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Forum topic by Dustin posted 07-19-2016 12:44 PM 476 views 0 times favorited 11 replies Add to Favorites Watch
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Dustin

140 posts in 201 days


07-19-2016 12:44 PM

Topic tags/keywords: question

So, my current (less than ideal) set up around my cheapo 8×12” HF lathe leaves a little something to be desired. The previous homeowner has a hastily built work bench with a 2 lamp T-12 shop light above it. After some initial trouble with the bulbs (one burnt out, the other flickering when the lathe was running), I replaced both. The lathe is running on the same circuit as the light fixture. Whenever I fire up the lathe (at its lowest speed), one bulb goes out. If I adjust the speed up to about 1/3 of its maximum, the light comes back on, and at that point I can reduce speed and keep the light going. I’ve metered out the socket the light is plugged into (outlet, not hard-wired), but don’t see any fluctuations that I’d perceive as less than normal. When the lathe starts up, the light outlet very briefly drops to about 98V AC, then comes right back and stabilizes between 114 and 120. I wouldn’t think the load on the lathe should drop this so much, but it seems like the light fixture (which is admittedly a very cheap one) must have a lousy ballast or something else affecting its operation if it only happens in one of the lamps. Yeah, I know fluorescents are more finicky than other light sources, but this seems to go beyond that.

Any thoughts?

-- "Ladies, if your husband says he'll get to it, he'll get to it. No need to remind him about it every 6 months."


11 replies so far

View CharlieM1958's profile

CharlieM1958

16241 posts in 3679 days


#1 posted 07-19-2016 01:02 PM

I’m not an electrician, but I solved a similar situation by simply buying an inexpensive new fixture with t-8 bulbs and electronic ballast. I don’t think your lathe is the problem.

-- Charlie M. "Woodworking - patience = firewood"

View TheGreatJon's profile

TheGreatJon

295 posts in 694 days


#2 posted 07-19-2016 01:04 PM

I would assume it is the amperage, not the voltage that is being overdrawn. Does the light stay off, or will it come back on once the lathe is up to speed? If you plug the lathe (or light) into a different outlet on the same circuit does it act the same way?

In general it is a good idea to have you lights and your outlets on separate circuits, but in this case it sounds like the light is just a lamp-style fixture that would be plugged into your outlet. For a time, I had an 18” Parks bandsaw that was wired for 115v. Whenever I turned it on, the lamp next to it would dim and flicker until the wheels came up to speed. This is because during run-up the motor is working near its capacity to overcome the inertia of the wheels. This was coming pretty close to overtaxing the little 15A circuit and was stealing juice from the lamp.

-- This is not the signature line you are looking for.

View bigblockyeti's profile

bigblockyeti

3666 posts in 1181 days


#3 posted 07-19-2016 01:22 PM

You didn’t mention how “briefly” the voltage drops to 98V, but that’s awfully low for a light to no load start up. This is especially true given the fact the Harbor Freight lathe you have only has a 1/3hp motor. The fact that the voltage drops low enough long enough for you to capture that reading is concerning to me. I’d find out how much wire and what gauge is run to the outlet you’re using. As for the light, I would have to agree with Charlie in that a better ballast would likely help your problems.

View muleskinner's profile

muleskinner

880 posts in 1897 days


#4 posted 07-19-2016 01:41 PM

A simple fix with out going into wire size and motor in-rush current and all that stuff is to replace your T-!2 fluorescent fixture with an LED fixture.

-- Visualize whirled peas

View crank49's profile

crank49

3980 posts in 2431 days


#5 posted 07-19-2016 02:20 PM

+1 On the LED replacement. T-12 fluorescents are obsolete and being phased out anyway.

I also agree that your light should not be plugged into the same outlet as the lathe because a sudden overload might make the light go out and then you are in the dark with spinning machinery .

