B2229/G9729 Power-on CB Tripping

[ealanm]

I have a new Craftex B2229 (similar to a Grizzly G9729). It often trips the power-on circuit breaker when I try to turn it on. Sometimes I have to press and release the E-stop button and attempt a restart half a dozen times, or more, before I get power.

The manual says there are three microswitches that can shut the machine down, one of which is supposed to be on the lathe drive cover door. I can't find any of them. I suspect one of those microswitches needs adjusting. Anybody know where they are, or have another suggestion?

Tedd

[hammermill]

one of the 3 safety switchs are opening,loose cover or door

http://cdn1.grizzly.com/manuals/g9729_m.pdf diagram is all the way at the end

when they open the hold circuit on the on switch/breaker realeses.

[ealanm]

Wow, that Grizzly manual is way better than the manual I got with my Craftex! Thanks for the link.

Unfortunately, I still can't find the actual microswitches -- none of them. Also, I can turn the machine on when the lathe-drive door is wide open, so if there is a microswitch on that it's not doing it's job.

I just realized that there's one other factor that could be important. I haven't finished wiring my shop yet, so the machine is plugged in through an extension cord. It's a 6-foot block heater cord, so I doubt it's having much affect on the voltage, but I suppose it could be the problem.

Tedd

[Torch]

Wow, that Grizzly manual is way better than the manual I got with my Craftex! Thanks for the link.

Unfortunately, I still can't find the actual microswitches -- none of them.

The Craftex and the Grizzly are very similar -- but not necessarily identical. Plus there can be changes and refinements in either one as time goes on. So don't take the Grizzly manual as gospel. There's a good chance your machine doesn't have switches.

Do you have access to an amprobe current meter? It might be educational to see what the start-up current actually is, and if it approaches the locked rotor current on the rating plate. Locked rotor current is the current the motor will draw when if the motor is seized. It's considerably higher than the normal running current draw. Start-up current lies somewhere in between. It will be very close to the LRC for a few milliseconds, then quickly drop to the running current (or less, if there is no load on the motor). If the breaker is too sensitive, it will trip during those few milliseconds. BTW: are you talking about the breaker in the building panel, or a circuit breaker on the motor itself?

OTOH, if the current stays high, that's an indication of a problem in the motor or low voltage supply. Inadequately sized supply wiring is a distinct possibility -- resistance is directly proportional to wire size, wire length (from the panel, not just the plug!) and current. During that inrush, the high current through high resistance can lead to sub-normal voltage at the motor, so it takes much longer for the current load to drop off to normal. One trick that sometimes overcomes this is to "bump" the unloaded motor a couple of times to get it spinning without tripping the breaker.

Another possibility is on the motor itself. IIRC, that machine has a 3/4 hp capacitor start AC motor. The capacitor is necessary to alter the phase of the power on one winding temporarily to get the motor rolling. Without such a starting circuit, the motor will just vibrate back and forth 60 times per second and draw locked rotor current until the breaker trips. The starter circuit is not efficient for running though, so there is a centrifugal switch to cut the capacitor out of the circuit once the motor starts spinning. (It's hard to hear the switch operate as the motor starts, but there is often a distinctive "click" as the motor winds back down when the power is shut off).

If the capacitor fails, the motor won't start spinning or it will draw excessive current. If the switch fails to disconnect when the motor starts spinning, running current will be excessive. If the switch fails to reconnect when the motor stops, the motor won't start spinning next time it's powered.

The thought occurs to me that your machine has two motors -- one for the mill and one for the lathe. It's unlikely that both would fail simultaneously, so if you have the problem with both the lathe and the mill then I'd suspect wiring to the machine. Since you are still in the process of wiring the shop, consider running heavier wiring to a dedicated outlet for the machine. #14 might normally be code for a 15 amp circuit, but it wouldn't hurt to run #12, especially for motor starting. The machine will be happier in the years to come, and you will save slightly on electricity costs too.

[hammermill]

glad to hear that it may have proven informative.

up sizing power wireing to you machine is always a good idea althouh i doubt it is your current problem.

note the new eletrical codes are not allowing 14 gauge wire in residental
construction anymore so it may even be hard to find anymore.

12 gauge and 10 gauge if runs of any distance are involved is solid advice
as is check currents with a amp meter. a inexpensive analog will even prove usefull

[ealanm]

Thanks everyone for the ideas. I don't have a current-clamp type meter, but I'm certain motor current isn't the problem. The CB trips when I turn the machine on, not when starting one of the motors. That is, it trips as soon as I hit the start button, with both motor switches in the off position. There's a brief flash of the power light and a clunk from the CB -- or perhaps it's actually a relay. Anyway, it trips immediately. Sometimes I have to reset the E-stop button and try starting five or six times before the power stays on.

