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Flickering LED

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ndan305

Member
Location
Seattle, WA
Occupation
Engineer
Hello, we just completed LED light installation in a building and the lights would flicker for a bit when the motor on the gas/dx HVAC units turn on. What could be causing the issue and is there any way to fix it?
 
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ndan305

Member
Location
Seattle, WA
Occupation
Engineer
ptonsparky said:
Voltage drop.
Anything from and including increased POCO transformer and wire size all the way to the HVAC equipment.

You need to take voltage measurements to determine which areas need to be addressed first.
Click to expand...
How is that possible? The building had fluorescents and was retrofitted with LEDs so the load should have decreased. Are LEDs just more sensitive to voltage drop? Is there a capacitor or something that can be added to eliminate the increased current draw when the HVAC motors are turned on?
 
ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
ndan305 said:
How is that possible? The building had fluorescents and was retrofitted with LEDs so the load should have decreased. Are LEDs just more sensitive to voltage drop? Is there a capacitor or something that can be added to eliminate the increased current draw when the HVAC motors are turned on?
Click to expand...
Yes, that sensitive.
Capacitor, possibly.
 
Flicker Index

Flicker Index

Senior Member
Location
Pac NW
Occupation
Lights
ndan305 said:
Hello, we just completed LED light installation in a building and the lights would flicker for a bit when the motor on the gas/dx HVAC units turn on. What could be causing the issue and is there any way to fix it?
Click to expand...
Did whatever that was there flicker? If it's due to a genuine voltage drop, incandescent lamps would flicker as well. If it's not voltage drop, it could be transients (spikes or notches) causing the LED ballast to glitch out.
 
N

ndan305

Member
Location
Seattle, WA
Occupation
Engineer
Flicker Index said:
Did whatever that was there flicker? If it's due to a genuine voltage drop, incandescent lamps would flicker as well. If it's not voltage drop, it could be transients (spikes or notches) causing the LED ballast to glitch out.
Click to expand...
It was not noticeable before if it was flickering. The LED retrofit should have reduced overall electrical load, not increase it.
 
G

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
230228-2126 EST

ndan305:

Get a Cree 10 W LED, actual load is about 9.5 W. Connect this Cree bulb at the end of a piece of #18 rip cord about 50 ft long. The loop length ( 100 ft ) will be about 0.6 to 0.7 ohms. Also put a duplex outlet at the bulb location. At the bulb location plug in a 120 V 1500 W heater with a switch.

A 1500 W heater at 120V is about 12.5 A. The voltage drop from a 1500 W load on 50 ft #18 loop is about 8 V. Note that 12.5 A is too high a current for #18 copper, but for a short time it is not a problem, a few seconds. Does the Cree bulb flicker from turn on and off of the of the load
resistor. My test indicated NO.

Do the above test and see what happens with your present bulb, then repeat with a Cree. Report back.

.
 
S

SSDriver

Senior Member
Location
California
Occupation
Electrician
Cheap LEDs have really bad flicker issues if everything isn't perfect. What brand of LED. Try a different brand in a few spots if possible
 
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