And, another point I haven’t seen mentioned is that fluorescents act like strobe lights at times so there is a danger you might not see something in the lathe spinning or it might look like it’s spinning at a different speed than it actually is.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

View Dustin's profile

Dustin

140 posts in 201 days


#6 posted 07-19-2016 02:44 PM

Thanks for all the replies.
Jon, the one lamp stays off until I dial the speed up. Once it’s up, the light comes on, and I can dial it back down. And this happens on both of the outlets by the bench (the junction box with the outlet is then piped up to an outelet box in the ceiling, where the light is plugged in).

The electrician who owned the house did a number of goofy things, but of the work I know he did (it’s actually my childhood home, was only out of it for two years before coming back and buying it) and have inspected, his work is pretty solid: i.e., proper gauge wiring, proper grounding, good splices with appropriate wire nuts, etc. I have a littel electrical experience, but primarily worked on the low-voltage systems side of things.

I think I’m just going to get a new LED fixture. They’ve got some nice single bulb high output lamps on sale at Rockler right now, and I’m a bit of an LED enthusiast to begin with (aquarium hobbyist for a time). I figured it was the $20 T-12 fixture, but thought I’d check before taking further steps.

Again, thanks for all the responses!

-- "Ladies, if your husband says he'll get to it, he'll get to it. No need to remind him about it every 6 months."

View DrDirt's profile

DrDirt

4167 posts in 3203 days


#7 posted 07-19-2016 02:55 PM

You might also check if it is actually a T12 Ballast. T8 (the 1 inch lamps0 and T12 fit in the same socket. But have to be paired to a propper ballast.

All the ‘cheap’ fixtures for teh past 10 years have been T8. So it may be that it is a mismatch, more than a voltage issue.

If you indeed have a T8 ballast – - there is an LED bulb as direct replacement, that does NOT require cutting out the ballast/rewiring the fixture.
Just take out Fluorescent bulb… put in an LED Tube. 10 bucks at Menards (won’t work if you indeed have T12)

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

View rwe2156's profile

rwe2156

2190 posts in 941 days


#8 posted 07-19-2016 03:01 PM

I would check the ballast. See if its really hot. A bad ballast will pull more current.
Thing, is, the cost of a ballast you might as well buy a new fixture.

T8’s are a definite step up. T5 is even better for work area light.
I am very happy with the 8’ T5 light over my workbench.

The LED tube bulbs don’t seem bright enough for a shop to me.

-- Everything is a prototype thats why its one of a kind!!

View crank49's profile

crank49

3980 posts in 2431 days


#9 posted 07-19-2016 03:34 PM


The LED tube bulbs don t seem bright enough for a shop to me.

- rwe2156

They make LED lights that can replace 1800watt metal halide ball park lights. You just have to buy the correct LEDs.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

View bbasiaga's profile

bbasiaga

754 posts in 1456 days


#10 posted 07-19-2016 05:37 PM

I know at work some variable speed devices need to have capacitors installed up front in order to stoprovide some kind of feedback from messing up the main line. Perhaps this is what is happening with your lathe. At low speed, where it is altering the incoming juice the most, it is feeding back on the circuit and causing problems with your light. Try plugging in a lamp with an incandescent bulb and see what that does. If it still dims it’s a current draw issue. If it seems fine, it may just be frequency interference from the drive.

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View Dustin's profile

Dustin

140 posts in 201 days


#11 posted 07-19-2016 06:29 PM



I know at work some variable speed devices need to have capacitors installed up front in order to stoprovide some kind of feedback from messing up the main line. Perhaps this is what is happening with your lathe. At low speed, where it is altering the incoming juice the most, it is feeding back on the circuit and causing problems with your light. Try plugging in a lamp with an incandescent bulb and see what that does. If it still dims it s a current draw issue. If it seems fine, it may just be frequency interference from the drive.

- bbasiaga

Ooooh, nice one. Didn’t even consider the possible voltage backfeed. I’ll have to give this a looksee, just to make sure it isn’t pulling to much amperage. I know it’s unlikely, but this thing is a HF, and I’d hate to have some freak accident damage the lathe or anything else plugged into this circuit.

-- "Ladies, if your husband says he'll get to it, he'll get to it. No need to remind him about it every 6 months."

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