View Full Version : Circuit breakers tripping?

02-20-2006, 07:02 PM
Got a couple of customers with 600-900w transformers tripping breakers. Amp meter reads avg. 6 amps 7.5 right when it clicks on.
All wiring been checked. All lights checked for proper voltage. All wiring sized and calculated correctly.

Nothing else installed on the breaker. Just a receptacle dropped out of a panel.


Inrush amps & amps pulling.

Anyone run across similar problems.

02-20-2006, 07:04 PM
my suppliers (John Deere & Smith Turf) and the manufacturer (vista) are coming up with limited answers.....

02-20-2006, 07:19 PM
Primary or secondary (which one) breakers tripping?

02-20-2006, 07:21 PM
How are you switching the transformers?

15 or 20 amp primary breaker?

02-20-2006, 07:23 PM
is it on the same circut as the bathroom???
if so when a hair dryer is used at night it will kick off the breaker if your lights are on as well..

02-20-2006, 07:24 PM
Yard pro, initial post stated dedicated circuit

02-20-2006, 08:19 PM
how far is the outlet located away from the panel??? if more than 15ft that should not be a problem..if closer that could be causing primary to trip.

02-20-2006, 08:27 PM
if the secondary is tripping and you are using a multi tap transformer do what you've done and measure the cable for amperage. the amperage result should be multiplied by the voltage tap to which the cable run is connected. this will determine the actual (dynamic) wattage requirment.
hope this helps

02-20-2006, 09:01 PM
Breaker on service panel tripping. 20amp breaker SqrD QO

Another customer GE 20amp beside service panel doing same thing.

Transformer mounted beside the service panel.

Dedicated breaker.

02-20-2006, 09:57 PM
distance from the transformer to a primary breaker does not matter most of the time, but to avoid potential nuisance tripping the transformer should be mounted 15' away from primary breaker.

02-20-2006, 10:55 PM
Yard pro, initial post stated dedicated circuit

oops.. missed that

02-21-2006, 07:25 PM
We installed a 30 amp breaker & so far no problems.

02-21-2006, 08:11 PM
I always hate to be a kill joy, but what size wire is on that breaker? If you have 12/2 wire on it, you are not complient with NEC. The better fix would be to move the transformer 15' from the panel. Remember, if something bad happens, you will be liable.

02-21-2006, 08:56 PM
A licensed electrican installed the breaker. im sure its 12 guage wire though.

02-21-2006, 09:02 PM
Paul is correct if it's 12 gauge and you've changed it to a 30 amp breaker you have created a code violation. You're going to need to change the wire to 10 gauge. However I don't believe the breaker or the wire is your problem.

02-21-2006, 09:23 PM
Are you amp probing the breaker at the panel with the lights on and presumably everything else on the circuit on?
If you're using one of those cheap plug in timers pitch it in the woods and plug the plug directly into the belly of the transformer. If you have a photo cell yank it too. It's a process of elimination my friend. See Paul I can help too.

02-21-2006, 11:23 PM
NEC 450-3 - the over current device ( breaker ) can be up to 300% larger than the conductor rating - in this case greater than 2 amps less than 9 amps - less than 600 vac - Most circuits that supply transformers and motors see the same type of current inrush - you can use a 125 % rated device or 25 amp breaker and go up to a 60 amp and keep the same # 12 wire. ( I would also suggest secondary transformer protection ) if you did this. I have installed up to 800% on 400 hp - 480 motors .

02-21-2006, 11:36 PM
Tell that to the local city inspector . It's a code violation don't listen to such jibberish. Are you challenging me and Sr.?

02-22-2006, 07:06 AM
As far as City Inspectors - yes they do have final jurisdiction - no this is not a challenge

02-22-2006, 11:12 AM
I failed to provide the complete National Electrical Code reference - 2005 Edition Article 450 -- Table 450.3 (B) ( 600 Volts and less )Overcurrent protection for Transformers