Sparks when checking voltage?

[Jhunter1313]

So, I have some highbays in a warehouse, that were originally unswitched (wire went straight from the breaker to the lights), and they have been working fine. The customer now wants to be able to switch the lights. So I ran a series of contractors and a time clock/switch, re-routed the wires from the panel to go from breaker to contactor, then contactor to lights.

Jumping off of one of the highbay line sides of the contactors, I brought power to my time clock/switch.

When I turned everything back on, the time clock/switch did not turn on, even though power was present.

I checked voltage on all the line sides of my contactor points (10 spots in total) and each one of them produces a small little spark where my multi-meter lead touches the ground screw....and i am not understanding why.

A little more background info in case it helps:
The voltage is 277;
Each breaker is a 2-pole breaker, one pole is the switched line, the other is the emergency circuit that goes straight to the EM lights;
The time clock/switch is jumping off of one of the breakers, and then switch legs out to hit each contactor coil (3 of the contractors are about a foot away from the switch, the last one is about 500' away at the other end of the warehouse, where it hits just the coils of the 4th contactor);
The 4th contactor is powered by the time clock/switch, but the circuits it passes through are from a different panel (still the same exact scenario...2-pole 277v, etc);
I have a ground going through every conduit and raceway, and is terminated and/or grounded in every junction point;
Going through the chase nipple from the original panel to the contactor box, I have about 22 wires (10 hot wires from breaker to contactor, 10 hot wires from contactor to the lights, a neutral going from contactor coil to panel neutral bar, and a ground, tied in with the other grounds, and landed on ground bar in the panel).

 

[ptonsparky]

Your meter passes a little bit of current when it is added to the circuit. Just as any other load. You may be able to see it spark as you interrupt the current flow.

 

[StarCat]

This post is vague and hard to follow
." When I turned everything back on, the time clock/switch did not turn on, even though power was present." This seems to indicate you used a Solid State Time clock, and its not switching power when you want it to. If you are reading applied power to any load, ground is not a good reference for troubleshooting in many cases because you are not reading what the load is seeing. An exact wiring diagram of what has been installed would be helpful. If you are running incandescent lighting, you need contactors rated for that duty. There are a lot of neutral connections in this picture. I would not wire the controls with solid core wire.

 

[Jhunter1313]

I tried to draw up a diagram to post but it won't let me load the picture I took.

The time clock/switch is a digital time clock with a manual override "on/off" button. And what I mean when I say it did not turn on when power was present, is that the digital display did not power on when I turned the breaker on. So there was no way to program, or manually operate the switch.

 

[electricguy61]

Was the time clock control rated at 277V?

 

[480sparky]

Was the time clock control rated at 277V?

That would be what I would check. It could be a 120v motor, which now has all the magic smoke let out of it.

 

[ptonsparky]

Was the time clock control rated at 277V?

I was curious about that, too. Guessing the smoke has been let out as 480 suggests.

 

[electricguy61]

I checked Intermatic's website, and their common electronic timers are in fact rated for 277v, but........ you need to run a neutral, other wise you’d be hitting the control with 480v, which it’s not rated for. Just something to check.

 

[Jhunter1313]

So. Yes the clock is rated for 277v, and it seems the issue is that the clock does not actually operate on line voltage, but strictly off of the battery (that I did not initially install, because I was hoping it would work off line voltage only, and eliminate me having to go back in 7 years to change a battery...).

So that issue seems to be resolved, though I still don't have any clue why there is a little spark while I check voltage to my ground screw in my contactor box. But, everything is operating properly so, maybe just let the sleeping bear sleep? Haha

 

[hbiss]

What meter are you using? A low impedance meter (like we all should be using) will draw some current unlike the usual high impedance meter. The current draw at 120V might not be enough to cause a noticeable spark but at 277 it could be, especially in subdued light.

-Hal

 

[LarryFine]

I get sparks when using my Knopp solenoid tester, and I expect to.

