At what HP do you replace a motor vs rewind or overhaul?

For the Beneluw we redeliver up to and including 11kW 2 and 4pole standard IEC/DIN motors

It usually depends on dollar value of a new motor purchase as repair by replacement versus the cost of repair. Some large end users replace all T frame machines below 100 hp.

For new bearings between 20 and 50 hp, 6 and 8 pole at 20 hp normally. This is also factor of delivery time which also relates to items such as shaft size. If repair is more than 60% of new motor cost then normally replace.

As the major expense of a motor is operating cost, it depends in part on how often the motor runs. A lower efficiency motor which operates under significant load 16-24 hours per day would be a good candidate for replacement with a premium efficient in most cases. Modern repair materials and methodologies allow for maintaining efficiency on rewinds so repair of a premium efficient motor probably makes sense in most cases unless the damage is significant. Many plants use a rule of thumb that if the repair is less than somewhere around 60-75% of the price of new they will repair although some go as low as 50%.

In general, the cost of repair for even the most basic recondition is hard to justify below 15HP for standard NEMA frame and most metric frame motors. If it's a rewind that would go up to 30-40HP. If there is machine work involved 60-75HP. For special design motors and those with long lead times these rules of thumb don't apply.

I have noticed that my customers used replace anything under 100HP but now they are watching their dollars and now consider repairing some of the smaller units depending on damage and stock availability of new

Best recommendation is to do a quick calculation on energy costs. Best rewind practices will typically sacrifice 1-2% efficiency considering existing efficiency. $.08 KWH running 6000 hours annual, 100hp motor, 112 FLA, 95.4% eff. Operating cost would be approximately $12518 for the new design motor, $38,812 for an existing motor at 92.26% eff. (generous if an old design, rewound).
The difference will only be larger for larger horsepower and different energy costs. Payback will be less than 6 months with replacement and installation costs included.

Here we go again, the rewind shops getting a bad rap. The many getting tarred with the same brush as the few. There are good rewind shops out there that spend good money on good equipment: that spend good money on QA programs: that spend good money on good people and spend good money on developing procedures that maintain efficiency. Having said that, there are many rewind facilities who don't have the proper equipment. These are the repair facilities that rewind motors for a lesser cost. End-users and anyone else looking for the cheapest price out there will probably experience a drop in efficiency. Depending on the level of care, yes it could be anywhere between 1