Mark Bolton
08-07-2017, 6:11 PM
We have a slider with a scoring motor in the shop and each have mag starter switch in the control panel with a CHINT NR2-25 thermal overload (25A on the main motor and smaller on the scoring). The other day was a big day, saw was running almost non stop all day and then I worked late into the evening and was breaking down a bunch of 12/4 hard maple for table legs. A few legs in the saw quit. I had hit the thermal overload a couple times in the past few months and would wait a bit, hit the reset on the thermal behind the panel cover, and the saw would be fine.
Well this time, no such luck. Did a bunch of other stuff, waited, hit the reset (never felt like it reset), waited some more, wash-rinse-repeat. Left it over night. Next day, still nothing. Manually close the mag switch and the main blade runs like a champ. I figure the thermal is fried. I pull it out, grab the fluke, test the leads, and it seems fine? Continuity is straight through. Put it back in, saw has dual controls, one set on the body, one on the slider, nothing. Test the transformer sending 28vac out to the slider and body controls, AOK. Do a bunch of testing in the panel, all seems good. Still nothing. Pull the thermal 2-3 more times and test and it always test fine. Each time I put it back in, nothing. Bypassed the thermal and connect motor leads direct to the mag. runs like a champ which I knew because even with the thermal in the saw would alway run depressing the mag manually. Re-test the continuity on the thermal, all looks good, reconnect thermal, zip. I do this for an entire day off and on.
Each time however, the prongs of the thermal going into the mag switch would kind of fight me. They wouldnt just slip in and tighten. One time the left pin would slide loose, another time the right pin would slide. Finally pulled the mag out of the panel and got the thermal locked in dead tight. Low and behold, I push the mag in manually and SNAP, it runs. Go to the slide controls, they work fine, controls on the base, work fine.
So Im left wondering.
a. The overload couldnt have been stuck or something because it tested multiple times with continuity test that it was passing power through. and it ran with the thermal in and manually closing the mag(yet the motor never fired**edit, never fired with the controls, the motor always ran when depressing the mag manually**
b. Could there have been a bad connection from the factory (fighing with getting the thermal pins tight into the switch) from the factory and we just got it hot enough to rear its head? (nearly 10 years)
c. Is the thermal on its way out? Doesnt make sense base on the continuity tests.
d. Probably the real answer that I just dont know?
I ordered a new thermal overload to have on the shelf, and we could have always run the saw jumping out the mag switch, but would of course rather not do that.
Well this time, no such luck. Did a bunch of other stuff, waited, hit the reset (never felt like it reset), waited some more, wash-rinse-repeat. Left it over night. Next day, still nothing. Manually close the mag switch and the main blade runs like a champ. I figure the thermal is fried. I pull it out, grab the fluke, test the leads, and it seems fine? Continuity is straight through. Put it back in, saw has dual controls, one set on the body, one on the slider, nothing. Test the transformer sending 28vac out to the slider and body controls, AOK. Do a bunch of testing in the panel, all seems good. Still nothing. Pull the thermal 2-3 more times and test and it always test fine. Each time I put it back in, nothing. Bypassed the thermal and connect motor leads direct to the mag. runs like a champ which I knew because even with the thermal in the saw would alway run depressing the mag manually. Re-test the continuity on the thermal, all looks good, reconnect thermal, zip. I do this for an entire day off and on.
Each time however, the prongs of the thermal going into the mag switch would kind of fight me. They wouldnt just slip in and tighten. One time the left pin would slide loose, another time the right pin would slide. Finally pulled the mag out of the panel and got the thermal locked in dead tight. Low and behold, I push the mag in manually and SNAP, it runs. Go to the slide controls, they work fine, controls on the base, work fine.
So Im left wondering.
a. The overload couldnt have been stuck or something because it tested multiple times with continuity test that it was passing power through. and it ran with the thermal in and manually closing the mag(yet the motor never fired**edit, never fired with the controls, the motor always ran when depressing the mag manually**
b. Could there have been a bad connection from the factory (fighing with getting the thermal pins tight into the switch) from the factory and we just got it hot enough to rear its head? (nearly 10 years)
c. Is the thermal on its way out? Doesnt make sense base on the continuity tests.
d. Probably the real answer that I just dont know?
I ordered a new thermal overload to have on the shelf, and we could have always run the saw jumping out the mag switch, but would of course rather not do that.