Tech 2 Circuit Monorail

E

eds

Senior Member
Trouble shooting a two circuit monorail system that is tripping a qo 20 amp breaker only when the system is shut off. System contains (3) transformers, each transformer enclosure has (2) 300 watt transformers. In this application there are two switches per track, one switch controls the top rail, the second switch controls the middle rail, with the bottom rail the common. Inside the transformer enclosure are 2 common leads, a x1, x2, x3, x4, y1, y2,y3, and y4 leads. Only install instructions that have found You, tie common from the x side to y2 which is the common for the system, x2 is one hot lead, and the other common is the second hot lead. I am probably have a senior moment, but why wouldn’t you just tie the two commons together?

I have reduced the system down to one 300 watt transformer with (5) 50 watt 12v halogens installed, I can cycle the switch anywhere from 1 to 20 times with the breaker tripping randomly in this cycle, always when turning off the load. Doesn’t make any difference which of the 3 transformers I set up this way. Any thoughts?
 
E

eds

Senior Member
I am going with senior moment. As of now voltage from x2 to x common is 11 volts, y2 to y common is 11 volts these are taken with a 250 watt load on each transformer. Wired right now as both commons are brought to gutter and tied to a single common run to the 2 circuit rail. X2 and y2 respectively as hots run to the same 2 circuit rail. Old wiring diagram that I found shows x common tied to y2 ( this becomes the overall common for the system) x2 and then the common for the y side are hot 1 and hot 2.
as of now breaker trips when system is turned off
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Why are you connecting the transformer primary to the secondary, if your secondary voltage is <24V?
Why not wire it as an SDS, like a doorbell transformer is?
 
tortuga

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
eds said:
Only install instructions that have found You, tie common from the x side to y2 which is the common for the system, x2 is one hot lead, and the other common is the second hot lead. I am probably have a senior moment, but why wouldn’t you just tie the two commons together?
Click to expand...
Yeah its odd I wondered that also when I have installed quite a few of these in the past.
If I recall correctly with X-common to Y2 you have parallel operation of the transformers so the secondary line to line voltage is 12 volts.
If you connect the secondary commons it would be a more standard 12/24 volts split phase.
the L-L voltage is never used by the lamps but might be some other components that are only 12V rated, or UL issue with the exposed conductor..
I have had issues when people put LED's in these things, check if any lamps are LED and test it without them.
 
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