Flourescent Lighting

[Schnidly8563]

Dear Forum

I am trying to figure out a flourescent lighting scheme at work. There are two toggle type switches controlling a lighting circuit. The toggle switches come to rest in the Off position in the center after they are either toggled up or down to turn on or off the lights. I thought they were simple three way switches with one hot lead to the common terminal on one switch. I checked both switches with the wires removed, there are three wires to each switch, and the black wire in each box are HOT with 120volt power. The problem I am having is the the only way to turn the lights off is by switching the circuit breaker on or off? The lights stay on and neither switch will shut the lights off?????? Like I said, the only way to shut the lights off is with the circuit breaker. Also, the lights stay on even with both switches completely disconnected from the circuit???? I figure there has to be a lighting contactor up in the ceiling somewhere with the contacts fused closed to keep the lights on, thus bypassing the control(120 volt) circuit used to close or open the contactor with shutting the lights off or turning them on??? Id greatly appreciate your help with this! There are also two circuit breakers, one for half of the lights and one for the other half of the lights in the room???? Both sets of lights come on and stay on when the circuit breakers are on, even with the two switches disconnected.

 

[jumper]

I am guessing you have two Double-Throw Ctr-OFF Momentary Contact Single-Pole Switches that are supposed to control two Mechanically Held Lighting Contactors.

The switches are supposed to pulse a signal/voltage to the contactors to either the open/off or closed/on position.

While you could have a problem with the plates/contacts welded together, I suspect it will be a problem with the control wiring.

 

[iwire]

My first stop would be the contactor and check the condition of the 'open' coil.

Typically mechanically held contactors have a coil to open and a coil to close.

If a coil is burned up I would verify that the coil was not getting powered 24/7.

 

[dicklaxt]

Questions:

1. Are we to assume that at the initial closing of the circuit breaker,,,, that the lights are off and must be turned on with either of the switches?

2. If the lights have to be turned on from either switch will both on & off positions turn them on or just the on position?

3. Are the 2 hot wires at the switches common to each other and do they remain hot at all times?

4.Are you sure all 3 wires from each switch are actively wired into the circuitry?

5.Are there any jumpers on either or both of the switches?

6.Have you verified that the switch is truely a SPDT momentary with center return off?

Sorry for all the questions but I'm trying to determine how to mimic this circuit on paper and need to know the particulars.

dick

 

[infinity]

Sounds like you've got a contactor problem. As you can see from the various questions there are many variables to consider when troubleshooting a system like this. From a design stand point one of the reason you would use momentary contact switches is so that you can wire a momentary time clock in parallel with the switches to provide timed on/off. Otherwise you could just use a three way switch for control depending on the type of contactor.

 

[iwire]

Questions:

1. Are we to assume that at the initial closing of the circuit breaker,,,, that the lights are off and must be turned on with either of the switches?

2. If the lights have to be turned on from either switch will both on & off positions turn them on or just the on position?

3. Are the 2 hot wires at the switches common to each other and do they remain hot at all times?

4.Are you sure all 3 wires from each switch are actively wired into the circuitry?

5.Are there any jumpers on either or both of the switches?

6.Have you verified that the switch is truely a SPDT momentary with center return off?

Sorry for all the questions but I'm trying to determine how to mimic this circuit on paper and need to know the particulars.

dick

Dick, I think a few of us are picturing this arrangement.

L = line connection on the contactor

O = open coil on the contactor

C = close coil on the contactor

This is a typical mechanically held lighting contactor wiring diagram, with this wiring you can add as many switch locations as you want and all of them can at any time turn the lights on or off.

 

[infinity]

Dick, I think a few of us are picturing this arrangement.

This is a typical lighting contactor wiring diagram, with this wiring you can add as many switch locations as you want and all of them can at any time turn the lights on or off.

Yes, that's the other advantage that I left out of my first post, multiple control locations and devices.

 

[dicklaxt]

OP stated that he could remove switches from circuit and lights would stay on,

Here is a sketch that will satisfy that if the switches are SPDT maintained last contact position.Toggle only returns to center.

Sequence of operation:

1.Close breaker

2.Toggle either switch

3.This energizes contactor and seals it self in with the holding contact.

4.The main power contacts close turning on the lights.

5.Either switch can be toggled and lights stay on.

