It is rated 16(10) so should be fine with or without PFC. I will probably use a smaller capacitor, will look to see if i still have some 12uF units around.

Smaller capacitor would encounter overvoltage at power OFF (when that happen at the moment of the peak in coil current), what would shorten their life. The energy in the ballasts would transfer to the capacitors. If the capacitor's value is smaller, it would charge to higher voltage. If the capacitance is too small, such voltage would exceed it's breakdown and the capacitor would degrade.

Currently the sign is in, without PFC. Looks like it will only be there on the first relamp, as it is now riveted closed, and I am not really going to remove a 10m long acrylic front single handed to put one in. Cabling is long enough to reduce the spike somewhat, and I will be putting the time switch in the distribution board it is fed from, instead of near the sign. Will add a small capacitor across the contacts as a snubber instead. 0.22uF as I have a really large number of these, class X with flexible leads.

The small capacitor would fail there because of the overvoltage.
If there would be no capacitor, the arc would develop across the contacts and so clamp it to few 100's V. Then majority of the energy stored in the winding would return back to the mains.

The 0.22uF would only prevent the arc from building up, so it would be the only voltage limiting component by itself. And so the voltage may go up to to 6.8kV, what would kill the capacitor instantly, maybe even damage the wiring and/or the relay (it would flash over the contacts, when the capacitor would cause large peak current, on top of the high voltage stress).

The capacitance would have to be at least 80uF to stay within the operating range of the (X-rated) capacitors, while the 80uF is about the correct compensation capacitance for the 700W discharge load (I expect about 90V arc voltages, so total about 8A before the compensation, the same figures I used for the previous calculation).

So either use the correct compensation capacitor, or use none at all. Anything between would damage something in the setup...


If you only want to relieve the contact from dissipating the energy, better use VDR to clamp the overvoltage. With that the "resistive" contact rating is relevant (the voltage kick is limited, so the energy is not dissipated on the contacts).

With VDR and without compensation capacitor you may use solid state (triac) switch, you have to only make sure, then the VDR is capable to clamp the voltage below the triac rating.

Is it an option to leave the PFC connected all the time and switch just the existing lights as is ?

Is it an option to add capacitors in series with 1/2 of the lamp circuits, so making it lead / lag with high overall power factor, without any capacitor parallel to the mains ?

Is it an option to leave the PFC connected all the time and switch just the existing lights as is ?

Yes, but capacitor's life would be consumed even when the lights are OFF.

Is it an option to add capacitors in series with 1/2 of the lamp circuits, so making it lead / lag with high overall power factor, without any capacitor parallel to the mains ?

Not one common capacitor, as for this configuration the capacitor impedance have to be exactly twice the inductor impedance. While it may work well with all the branches behind the capacitor running, when some of them fail, the capacitor value would become too large, so nulling the impedance of the ballast chokes, causing severe circuit overload.
But with, each choke (form the half to be operated as lead) have it's own, separated capacitor, it would work well.
But still the switch have to be rated for the inductive load (here is not important the phase on 50Hz, but what the impedance does at higher frequencies; as all use inductors, the high frequency impedance is high, so the overall current should be treated as an "inductive" load), only about half of the current.

The capacitor will have a series resistor, as the cheap timer I have ( no stock of the better one I wanted at moment, only next year) has contacts that are china rated. The snubber will prolong the contact life, and as it only does one operation a day I hope to get a year out of it.

You can run a well rated contactor (big relay) with the timer, then all the lights on the contactor

I did that where I live, using a surplus 80A 3 phase contactor, with a 220V coil. A little overkill wiring all 3 poles in parallel, as the load was only 10A of incandescent lighting ( later on changed to 20 odd flourescent fitting, a mix of 18W linear flourescent and Pl fixtures. Lamp life is now years, and output higher. When the contactor closes You can hear it throughout the building if it is quiet.

I did add a LED sensor light on last weekend ( without the crappy sensor, it runs all night now) to add more light to the side. Might add one to the front near it as well, as it is a dark area. Cheap Euroluc fittings, got for free ( poor light output and poor sensor performance compared to a halogen unit in same housing size) recently. The LED panel inside is reasonable, runninthe LED strings at rated current, not overrunning at all. Even has surge supression components and a limiting resistor for the capacitive dropper, and an avalanche diode to protect the LED strings from overvoltage.

Two years ago they replaced all the parking lot lights that were on a timer to shoe box lights that had photovoltaic cells, so it is likely they did the same thing with what you described.

Years ago I remember parking lot lights coming on the same time and going off the same time everyday. Even when it was cloudy or getting dark out they wouldn't come on until the programmed time. Now with the shoebox light fixtures they seem to come on everyday at different times depending on the weather conditions. My question is, were lights years ago programmed from the inside of a store or where did they program them from? Second question is, do the shoebox lights have a sensor on one in the set that make them all come out at the same time or what? Just curious?

Years ago, Parking lot lights were either on a electro-mechanical timer inside of a box inside of the store's electrical room, or used a roof-mounted photocontrol to operate all of the lights at once. That system is still used a lot today. I know this since The school that I work at uses rooftop mounted photocontrols to control all of our parking lot streetlights and breezeway lighting at the same time. Some of the photocontrols also have timers built into them too such as the ones on our school; these are usually set by the electrician. Usually, the main electric timer is located in an electrical room and the timer trips a contactor switch to turn the lights on and they usually has an override switch to operate the lighting contactor switch, when the lights need servicing. The school district I work for uses this system on most of the schools. Some of the schools use a timer only system, which activates the contactor, located in a separate box at the programmed time, no matter how dark or light it is outside. The wallpack lighting on portable classrooms use individual built-in photocells. It is also possible that the "shoebox" fixtures might be wired in series, being activated from the photocontrol on one light, thus controlling the other lights, too.

I've seen old Mercury vapor lights in parking lots around here that don't use any type of photocell or timer; they usually are just turned on at the breaker switch inside of the store! Sometimes they are on after dark, sometimes they're not!

The purpose of the Photocontrols used in conjunction with timers, is to save energy and lower operating costs.

I hope this answers your questions. I was curious about this at one time too!

At the ice rink I work at at home, all the parking lot and security lamps are on a simple mechanical timer.  The building engineer has to manually update it for the change in seasons. One thing that seems to becoming popolar with the larger installations (large cities) is wirelesly controlled group switching that communicates with a main computerized controller so different zones come on exactly when needed.

Most of the church buildings I work on have a photocell and timer setup for the parking lot lamps.  The Timer kills the parking lot lights at about 12 or 1AM then clicks back on at around 4:00PM to allow the lights to come on via photocell when dark enough. While the exterior building lights will stay on via photocell or timer all night.  To save electricity for parking lot and exterior building lights, I always recommend having a photocell and timer on the same circuit, to prevent unneeded lighting during the day time when a storm rolls in or it gets a little too dark for a short period of time then lights up again.  This is particularly true where photocells are located in a shaded or darker side of the building.