 

[ptonsparky]

Once, well three or four in a row cause I’m slow, I saw sparks and got suspicious because they were about a half inch long and followed the tester probe each time. My real meter showed I had over 700 volts. Last time I ever hung a tester from my neck as I used it to test voltage.

 

[LarryFine]

Once, well three or four in a row cause I’m slow, I saw sparks and got suspicious because they were about a half inch long and followed the tester probe each time. My real meter showed I had over 700 volts.

What were you testing, fluorescent ballasts? :blink:

 

[Hv&Lv]

It’s not funny, but this thread brought it to mind...

We have a couple of 4160 secondary services to mills. Not many, but a couple. One is a pad mount. The others are platform banks...

anyway, a few years back the mill called with a problem. Not sure now what it was, probably a dropped phase or something...

our service guy went there to troubleshoot and went to check voltage with a 1000V meter... on 4160...
he had on PPE, and was fine, but I can’t say the meter fared too well...

since then labeling on the secondary, guards, and shielding is mandatory on secondary sides on transformers like this..

talk about sparks when checking voltage...:slaphead:

 

[ptonsparky]

What were you testing, fluorescent ballasts? :blink:

It was a 480 v grounded delta transformer bank. Motors wouldn’t run.

I called POCO, put tools away, thought about the what ifs /how comes and met the POCO trucks on the way out with new transformers.

The original bank had served a hay mill that would have had several hundred HP for load. More than enough available fault current. Testers and meters were just starting to come out with the Cat ratings. Even my 87 didn’t have one at the time

 

[broadgage]

Some digital time switches contain a very small battery, to remember the time of day and the switching times during a power failure. Often they wont work until this battery is charged which can take many hours.
I recently installed such a timer, it was marked 220/277 volt 50/60 cycles. Since we don't normally use 277 volts or 60 cycles over here, that suggests that the same item is also sold in the USA. It worked fine after charging the battery overnight.

 

[kwired]

So. Yes the clock is rated for 277v, and it seems the issue is that the clock does not actually operate on line voltage, but strictly off of the battery (that I did not initially install, because I was hoping it would work off line voltage only, and eliminate me having to go back in 7 years to change a battery...).

So that issue seems to be resolved, though I still don't have any clue why there is a little spark while I check voltage to my ground screw in my contactor box. But, everything is operating properly so, maybe just let the sleeping bear sleep? Haha

Did you connect it line to line or line to neutral? Line to line, probably burned out the power supply portion of it. There is a chance that battery is there to maintain memory during power failures and you may need to reprogram it every time power fails if you don't install it. Is also possible it won't work at all without battery installed.

Low impedance meters will draw enough current that it can and often does spark a little when making contact with probe.

 

[hbiss]

Any of the time clocks I have seen uses the battery for backup during power failure, not as the primary power source. Who makes it?

No battery is going to last 7 years powering it. That should be your hint that it's for backup.

-Hal

 

[StarCat]

I came onto a new property around 2011 and one of the first failures was a digital defrost clock on a walk in remote condenser. I very quickly removed the offending piece of gear and replaced it with a Paragon 8145-20 electromechanical time clock. Its still running to this day. Some of those digital devices are quite unreliable, and also incomprehensible. Notice how most of the so called Tech DOCs anymore are written in some " Off World " type of newspeak.
Working in HVACR for 30 years. One of the prime service call creators are Digital Programmable Thermostats. The battery powered ones are especially time wasters and not worth having. All it takes is one more control conductor to power a " REAL " thermostat." A major lot of this transistor Tech is worthless in real terms. It only gets more reliable when you get in the industrial range such as Centravac machines of 1000 tons or more. They have to work, so are Engineered better. The low end stuff just keeps getting worse.

 

[hbiss]

Working in HVACR for 30 years. One of the prime service call creators are Digital Programmable Thermostats.

One of my favorites is the Nest that I don't hear too much about anymore. Customers read the hype and get all excited with having them installed then find out what a PITA they are.

-Hal