48.8 Hp 480 Motor

[kwired]

From what I have seen in the HVAC field and have run into this many times that OEM motor amps and horsepower don't always match standard motors.

We had a cooling tower replacement and it was an exact replacement. The customer has forgot to anti freeze the tower and whoops it froze up.

The old tower had 30 hp motors 480 volt. The new tower came in with "30 hp" motors 480 volt but the amps was like 30% more. (I don't remember all the #s)

Obviously this would require a completer rewire to use these. pipe, conductors starters and breakers.

I called Reliance in TN. and bitched. They told me "they are oem motors we can mark them any way we want" They were 50 hp motors with 30 hp name plates and they told me that was perfectly fine to do.

They changed there tune when they found out they were not getting paid for the tower. They sent a guy up from TN and he swapped out the motors for standard 30 hp motors

But that doesn't change the OEM thing. It goes on all the time and I have never gotten an explanation on it.

You look on a lot of packaged AC unit motors and you will find horsepowers and amps that don't line up with "CODE" stuff.

I was always told if you replace an OEM motor in a packaged unit go by amps and forget the HP marking. And it works

They get away with this because on packaged units we wire to MOCP & MCA

These water towers had sep 3 phase feeds for the blower motor (the ones I questioned) and separate feeds for the pumps and basin heaters

With the cooling tower it very well is a listed assembly and the nameplate for the entire assembly is what you use to determine supply circuit. It likely either falls under art 422 or possibly 440, and is not directly a 430 application.

50 hp motor with a 30 hp nameplate could give you trouble with across the line starting if you don't have high enough instantaneous trip settings. Otherwise may not give you much trouble if by appliance design is never loaded to more than 30 HP.

I've seen that the other way around more often though - motor with smaller HP base design used to deliver higher HP rating - usually because motor is intended to be located in an airstream during operation and that keeps it running cooler. Also is variable torque application as a general rule. The motor is driving the air stream, if you restrict the flow for any reason the hp demanded will decrease so still not really a problem for dispersing motor heat as less will be produced.

 

[paulengr]

From what I have seen in the HVAC field and have run into this many times that OEM motor amps and horsepower don't always match standard motors.

We had a cooling tower replacement and it was an exact replacement. The customer has forgot to anti freeze the tower and whoops it froze up.

The old tower had 30 hp motors 480 volt. The new tower came in with "30 hp" motors 480 volt but the amps was like 30% more. (I don't remember all the #s)

Obviously this would require a completer rewire to use these. pipe, conductors starters and breakers.

I called Reliance in TN. and bitched. They told me "they are oem motors we can mark them any way we want" They were 50 hp motors with 30 hp name plates and they told me that was perfectly fine to do.

They changed there tune when they found out they were not getting paid for the tower. They sent a guy up from TN and he swapped out the motors for standard 30 hp motors

But that doesn't change the OEM thing. It goes on all the time and I have never gotten an explanation on it.

You look on a lot of packaged AC unit motors and you will find horsepowers and amps that don't line up with "CODE" stuff.

I was always told if you replace an OEM motor in a packaged unit go by amps and forget the HP marking. And it works

They get away with this because on packaged units we wire to MOCP & MCA

These water towers had sep 3 phase feeds for the blower motor (the ones I questioned) and separate feeds for the pumps and basin heaters

The crazy HP ratings on compressors is easy to figure out. The manufacturers know they need a specific torque to start the motor but based on duty cycles and mechanical load the mechanical rating is a little but less. They will label the compressor according to the mechanical average rating then adjust the service factor so that the motor gets the number they want. So a service factor of 1.2 to 1.3 is pretty common. So a “200 HP” compressor might have a 1.25 SF, so it’s really a 250 HP motor. The average load will be 200 HP although it will run well into the service factor when it is loaded. If you replace it with a non-OEM motor watch out for this. Also they often use nonstandard ratings on bearings so be careful of the beating tolerances.

 

[Fordean]

Wow, that's hard to read, but it looks like it is 69.5A FLA? That's a far cry from 48A!

That makes me wonder if they have some sort of VFD integrated into the unit and they are using that to limit the output to 48A, then using that value on their chassis label... very strange way of doing things.

Redid it

Sounds like a 40 KW rated motor maybe? Make sure you are using full load amps and not some running current. The Germans love to give you brake horsepower for the load driven and the corresponding running current because they don't NEC, then ship you an NEC compliant motor nameplate that does not match the info they gave you previously. All of the sudden your entire service is undersized. I see it all the time on submerisble pumps.

Sounds like you have the motor in hand though so you should be good.

At The 60 % duty. What the motor is now rated at a lower voltage. Im guessing. That's why the chassis is 48.8

480volt = 62 amps continuous . x 125% = 77.5 amps. x nameplate duty cycle 60% = 46.5. Chassis says 48.8amps

Am I doing something wrong on the math.
Can this unit be sized at the lower value?
Also contains a Soft Start.
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