Power factor for scoreboard required?

[Mr. Chippers]

I have a client installing a large 208V-3ph-3w, 35kw scoreboard. I calculated the disconnect and feeder size to be 125A, 2"C., 3#1 & 1#6Gd. considering continuous load. The manufacturer is using a 0.85 power factor in their calculations, which changes the OCPD to 150A, thus increasing the feeder size. Are they correct in including power factor in this type of situation?

 

[Jraef]

Depends on the design of the scoreboard. If this was 1962 and the board consisted of 350 100W incandescent bulbs, then no. But that’s not likely the case any more and any kind of electronic power supply is going to have a power factor.

 

[Mr. Chippers]

It is an LED board. And I believe it has some fans in it for heat sink/cooling.

 

[Beaches EE]

Back in the day I was PM for the color display final design and installation at the LA Memorial Coliseum for the 1984 olympics. 100 volts DC to the lamps, massive rectifier cabinets on every level and lots of 500 mcm CU (wasn't kcmil then) feeding those cabinets.

 

[Jraef]

LEDs use what's called a "driver", but that's just their term for a switch mode power supply. It has a power factor.

 

[zbang]

The drivers do have a PF, but some are "high PF" units. Hard to answer otherwise without knowing about which drivers and other electronics.

 

[winnie]

But I think the key point is that the manufacturer will specify the power factor or the circuit ampacity required.

One might question if the manufacturer is in error or overly conservative, but you need to follow the manufacturer's number for the install.

-Jon

 

[Jraef]

But I think the key point is that the manufacturer will specify the power factor or the circuit ampacity required.

One might question if the manufacturer is in error or overly conservative, but you need to follow the manufacturer's number for the install.

-Jon

Yep. 110.3...

 

[kwired]

If they would rate it in kVA instead of kW then power factor should be included.

Better yet for designing supply circuit would to be to specify maximum input current.

 

[texie]

Is this thing listed by an NRTL? I can't see how an NRTL can allow a data plate that does not spell out the amps of the unit. Many things operate at less than unity PF but the amps is always listed so it is mostly irrelevant.

 

[zbang]

I'd be somewhat surprised of the entire unit is listed since those things are often built to-spec out of usually-listed components. Actually, I can't imagine the entire unit was sent out for lab testing. (Been wrong before, though.)

 

[kwired]

I'd be somewhat surprised of the entire unit is listed since those things are often built to-spec out of usually-listed components. Actually, I can't imagine the entire unit was sent out for lab testing. (Been wrong before, though.)

I think I agree with you.

Custom signs and custom machinery are same way, may be built according to some listing standards in an approved shop, but not many are identical in every aspect like mass production items often are.

 

[zbang]

(wondering if there's a UL standard for outdoor electronic display panels, I assume there is for "signs", haven't thought about that)

 

[kwired]

(wondering if there's a UL standard for outdoor electronic display panels, I assume there is for "signs", haven't thought about that)

I'm pretty certain there are sign shops that custom build signs to a listing standard. 600.3 says those signs must be listed. Look at how many one of a kind or at least limited number of a kind signs are out there. They are not the same thing as a common item like a circuit breaker that is mass produced and only a small amount are evaluated for listing purposes because they area all identical. AFAIK they are made in a shop that is qualified to put a listing label on the finished product because that shop is evaluated in it's procedures periodically to some level.

My guess is the electronic displays are similar or fall into same category. Many those displays are installed by sign companies.