Help with Electrical Issue Drill Press/GFI

[Wilsoncb]

My drill press will trip the GFI when it gets hot. (Not really that hot, but seems to work fine after not running it for a couple hours/cools down). If I plug it into a non-GFI circuit, it works fine. How do I troubleshoot this problem?

 

[tvrgeek]

One of several things. Clearly your drill press has an issue. Likely the run cap getting hot and leaking, could be dust/gunk build up that is leaking, could be winding insulation breaking down and leaking, could be a wire has chaffed and the insulation is just barely there. In any case, I believe you do have a safety problem and it is a good thing the GFI is telling you that.

So, blow out the motor, blow out behind the switch etc. Basically get everything clean.
Look for any discolored wiring, pinched wires, chaffed wires. Fix. ( self vulcanizing electrical tape is my favorite, not the standard black vinyl)
Look at the run cap. Does it look like it has been hot? Bulging, blisters? Might replace it.
Motor windings: New motor, or a great excuse for that Nova we all want but can't justify

What is the drill press? How old is it? Might be a hint.

 

[ssmith]

Inductive loads, like motors, can cause nuisance trips on GFCI breakers even when there's nothing wrong since motors can cause the hot and neutral to be slightly out of phase.

Still, if this was running before with no issue, something's changed so it would be prudent to do a thorough check as @tvrgeek stated. It's also possible the GFCI itself is the problem, so you may want to try your drill press on another GFCI circuit, if you have one.

 

[Wilsoncb]

Thanks for the feedback. I'll take it apart today and check it out. Here's a picture of the motor plate and product tag. Looks like it's a 1984, so almost 40 years old. It hasn't had a lot of heavy use, so everything else it in good working shape.

 

[Oka]

I know this drill, they made the same drill under a bazillion names. Generally they work well. But, why are you plugging into a GFI? Not necessary for most tools save a wet cutting application (ceramic tile).

 

[Gofor]

You don't by chance have anything else on the circuit drawing power that gets it close to tripping, do you? (ex: shop vac). My TS would run fine with my shop vac until I put a load on the saw, and then most times the GFI would trip before the breaker. Had to find a different circuit for the vac. Just a thought.

Casey: A lot of code inspectors require GFIs on every outlet circuit if its in a garage,etc. Not sure if that is the case here.

 

[tvrgeek]

Inductive loads, like motors, can cause nuisance trips on GFCI breakers even when there's nothing wrong since motors can cause the hot and neutral to be slightly out of phase.

Still, if this was running before with no issue, something's changed so it would be prudent to do a thorough check as @tvrgeek stated. It's also possible the GFCI itself is the problem, so you may want to try your drill press on another GFCI circuit, if you have one.

Yes, good call on the phase, though the temp sensitivity leads me to the other problems.

Early GFI breakers had some issues, but newer ones should not. I use panel breakers, not GFI outlets as they seem to be more reliable.
Most codes say any outlet within 3 feet of water, so kitchen, bath, close to doors, and outdoor, as well as garage and shop. AFGFI have issues, but GFI should not.

I bet that drill is over 10 years old. Caps dry out.

 

[Wilsoncb]

OK, I took this thing apart and it's pretty clean. (I think I cleaned it about a year ago with this first started to happen). The wires on the switch connection look like they were hot at one time. Capacitor looks good, but is there a way to check it with a meter? Either way, I think I'll order a new capacitor and switch. Both are cheap and as long as I have this taken apart, I might as well replace them. I'd like to just replace the motor with a 3/4 HP, but we're talking about $200.

Concerning the GFI questions. The GFI circuit it's currently running on was done with the house/garage build in 2007. I have a radio running on the same 20 amp circuit. When this happens, it will trip the GFI with or without the radio on. I added another 20 amp circuit 4 years ago and used a GFI outlet in that one as well. When tested on that circuit, it did the same thing. It seems like it's not the GFI's, but I'm not ruling them out yet.

 

[ScottM]

I am telling you to ignore the codes but let me tell you a little story. We built an addition to our church two years ago. The addition included a new kitchen in which we had a dedicated circuit for a commercial refrigerator and a separate dedicated circuit for a commercial freezer. Code dedicated every outlet in the kitchen had to be on a GFI. From almost day one the freezer started blowing the GFI. Three service calls and three GFI outlets later the company replaced the freeze. You can guess what happened. Yup tripped GFI. Two of our church members are retired EE’s who measured the circuit and load and all in specs. So we replaced the GFI outlet with a regular 20 amp outlet and two years later the freezer is working fine.

 

[Gofor]

When my house was built, they allowed a dedicated outlet (for a freezer) in my garage to not be GFI protected. With today's code, you have to hard wire the item in to bypass the GFI requirement.

 

[Oka]

Yeah I know, you put in what you need in code, however, when you convert your garage to a shop, now there is a different standard. Shops do not require arc faults or GFI's, so that said Most of the fires are caused by poor wiring not sparks ......... maybe I am just becoming cynical with all the attempts to idiot proof things - just remember it is impossible to idiot proof things ... the idoits are more in numbers and much more creative in their lameness -

You don't by chance have anything else on the circuit drawing power that gets it close to tripping, do you? (ex: shop vac). My TS would run fine with my shop vac until I put a load on the saw, and then most times the GFI would trip before the breaker. Had to find a different circuit for the vac. Just a thought.

