Restaurant exhaust motor tripping breaker in cold weather

[Anovacco88]

A small pizza place has a small hood system since the colder weather hit everytime they turn on exhaust system it trips the breaker multilpe times until it finally holds. (takes about 5-10 attempts). They were using the breaker to turn is on and off, I installed a switch and changed the breaker thinking the coil became weak inside the breaker. It still trips in the mornings when its cold my thought it that the motor being outside its drawing more power to start moving. Is there anything i can do to help to motor start up. It is single phase 120volt. Any suggestions are greatly appreciated.

 

[iwire]

A small pizza place has a small hood system since the colder weather hit everytime they turn on exhaust system it trips the breaker multilpe times until it finally holds. (takes about 5-10 attempts). They were using the breaker to turn is on and off, I installed a switch and changed the breaker thinking the coil became weak inside the breaker. It still trips in the mornings when its cold my thought it that the motor being outside its drawing more power to start moving. Is there anything i can do to help to motor start up. It is single phase 120volt. Any suggestions are greatly appreciated.

I would look at the motor nameplate and make sure the breaker they have installed is the correct size. Keep in mind motor loads are different rules and the breaker size is often bigger than expected to handle start up current.

I suspect that either the grease in the bearings or belt, or both, stiffen up when cold and are causing higher start up currents.

You should also make sure the motor has some type of thermal overloads connected to it.

 

[kwired]

I have to agree with Bob, stiff grease in bearings - either in the motor or the driven load (and more likely the driven load) very well making this harder to accelerate when cold.

If it has worked in the cold before - maybe even have a bearing that is going bad and just happens to be worse conditions when cold.

May even have frost/ice buildup that is causing problems.

 

[iwire]

stiff grease in bearings - either in the motor or the driven load (and more likely the driven load) very well making this harder to accelerate when cold.

I agree it is more likely bearings outside the motor.

I don't want to side track to far but we used to adjust the speed of roller coaster cars by changing the viscosity of the oil in the wheel bearings. We would start with 20 weight in the spring when the tracks were rusty and by mid August we would be using 90 weight gear lube to slow them down.

 

[Aleman]

Put a clamp on it and see what it draws compared to nameplate on motor and your breaker. Some of these fans have adjustable sheaves and you can lower
the draw by slowing the fan. Since it's cold weather related it's probably caused by worn bearings and or old grease as mentioned. I recently worked on an EV
charger that tripped even though current was ok. The curve on the breaker changed itself to a faster break and the surge was causing trips. Replaced that and
has been working since.

 

[kwired]

If you have a single phase capacitor start motor, it could even be that the centrifugal governor that operates the starting winding cutout switch is sticking and not allowing the start capacitor to be in the circuit while starting - this could be a problem that is resulting because of cold conditions. Or you may just have similar problem that coincidentally just happened when the weather got cold.

 

[iwire]

It is single phase 120volt. Any suggestions are greatly appreciated.

To go further with this any or all of the following would be helpful

• Type of fan, direct drive, belt drive etc.
• The location of the motor
• All of the motor label info (A picture would be great)
• All of the fan label info (Again a picture would be great)
• The size of the breaker.
• Amp clamp readings during steady running and during start up.

At the very least give us the motor horsepower and breaker size we already know it is 120 volts.