating the lighting relay. If the relay operates the lights with mechanical operation, this leaves the closing coil circuit and the mechanical condition of the relay. If one relay of the several is not closing then the problem narrows to that relay alone and not with the 24v relays.

Step 1. Check connections to be tight on both ends of control circuit.

Step 2. Validate voltage readings at both control coil terminals to be similar to neighboring coils whose contactors are pulling in..

Step 3. Hold a small insulated magnet near (but don't touch) the coil and feel for vibration. Should be same as neighbors.

Step 4. Validate physical ability of contactor to move and close. If physical closure has a problem, then the contacts are also suspect since age or high loading damage could have caused the problem. Highly resistive contacts due to burning etc. can result in the 40v reading with the other 80v dropping as heat across the contacts. which by the way can burn out the closing coil from proximity heating of the bad contact.

Step 5. Be ready with the replacement lighting relay, since that appears to be the likely cure from the details you have provided so far.

Many excellent previous posts duly noted. What an ecxellent forum.

yeah, thanks for the advices, i changed the contactor. it seems that the electro magnet inside wasn't doing its work, who knows why, great comments by the way, thanks again, and I liked that one that says... if its working right dont FUCK WITH IT HAHAHA very true tho, in some cases like this one

ANSWER TO THE GUY FROM BRAZIL and in general (see Naviero1's last few words, 11-26-08), this is specifically what I'm talking about. Nice that our profession can be so very professional.

It could be the leads on the contactor, corrosion maybe. If that contactor has been opened and closed alot then it could definitly be bad. Replace the contactor.

See post 11 above.

naviero1, take the picture off please, you broke your family 4ever, don't play like you have one. I hope I answer your question.