Photcells on outside flood lights?

[Keith Baker]

I'm going to replace my 1000 watt HPS lights this summer with 400 watt pulse start on my 30' poles. Right now, all of the outside lights come on by a timer. I am considering adding a photocell to each of the 5 fixtures and still leave the lights on the timer circuit. That way I could turn on the bay lights on cloudy days and let the flood lights turn on when it gets dark. It might also cut the power company's "Demand Revenue Charge" on my bill.

Do photocells fail often? There would be no cost savings if I had to rent a lift to repair a light before the bulbs needed replaced. Does anyone else have theirs set up this way?

Thanks:

Keith

 

[Eric H]

I had issues with one photocell about 10 years ago. it took 3 replacements to get it to work correctly for more than a about 3 months. I have 4 circuits that have photocells that have been no trouble at all.
I do prefer using multiple timers for different lighting. For example, at one wash all of my parking lot lighting is on 1 timer, half of the bay lighting on another, and the other half of the bay lighting is on another. Half of the bay lights come on 1 hour before dusk, the other half come on near dusk, and the parking lot lights come on shortly after that. then half of the bay lights turn off from 11pm to 5 am. This set up allows me to manually turn on bay light during the day depending on wether conditions: overcast, rain/snow, etc.

 

[sparkey]

I don't know about total failure, but the lenses on the eyes seem to fade out rather quickly which causes the lights to stay on much longer than they should.

 

[wash4me]

Can you mount a photocell and Contactor at the base of the first pole in the circuit? This is accessible and fairly inexpensive. You will have problems with 1000 on a photocell. They are rated for it but premature failure is eminent.

 

[mjwalsh]

I see where both Keith & Eric mentioned the need for lights to be turned on during darker overcast days within the bays. We do not regret setting up ... on already available analog in- 24vac out modules (for control relay) ... on an existing PLC for tweaking just that. That way the ladder logic can also include some time of day & other finesse.

The analog skylight sensor (0-10V) within the below linked list has worked reliably for us with a PLC now for well over 4 years. The 4-20 ma analog version appears to be another option. Last fall we also included the ladder logic to go from 1/3 balanced (lull time) lighting of our brand new G&G leds (2 foot segments) to full lighting (2amps to 6amps) after the meter starts. Doing a google search will probably yield a better price than shown below.

http://www.kele.com/lighting-controls/mk7-b-series.aspx

mike walsh http://kingkoin.com/USA_Deficit_Reduction.html

 

[Randy]

I've got 2 photocells installed at my wash and I've never had any problems with them. Both are well over 25 years old.

 

[PaulLovesJamie]

I have a timer and photocell in series for some of my lighting. I definitely recommend it, keeps the lights off on rainy days.

I use the intermatic K4123C photocell, rated for 208-277V 15A. Years ago they seemed to fail regularly, often enough that I looked up troubleshooting info which told me either
a) contacts welded due to excessive load
b) if you can see burning/arcing across the serpentine pattern, the failure is caused by nearby lightning or other high energy transients.

Maybe thats worthless trivia

Anyhow once I switched to lower wattage flourescents, I havent had any trouble at all with the photocells.
I THINK I'm using a lower rated photocell now, but I dont have the model# handy.

 

[MEP001]

I'm going to replace my 1000 watt HPS lights this summer with 400 watt pulse start on my 30' poles. Right now, all of the outside lights come on by a timer. I am considering adding a photocell to each of the 5 fixtures and still leave the lights on the timer circuit. That way I could turn on the bay lights on cloudy days and let the flood lights turn on when it gets dark. It might also cut the power company's "Demand Revenue Charge" on my bill.

The demand charge is when they charge you more at your peak current draw off the system, such as dryer motors starting. Changing your lighting won't affect that in a manner that will save you money. FWIW, our electric provider contacted us and said they could save us on the electric bill, and all they did was change it from demand to a flat-rate. It has cut the bill a lot.

Do photocells fail often? There would be no cost savings if I had to rent a lift to repair a light before the bulbs needed replaced. Does anyone else have theirs set up this way?

It's the contacts that usually fail. I'd recommend mounting a single photocell for your light pole on the building and using a contactor to take the load.

 

[Keith Baker]

My lights are all wired out of the same breaker sub-panel to come on at the same time. A timer and contactor control this. When the wires leave the breaker panel, you don't have access to it until they get to the light fixture. It would not be worthwhile to try to separate parking lot lights from bay lights. If I were to change anything, I'll just add a photocell to each outside fixture separately.

The way the demand revenue charge was explained to me several years ago was that it came into play when you had a large surge on your meter. It would register the event and they would calculate it into your bill. When all of lights come on at the same time, I have an approximately 65 amp instant load. Adding photocells to the outside lights should keep them from turning on simultaneously. My demand revenue charge on last month's bill was $98.42 on a $424.05 charge.

Thanks for your responses:

Keith

 

[mjwalsh]

My lights are all wired out of the same breaker sub-panel to come on at the same time. A timer and contactor control this. When the wires leave the breaker panel, you don't have access to it until they get to the light fixture. It would not be worthwhile to try to separate parking lot lights from bay lights. If I were to change anything, I'll just add a photocell to each outside fixture separately.

The way the demand revenue charge was explained to me several years ago was that it came into play when you had a large surge on your meter. It would register the event and they would calculate it into your bill. When all of lights come on at the same time, I have an approximately 65 amp instant load. Adding photocells to the outside lights should keep them from turning on simultaneously. My demand revenue charge on last month's bill was $98.42 on a $424.05 charge.

Thanks for your responses:

Keith

Keith,

About the demand meter. Your explanation on the specifics of the demand cost is closer to our experience. In fact since the car wash (1968) was built after the laundromat (1959) we wound up with two separate meters. We thought we would gain by consolidating the two meters into one since we eventually went to 3 phase in the car wash anyway back in 1987 with our at that time brand new equipment. We got detailed explanation from an analysis from one of the MDU engineers who is also one of better customers. He took the time to show us how the demand would very much be a factor like you describe.

As far as doing something with relatively simple controls & relays ... I see where you are coming from with existing wiring already completely done. Just a thought ... it could be that all the conduit could still stay in place & the branching out with the controls could occur just by some minor extra box next to your main panel routing the initial power from the specific breakers to & from the new extra box. In our case we had to rearrange wires to accommodate more power for our revised Blo Dry so it was worth it. In the case of the controls for our dog wash four years ago ... it was all new wiring & new conduits so it was even more of a non issue for us than your situation during that specific project.

I wonder if putting a clamp on ammeter would give you enough information on how much of an extra cost demand surge is occurring when all the lights come on at once vs having delays via simple controls? If new LEDs are feasible lumen-wise & 30' up like you have ... I would imagine that the power supplies because of potential DC voltage drop would be better closer to the lights but still accessible.

mike walsh www.kingkoin.com