6. The switches can be removed from the circuit.

7. Breaker needs to be opened to reset scheme.

Not a very well designed circuit but fits the OP with using SPDT maintained switches,note that switch contacts shelf position are cross wired to the other switch,ie: NO to NC

dick

 

[Schnidly8563]

lighting contactor

lighting contactor

Dear Forum,

I have both switches out completely, three wires to each switch, one wire in each of the two boxes is a hot black wire. Then there are two runners in each box. I believe these two wires run between the boxes. After finding the hot wires in each box I wire nutted the two remaining wires together and checked continuity and they were both common to each box. That is, they ran from one box to the other and were connected on two of the three terminals on each switch. Even with the switches completely removed from the boxes and all the wires nutted seperately of course, I still could turn the lights on and off with the circuit breaker. If the circuit breaker was on the lights were on, if I turned the circuit breaker off the lights went off. I am thinking the contactor contacts are fused together and the 208volt lighting is being turned on by the circuit breaker???? Even with the switches in the boxes and the wires all connected the lights come on when the circuit breaker is turned on. The only control I have as far as on and off of the lights is by the circuit breaker at this time.

 

[Dennis Alwon]

Are these switches momentary contact switches as Bob posted? Bob's diagram would explain exactly what you could have in which case the contactor is stuck in the on position.

 

[dicklaxt]

Aha!!!!! Now we have more pieces to this puzzle

1. We know now we have a control circuit that is 120VAC

2. We know now we have 208VAC lighting

3.We still are in the dark on the contactor as to one coil or two,the type of switches(momentary w/2 NO or maintained w/1NC & 1NO),where does the control power come from(separate circuit or from a CPT off of the 208VAC legs,is it 208VAC 1 phase distribution or 3 phase distribution?

Its 8:50PM and I'm going to bed,I'll play with this when I get up if someone doesn't figure it out with all scenarios by the OP adherred to.There's more than likely more than one answer but we really need to know what we have to play with.

dick

 

[dicklaxt]

If I expand the schematic above by Bob by adding in the seal and break contacts as shown in schematic-1 attached ,we get a good system as probably desired based on a dual coil contactor,,,,,,,,,this of course is using the aux contacts in series.

Now if I put those aux contacts in parallel as shown in schematic-1A attached,we now have an error in function that fits the OP in every facet I believe,,,,,,,,,please holler if you see an oops.

dick

 

[gar]

100823-0831 EST

Schnidly8563:

The real title of of your question is probably "Lighting circuit switching theory question".

I like iwire's post #6 as being the best system.

Meaning it uses a bistable mechanical (could be electronic) relay (contactor). To make it clear, as others have described, this is a relay that has two mechanically stable positions, two coils, pulsing one coil moves the relay to one state, and pulsing the other coil moves the relay to its other state. This type of relay has the advantage that there is no continuous power dissipation in the coils.

A GE RR type relay is of the above bistable type. But these are not normally powered at 120 V.

The great advantages of this type of circuit are:
(1) No continuous coil power.
(2) Wired "or" control. This means the logical "or" function. With a wired "or" function you can have as many control points as you desire with very simple wiring.
(3) The "on" position of all control switches can be in the same orientation. And likewise for the "off" position.
(4) Momentary "on" and "off" pushbuttons could be used instead of the spring return to center off SPDT switch.
(5) More complex switching functions can be performed. For example: one switch could turn on all the lights in an area, while other switches could control different regions.

You need to find the contactor or contactors being controlled by the switches. Find out how the contactor works.

There are some tests you can perform from the switch location.

From your description there is a common hot wire to the wall switches. Find the breaker that supplies this hot wire and turn it off. After turning off this power verify that there is no voltage on the hot wire. If you use a high impedance meter you may see some capacitive coupled voltage. If so load the wire with a 15 to 100 W bulb and the voltage should go to near 0 millivolts.

To a known good neutral and/or ground measure the voltage separately to both of the switched wires. Should be zero. Again there may be capacitive coupling. If voltage is zero, then measure the resistance from each control wire (the switch outputs) to neutral. Resistance should not be 0 nor high. If our guess on the circuit is correct, then you should be measuring a relay coil resistance. I have a #2 motor starter with a 120 V coil and its resistance is 40 ohms.

If the "on" coil reads a likely good value, and the "off" coil is high, then the off coil is burned out or there is an open circuit in the loop.

There are non-mechanical latching relay circuits that could work with the momentary control switches. If these are powered from a different breaker, then your on-off test with the power breaker to the lights might not unlatch an electrically held circuit. But my guess from your breaker power on-off test is that you have a mechanically latched relay.

Find the relay (contactor) and provide us with some information on the device.

.

 

[dicklaxt]

All good and exacting info but why is everyone assuming a coil or the contactor is bad?

