While our customers are wholesalers, Packard knows that you, the contractor, have a choice. You are often presented with many buying options, and being well-informed about your purchase can help make your job easier and more successful.
This is why we have dedicated a section of our site for contractors. In this section, you will find helpful product tips, tools and some clips from our training classes. We’ve also provided a distributor locator so you can find the nearest wholesaler who can give you access to Packard products.
Multi Speed or Multi-Horsepower…what is it?
Many technicians are puzzled by “multi-speed” and “multi-horsepower” direct drive blower motors. Part of this confusion stems from how manufacturers may identify and label these motors differently. With three-speed motors, for example, they may be labeled as three-speed with one horsepower rating. An equivalent motor could also be identified as three speed with three different horsepower ratings. In either case the motors could be identical.
Three-speed motors are designed to operate a single load. Let’s examine the motor identified with a single horsepower rating first. If shown as a 1/2 HP it is designed for a 1/2 HP load. When connected for medium or low speeds, the strength or torque on that connection is weaker than 1/2 HP. When operating a 1/2 HP load with less than 1/2 HP torque, the motor cannot operate as fast as its rated speed. If the motor is rated 1075 revolutions per minute (RPM), it will operate a 1/2 HP load at that speed when connected on high. When connected for medium it will operate the 1/2 HP load at about 100-150 RPM less since medium speed is weaker. When connected for low it will operate the 1/2 HP load at about 100-150 RPM less than medium.
In the case of a three-speed motor identified as 1/2-1/3-1/4 HP it is also designed for a 1/2 HP load. The additional HPs shown indicate the strength of the motor on the different connections. Again, when a 1/2 HP load is applied to this motor, and it is rated 1075 RPM, and connected on high, the motor torque is equivalent to 1/2 HP and the motor will operate at its rated speed of 1075 RPM. When connected on medium, the motor torque is about 1/3 HP. With a 1/2 HP load on the motor the medium connection is not strong enough to achieve 1075 RPM and the motor will operate about 100-150 RPM less. The same situation occurs when connected for low speed, which has torque of about 1/4 HP. With a 1/2 HP load applied on low the motor does not develop the torque needed to operate at 1075 RPM. The RPM will be about 100-150 less than medium.
The three speed motors show one amp rating. That represents the rated amps when the motor is operated with its rated load connected on high.
Multi-horsepower motors are designed so that different horsepower loads can be applied to them. For example, a motor identified as multi-horsepower and rated as 1/2-1/3-1/4-1/5-1/6 can have a 1/2 HP, 1/3 HP, 1/4 HP, 1/5 HP, or 1/6 HP load applied to its shaft. The applied load determines how the motor is to be connected. In this example, if a 1/2 HP load is applied to this motor it should be connected for 1/2 HP which will be used as its high speed. In this case, the 1/3 HP and 1/4 HP connections could be used as medium and low speeds. If a 1/3 HP load is applied, then the 1/3 HP connection is used as high speed. The 1/4 HP and 1/5 HP connections can be used as medium and low.
For the multi-horsepower motors there will typically be one amp rating associated with each horsepower. When loaded to that horsepower the amps should be within the range for that horsepower connection as high.
Remember, three-speed or multi-speed motors are designed for one load. Multi-horsepower motors are designed so that different horsepower loads can be applied.
This can be a difficult concept. The Packard Academy provides much more detailed information on this topic during some of our training classes.
Packard has developed a complete HVACR critical components training program, which has received approval by North American Training Excellence (NATE) - the leading certification program for HVACR technician, and the only test approved by the entire industry. Below are some video excerpts from our instructor led training courses which we hold at Wholesaler locations nationwide.
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