Casey: A lot of code inspectors require GFIs on every outlet circuit if its in a garage,etc. Not sure if that is the case here.

 

[tvrgeek]

There are also a lot of cheap GFI outlets. I have never had an issue with a GFI breaker.
Just like outlets and switches that come in three grades, from bulk crap contractors install, to half decent last a few years, to the better quality "comercial" spec. Many do not notice the markings, but switches are rated for inductive loads or not. My compressor is on a wall switch, and it has an inductive rated switch. Only a few bucks more.

I see by the picture, those fast-ons have gotten hot. I hate them. Give me a ring lug I can screw down. Crimped and soldered. OK, I am biased, but that is what working as a quality engineer in a failure analysis lab does to you. I also restore old British cars, so crappy connections I am well versed in.

 

[pop-pop]

I also restore old British cars, so crappy connections I am well versed in.

Lucas Industries, known as the Prince of Darkness.

 

[ssmith]

Not discounting the other possible causes but is that exposed wire in the 1st pix? If so, could it be contacting something inside the press when you reassemble it?

Another possibility - the insulation is damaged from overheating and you're getting leakage between the hot and ground inside the black sheath. Can't tell for sure from the picture.

It is possible to partially check certain types of capacitors with an ohmmeter but exactly what you'll see on a good one varies with the ohmmeter and capacitor. More realistic to just replace it unless you have a cap tester.

 

[Wilsoncb]

Not discounting the other possible causes but is that exposed wire in the 1st pix? If so, could it be contacting something inside the press when you reassemble it?

Another possibility - the insulation is damaged from overheating and you're getting leakage between the hot and ground inside the black sheath. Can't tell for sure from the picture.

It is possible to partially check certain types of capacitors with an ohmmeter but exactly what you'll see on a good one varies with the ohmmeter and capacitor. More realistic to just replace it unless you have a cap tester.

Thanks for checking out the pictures. It’s not an exposed wire you are seeing, but I can understand how it looks like it in that picture. Either way, I think I will re-do that connection. I ordered a new switch with paddle type ”off” to replace the old toggle so I may need a different connector anyway.

Also ordered a new capacitor. While living in Texas for a few years I got used to replacing the AC capacitor annually. The TX heat was really hard on them so perhaps it took its toll on the DP cap as well. It seems like the capacitors that came on the AC unit from the factory would last about 5 years, but the cheap replacements were only good for 1 year.

 

[petebucy4638]

I am telling you to ignore the codes but let me tell you a little story. We built an addition to our church two years ago. The addition included a new kitchen in which we had a dedicated circuit for a commercial refrigerator and a separate dedicated circuit for a commercial freezer. Code dedicated every outlet in the kitchen had to be on a GFI. From almost day one the freezer started blowing the GFI. Three service calls and three GFI outlets later the company replaced the freeze. You can guess what happened. Yup tripped GFI. Two of our church members are retired EE’s who measured the circuit and load and all in specs. So we replaced the GFI outlet with a regular 20 amp outlet and two years later the freezer is working fine.

As a general rule, most interpretations of the NEC allow the use of non-GFCI protection on dedicated branch circuits that supply refrigerators, freezers, or other appliances that remain plugged in all the time.

 

[tvrgeek]

Multiple comments

Actually, with the exception of their alternators, 99% of the problems are just like the switch photo above. Poor connections done by the auto manufacturer, really poor design often with too small wire for the load, and like all cars of the era, no grease to protect connectors. Add in age and the grease inside switches ( like the switch above) dries out leading to corrosion and high resistance. Usually the fuses are unprotected.

FWIW, half the alternator problem is the brand picks one too small. 27A in the TR-6! So, how far can you drive at night in the rain with the heater fan blowing? People wonder why the headlights are dim. Well you are running on the battery at 12V or less instead of the alternator at 14. Other problem is a diode that leaks draining your battery.

A GFI should trip with about 5 mA difference between hot and common within about 1/10 second. It sounds like even the newer GFIs will trip with inductive loads. It does seem like a problem as dish washers, washers, disposals, jacuzzis, and garage outlets all will see high inductive loads, yet code says they must be on GFI. I thought I saw a reference to a GFI outlet intended for inductive loads, but can't find any reference now. One might assume that the larger the motor and heavier the startup load, the longer the phase lag so the more likely of a false trip. I can't find any data on the integrator timing within a GFI outlet. ( if there is one) If 1/10 second, then it should not trip with a 60Hz load if the circuit was well designed. So, the GFI plug end on my power washer does not trip. 10A inductive load. What is different in it's design?

No, you can't test the run cap at home. You would need an environmental chamber and a megger.

Unfortunately, a leakage current meter costs several K.

Yes, a lot of modern replacement parts ( China) are crap. Ignition condensers are the worst. There are none made anymore of any quality. None. Cheap internal termination issues.

Anyway, the OP says it only trips when hot, so that still leads us to broken down insulation or leaky run cap. ( not compensating for phase lag) I bit dicey, but one could test for leakage by opening the ground lead and putting the drill on a mat. If it still trips, it is not leakage to ground. If it does not trip, do not touch it!