I assumed that it was a final commissioning and not a worked right for a long time scenario then failed.I guess it could be either way but I would think looking at the physical wiring would be a lot easier than all the testing.The OP did nor say so its a flip of the coin but then again the OP was not sure what was there so I guess it must be a failure and not a commissioning.

I am anxiously awaiting the actual outcome and just what is there.

dick

 

[gar]

100823-1036 EST

dicklaxt:

From the original and subsequent posts of Schnidly8563 it appears he did not install the circuit and is not familiar with what is probably the circuit. This seems to imply a service job. It also seems he needs some background to understand what he should be looking for in his troubleshooting task. We may be wrong in our guesses but they should still help him.

.

 

[dicklaxt]

Right you are Gar..

dick

 

[Schnidly8563]

Lighting Contactor Circuit

Lighting Contactor Circuit

OK, I think I have a diagram to the best of my abilities of what my lighting circuit looks like. Here it is:

View attachment 4966

Hope this attached properly! My situation is that the lights stay on all the time when the two circuit breakers are on, even with the two momentary switches removed completely from their wall boxes!! Im suspecting the contacts in the contactor are fused????

 

[dbuckley]

I'm suspecting the contacts in the contactor are fused????

That would explain the problem, or if the 'off' coil is knacked, or something mechanically busted about this mechanically held contactor. You've got 120V available, so the transformer must be working.

The wiring diagram looks correct. It looks like a three phase contactor is being slightly misused as a two hot and neutral contactor; electrically that is perfectly acceptable.

If you get someone to operate the switches while you have your head next to the box you should hear the coils hum as the switch is moved. No hum means either no power to the coil (confirm with wiggy across coil) or the coil is not working.

 

[dicklaxt]

Your wiring diagram is missing a couple of things,,,,,,,,,,,,,the L2 connection from CB#17 to the transformer and the neutral connection from the transformer to the coil.

Per the diagram and your description when ever you toggle either switch you are switching the hot into the coil,there are not any seal in contacts or break contacts shown and you need to confirm if there is a second coil or not.

The lights are dropping 104 volts across each is that what you have or should 240V replace all 208v referenced?

All of the pieces to this puzzle are not here yet,you may be correct that the main contacts are fused or the coil is energized holding them closed.Its impossible to tell what you have from this wiring diagram,assumptions can be made but that really doesn't correct your problem unless one knows just we we are dealing with.

dick

 

[gar]

100824-1953 EST

Schnidly8563:

You may have welded contacts, but unlikely.

Your problem with having a good understanding of the logic of the circuit is in the way you have drawn the circuit.

Redraw the circuit as follows:

Draw a square box for your something to 120 V transformer. I do not care what the source voltage is for this transformer for the moment. Your 208 input circuit looks to have a problem. Unimportant at this point.

Your 120 V to the switches is correct if the connections on the left are to the center point of the SPDT switch. You can check this as follows: label the left point C and the other two points A and B. When the switch is in its midpoint, then C to either A or B should be open. When held in one position C should connect to A and in the other position to B.

Where you have a box labeled "coil" we believe you actually have two coils. A common point between the two coils goes to one side of the secondary of your transformer. Not shown in your drawing.

The other side of the 120 V secondary is what you have labeled as 120 V Hot. The free ends of the coils go to the switches as you have shown.

This coil thing and transformer should be disassociated from the contactor. The only coupling from the coils to the contactor mechanical mechanism is magnetic. Usually on a schematic drawing a coil will be drawn as a round circle with two wires to opposites sides of the circle, and some sort of labeling internal to the circle and beside it.

Now we are to the contactor itself. If common is the neutral of a 208/120 three phase supply, then you really have two single phase 120 V circuits. These can be considered independent other than that they are switched in common by the contactor.

If your circuit is really as shown, then breaker #17 should turn off one group of lights, and #13 the remaining group. Not implied by previous comments.

If your transformer primary is really a 208 input, then is it bridged across #13 to #17. For the control circuit to work both breakers would have to be on. Either breaker off would disable the control circuit. Alternatively the transformer could be 120 input and then #13 would need to be on for the control circuit to work, and the primary would be connected from neutral to #13. Are #13 and #17 part of a common lever 3 phase breaker, or are they two single phase breakers. If a common mechanism, then you should show a mechanical linkage between them. Usually some sort of dashed line. Or at least a label as to the common function.

You have not yet described to us what the mechanical structure of the contactor looks like. Nor have you run the resistance checks on the coils I have suggested.

We need clearer information, but you are progressing.

If you disable all power to this contactor, then you should likely be able to manually change the state of the contactor. Can you see the mechanics of the contactor?

.