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Posted By: Dave55 MH High-Bay Lights - 03/11/05 04:12 AM
I'm having a problem with some 400W MH commercial lights. When they are switched on in the morning they trip the breaker. If I reset the breaker sometimes they'll start fine, other times it'll trip again. I'd describe these as lighting units 20 through 30 of the same brand and configuration. Any suggestions?

Posted By: frenchelectrican Re: MH High-Bay Lights - 03/11/05 04:47 AM
there are few suggestion with the trouble shooting Dave55,,

one is check the starting current and running current if 400 watts MH CWA ballast the starting current useally lower than running current btw ,,

second thing you can do is check the breaker to see how much inrush current during start up if not very high maybe the breaker is weak from all the abuse of inrush current there and there is a breaker that can dealt with high inrush current assocated with HID or transformers in the circuits

the other thing you can do is put the indivual fuseing for each lumiaire but that will drive up the cost for time and materals

hope this can help you with some question you are asking this one dave

Merci , Marc
Posted By: Celtic Re: MH High-Bay Lights - 03/11/05 05:14 AM
I would check the load also...that breaker may have become "unstable".
The last batch of poles we illuminated had in-line fuses for each head in the base.
Posted By: Trumpy Re: MH High-Bay Lights - 03/11/05 10:29 AM
With the lights being turned on in the morning,
are you sure it's not a moisture problem in one of the fittings or in a junction box?. [Linked Image]
Posted By: HotLine1 Re: MH High-Bay Lights - 03/11/05 07:25 PM
Dave: Suggestions & comments:
MH start current is higher than 'run'
Is the CB a HID rated/labeled breaker?
How many fixtures on the circuit?
What is the voltage?
Does the breaker 'trip' instantly?
or do the lights 'start-up' partially?
IF they do, then the ones that 'started' may require a 'cool-down' before re-striking; lowering the start-up current!

I would replace the breaker with a known 'good' (or new) breaker and clamp the circuit to get more info.
You may have a bad breaker; or you may have a ballast that is going bad.

Another reason I try to spec fuses at each hi-bay, and at each pole or head. Better to have one light out then the whole circuit!

Posted By: Dave55 Re: MH High-Bay Lights - 03/11/05 11:24 PM
Thanks, guys, I really appreciate your responses.

These are interior 400W MH multi-tap lights approx. 18' off the floor. I have them in the 208 volt leg, and the voltage is high, approx. 218 volts. There are six of these units on a 20-amp cicuit protected with a std. Square D QO SP breaker. It just occurred to me that this breaker is probably rated 120 volt, and I should be using the 120 volt tap on the ballast.

The breaker seems to be tripping instantly, and usually resets fine. It is also an intermittent problem. This area has gas heaters, so I'd describe it as very dry.

Posted By: golf junkie Re: MH High-Bay Lights - 03/12/05 01:31 AM
Sounds like you are running these off the "wild" leg of a 240v, 3 phase service. That is definitely not the proper set-up.

You can't get 208v off of this service without an additional transformer. You would have to either split all the circuits in two to run them 120v or run them 240v.

I would recommend that you call a pro.

If my assumptions about your service are incorrect.................
well then just nevermind [Linked Image]

[This message has been edited by golf junkie (edited 03-11-2005).]
Posted By: CRW Re: MH High-Bay Lights - 03/12/05 05:34 AM
I'd say change the circuit to 240v, 2 pole breaker, although your wire colors may be wrong if it's black and white in conduit. 6 fixtures at 400W will be too much for a 120V 20A circuit. You should calculate at 125% since those lights will be a continuous load. No matter what, using a single pole breaker for the 208V high leg is not correct.
Posted By: Dave55 Re: MH High-Bay Lights - 03/13/05 01:11 PM
Maybe golfjunkie and CRW could suggest another use for the 208V tap on this multi-tap ballast?

I used this tap to bring the current from 19A to 11A. If changing the breaker to one rated for 213V, or rewiring to the 240V tap is the solution, that's simple enough. I was curious if anyone else had this experience, especially as I have four other lighting circuits set up this way with no such problems. I should mention also that these tripped more on installation than they do now, and one of the units self-destructed. I was wondering if one of the lights would cause this.

BTW, it's an instant trip when throwing the switch. I'll take some current measurements this week. A fuse at each light would be a great way to troubleshoot an individual light, but these units are difficult to get to after installation with machines or racks.

Posted By: golf junkie Re: MH High-Bay Lights - 03/13/05 04:42 PM

Unless you have a 208/120, 3 phase service you can't use the 208v tap. The 217v to ground that you are measuring is the normal voltage for the "wild" leg on a 240v, 3ph. service.

Do not use the wild leg except for 240v loads. It is not a 208v leg.
Posted By: Dave55 Re: MH High-Bay Lights - 03/13/05 06:35 PM
It is a 3PH, 4-wire delta-connected system. The high leg (it is a 208V leg)is connected to the 208V tap on the ballast. What other possible use would this 208V tap have? If there's a violation in this installation, please be specific to the NEC, golf junkie.

Posted By: Redsy Re: MH High-Bay Lights - 03/13/05 07:01 PM

I'll agree with golfjunkie & CRW here.
The 208 tap off the ballast is for two hots off a 3-phase, 4-wire, 208/120 wye system.
You have a 240/120 delta with the midpoint tap delivering a higher L-N voltage.

I believe the reason you see one smaller transformer in a 3-transformer delta bank is because the expected load on the smaller one is less, because of the fact that you shouldn't use the high-leg for L-N loads.
(Utility workers, please verify this ?)

[This message has been edited by Redsy (edited 03-30-2005).]
Posted By: renosteinke Re: MH High-Bay Lights - 03/14/05 01:32 AM
Forgive me for suggesting the obvious.....but, is the breaker approved for HID use?
Posted By: HotLine1 Re: MH High-Bay Lights - 03/14/05 07:05 PM
The situation you explained is:
1: Dangerous
2: Wrong.

Using the high leg for a line-to-neutral circuit is 100% wrong, and dangerous.

The QO CB is rated for 120 volt to neutral/ground, not 200+.

The lights have to be connected either 120 volts, or 240 volts, based on your available voltages. Using 120 volt will result in an approx 2700 watt load, 22.5 amps, and should be on #10, based on 125% for a continuous load.

The high leg is NOT to be used for line/neutral circuit, only line-line (240 volt), single or three phase circuits.

BTW, the QO cb should be discarded in the trash. HID lighting requires a HID labeled breaker. (QO's are usually HID labeled)

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