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Posted By: Merlin 100 W HPS fixture issue - 03/15/12 05:07 AM
I have a customer with a 100W HPS fixture on an outbuilding. The fixture is photoeye controlled. Almost everytime that a large load starts in the house (A/C, sewage ejector pump, ect.), the light shuts off and eventually comes back on.

The outbuilding and house are both on seperate loadcenters and feed from the same main panel at the meter. It appears to me that this is caused by voltage drop. Correct?? I even switch the fixture circuit to the opposite phase and it still does it. Could this be simply a photoeye problem, or utility service voltage drop???? Any suggestions?
Posted By: sparkyinak Re: 100 W HPS fixture issue - 03/15/12 08:02 AM
Possibly the transformer is over loaded by other services. What's the incoming voltage at night? It tends to be a little lower in the evenings then the day
Posted By: wire_twister Re: 100 W HPS fixture issue - 03/15/12 01:34 PM
+1 with sparky, check the voltage in the evening, and look at the size of the transformer, and its load. Call the POCO and ask for someone to come out and look.
Posted By: Merlin Re: 100 W HPS fixture issue - 03/15/12 01:58 PM
This is in a rural area, only service on this transformer. voltage. Under start-up surge from A/C or sewage pump, I saw it drop to 112 for about 1/2 second. I switched the fixture to the "higher" phase (121) and it still dropped out under surge.
Posted By: HotLine1 Re: 100 W HPS fixture issue - 03/15/12 02:33 PM
Merlin:
Did you ck the voltage at the fixture, or the source panel?

Sure sounds like a Vd issue...at the fixture.
Posted By: jdevlin Re: 100 W HPS fixture issue - 03/15/12 02:37 PM
One side higher than the other would indicate possible loose neutral issue.
Posted By: twh Re: 100 W HPS fixture issue - 03/15/12 04:21 PM
It's probably voltage drop, but try a new bulb to eliminate that before you spend a lot of money on it.
Posted By: sparkyinak Re: 100 W HPS fixture issue - 03/15/12 04:51 PM
Originally Posted by jdevlin
One side higher than the other would indicate possible loose neutral issue.


I agree with jdelvin that it could be a loose neutral. When A heavy load start on this service, does any lights on the premises get brighter?
Posted By: wire_twister Re: 100 W HPS fixture issue - 03/16/12 12:24 AM
I agree with the possible loose neutral situation also. As far as the transformer, My house is the only load on a 15 KVA pole pig, it is about 60 feet from the pole to my meter, every time my 4.5 ton AC compressor starts there is a noticible flicker in the lights. Put this same load on a 10 KVA pot and it could pull down enough to turn the light out. What kind of meter did you use to measure the voltage when AC started? Most DVOMs are not fast enough to catch the dip, so it is likely the reading you got was on its way back up before your meter settled down. Just my 2 cents.
Posted By: Tesla Re: 100 W HPS fixture issue - 03/16/12 02:32 AM
Rewire your High Pressure Sodium fixture across 230 VAC instead of 120 VAC.

I'm presuming it has a CWA ( Constant Wattage Autoformer ) with multiple taps.

I also suspect that the wire gauge used to feed it needs 240 VAC.

You've made no mention of the distance to the outbuilding.

Check if the photo-eye can be replaced with a 230 VAC sensor, too.

Every time its voltage pulls low it changes its logical state -- which is the primary cause for the HPS to cut out.



Posted By: Merlin Re: 100 W HPS fixture issue - 03/16/12 05:05 AM
I checked the voltage at the panel. The customer has changed the bulb a couple times and it still does it. I didn't get any complaints about lights getting brighter but they do dim when A/C starts.

I'm not sure of the transformer kva. However, the meter/main (200 amp) disconnect is approx. 180 feet from transformer. Then about another 60 feet the the house distribution panel (also 200 amp). The pole barn also taps from the main panel and travels about 200-250 feet to the pole barn. This is #2 aluminum wire feeeding a 100 amp loadcenter with very little load.

This problem just started within the last few months. Makes me think it is a PoCo issue ahead of meter.
Posted By: HotLine1 Re: 100 W HPS fixture issue - 03/16/12 01:38 PM
There could be a lot of contributing factors, POCO loads on the transmission lines, Vd in the customer owned service feeder and sub-feeders, and the branch circuit.

Vd calcs for the above for starters. Thorough recording of events (Voltage and amperage) at main and sub panel(s) will give more details. You have 500' +/- of conductors. Also, the AC unit may be starting to have issues.

One side ? for my curious mind....AC on at this time of year?

The amount of time that would be required to do what I suggest, vs. the swap to 230/240 volt fixture may take care of the HPS light issue.

