• We will be performing upgrades on the forums and server over the weekend. The forums may be unavailable multiple times for up to an hour each. Thank you for your patience and understanding as we work to make the forums even better.

Square D 480 volt starter with 480 coil

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
There is not.

The only time I have seen it in the past 20 years or so, was only for the coil on size 4 and 5 starters, but even there there was an interposing relay and 120 volt CPT and control circuit. The coils for larger starters will require a much larger CPT if the coil voltage is 120 and the use of a 480 volt coil solves that issue.

The last time I saw an actual 480 volt control circuit was in the 70s at an old industrial plant.
Some Home Depot’s use that same setup for 200 amp latching lighting contactors. Usually 120 is preferred because the control contacts are rated 250 or less.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
You still talking about MCC's I assume.

...
MCCs and some stand alone combination starters...have never even seen a pump panel like you are talking about.

What happens to that control circuit if the grounded safety conductor shorts to ground?

Long control circuits can have that issue, and as I recall, the shunt capacitance gets worse when the size of the control conductor is increased.
There was a good Square D paper on long AC control circuits. Not sure if it is still available.
 

kwired

Electron manager
Location
NE Nebraska
Occupation
EC
MCCs and some stand alone combination starters...have never even seen a pump panel like you are talking about.

What happens to that control circuit if the grounded safety conductor shorts to ground?

Long control circuits can have that issue, and as I recall, the shunt capacitance gets worse when the size of the control conductor is increased.
There was a good Square D paper on long AC control circuits. Not sure if it is still available.
That always been my question. You end up bypassing limits. I don't know why they do this. Only one that I am aware of that does it, and has been doing it probably since they first started building these. They can use one less conductor in the cable that is run on these systems than what everyone else uses is the only advantage but there is disadvantages as have been brought up. I'm pretty sure they are listed. This company been building them that way for 50 or more years.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
That always been my question. You end up bypassing limits. I don't know why they do this. Only one that I am aware of that does it, and has been doing it probably since they first started building these. They can use one less conductor in the cable that is run on these systems than what everyone else uses is the only advantage but there is disadvantages as have been brought up. I'm pretty sure they are listed. This company been building them that way for 50 or more years.
I think I would have to red tag the installation based on this:
430.74 Electrical Arrangement of Control Circuits.
Where one conductor of the motor control circuit is grounded, the motor control circuit shall be arranged so that a ground fault in the control circuit remote from the motor controller will (1) not start the motor and (2) not bypass manually operated shutdown devices or automatic safety shutdown devices.
 

garbo

Senior Member
Assuming this is a real device and not a test question: Make sure you buy 600 V pushbuttons. While 480 V control is perfectly legal per the NEC, I'd strongly advise replacing the 480 V coil with a 120 V coil and installing a control power transformer. Running 480 V pushbuttons and switches is an idea whose time has passed.
Can remember working on 240 & 480 volt 1 to 5 ton traveling hoists with some traveling outdoors on an I beam that had 240 or 480 volts to push buttons then by the end of the 1970's all of the hoist we purchased used 24 volts AC for the controls. Got shocked on a old hoist where the ground wire broke off. Installed a lot of Allen Bradley size 0 & 1 480 volt starters that had 480 volt start stop & light kit that were bolted to holes that were inside of NEMA1 starter enclosures. Had to knock out a piece on starter cover. Never had one short out or cause a problem. Large plant that I worked at had two old candy starch mogul machines that used 480 volt for all controls in dust filled space. Everything was done for explosion proof wiring except they refused to ever place sealing compound in any of the seal off fittings. Must have had at least halve a dozen limit switches feed with 480 volts and worst yet while changing over to 120 volt controls found they had the #14 guage control wire feed from a 30 amp time delayed fuse. Controls only fed about eight motor starter coils and some indicating lights.
 

kwired

Electron manager
Location
NE Nebraska
Occupation
EC
I would have to find and read the actual product standard that the equipment was listed to.
All I can say is this company been making them that way since the late 1960's and new systems today still use a grounded conductor as the "safety circuit" for the main control. Any limit throughout the system will interrupt the return portion of this grounded conductor. It runs all the way to end of the system, all intermediate motor contactors connect to it as a "common", but then a return conductor has all the safety limits in it on the way back to the main control panel. Back there it ties to the holding contacts on the main contactors. Start button bypasses the holding contact and allows the system to run while holding start button, this is how you get it back "in line" if it stopped because it was out of line. Of course you need to fix whatever caused it to get out of line or if you hold it too long it just gets further out of line, possibly until something breaks.

Newer systems in recent years have gone to a "safety relay" and changed some things a bit, but that is all within the main control panel, out on the system the same number and colors of conductors haven't changed from day one and the grounded conductor is still where this safety circuit is tied to at far end then it comes back to the main control panel through all the limit switches.

I don't know what listing requirements may be, pretty certain these units are listed though.
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
All I can say is this company been making them that way since the late 1960's and new systems today still use a grounded conductor as the "safety circuit" for the main control. Any limit throughout the system will interrupt the return portion of this grounded conductor. It runs all the way to end of the system, all intermediate motor contactors connect to it as a "common", but then a return conductor has all the safety limits in it on the way back to the main control panel. Back there it ties to the holding contacts on the main contactors. Start button bypasses the holding contact and allows the system to run while holding start button, this is how you get it back "in line" if it stopped because it was out of line. Of course you need to fix whatever caused it to get out of line or if you hold it too long it just gets further out of line, possibly until something breaks.

Newer systems in recent years have gone to a "safety relay" and changed some things a bit, but that is all within the main control panel, out on the system the same number and colors of conductors haven't changed from day one and the grounded conductor is still where this safety circuit is tied to at far end then it comes back to the main control panel through all the limit switches.

I don't know what listing requirements may be, pretty certain these units are listed though.
Oh, pivots.
I missed that detail somehow.
 

herding_cats

Senior Member
Location
Kansas
Occupation
Mechanical Engineer
I can't imagine there being much demand for 480 volt control circuits with an MCC.

The larger the MCC the less it might be desired, unless maybe every single motor were very related to one another in a particular process/sub process of the facility.

I can see 120 volt contactor coils being more desirable to be installed if the MCC were supplied by 208/120 and each supplied by line voltage rather than via control transformers though.
It's nice when coil voltage is the same as load voltage. Easy.
 

kwired

Electron manager
Location
NE Nebraska
Occupation
EC
Oh, pivots.
I missed that detail somehow.
I'm sure you are familiar with the Reinke center pivots and using the grounded conductor for the safety loop through the length of the system.

Every other center pivot maker uses a grounded conductor for this loop.
 

kwired

Electron manager
Location
NE Nebraska
Occupation
EC
It's nice when coil voltage is the same as load voltage. Easy.
For single motor or other somewhat limited applications.

For a more complex multimotor application particularly if there is interlocks between two or more items, timers counters, and other control devices who wants to have 480 volts for control circuits?

If you want to work on control circuits while things are in operation 24 volts is kind of becoming what is preferred because of relaxed or even nearly non existent requirement for PPE while working on it.
 
Top