Dadgum details. It was a simple project.The bigger issue is that if we assume the motor leads were sized for a 50HP motor, and now you have a 60HP motor, regardless of the actual current you are using, the conductors are required to be sized for the 60HP motor. So per the NEC charts, that means 77A x 1.25 = 96.5A rating for the 60HP, vs what you likely had was 65A x 1.25 = 81.25A for the 50HP. So that means you likely had 4AWG conductors, now you are required to have 3AWG.
I know, right?Dadgum details. It was a simple project.![]()
No way you have 56 and 76 amp motor (assuming same speed and voltage rating) and both are 20 HP.As a fun trivia I can tell you this (and more motors) are located in a building that a famous politician was found guilty today.
It works and it’s safe.
Both motors are 20 hp.
One minute is a short time in the world of small percentage motor overloads, especially thermal types. Holding up for one minute would not give me any confidence in the workability of the 56A nominal overload with that motor.There is a lot I have to learn about motors
. Here are old and new motor’s nameplates .
56A overload did not trip after a minute of running new motor which was drawing 65A.
Thermal overloads have an inherent +/- 1% repeat accuracy, that's why. If we do a quick math there, 56A setting would mean the tripping amps will be 1.15 X 56 = 64.4. But because of the inherent reproducibility of 1%, the thermal overload needs 64.4A X 1.01 = 65.044A ->thermal overload doesn't trip at just 65A! If your current meter also has an indication error of +/- 10%. 65A could be just 60A, it couldn't be 71.5A since the thermal overload didn't trip. As said by the person above me, small things matter, we're in a real world. If you want a tighter protection, set your thermal overload lower than the expected overload.There is a lot I have to learn about motors
. Here are old and new motor’s nameplates .
56A overload did not trip after a minute of running new motor which was drawing 65A.
Question:Thermal overloads have an inherent +/- 1% repeat accuracy, that's why. If we do a quick math there, 56A setting would mean the tripping amps will be 1.15 X 56 = 64.4. But because of the inherent reproducibility of 1%, the thermal overload needs 64.4A X 1.01 = 65.044A ->thermal overload doesn't trip at just 65A! If your current meter also has an indication error of +/- 10%. 65A could be just 60A, it couldn't be 71.5A since the thermal overload didn't trip. As said by the person above me, small things matter, we're in a real world. If you want a tighter protection, set your thermal overload lower than the expected overload.
You advised to set the thermal overload protection at 100% of the FLA of the motor. There is a built-in fudge factor of 1.15 in most TOR manufacturers. Say you have set 10A on the TOR, the TOR trips if the motor current exceeds 1.15 X 10 = 11.5A. The TOR will start waiting if the overload is just momentary or longer, it trips if the overload persists for a longer time, the I2Rt energy builds heat in the heaters ultimately separating the NO contact of the TOR.Question:
If it reads on an adjustable trip dial of overload protection f.eg. 10 amps
Does it mean it’s meant to be used on a 10 amp motor?
Or 8.75 amp motor?
That sure makes it code legal, as odd as it is to have such a wide variation in current for the "same" motor.As a fun trivia I can tell you this (and more motors) are located in a building that a famous politician was found guilty today.
It works and it’s safe.
Both motors are 20 hp.
The nameplate FLA would come from the mfg prior to any outside influences such as load pulley ratios.The reason new motor draws more amps is because engineers changed radius and ratio of pullies . They reduced spinning mass to have more efficient system. That’s my poor understanding of how things work. It’s an energy conservation project.