Perhaps it's E-stop button itself?

Tedd

[Torch]

That is, it trips as soon as I hit the start button, with both motor switches in the off position. There's a brief flash of the power light and a clunk from the CB -- or perhaps it's actually a relay. Anyway, it trips immediately. Sometimes I have to reset the E-stop button and try starting five or six times before the power stays on.

Looking at the 9729 electrical diagram, I don't see a circuit breaker. Just to clarify: are you having to reset the breaker in your house/shop supply panel, or is this something on the machine itself? Do you have to push some sort of reset, or are you saying it self-resets?

I do see a contactor in the schematic. A contactor is basically a relay -- magnetic coil pulls in the high-current contacts when the low-current switch is closed. I'm starting to suspect that this is your problem -- the contactor contacts are burnt or dirty or bouncing open again. Cycling the power (through the on/off switch or by activating the E-stop switch) re-closes the contactor and sometimes it actually makes contact. (if you are resetting a breaker manually, then I'm wrong and disregard this post!)

Depending on the design, you may be able to clean up the contacts with judicious use of a fine file and/or emery cloth, then cleaning all residue, oils, etc. off with electrical contact cleaner spray and a lint-free cloth. Failing that, you'll have to replace the contactor.

[ealanm]

I'm sorry, it's difficult to describe this accurately. I hope that a picture will save me a thousand words or so.

Start with the machine in a completely "off" state: the Lathe-Mill switch is OFF, the lathe motor switch is OFF, the mill motor switch is OFF, and the E-stop is pressed. I release the E-stop and hit the green Power On button. There is a brief flash of the Power light, a clunk from a CB or relay, and the Power light goes out. I press and reset the E-stop and repeat. After several tries, the Power light stays on.

This is a brand new machine. It has been in my shop about two weeks, has about ten hours on it, and started this behaviour within a few hours of the first time I started it up. So I don't think it's a wear or contamination issue, it's an "infant mortality" failure of some kind -- perhaps the E-stop switch or the contactor, as Torch suggested.

And, yes, that's my finger in the foreground of the picture, not Rover from The Prisoner.

[Torch]

This is a brand new machine. It has been in my shop about two weeks, has about ten hours on it, and started this behaviour within a few hours of the first time I started it up. So I don't think it's a wear or contamination issue, it's an "infant mortality" failure of some kind -- perhaps the E-stop switch or the contactor, as Torch suggested.

A brand new machine you say? Well that makes a difference -- now it's BusyBee's problem, not yours!! I kind of had the impression that this was a new-to-you machine, probably because of your post about the missing gib screw.

Which suggests yet another possibility: if the machine was subjected to enough vibration to shake loose a gib screw then maybe it also shook loose an electrical connection and all you have to do is tighten a screw terminal somewhere.

If the contactor is getting power, you should be able to see the centre of it move and hear it click (usually quite audibly) when you turn on the main switch. If it pulls in and stays in, but the power light flicks back off, then there's something wrong with the contactor itself. If it doesn't pull in at all, then it could be the coil in the contactor or the power to the contactor (eg: the main switch or the E-stop switch or a wiring connection).

How good are you with a volt meter? It can be dangerous poking around inside a live 120vac electrical box, but if you are very careful, know what you are doing, and take the proper precautions, it can be the best way to diagnose things. Otherwise, unplug the machine, check the connections physically and if that doesn't fix it, track down someone local who knows what they are doing to help with further diagnosis.

Obviously you are in Canada. If you are anywhere near Muskoka, maybe I can slide over and help.

[ealanm]

Obviously you are in Canada. If you are anywhere near Muskoka, maybe I can slide over and help.

Thanks very much for the offer, but I'm in Surrey, BC -- about as far from Muskoka as one can get and still be in Canada!

I'm pretty comfortable with a volt meter, so I'll try poking around inside to see what I can find. I think you're right that the contactor is a likely culprit.

Because the machine is so new, when I started this thread I was half hoping somebody would say, "That happens all the time with Craftex machines, you just have to..." But no such luck! I'll do some testing and report back what I find.

Tedd

[steamin10]

It seems pretty obvious the first place to start is the relay and latch circuit. Any loose wiring or bad connection would interupt the latching relay just like the E-stop. So everything on the power and stop circuit must be checked for solid connections. One thing that is a fooler is a worker will insert a stripped wire too far, and get some insulation under the terminal screw. These can act like an intermittent, and be frustrating to find. SOoooo, on some of my machines I have run ALL the connnections to assure they are there correctly terminated.

[Torch]

Thanks very much for the offer, but I'm in Surrey, BC -- about as far from Muskoka as one can get and still be in Canada!

Yeah, I don't think I'd have much time left over for visiting if I took an afternoon to ride over. Good luck with it, and let us know what it turns out to be.