lighting problem

[ds124]

This post will be a bit long but I want to give as much information as I can. I am working on a problem with the lighting inside a restaurant/bar. The lights will go up and down in brightness as if someone was moving the dimmer knob. Now here is what I know. This has been going on ever since the restaurant was built 5 years ago. The restaurant lighting is divided in half with each half having 8 zones controlled by 8 dimmers. There is also 1 ceiling fan control for 2 fans for each half of the restaurant(total of 16 dimmers and 2 fan controls). This problem was with every zone but now is only happening in 2 zones. Each half of lighting is fed with a 3 phase, 4 wire circuit(total of 6 circuits). When I first started looking into this I found that all 6 circuits were on the 'A' phase in the panel. Unknown to the customer, this was how the original contractor and 3 other contractors solved the problem. I changed all the circuits back to the proper phases in the panel and even pulled in separate neutrals for each circuit. Turned all the power back on and sure enough every lighting zone was going crazy. I changed all the circuits back to 'A' phase and again it is down to 2 zones. While working on this I did check the load and dimmer sizes which are all correct. The power company has been out to verify that there is no problem on their end. I am looking for any suggestions on what to look for next. My thoughts are that there is a problem with 'B' and 'C' phase and should have an infrared scan done or there is a problem with the neutrals. Any thoughts???? Any suggestions??? One last thing. I know the owners of this restaurant which is in Nevada and I am in Ohio. I looked into this 2 years ago when I was last there but will be going back in a month to get involved with this more. Looking for as much information as I can get before I go back. Thanks for reading and any help will be appreciated.

 

[hurk27]

First trick is to isolate the cause, I would say would be to remove the dimmers, then rebalance them between the phases, I know of nothing that would cause what you have described, other then a stuck button on a wireless remote for a ceiling fan, the one you just push and hold to brighten or dim the light on the fan, but unless these dimmers are part of some kind of X-10 wireless system, I have no clue as to what would give you that kind of result.

Ok I do know one other thing that would, trying to get 240 volts from two inverters or generators series together that don't run in phase:roll:

What kind of fixtures are they Incandescents?,

 

[G._S._Ohm]

WAG:
Depending on the period of the change in brightness this could be a 'beat frequency' problem. 60 Hz and 59.9 Hz would give a beat frequency of 0.1 Hz with a period of 10 seconds.

 

[SG-1]

Since the dimmers have been behaving this way since the installation I would monitor the voltage input to the effected dimmers. If the voltage sags & swells, then check the voltage in the panel. Is there a load on the same phase that could be causing a voltage fluctuation ? You could try turning off different loads.

Does the voltage fluctuate on the main in the panel.
Are the service conductors sized properly ?

 

[ghostbuster]

Check the voltage waveform with a scope,to see if there is any notching or multiple zero crossings.:roll:

 

[rt66electric]

look for "circular piping

look for "circular piping

Normal piping and distrubution should fan out like a tree "branch", as opposed to a rats nest.
if the hots/switch legs are piped or routed in a complete circle then a electromagnet or soleniod is formed.

Another problem may occur when the hots go into a switch box via one pipe then exits via another pipe. The fancy long word is called the hysterisis(sp) effect, esscentauly forming another solenoid magnet. Under light loads problem do not arise but under heavy loading weird things like tombstones will melt off strip lights.

look into the dimmer panel and check to see if the hots/neutral/ switchlegs are in the same conduit or if the hots are in one conduit and the switchlegs are in another??

 

[ds124]

The feed to the bank of dimmers is underground. The only circuits in this conduit are for the lights. From there it is branched out within the walls with MC cable to the lights sharing neutrals. Panel wire size is correct but do not know the voltage. I was on vacation last time I was there so I did not have any meters with me to check the voltage. I am looking into renting a power quality logger to monitor the problem for 14-30 days. Here in Ohio, the power company would monitor the power for free but was told by Nevada Power that they do not offer this service at all. As far as I know, this panel is strictly for the lighting. There is no X10 wiring, its all hard wired. I did think about isolating the different lighting zones to see if I can narrow the problem down but the problem is not consistent. Thanks for all reply and any more help would be appreciated.

 

[LarryFine]

This sounds suspiciously like a shared-neutral problem, and causing the dimmers to somehow be modulating the light levels.

 

[muckusmc]

Some dimmer panels have a remote light sensor on the roof to adjust the lighting as per ambient outside (sunlight) brightness. Sometimes a passing cloud will cause the light to brighten. Worth checking - I know some Olive Gardens have this arrangement.

 

[ds124]

At one moment I am convinced that it is a neutral problem but then I go back to the fact that there seems to be a problem with 'B' and 'C' phase. This is an interesting problem and why I joined here.