do they have to right in the range or is higher ranges acceptable?
say a motor drawing 22 amps with overloads of 27 amps
say a motor drawing 22 amps with overloads of 27 amps
How close do Motor thermal overloads have to be
- Thread starter The Cobbler
- Start date
Dagny
Well-known member
I have never heard of a thermal cutout with an ampere rating all I have worked on are motor specific and only have a part no.
Now if you are talking a motor starter on a very consistent load heaters sized for a couple amps more than your motor is drawing will protect it well.
Now if you are talking a motor starter on a very consistent load heaters sized for a couple amps more than your motor is drawing will protect it well.
OP
sorry, maybe I used the wrong terminology. a magnetic motor starter with heaters . used to control a 5hp air compressor motor with the pressure switch wired to it
alfredeneuman
Well-known member
There should be a label/chart on the inside of the controller that has the necessary info
OP
there is a chart , the heaters with it are 2 higher than the amp rating on my motor
American Locomotive
Well-known member
What is the service factor on the motor? If it's 1.15, it will probably be okay. If it's 1.0, it probably won't.
OP
service factor is 1.15
fitter30
Well-known member
Unless the overloads are in a hot room would change correct heaters. Check ebay or google used electric equipment ,starter heaters used never had a problem.
OP
It's square D .
For those type of overloads they are based on the service factor of the motor and an ambient temperature of less than 40 C. Usually the manufacturer builds in an extra allowance according to that service factor. Selection is based on their chart along with your motor parameters.
SQ D should be no problem.
dutchgray
Well-known member
Standard is to set overloads to 125% of motor FLA, some overloads have the 25% over built in so you set to FLA, others you have to add it yourself, read the instructions with the overload.
You can set up to 140% FLA if necessary if you get trouble and you check actual amp draw and are not over FLA running.
You can set up to 140% FLA if necessary if you get trouble and you check actual amp draw and are not over FLA running.
OP
Is the motor 3Ø or 1Ø? The overload relay pictured is 3Ø, if single phase SQ D makes a jumper kit for 2 poles so only one heater coil would be required, but either jumpers or heater coils have to heaters tobe installed in order for the relay to reset, if 3Ø then all 3 heaters are needed, entering square d b32 into duckduckgo yielded a lot of hits & eBay had prices all over the place.
OP
my motor is single phase .
tool_scrounge
Well-known member
eBay can be a good source for cheap motor overloads.
wyliesdiesels
Well-known member
Has anyone priced put solid state motor overloads recently? Might be a better route to go as they are adjustable...
OP
I found used b32 local to me for $13 each.
I am told if I am running single phase motor to leave the center heater coil in place and wire the line & load to the 2 outer terminals . ?
I am told if I am running single phase motor to leave the center heater coil in place and wire the line & load to the 2 outer terminals . ?
You have no choice but leave the heater coil in or use jumpers, the relay will NOT reset without one or the other in place, if you doubt me, take one out & try to reset it.
SQUARE D 9998-S031 OVERLOAD RELAY JUMPER STRAP KIT SERIES A (BOX OF 2) NIB 10785901862618 | eBay
JUMPER STRAP KIT. OVERLOAD RELAY. You are purchasing one NEW.
www.ebay.com
The price has doubled since I looked for them some years ago.
wyliesdiesels
Well-known member
You could put a jumper in the center and one of the other heater spaces. Only need 1x since its 240v
OP
nice to know I only need 1 heater . thanks folks!