Wiring query--I've got a mental block it seems...

[dpb]

Taken from old silo unloader to use as second parallel from alternate location DC in shop...

240V coil relay, 240V 2hp-rated contacts of the mechanical spring type--load contacts a common and one open/one closed pair. Relay operates by momentary make/break--when cycled, the spring-loaded contacts switch positions rather than by being held by continuous load.

Switch is manual pushbotton, START is NO, STOP is NC and one side of each are common.

The wiring on the unloader was so decrepit I didn't try to trace it out when salvaging pieces/parts but I'll be darned if I can figure out how Dad had this wired to work (but I know it did, I was around for years while still were using it and it was sitting there as was removed and parked).

I can see how to get the START to work, what I haven't got my head around is the STOP function since it breaks a contact instead of makes one to cause the relay coil to momentarily energize/release to flip the spring-loaded contacts...

I'll see if I can manage an ASCII pictogram here...

X C X Contacts (C common) / / |

Coil L1-\/\-L2

x____x START / | \x x STOP ____

Anybody draw a schematic to start/stop a load across an X-C pair? There's a jumper from L2 to C for starters for supply...

[trader4]

I can see why you have a mental block. I have one too just from trying to read this.....

[Metspitzer]

Help us out. Just take pictures.

[Metspitzer]

[Ralph Mowery]

Look up a 3 wire stop start circuit. The stop button contacts are normally closed. The start button will be normally open. A set of normally open contacts from the coil are in parallel with the start button. When you push the start button the coil pulls in and the contacts parallel the start button to simulate keeping it pressed. When you press the stop button, the coil looses power and drops out the contacts in parallel with the start button.

[dpb]

On 6/19/2012 2:49 PM, Metspitzer wrote: ...

Of what, specifically do want a picture?

All I can take a picture of would be the face of the relay in the box and it'll show 3 relay contact screws at the top and the two coil connections (plus the jumper from one of them to the common terminal of the output contacts).

It's an old Furnas contactor and Furnas is, of course, long gone. AFAICT there's no part number to try to find old stock or reference diagrams from...

[dpb]

On 6/19/2012 2:52 PM, Metspitzer wrote: ...

through and see if anything seems to fit.

The diagram at is good when the relay is powered to hold the relay contacts closed but the kicker in this case that has me puzzled is that the contacts change position only when the coil is energized/de-energized because they're spring-loaded and it's the spring action when the coil de-energizes that causes them to switch position, not the coil magnetic field causing an actuator to move...

The switch is similar to

just a normal manual switch as shown in the above schematic as well w/ the one side of Start/Stop connected as shown there to be in series.

It's clear to get a coil pulse thru the coil to press "Start"; what's got me is then if the coil stays energized the contacts don't switch position to actually start the motor.

'Tis a puzzle (to me, at least at the moment still)...

I'm sure at some point the light will dawn and I'll be realizing how silly I've been in not seeing the obvious... :)

--

[dpb]

On 6/19/2012 3:23 PM, Ralph Mowery wrote: ...

Excepting for the kicker on this relay that the contacts only actually switch on a pulse instead of on/off--they're spring loaded and it's the spring action when the coil de-energizes that causes them to actually change position--they don't on power-on only.

So, I can start it w/ the momentary but can't figure out how to generate the pulse w/ the NC Stop contacts.

I initially thought both were NO until I went to wire it up this morning and discovered that isn't so and what I thought it was doesn't work...

--

[dpb]

...

...

And, I just wired up a test cord to make certain I wasn't seeing something I wasn't--that is precisely how it operates...

Head scratchin' time a little longer here...

--

[dpb]

On 6/19/2012 3:54 PM, dpb wrote: ...

...

Well, of course the magnetic field does cause the actuator to move, the thing is when it moves in the contacts don't move; they only change position on power removal when the spring action causes the contact changeover.

As noted in reponse earlier to follow up to Ralph I just went and confirmed the mode of operation w/ a test cord...

--

[basilisk]

The contactor has an auxiliary contact for control voltage that is NO and makes up with the pulling in of the main contacts.

control power hot goes into one side of the stop switch (nc) and is jumped to one side of the start switch (no), the other side of the stop switch goes to the auxiliary contact, the other side of the start switch goes to the other side of the auxiliary contacts and is jumped from the auxiliary to the coil of the contactor.

the other side of the coil is connected to the overload contact relay, withe the neutral hooked to the other connection of the overload relay.

The start switch temporarily supplies power to the coil until the power can come through the auxiliary switch, the stop switch breaks the circuit and allows the contactor to drop out.

If I remember correctly the auxiliary contacts on a furnas are built along side the main contacts. There will be two small connections at the bottom behind the motor leads that are the overload contact relay.

basilisk

[clare]

So you are saying the relay coil is NOT energized when the motor is running????? AND it uses a NO and an NC switch??? Sounds fishy to me. A "galopping ghost" relay starts with one pulse and stops with a second pulse - a modification of that circuit uses 2 separate NO switches and a spdt pilot switch to select which switch sends the pulse.

GENERALLY a NO/NC pushbutton starter uses an electrical "latching relay" circuit, the ON button momentarily closes the relay, and the pilot contacts of the relay close the circuit to the relay by bypassing the ON switch, with current flowing through the NC OFF switch. By pressing the OFF switch the circuit to the coil is broken, the relay opens, and the pilot contacts also open. To restart, control voltage is applied to the coil through the normally closed off switch and the pressed normally open ON switch, which pulls in the contacts of the relay to start the motor as well as the pilot contacts, which hold the coil in when the ON switch is released.

