out of ideas

[fruecrue]

I have a 2 hp squirrel cage blower kicking my ass. after about 200 hours run time max, motor #1 failed, overload stopped resetting. motor was drawing @ 10 amps, nameplate 11. Motor #2, drawing just under 11 amps, same sheave, same motor. #2 started cycling on overload after two weeks. when I was called, it was drawing 12.6 amps, cycling on OL, windings were chocolate color, checked capacitors, bought smaller sheave, motor draws 12.6 amps even unloaded. Replaced run cap., 12.6 amps. 4.15" sheave or 3.25" full open, 12.6 amps. WTF. Ok, motor is toast, got a new one,put it in.
New motor runs the same, 12.6 amps. Motors all the same- 208/230 single phase. Line voltage is 246.5 with unit off, 244.9 running. Block the return air with cardboard- 12.6 amps. run without belt, 12.6 A. 4.15" sheave, motor loaded as much as I can, 12.6 amps. 3.25" sheave, 12.6 A

UGGGHHHH.

Customer has a newbuild 15,000 square foot home with all low voltage lighting. I start trying to shed power to the lights to see if anything changes. My thought was that all those electronics may be somehow altering frequency or changing the incoming power . No help, 12.6 A. This is one of my two residential accounts but all the equipment is commercial. I started questioning the 246.5 applied voltage, but it is within 10% of nameplate. measured 60 hertz, with lighting energized and off.

I am out of options. right now my plan is to take both motors (#2 and #3) to be bench tested at a local electric repair shop.

Any ideas or suggestions would be appreciated. If you made it this far into my long post, thanks.
Dave.

[Dallas Duster]

What kind of equipment is it? If it's a air handler how much air is it moving? Is it TEFC ? I'll think of more later.

[fruecrue]

What kind of equipment is it? If it's a air handler how much air is it moving? Is it TEFC ? I'll think of more later.

Its a geo-thermal pool unit with de-hum, re-heat, waste heat recovery, the whole nine. I have not measured airflow. The arrogant engineer designed this system at 3200 cfm (8 ton) and claims to have done such a perfect job that no balancing dampers are necessary. I did not install the ductwork, nor did my company have anything to do with it. I simply set up the blower by amp draw.I am trying to Isolate just this component to simplify things.

TEFC? I'm drawing a blank on that one.

Other details I forgot to mention, I am able to run only the blower, through its contactor and nothing else but wires, all thoroughly checked for any defect.

[Dallas Duster]

Totally
enclosed
fan
cooled motor

[fruecrue]

Totally
enclosed
fan
cooled motor

No, open.

[jpsmith1cm]

Well, since it is a squirrel cage, we rule out an air restriction which would actually reduce amperage.

Honestly, since you say that the new motor was over amping, too, I have to vote for a mis-match. Call the manufacturer and verify that all components are correct for the application.

[fruecrue]

Well, since it is a squirrel cage, we rule out an air restriction which would actually reduce amperage.

Honestly, since you say that the new motor was over amping, too, I have to vote for a mis-match. Call the manufacturer and verify that all components are correct for the application.

manufacturer has supplied all motors. I toyed with the idea that 2 hp wasn't enough, but I can't even spin the blower, without moving air, at less than 12.6 A. Even without the belt, a motor is a motor, regardless of size, I would expect 5/8 to 3/4 fla.

thanks for the replies.

[jpsmith1cm]

So, the motor is drawing over FLA without a belt on it?

[fruecrue]

So, the motor is drawing over FLA without a belt on it?

yup- 11 A FLA, 12.6 A measured, two different motors, two different meters.

[Octopus]

Is the home supplied with 3 phase and your taping a single phase off of that?
Current Harmonics, and phase imbalance can occur on single phase equipment if i'm not mistaken. Are the start windings not DE energizing after motor spins up?


Reliable, long-term operation of most electrical equipment requires a voltage imbalance of less than two percent; which means your system has too much imbalance.

If you find voltage imbalances in your facility, the first place to look is not the power company. Instead, look for electrical distribution systems in which one leg of a 3-phase supply powers both single-phase and 3-phase loads. You may find single phase loads not evenly balanced across the phases. Or, look for in-line reactors installed to correct imbalances. These reactors usually have taps for adjustment, and somebody may have adjusted them. Or, the imbalance they originally corrected may have shifted over time. Circuits with tapped reactors rarely stay in balance indefinitely.

