Furnace inducer motor reading – problem?

The specs/ratings sticker on the motor reads 1.8 amps. A service tech measured it to be 1.83 while operating. He mildly suggested replacing the motor as it was out of spec. Was it really? Does running at or near the nominal rating indicate suboptimal performance and justify replacement? Or perhaps is 1.80 to be taken as a maximum acceptable value?

If the specs/ratings sticker on the motor says “1.8 amps,” it means it will draw a nominal current of 1.8 A RMS after startup when connected to 120 VAC.

Nominal is the key word there. Some of the motors produced by the OEM will draw slightly more current. Some will draw slightly less.

Sounds like the motor is fine.

Did he have a calibrated meter with the lead centered in the ring? I would not quibble over a really minute reading such as that. Especially since you do not know what the motor read last winter. It may have been that reading when it was a new install.
A motor will draw what it needs to do its job. An air blower will draw less air as the inlet reduces in size (example a filter plugs) which counter intuitively will decrease the motor amperage as the blower does less work. Something like an inducer is drawing air through ports and inlets into the combustion chamber. If the door is open or the seal is leaky, the air will come through easier which means more air which draws more current. Now, the bearings could be going out so I would make sure you know where to get one quickly if needed. My bearings tend to squeal a bit before hand though. Without being there or fully knowing the history of that particular equipment, the hip shot view is somebody was looking for a service call sale.
Cite: 25 years servicing, monitoring, and controlling industrial environmental and pollution control systems.

Inducer motors (and their starter caps) are common failure points on furnaces, so I can see why your tech would be eager to replace the motor at the first sign of problems.

Is the motor running hot? High current is often an indication that the bearings are wearing out. The greater bearing friction causes the higher current, more mechanical wear, and more heat being generated by the motor (which adds even more stress to the motor). I think your tech would have mentioned bearing noise if he had heard it.

If you’re handy, you can check the bearings by spinning the motor to see how easily it spins (make sure you disconnect the electrical plug first!). With some blowers it can be difficult to get to the motor to get it to spin. With some you can just spin the back of the motor (nice and easy), but with others you might have to do something like stick a screwdriver through the vent holes to spin the fan blades to get the motor to spin.

High current can also be a problem with the motor coils wearing out or shorting out due to failing insulation. If you are handy with a multimeter you can measure the coil resistance, and make sure that the coils aren’t shorting to the motor case or anywhere else they shouldn’t be touching. You’ll probably need to look up the coil resistance from the motor’s manufacturer.

Since it’s only 0.03 amps above the sticker rating, I seriously doubt that you have a major problem at this point.

The tech was probably cya. It is drawing at its upper limit, slightly over. It may last another 10 years. Or it may fail in a week. If it fails the customer usually get pissed and does not want to pay another show up charge and may even expect the motor to be replaced for no cost. If you are handy then no problem you can change it out yourself. But if it fails expect to pay the show up charge and the replacement charge.

Yes, 1.8 is the maximum current your motor should draw. Typically, motors are sized to run at less than their full load rating for any given application, so yours is maxed out, not a good sign. Just a WAG but I would expect to see a reading around 1.5 amps in your example, YMMV.

Motors are funny animals however, sometimes one will meter out fine and die a week later… then there’s the occasional one that you know is going south, yet it continues to run for months nonstop.

There is something askew in your case, be it a failing motor or, one that is undersized for the application. Either way, a motor should not run at or above it’s FLA for extended periods.