[dpb]

On 6/19/2012 9:16 PM, [e-mail] wrote: ...

Those are the pieces parts that were in use, yes...

Well, until I started wiring I had presumed the switch was to NO to do precisely that--a start and a stop pulse and was in process when realized wasn't so...

And now you see why I am left puzzled how Dad had this working on the old unloader from which I took the pieces... :) I'm virtually positive it hadn't been touched since last time it was pulled out of the silo and set in the corner for the auction (but it didn't sell; by then nobody else was filling upright silos anymore, either). So, I figured might as well use the parts for something...

If I can't dream up what he did tomorrow, guess I'll rummage around for something else and figure out another workaround -- it just bugs me that somehow this seemed to have been working before. I wish now I had tried to trace out the old wiring more carefully, but that ship has sailed at this point...

--

[Dan Coby]

wasn't--that is precisely how it operates...

Have you tried connecting the relay the same as a normal holding relay?

I think that it will work. The Start button energizes the coil. When the Start button is released the coil is de-energized. Then the relay toggles and power is sent to the load. That also allows current to be sent back to the coil via the normally closed contact of the Stop button. However the relay stays in its same position (i.e. still sending power to the load) until the current to the coil is interrupted. This happens when the Stop button is pressed.

Even though this relay does not need to have it coil energized during normal run operation, it would be in this case. Hopefully this does not cause the coil to over heat. Since you said that your father used this arrangement for years, I am guessing that this is not a problem.

A loss of input power while running would also toggle off the relay. That is a nice safety feature.

/ / Line C / NO LOAD ------+-------O/ O-------+---------------- | | | | +--* | +--*| | Start | Stop +--* | +--*| | | | | +---------+------------+ | * L1 | Coil | * L2 Neutral | ----------------+-----------------------------

Dan

[dpb]

On 6/19/2012 10:34 PM, Dan Coby wrote: ...

...

That may be (probably was?) the way it was; it's too long ago that I have no way of knowing. I can give it a try; I did notice it's pretty noisy when actuated altho in the silo 50 ft in the air w/ the unloader fan running who would have noticed? :) It won't take long to see how much heat it dissipates altho I've only cycled it in playing around so far.

It's a 240V coil; I tried it w/ 120V and it doesn't have enough oomph to move it so it's both hot legs instead of a neutral/hot, but that's a detail; the path is the same if your supposition is right (that that's the way it had been used and I've been trying to make it more complicated than it was, not that it won't work). I just had a mindset when I started that it was only momentary and kept trying to work around that idea that just doesn't seem that can be (or ever was so)...

Appreciate the input from all; anybody gets any more really clever/strange ideas... :)

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[Evan]

If you don't have an installation manual or circuit diagram to work from you should have taken a picture at the very least before pulling everything apart...

It is sounding more and more like you should go and buy a new motor controller which works in the more conventional way...

What are you trying to control anyway ?

[dpb]

On 6/21/2012 12:15 AM, Evan wrote: ...

Easy enough to say now... :)

Having set out for 20+ yrs since last used, it was already well gone as far as the wiring between boxes so...besides who'dda thunk there was anything unique going on, anyway?

Not agonna' happen... :) (Altho if there isn't something in the pile of other pieces-parts in the barn that makes it more convenient (haven't had time to dig through yet) I did locate a P&B relay at Newark for

[Morgans]

Taken from old silo unloader to use as second parallel from alternate location DC in shop...

240V coil relay, 240V 2hp-rated contacts of the mechanical spring type--load contacts a common and one open/one closed pair. Relay operates by momentary make/break--when cycled, the spring-loaded contacts switch positions rather than by being held by continuous load.

Switch is manual pushbotton, START is NO, STOP is NC and one side of each are common.

The wiring on the unloader was so decrepit I didn't try to trace it out when salvaging pieces/parts but I'll be darned if I can figure out how Dad had this wired to work (but I know it did, I was around for years while still were using it and it was sitting there as was removed and parked).

I can see how to get the START to work, what I haven't got my head around is the STOP function since it breaks a contact instead of makes one to cause the relay coil to momentarily energize/release to flip the spring-loaded contacts...

I'll see if I can manage an ASCII pictogram here...

************************ When you turn the thing on, part of the current goes through the stop switch circuit and that current holds the contacts together with the electromagnet coil. You press stop and the circuit holding the magnet is broken, so the contacts come apart and no power goes to the machine or the holding coil.

-- Jim in NC

[dpb]

On 6/21/2012 8:48 PM, Morgans wrote: ...

Not if the it is a pulsing relay...

The mystery has been resolved elsewhere in the thread...

[dpb]

...

OK, I now know how it was done...as concluded earlier, I was overlooking/forgetting a key part and now it has come to me what that is...

This switch and relay were mounted on the unloader up _in_ the silo; normally, however, the whole point of the unloader was to avoid having to climb the silo every (cold winter, particularly :) ) morning and throw feed down manually. But, on occasion it would malfunction by digging in or somesuch and it was necessary.

The controls I've salvaged were therefore in parallel to the "real" motor starter on the ground and connected via the umbilical cord that went from the unloader down the silo chute to the ground. The rest of the control logic and power feed for the motors was there...

Mea culpa, sorry... :(

For my present purpose I've ordered a rated DPDT Form C from Mr Newark that'll work as desired as couldn't find anything suitable w/o being way overkill in the various salvaged pieces-parts in the barn...

Anyway, thanks for the input even though it was a snipe hunt owing to me thinking only of the part of the puzzle was holding in hand when posted...

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