Now, here's a practice question. You go out onto the floor and find a 460V motor with phase voltages of 458V, 465V, and 480V. Is there a problem or not? There sure is.

Lowest voltage is 458V. First, calculate your four percent. 0.042458V 418.32V. The difference between the highest voltage (480V) and the lowest voltage (458V) is 22V (480-458). Since the difference (22V) is greater than 4% of the lowest voltage (18.32V), the phases are too far out of balance to ensure continued, reliable operation of electrical equipment.

[dandyme]

is motor multi-voltage?


when you get the next motor.........ohm it out

have mfg give you the spec resistance of windings

[fruecrue]

single phase, 400 amp service. Start windings do de-energize, motor reaches operating speed.

Multi voltage motor, 115/208-230. Ohmed out 1st and 2nd motors. checked capacitors on all. the newest motor, I regret to say, has not been read with an ohmmeter. I condemned the second motor even though it still ran and capacitors were ok. I assumed breakdown of the winding insulation due to operating characteristics, repeated OL trips and winding appearance. I guess I got complacent with the third motor and frustrated when it showed the same operating parameters as the previous motor(which I had condemned based on these parameters).

I have not asked for specs on winding resistance, that's a good idea. I'm sure I can get those.

The most troubling part, I think, is that I was able to achieve proper amp draw in the past. This tells me something has changed, I want to say incoming power, but if voltage and frequency are correct, I'm back to square one.

[DPinst]

It almost sound like it is miswired if it draws FLA without any load on the motor.

[CoolWine]

for kicks I would wire it directly to the panel on another breaker. rule out any wiring issues.

[kdocsr05]

3200 cfm on a two hp motor is extremely high. Is it 1600 cfm on two separate fans, or parallel fans on a common discharge duct?

The current on initial start up seems high; typically, manufactures select a motor, which runs at 80% Fla for the selected airflow and tsp. By doing so, it provides latitude in the event a speed increase will be required due to unexpected duct friction losses, air leakage etc.

I would reach out to the manufacture and ask for the fan curve on the selected unit. Then ask the designer for the selected airflow and tsp. I think you are going to find the fan is moving more air, exceeding the bhp of the motors.

Motor current runs up the cube of the flow increase that is the key here.

[Aircooled81]

Try pulling wires straight from disconect to motor, then fire it up. if it runs fine, you'll see it in the amps.

[fruecrue]

thanks to all for the replies.


I've checked that it is wired right about twenty times.


I haven't wired it directly to the panel, but its in the same room, less than ten feet of #6 wire to the unit, into a terminal block, through the contactor and to the motor. All short runs, all exposed, no voltage drop on the contactor.

I agree that 3200 cfm is high for 2hp. There is only one fan. I have had this blower running at 10 and 11 amps in the past. I know I'm pushing it but I did call the manufacturer originally due to condensation issues in the pool room and was told to set up the sheave for FLA.

Again, thanks. I'm hoping to have one of those AH-HA moments at some point. Maybe I'm getting the same run of junk motors out of the factory?

[Dowadudda]

being at 11 amps with no load on that baby is flat out a problem. So.

what about wire size?

[DeltaT]

If this pool room dehumidification systems also has an air reheat coil, the switchover valve or its controls could not be working.

What can happen is that the new motor, set-up and running correctly, ends up getting a higher air over temp that will eventually heat the motor up to thermal overload. If this happens over and over it can ruin the motor permanetly yet there seems to be no problem with the motor it self.

Check the entire operation of the dehumidifier/heat pump portion of the system to make sure that the system is working correctly in all of its desiged stages. And this includes: pool water temperature heating and controls; dehumidification cycle and its controls; air temperature cycle and its controls; and, especially, make sure the fan runs 24/7 and the bearing are good.

Sometimes on larger blowers the pool room conditions start to ruin the bearing where they will start to freeze up thereby producing an extra and unsustaniable load on those bearing.

All of this needs to be checked with all the inspection/service panels in place and the pool water, air temp and humidity at normal levels.

One more thing, check the simple things such as all the air vents are open. Just had a customer with repeated safety trips on one system only to find out his kids were closing off all the supply air registers.

[fruecrue]

being at 11 amps with no load on that baby is flat out a problem. So.

what about wire size?

wire size is adequate. 244.9 measured at terminals inside motor junction box while in operation.