Good Luck
Posted By: gfretwell Re: 100 W HPS fixture issue - 03/16/12 05:06 PM
You really need to hang a power line monitor on the service if you want to start pointing fingers at the PoCo. I have done it but they usually deny a problem until you show them the tape and they still try to say that is within the nominal tolerance if they can.
Posted By: HotLine1 Re: 100 W HPS fixture issue - 03/16/12 07:16 PM
IMHO, someone has to draw a line on how much $$$ to spend, IF the only issue is the HPS fixture.
Posted By: gfretwell Re: 100 W HPS fixture issue - 03/16/12 09:36 PM
It's too bad Merlin is so far away. I would loan him my Dranitz.
Posted By: Merlin Re: 100 W HPS fixture issue - 04/13/12 05:02 AM
I thought we had an underground problem. So, I done a fault locate and found 2 spots with leakage to earth. I dug them up only to find minor nicks in the cable and fixed them. After further investigation and watching voltages and current on cables, I think it is just a case of voltage drop.

I got out my measuring wheel and determined it is 400+ feet from main distribution panel to building with the issue. I decided plug all the information into my electri-calc. With the 400', #2 AL, 121 volts, and 11 amps....it tells me that i have a VD of like 4.4 volts. That is about what I'm seeing.

BUT, I still don't understand why equipment in the house is affecting the light in this building. The voltage drop is on the service wire feeding the building only. No effect on the main panel. And there is no other load on in this building at night when the light is on.
Posted By: HotLine1 Re: 100 W HPS fixture issue - 04/13/12 08:49 PM
Merlin:
Did you check the voltage at the source of this 'feeder', and see IF it varies.

Anything cycling to affect the load, like the HPS variation in startup and full luminance?

Posted By: Tesla Re: 100 W HPS fixture issue - 04/14/12 07:51 AM
The repaired conductor must be Megged.

Aluminum is at extreme hazard when in contact with the earth.

It corrodes ENDLESSLY in the presence of chlorides. ( table salt )

Unless you used epoxy encapsulation -- you shouldn't trust your underground repair.

The light is controlled by a photo-eye. That's what's dropping out the lamp. It can change its logical state in microseconds. Ordinary field test equipment is not going to spot that.

Posted By: Merlin Re: 100 W HPS fixture issue - 07/05/12 04:47 AM
An issue still continues with this service. I followed some advice (and my gut feeling). I decided to change the fixture over to 240 volts. This required changing the fixture ballast, photo-eye, and some minor rewiring. And after all that.....the problem still occurs! When a heavy load starts, the light goes out. Any more ideas aside from replacing 425 foot of URD all for a simple light?
Posted By: sparkyinak Re: 100 W HPS fixture issue - 07/05/12 05:08 AM
You mentioned earlier that the lights dim win the AC compressor kicks on. It still sounds like a voltage drop issue. If you can and have a voltage recorder of a max/min setting on your meter, I'd track the voltage as close as possible to the light.

Can you guesstimate the wire size of the utility's triplex? I remembered doing a service upgrade one time and the old service had #6 or possibly #8. It was and old 60 amp service put in a 200 amp service. The poco showed up and just reconnected the existing service drop
?=^P
Posted By: Merlin Re: 100 W HPS fixture issue - 07/06/12 01:34 AM
It is about 250 feet of 4/0 URD from PoCo transformer to meter base. Then about 40 feet of 4/0 URD from meter to house. And 425 feet of #2 URD from meter to pole barn where the light is located. I know that there is a substantial VD at the pole barn with any load running. But the light is the only load on the pole barn service at night when the issue occurs. I changed the light ballast and photo eye to 240 volt. Still shuts off when A/C in house starts or any other large load. It just baffles me that the A/C at the house affects the barn light.
Posted By: HotLine1 Re: 100 W HPS fixture issue - 07/06/12 02:46 AM
Merlin:
Think about the Vd at the house when the ac starts, then use that voltage for a 'source' to calc the additional Vd in the 425' to the barn.

By any chance, is the ballast a multi-volt?....You could use the 208 volt tap if it is. That may be a quick fix.

Posted By: Tesla Re: 100 W HPS fixture issue - 07/06/12 08:30 AM
It's the photocell not the ballast.

That's my bet.
Posted By: Merlin Re: 100 W HPS fixture issue - 07/06/12 12:11 PM
It is a multi-tap ballast. What would that do under "no-load" circumstances by using 208 tap? I did change the photo-cell to a 208-277 volt cell.
Posted By: HotLine1 Re: 100 W HPS fixture issue - 07/06/12 01:56 PM
IMHO, it should be OK, unless the no load voltage is 240.

Worst case, for the chance of blowing the ballast, it may be worth it.

Posted By: LarryC Re: 100 W HPS fixture issue - 07/07/12 05:00 AM
To separate the issue from the photoeye and the light fixture, temporarilly bypass the photoswitch.

If the fixture still drops out, it is a significant Vd problem. If the lamp flickers or is not affected, then the photoswitch is too sensitive.

PoCo issue question. Was there any tree damage to the utility's lines prior to the lamp problem showing up? My thought is that a utility line may have gotten damaged and you now have low voltage under load.
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