fractional HP motor reversing???

[g-and-h_electric]

Long story short, I replaced a draft inducer on a single phase rooftop furnace, and wired it exactly according to the printed wiring diagram which appeared both on the new inducer and the unit schematic . It had draft issues after I got done. Shop sent another another tech, and for "snicks and grins"
he reversed the wires on the draft inducer feeding power from l1 and l2, and leaving the lead to the capacitor where it was. This reversed the motor, creating a proper draft .

I never knew it was "that easy" to reverse a capacitor run motor...... Did he just get lucky, or will this always work?

I am attaching a diagram of the wiring diagrams for clarity


Howard

 

[LarryFine]

It appears to alter the relationship between the start and run windings.

 

[g-and-h_electric]

Got it. So, now my bigger question is, is this a permanent fix, or might this noticeably shorten the life of the motor?

As supervising electrician gor an hvac shop, I am curious mainly in case i had to do a holiday or weekend repair with a fan motor is running the wrong way. If it can be permanent, i wouldnt have to make a second trip with another motor.

Again, I am trying to keep learning, snd not have the brain turn to mush.

Howard

 

[Jraef]

It’s a permanent fix, no harm to the motor whatsoever.

Some 1 phase motors are designed to be easily reversed, basically just by giving access to the terminals for the cap and aux. winding connections. Some do not, although technically if you COULD get to those connections, they would reverse. It’s a couple of extra steps in the manufacturing process, so it adds a few dollars to the cost, hence if the application doesn’t need reversing, they don’t bother.