UL Listed Power Supply for Motor

[Shujinko]

I have a project at a University where there was an Observation Dome (OD) installed on the roof of the building for the Astronomy Department. The OD rotates 360 deg. The inspector has cited the NEC saying that the power supply for the motor that rotates the dome has to be listed by a Nationally Recognized Testing Lab (UL listed or equivalent). (NEC 725.121.A.2). The power supply that came with the observation dome has a 120V input & 17V output for the power supply. The AHJ wants a UL listed power supply that doesn't have an adjustable output voltage. The ones that the contractor and design team have found online have adjustable voltage dials, which isn't acceptable to the AHJ. Can anyone recommend a cost effective solution for this issue? A Power Supply that is UL listed, with a set non-adjustable voltage, and cost effective?

 

[Todd0x1]

How much current? When you say adjustable dial, are you talking about a knob? Or a small trimpot where a screwdriver would be used to tweak the voltage? For example Meanwell makes a 15v power supply with an adjustment range of 13.something-18v. You set it to 17v and glue the trimpot.

The issue is the listing, by their nature most of the power supplies that would be suitable for this are RU recognized component, which are indended to be part of a listed assembly. Would budget allow for having a UL508 panel shop stick a power supply in a box and label it "17V motor drive"?

 

[don_resqcapt19]

Just use a power supply with an output that is greater than permitted for a Class 2 power supply. Then that section does not apply. The Class 1 power supply rules do not include a listing requirement.

 

[Barbqranch]

Also, talk to the people that use it. When I installed a dome and drive, the 120 volt motor caused too much interference w/ the electronics, and I ended up w/ a DC motor and a drive that would ramp the voltage up when started. Also everything was shielded.

 

[Shujinko]

How much current? When you say adjustable dial, are you talking about a knob? Or a small trimpot where a screwdriver would be used to tweak the voltage? For example Meanwell makes a 15v power supply with an adjustment range of 13.something-18v. You set it to 17v and glue the trimpot.

The issue is the listing, by their nature most of the power supplies that would be suitable for this are RU recognized component, which are indended to be part of a listed assembly. Would budget allow for having a UL508 panel shop stick a power supply in a box and label it "17V motor drive"?

Talking to the dome manufacturer we will need to provide 30A at 18V for the power supply output to the motor. Since we need 18V max maybe your suggestion from Meanwell will work as long as it's UL Listed. I'll take a look. Do you have any other manufacturers to recommend?

 

[hbiss]

Just use a power supply with an output that is greater than permitted for a Class 2 power supply. Then that section does not apply. The Class 1 power supply rules do not include a listing requirement.

The inspector has cited the NEC saying that the power supply for the motor that rotates the dome has to be listed by a Nationally Recognized Testing Lab (UL listed or equivalent). (NEC 725.121.A.2).

I believe 30A at 18V is Class 1. So I don't see how that section applies.

-Hal

 

[texie]

Talking to the dome manufacturer we will need to provide 30A at 18V for the power supply output to the motor. Since we need 18V max maybe your suggestion from Meanwell will work as long as it's UL Listed. I'll take a look. Do you have any other manufacturers to recommend?

30 amp@ 18 volt is a power circuit and normal Chapter 3 methods would apply. This would not be even in the realm of Article 725.
That said, maybe your jurisdiction requires listed products in situations like this but Article 725 has no bearing on this.
Is this AC or DC?

 

[Jraef]

17V or 18V is a value typically associated with PWM controlled servo or stepper motors, you may not be able to just use some commercial off-the-shelf power supply on it. Did the dome manufacturer say that you could? If it is a PWM drive that you need, and there is no UL listed version available, you can have a UL508A listed panel shop build you a little box to power it from a Class 2 transformer and put a GFCI ahead of it on the 120V input, then they can UL label that assembly and you are off to the races.

If it can be powered from any DC source, I would ask the manufacturer if the motor has an acceptable tolerance. 15V power supplies can usually only be turned up to 16.5V, which may be too low and cause the motor to lose torque and over load. A 24VDC power supply can usually be adjusted down to 22.5VDC, which may be better for the motor than not getting enough, and you could always drop it further with a series resistor if you had to.

 

[Todd0x1]

I wonder why they dont do it like the gate opener people and have a couple batteries that actually run the motor and a trickle charger from the ac supply.

How does this dome work? Is the power supply going through some sort of electronic motor control or is the motor switched directly or with a relay? Whats the peak or inrush current? Does the motor need a 30 amp power supply? Or does it actually draw 30 amps and needs a much larger powersupply?

