HOW LOW IS LOW? Voltage, that is.
toolbear
| Posted in Energy, Heating & Insulation on
HOW LOW IS LOW? Voltage, that is.
RE: AREA LIGHTING
Hundreds of feet of 12g underground. In one sector of the system, the voltages at the pins in the lamps are 98.9, 94, 95.2, 93V. There are also a lot of lamps out or flickering (fluorescents).
What voltage do these fluorescent lamps need?
At what voltage do they start having issues?
At what voltage will they not even light?
The ToolBear
“Never met a man who couldn’t teach me something.” Anon.
Replies
Lots of problems start to appear between 98 volts and 93 volts!
The short answer is: 105 Volts is the lower end.
Service life for power supplies will be considerably shorter with voltages under 100 volts that you are seeing primarily from higher current draw (more heat).
Depends on the ballasts, the lamps, and the desired minimum starting temp. There are commercially available ballasts that will operate at nominal voltages of 100VAC. The range of lamp types that these ballasts will operate is very limited.
See the website of Advance Transformer (http://www.advancetransformer.com) for info.
One other thought, most fluorescent lamps need a good equipment ground to the fixture to light off without flickering. If the fixtures are not well grounded (to the neutral/equipment grounding bar at the service point), it may take a while for the lamp to fire. Especially when the humidity is low.
Good luck,
Cliff
@@ One other thought, most fluorescent lamps need a good equipment ground to the fixture to light off without flickering. If the fixtures are not well grounded (to the neutral/equipment grounding bar at the service point), it may take a while for the lamp to fire. Especially when the humidity is low
Why am I having a Bad Thought?
This project was done in the '60. My condo was done in the '60s and they ran hot and neutral and grounded to the EMT.
Better open the panel and see what they did, but if they used the rigid as the ground and it's rotted out...
We will get to explore four decades of legacy wiring repairs on this job. The ToolBear
"Never met a man who couldn't teach me something." Anon.
Exactamento.
I recalled your many woes on this UG lighting wiring job, figured this fluorescent deal was part and parcel.
Hope you/your company bid it T&M.
Good luck.
Cliff
@@ Hope you/your company bid it T&M.
No, gave em a price per unit - but any wiring repair is extra.
There will be some. Not too many raintight boxes, so we have hopes. Those seem to have galvanic corrosion where the wires enter the box. The ToolBear
"Never met a man who couldn't teach me something." Anon.
I don't know about measuring at the pins of flourescents. Measuring hot to neutral as it enters the fixture should give you a lot more than that.
The DWP here is required to provide the nominal voltage +/- 5% at the service entrance, and the building wiring is allowed to drop no more than another 3%. That works out to a lower limit of 110.6.
So, start by measuring at the service entrance, and at the far end of the run. If there's a big difference, measure again at the box nearest the middle. If that matches one end or the other, you've isolated the problem to the region between there and the end that doesn't match. Repeat the process, dividing in half each time, until you find it.
Another thing to do is check the current with a clip-around ammeter at the breaker that serves this circuit. If it's significantly more than the lights should consume, this being an underground run, it could be that the insulation has been compromised down there, and the electrons are getting wet. ;-)
-- J.S.
Your point is well taken, but ... I like measuring at the pins. I can get at them when I relamp the fixture. Pull the old lamp, check the voltage, stick a new one in. I even log the voltages on a spreadsheet. The other way involves taking things apart.
We are going to replace 65 area lights, so we get to take them all apart and I will be logging volts as we go - before the lights go on.
Question is - what should the pin voltage be? What voltage will make the light a happy camper? In this complex I have pin voltages in the 100+ range. Is there a standard drop across the ballast that can be allowed for? The ToolBear
"Never met a man who couldn't teach me something." Anon.
The voltage drop in the ballast varies to maintain a relatively constant current in the lamp. It will vary considerably with temperature and lamp age.As others have said, probably around 105V is the minimum that will produce reliable operation, depending quite a bit on the type and age of the components. It may be (or may not be) that electronic ballasts would give slightly better performance in these low-voltage conditions.Another option (besides larger wire) is an autotransformer to boost the voltage. The old heavy iron units were a bit expensive, but there may now be solid-state versions available cheaper.
People never lie so much as before an election, during a war, or after a hunt. --Otto von Bismarck
If you can energize the whole circuit with no fixtures installed, check the amps at the panel. The worst case here would be that you have insulation damage underground, and that would show up as current flowing with nothing intentionally connected.
If that's the problem, the dirt between the damaged hot and the dameged neutral, ground, or ground rod acts as a big resistor. If the resistance there is, say, 120 Ohms, you'd expect to see 1 Amp. If it's 10 Ohms, you'd be losing 12 Amps, which could be enough to load down the voltage, and heat up the dirt to the tune of 1440 Watts.
With a really good meter, you won't get zero Amps, because capacitance across the romex will draw something -- a few mA or less. Anything more is real bad news.
-- J.S.
@@@ Another thing to do is check the current with a clip-around ammeter at the breaker that serves this circuit. If it's significantly more than the lights should consume, this being an underground run, it could be that the insulation has been compromised down there, and the electrons are getting wet. ;-)
Got one and can do that.
Had to put an entension on my bilge pump to get all the water out of the lamp post cores. Hard to make up good rapidset with 12" of rusty water. They transition from rigid to P40 in the post.
The ToolBear
"Never met a man who couldn't teach me something." Anon.
Don't try measuring the voltage on the pins of the fluorescent lamps. The voltage will always be lower than line voltage (due to the ballast), and in some cases may be substantially lower. You need to measure the voltage feeding the ballast.
Often fluorescents fail to "ignite" properly due to the failure to properly ground the fixture, or because hot and neutral got swapped somewhere.
Don't try measuring the voltage on the pins of the fluorescent lamps. The voltage will always be lower than line voltage (due to the ballast), and in some cases may be substantially lower. You need to measure the voltage feeding the ballast.
I can do that when we replace the light. There is an access port at the base - which is where they usually rust through.
One we DXed in that area shows 100 v before the ballast.
The ToolBear
"Never met a man who couldn't teach me something." Anon.