When is a motor controller needed

[greenspark1]

I would think this is a simple question but I have never received a good or simple answer. Presently I am purchasing a 1.5 HP 208V Taco pump and am wondering if we need a controller or can use an existing 24V relay and fuses to protect and control it. Thanks for any help.

 

[charlie b]

Whatever you use to turn the thing on and off, be it so rudimentary as a motor-rated snap switch, is that motor's "controller." The code is not going to design the controller for you. There must be protection for the circuit and the motor itself. As long as you have that covered, you don't need to buy something that is marketed under the name "controller."

 

[greenspark1]

Great, thank you. Maybe the better question is what size do motors typically stop having integral overload protection.

I have 11A FLA so per 430.32 the OL fuses can be 115% = 12.65 A. Is there a provision to round up to 15?

 

[augie47]

For overload protection I do not believe there is a "round-up" provision

 

[greenspark1]

Thank you, I didn't find one either.

 

[ActionDave]

I would think this is a simple question but I have never received a good or simple answer. Presently I am purchasing a 1.5 HP 208V Taco pump and am wondering if we need a controller or can use an existing 24V relay and fuses to protect and control it. Thanks for any help.

Great, thank you. Maybe the better question is what size do motors typically stop having integral overload protection.

I have 11A FLA so per 430.32 the OL fuses can be 115% = 12.65 A. Is there a provision to round up to 15?

I would think a motor that size and style would have internal protection. Is there a TP anywhere on the nameplate?

 

[DrSparks]

I would think this is a simple question but I have never received a good or simple answer. Presently I am purchasing a 1.5 HP 208V Taco pump and am wondering if we need a controller or can use an existing 24V relay and fuses to protect and control it. Thanks for any help.

The motor nameplate will indicate whether it is internally thermally protected or not. Sometimes water pumps especially in dishwashers have internal switches that connect to an external controller. This may be the case for a motor that size.

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[kwired]

The motor nameplate will indicate whether it is internally thermally protected or not. Sometimes water pumps especially in dishwashers have internal switches that connect to an external controller. This may be the case for a motor that size.

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With the dishwasher example that motor is typically part of a listed appliance and we don't ordinarily need to concern ourselves with overload protection of that particular motor, it is already taken care of in the factory assembly of the appliance, unless instructions tell you otherwise.

 

[kwired]

Maybe the better question is what size do motors typically stop having integral overload protection

Really is no general rule to this. Most single phase general purpose motors typically do have integral overload protection though.

But when you get into OEM motors there is all sorts of variances out there from what a similar general purpose motor typically has, no internal overload protection seems to be around 50-50 especially for under 2 or 3 HP.

 

[DrSparks]

With the dishwasher example that motor is typically part of a listed appliance and we don't ordinarily need to concern ourselves with overload protection of that particular motor, it is already taken care of in the factory assembly of the appliance, unless instructions tell you otherwise.

Good point

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