Goofy Control Circuit

jerjwillelec

Senior Member
Location
Nevada, IA
Anybody recognize this type of setup? This cabinet houses starters for two 30 HP 480 volt Exhaust Fans on top of the Annex at a Grain Elevator. (The third smaller starter is for a Grain Drag) There is an identical cabinet behind this one for two more fans.

I'm troubleshooting these two fans right now. The control circuit is doing Goofy things. Fan #4: The stop button will shut it off until I release (the button) and it will kick it right back on. Fan #3: was doing the same thing a couple of months ago but now won't turn on at all. Sometimes, when I shut the control circuit off, and turn it back on, Fan #4 will go back to normal operation again...not everytime though. Fan #3 still doesn't operate.

I'm not familiar enough with this 'pushing 40 years old' setup to know really what to do. Any thoughts?

Thank you!

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don_resqcapt19

Moderator
Staff member
Location
Illinois
You are going to need to draw out a schematic of the control circuits to troubleshoot this.

Is the control system a 3 wire start/stop system? If so and if it starts when you release the stop button, then the starting button or device is stuck closed.
 

jerjwillelec

Senior Member
Location
Nevada, IA
You are going to need to draw out a schematic of the control circuits to troubleshoot this.

Is the control system a 3 wire start/stop system? If so and if it starts when you release the stop button, then the starting button or device is stuck closed.
It is a 3 wire system yes, (old GE S/S station). I can physically see the stop make and break contact when I push it in and let it out...same with the start...just doesn't make any sense

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Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
It is a 3 wire system yes, (old GE S/S station). I can physically see the stop make and break contact when I push it in and let it out...same with the start...just doesn't make any sense

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Most likely your N.O. seal-in contact of the starter is sticking closed. Those old GE starters were notorious for that, the mechanical link that moves the contacts gets old and brittle, so it either breaks and jams, or just gets so worn that it doesn't work right.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Engineer
I'm troubleshooting these two fans right now. The control circuit is doing Goofy things. Fan #4: The stop button will shut it off until I release (the button) and it will kick it right back on. Fan #3: was doing the same thing a couple of months ago but now won't turn on at all. Sometimes, when I shut the control circuit off, and turn it back on, Fan #4 will go back to normal operation again...not everytime though. Fan #3 still doesn't operate.
You have a 'holding circuit' contact that is not releasing properly.

Check your start button, there should be a set of wires running to one of your contactors or relays. Follow these to your other devices, as you are doing this create a wiring diagram as suggested by Don.
 

sparkyrick

Senior Member
Location
Appleton, Wi
You have a 'holding circuit' contact that is not releasing properly.

Check your start button, there should be a set of wires running to one of your contactors or relays. Follow these to your other devices, as you are doing this create a wiring diagram as suggested by Don.
Yup. There should be a N/O contact on one of the starters that parallels the start button, that is the holding contact. It sounds like that N/O contact is stuck closed.
 
Goofy Control Circuit

from the picture, it appears that there are auxiliary relays that are performing the 'hold' function

they are just to the left of the 3-pole contactors at upper center and middle-left side

Just a wild-arsed guess, you understand..........
 

jerjwillelec

Senior Member
Location
Nevada, IA
Does anyone know what the "transormer" looking things are? My guess is an old school soft start...but that being said, I don't have really any experience with them.

I get the holding circuit likely being the problem but looking at this massive setup...just didn't know where to start looking for it

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jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Engineer
from the picture, it appears that there are auxiliary relays that are performing the 'hold' function

they are just to the left of the 3-pole contactors at upper center and middle-left side.
I think those might be the timing relays for the reduced voltage starting, but that doesn't preclude them from being part of the holding circuit.
 

ATSman

Senior Member
Location
San Francisco
Motor Starting

Motor Starting

I think those might be the timing relays for the reduced voltage starting, but that doesn't preclude them from being part of the holding circuit.
I agree. From what I can recall it looks to me that the "transformers" are auto-transformers (AT) that are used in a reduced voltage scheme to limit the starting current of the motor until it is up to proper RPM. When the start button is pushed the 1st contactor (and timer energizes) closes to feed the motor from the AT and after the preset time the timer drops off the 1st contactor and energizes the 2nd contactor to feed the motor direct with full line voltage. These schemes were used along with Resistance Start, Part-Winding and Delta-Wye (Wye-Delta?) Starter schemes before the newer solid state Soft Starts and VFDs took over.
See typical AT scheme attached, although it does not show the timer circuit.
 

Attachments

templdl

Senior Member
Location
Wisconsin
from the picture, it appears that there are auxiliary relays that are performing the 'hold' function

they are just to the left of the 3-pole contactors at upper center and middle-left side

Just a wild-arsed guess, you understand..........
Yes, there is a lot of guessing that goes on all right. Without a wiring diagram the OP must have knowledge of a control circuit in order to ring out/ troubleshoot the control circuit. If there is an interposing relay a wiring diagram would certainly be of some help.
 

jerjwillelec

Senior Member
Location
Nevada, IA
Yes, there is a lot of guessing that goes on all right. Without a wiring diagram the OP must have knowledge of a control circuit in order to ring out/ troubleshoot the control circuit. If there is an interposing relay a wiring diagram would certainly be of some help.
I have basic knowledge of control circuits. I am TERRIBLE at drawing out my own schematics but can follow them pretty well. What do you mean by "interposing relay"?
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
I have basic knowledge of control circuits. I am TERRIBLE at drawing out my own schematics but can follow them pretty well. What do you mean by "interposing relay"?
It is a smaller relay used to control a larger. A PLC relay output may not have an ampacity rating to pull in a size 4 starter or the voltage ratings are different, so you use another to pull in the larger.
 
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