 

[Shujinko]

Info for the motors that the power supply is feeding is below. Info from manufacturer.

Rated Voltage: 13.5 VDC

Rated Speed: 50 RPM

Rated Load: 60 Watts

Rated Torque: 11.5 N-m ; 8.5 ft-lb

Cut out on 6 amp per motor



(Note that rotation has 4 motors and shutter has 2 – Rotation and shutter cannot run at same time)

 

[Shujinko]

The Observation Dome (OD) rotates 360 deg using 4 motors. The inspector has cited the NEC saying that the power supply that feeds the motors that rotate the dome have to be listed by a Nationally Recognized Testing Lab (UL listed or equivalent). (NEC 725.121.A.2) Class 2 circuit.

This OD uses four (4) motors each rated at 60 Watts/13.5V. The total load the power supply feeds is 240W (4 motors x 60W). Since 240W is over the Power supply maximum nameplate rating for a class 2 circuit per the NEC Chapter 9 Table 11(b), can we consider this a Class 1 circuit and have the manufacturer provide a Class 1 UL listed power supply with over-current protection for a Class 1 circuit as required in NEC 725.43? Would this violate any codes? Any recommendations on a Class 1 UL Listed power supply as far as manufacturers?

 

[ActionDave]

Are bringing power to a disconnect where factory assembled wiring and controls take over?

 

[ActionDave]

Never mind. I thought this was a new question/thread.

 

[Jraef]

The Observation Dome (OD) rotates 360 deg using 4 motors. The inspector has cited the NEC saying that the power supply that feeds the motors that rotate the dome have to be listed by a Nationally Recognized Testing Lab (UL listed or equivalent). (NEC 725.121.A.2) Class 2 circuit.

This OD uses four (4) motors each rated at 60 Watts/13.5V. The total load the power supply feeds is 240W (4 motors x 60W). Since 240W is over the Power supply maximum nameplate rating for a class 2 circuit per the NEC Chapter 9 Table 11(b), can we consider this a Class 1 circuit and have the manufacturer provide a Class 1 UL listed power supply with over-current protection for a Class 1 circuit as required in NEC 725.43? Would this violate any codes? Any recommendations on a Class 1 UL Listed power supply as far as manufacturers?

Can't you just use 4 separate Class 2 power supplies, one for each motor?

 

[texie]

The Observation Dome (OD) rotates 360 deg using 4 motors. The inspector has cited the NEC saying that the power supply that feeds the motors that rotate the dome have to be listed by a Nationally Recognized Testing Lab (UL listed or equivalent). (NEC 725.121.A.2) Class 2 circuit.

This OD uses four (4) motors each rated at 60 Watts/13.5V. The total load the power supply feeds is 240W (4 motors x 60W). Since 240W is over the Power supply maximum nameplate rating for a class 2 circuit per the NEC Chapter 9 Table 11(b), can we consider this a Class 1 circuit and have the manufacturer provide a Class 1 UL listed power supply with over-current protection for a Class 1 circuit as required in NEC 725.43? Would this violate any codes? Any recommendations on a Class 1 UL Listed power supply as far as manufacturers?

I would think that the motors are likely only listed for connection to a class 2 power supply. Even if you could use a larger power supply you would need chapter 3 wiring methods which you don't likely have installed.
Is this system listed by an NRTL?

 

[Shujinko]

I would think that the motors are likely only listed for connection to a class 2 power supply. Even if you could use a larger power supply you would need chapter 3 wiring methods which you don't likely have installed.
Is this system listed by an NRTL?

No it is not listed by an NTRL. That's the problem the code citation that the inspector is citing is that for Class 2 power supplies they need to be listed. (NEC 725.121.A.2). But you make a great point about the motors and the wiring methods between a Class 2 & a Class 1 installation.

 

[Shujinko]

Can't you just use 4 separate Class 2 power supplies, one for each motor?

No, apparently the Observation Dome Manufacturer is not willing to do this because they would basically have to re-wire their entire electrical system in the Observation Dome.

 

[hbiss]

I think your biggest problem is going to be finding a fixed power supply that provides 18 VDC (or is it 13.5 VDC??)

-Hal

 

[Shujinko]

I think your biggest problem is going to be finding a fixed power supply that provides 18 VDC (or is it 13.5 VDC??)

-Hal

It's 13.5VDC. The OD manufacturer gave me the wrong voltage originally.

 

[PaulMmn]

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