Strange Ampacities

[metro2387]

System is 277/480 3phase. Lighting circuits are all 277 run through a Lutron relay panel. Circuits are individually controlled in sets of three by these relays. The devices are HID Low Bays. Breakers are 20 amp, relays are 16 amp cont load.

System has blown four Lutron Relays(rated 16A cont load). Previous techs found no anomolies(?). I tested and found all amps in range at 14 to 15.9 amps. Then I de-energized all units and re-energized single line. Amp rose to 18.8 for ten minutes. Then settled at 15.9amps. All circuits with 18 plus fixtures demonstrated same behavior. With shared hots on the circuit would go no higher than 15.9 amps. Is this EMF? Why do we only see the 18 amps with the other conductors de-energized?

 

[76nemo]

Restrike?????

 

[mivey]

Restrike?????

I think he said the restrike was 18+ amps if the other circuits were off, but only 15.9 amps if the others were on? correct?

 

[metro2387]

Restrike

Restrike

That would be correct. With other circuits on and retrike I see 15.9 Amps. With all circuits off and restrike I see 18.8 to 18.9 amps. Relay is rated for 16 amp max cont. Any idea's

 

[hardworkingstiff]

That would be correct. With other circuits on and retrike I see 15.9 Amps. With all circuits off and restrike I see 18.8 to 18.9 amps. Relay is rated for 16 amp max cont. Any idea's

I'm assuming MWBCs

Voltage drop?

If only 1 circuit of a MWBC is on it carries all of the VD. If all circuits of a MWBC are on, the VD is shared and is a lower % per circuit.

Just an idea (valid or not).

 

[donselectric]

i think i would call the manufactures first explain whats happening
or try a 20a relay. other thoughts, as lamps age they take longer to ignite and draw (strike)for a longer time thus more heat frying the relay contacts...
it is the contacts your mean by blown and not the coils ?
how many on the circuit? what phase is it on? all splices/terms tight?

 

[jrannis]

System is 277/480 3phase. Lighting circuits are all 277 run through a Lutron relay panel. Circuits are individually controlled in sets of three by these relays. The devices are HID Low Bays. Breakers are 20 amp, relays are 16 amp cont load.

System has blown four Lutron Relays(rated 16A cont load). Previous techs found no anomolies(?). I tested and found all amps in range at 14 to 15.9 amps. Then I de-energized all units and re-energized single line. Amp rose to 18.8 for ten minutes. Then settled at 15.9amps. All circuits with 18 plus fixtures demonstrated same behavior. With shared hots on the circuit would go no higher than 15.9 amps. Is this EMF? Why do we only see the 18 amps with the other conductors de-energized?

Am I missing something or are the relays undersized?

 

[infinity]

Am I missing something or are the relays undersized?

I was thinking the same thing. A 16 amp load on a 16 amp relay is kind of asking for trouble.

 

[augie47]

it;'s been a long time, so you guys correct me, but is there not one type of HID lighting that starts high and current drops as it reachs nominal output (ignoring restrike)
I though HPS did so and MH did the opposite but sometimes my ole brain conjures up wivestales for facts.
In any event, I would agree the relays are undersized.
I would also suggest you check manufacturing data on te relays. Some equiment carries different ratings for tungsten vs ballasted loads.

 

[LarryFine]

It sounds like you need at least 30a contacts. Also, opening under load, especially with a highly-inductive load, reduces contact life.

 

[jdsmith]

it;'s been a long time, so you guys correct me, but is there not one type of HID lighting that starts high and current drops as it reachs nominal output (ignoring restrike)
I though HPS did so and MH did the opposite but sometimes my ole brain conjures up wivestales for facts.
In any event, I would agree the relays are undersized.
I would also suggest you check manufacturing data on te relays. Some equiment carries different ratings for tungsten vs ballasted loads.

I was just reading a Crouse-Hinds lighting catalog on Friday and this sounds very familiar. I will check again when I go into work on Wednesday.