electric motor keeps tripping circuit breaker 1

[trtle07]

I'm using an electric floor burnisher with a 110v motor. The voltage spikes up very high when first turned on then goes back to an exceptable level. The voltage goes up and down during operation until it eventualy trips the ciruit breaker. Does anyone know how I can fix this problem? Thanks!

 

[jraef]

I'll assume you mean current is spiking and not voltage (breakers do not trip on voltage, only on current). It is possible that your extension cord is too long or too small. Either (or both) conditions will cause a voltage DROP at your polisher, which will casue it to pull more current and eventually trip the breaker. What is the power rating (HP or kW) of the polisher, what size cord are you using (gauge), and how long is it?

"Venditori de oleum-vipera non vigere excordis populi"

 

[rbulsara]

Motor may be too big for the breaker. Post the nameplate (ampere, HP) of the motor and rating of the breaker feeding it.

Successive start/stop operations can overheat the breaker and eventually trip it.

 

[trtle07]

Thank you for your suggestions on my problem. I had the wrong size motor stated in my question. The motor is 1.5hp, 120v, 15a, 50/60HZ. The power cord is 75ft. 14/3 Satety yellow. This burnisher is only 6 months old. Now that I have the correct specs., are there any new suggestions on this problem? Thanks!

 

[trtle07]

Thank you for your suggestions on my problem. I had the wrong size motor stated in my question. The motor is 1.5hp, 120v, 15a, 50/60HZ. The power cord is 75ft. 14/3 Satety yellow. This burnisher is only 6 months old. Now that I have the correct specs., are there any new suggestions on this problem? Thanks!

The voltage spikes up very high when first turned on then goes back to an exceptable level. The voltage goes up and down during operation until it eventualy trips the ciruit breaker. Does anyone know how I can fix this problem? Thanks!

 

[rbulsara]

You need at least a 30A or 40A breaker for this motor, specailly for freuent start and stop. If you are plugging this in a 15A or 20A circuit, it will trip the breaker.

Also 14/3 cord is too small to meet NEC, it should at least be 12/3.

 

[dpc]

A 15A load is going to trip a lot of 15A breakers eventually, even if there is no other load on the circuit.

If this is a fixed location, try a different outlet on another circuit.

But as others have said, basically, you need a larger circuit breaker upstream. If it's on a 15A circuit, a 20A circuit could help. The 20A circuit requires #12 wire. To go above that, you'll need even bigger wire and special receptacles and plugs.

 

[rbulsara]

dpc:

just a code clarification, and I know that you know, the motor brach circuit conductors need to be only 125% of FLA while the branch breaker can be up 250% of FLA. This is one of the exception in NEC rule permitting breaker larger than the condcutor ampacity. So in this case 1.25*15A=18.75A and #12 AWG is fine for the cord with up to 40A CB. The receptacle can not be rated more than 20A though. ( I am assuming the cord is plugged in to a receptacle)

If the CB is wired to a receptacle rated more than 20A then of course you need larger size wire to match the breaker.

 

[dpc]

rbulsara,

Yes, I was talking about the branch circuit conductors serving the receptacles. I should have been a little more clear.

 

[jraef]

Actaully when refering to portable cord, 12/3 is only good for 47ft at a 15A load (your 14/3 was only good for 30ft). You will need a 10/3 extension cord to go 75ft with that unit. Once you solve that problem, the breaker may work out OK for you because even though the motor is labeled for 15A, it probably draws less in normal operation. This is important for you because you may not be able to pick the breakers and circuit wiring you need at every jobsite. Plus the burnisher manufacturer would not (or at least should not) have put a 15A plug on the end of their cord if they knew it wouldn't work, and/or they have another internal circuit breaker that will trip if it overloads.

Buy a larger guage cord (or a much shorter one) and you will probably be fine.

"Venditori de oleum-vipera non vigere excordis populi"