My 1.5 HP Delta dust collector is perfectly predictable. It trips its 20 amp circuit breaker every other time I turn it on. It drives me nuts. Any ideas on how to cure this problem??
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Replies
What else is on the circuit?
John
What size and how long is the cable between dust collecter and recepticle
Is it the motor's own protection device, or the branch circuit protection that's opening? DC's are hard starting to begin with (high enertia, and they start under load), and 1.5 hp on 120V is pushing it. If it's the circuit breaker in the panel, and there is nothing else on the circuit, the wire is 12 ga or heavier and not excessively long, and the motor spins freely by hand, try replacing the circuit breaker. The conventional wisdom is that the more they open from overload, the less able they are to handle heavy start loads. I don't know this for fact, it's just what's commonly proffessed here. A single-pole breaker is less than $10.
Alternatively, you could run a new 30A 120V circuit, with a new 30A plug and receptacle, or for the same amount of effort, reconfigure the motor for 240V and run a new 20A circuit (new plug also required).
If the problem is the DC itself, here's a recent thread on Knots that may be useful.
http://forums.taunton.com/tp-knots/messages?msg=10232.1
Be seeing you...
Edited 2/13/2003 8:33:04 AM ET by Tom Kanzler
Good questions.
1) This is the only thing on the circuit.
2) Now that you mention it, I should try a different extension cord. The cord running to the DC may be both undersized and too long. I will buy a 12 guage short length cord tonite at HD and see what happens.
3) By the way, this is the second breaker that has been installed. First one did the same thing.
Will try the new cord and if that doesn't work, try the electrician. I don't screw around much with anything having to do with fire (electrical work) or water (plumbing). More a feature of inexperience than fear of my wife's retribution should I burn the house down!!
BW
Extension cord, eh? May I suggest you try plugging it directly into the receptacle first, just to see what happens? If you have a duct system, you might also try closing all blast gates while it starts (inertia is still the same, but without air to move, the developing load will be limited). But if you must use an extension cord, the shorter and fatter it is, the better (or less harmful, at least). If you don't want to move or add another receptacle closer to the machine, you might also want to consider replacing the existing flex cord with a heavier one that is long enough to reach the receptacle without using an extension. I would also probably replace the receptacle with one rated 20A, for it's heavier construction and better contact with the blades. But do consider reconfiguring for 240V operation; the problem will be permanently solved.
Edit: p.s. I seem to recall some others with the same DC complaining that the start capacitor had gone bad. It's certainly possible that yours is going bad too, if the problem is a recent development.
Be seeing you...
Edited 2/13/2003 10:30:20 AM ET by Tom Kanzler
Tom:
Yeah. Extension cords. My shop is currently on one end of the basement with big tools on mobile units. I had the room powered with new outlets at chest height in the section where I plan to have a more permanent shop. So for now, it is extension cords.
For the way you asked the question, I guess I feel kind of dumb. Are extensions typically a no-no in the shop? Would have thought I might have learned that by now. Oh well.
I do not yet have an extension as for now, my DC evacuates only my saw and planer. I don't have a blast gate on the table saw connection and only hook up the planer when I need it. Should I consider puttiing a blast gate on the table saw hose just to help with start up?
This dust collector has been doing this since day 1. It is not a recent occurence. It is the reason I had the electrician come over and switch out the breaker.
Guess 240 is an alternative.
BW
Induction motors draw more current as the voltage drops from the nameplated value (115V and 230V for typical single-phase stuff), and long, light-gauge cords can make an already marginal circuit much worse in terms of voltage drop. Start-up will take longer as voltage drop increases (or rather, as voltage decreases), exposing the breaker (and the motor) to extended periods of overcurrent. Breakers (of the type in your panel) can absorb large overcurrents for short durations, and small overcurrents for long durations (minutes, even), but the combo of long, light wiring, and multiple connections may extend the start period enough to trip the breaker. Light wiring will also increase the current drawn by the motor under normal loading conditions. There's someone on this forum who designs circuit breakers who could probably give more insight into the time-current relationship.
So, in short, I'm not fundamentally against extension cords, but you have to remember that all wiring causes voltage drop under load, so you want to minimize the harm by keeping it short and heavy, comensurate with the connected load. I'm not usually one to recommend switching to a higher voltage just for the heck of it, but a 1.5 (real) hp DC like yours is really a good candidate for 240V operation. You're pushing the abilities of a 20A circuit breaker to start with, and light-gauge extension cords can only make it worse. At the very least, use the shortest, heaviest extension cord you can find.Be seeing you...
Just to amplify the prior post, you should get yourself some #10 cord and make up an extension cord of the appropriate length. Very easy to do and not expensive.
John
Thanks all. Just got off the phone with Delta. Was very surprised at the result.
Bob there told me that the DC will easily draw 7 times the amperage in the start-up mode. The solution he stated was to dump the "standard" 20A circuit breaker. Replace it with a "time delay 20A circuit breaker." Apparently these are made specifically for motor start-up and would be available only at an electrical supply house.
Whaddya guys think of them apples???
Never heard of one, but this looks like the solution. Unless the motor can be converted to 220 volts, and you want to go that route as an alternative.
John
All motors have a high inrush of current at startup, older motors were typically 6 times, some of the newer high efficiency motors can be as high as 18 times. Time delay breakers are available from the company I work for (CutlerHammer and Westinghouse). I assume they are available from most everyone.
Just bought the 10 guage extension cord. Boy, it is heavy and expensive ($36 at Home Depot). 50 ft. was the shortest I could get there. Will try Menards later today.
Will let you know if it helps things.
I'd suggest (and I think I did already) that you wheel the DC over to the receptacle, and make repeated starts, just to see if it stops the tripping. If it doesn't help, the extension cord, no matter how heavy, will only add to the problem. Every conductor has resistance (ok, impedance in AC), so it's always a matter of how much is tolerable, and how to keep it low enough. That's where 240V helps, since the voltage drop, as a percentage, is reduced at 240V to 1/4 of what it is on 120V, for a given conductor size and length, connections, etc.
Motor performance is very sensitive to voltage drop (or more accurately, % voltage drop), and while adequate wiring (say 12 ga to 50' for a 20A 120V branch) will have little effect on a motor running at or below it's rated load (it's less than 3V for 14A), starting and being overworked (think ripping on a contractor saw, here) is where the performance degradation begins to snowball, since current draw is way outside the normal running values. Be seeing you...
Tom:
Good call. Thanks.
Read your post while sitting in the basement just feet from my shop. Moved the DC closer and plugged in directly to the outlet. No difference whatsoever. Still shuts down the circuit every other start.
My $36.00 10 guage extension is not going to help much with this problem.
So, I will be checking out my panel and heading off to see how and where I can find a "motor start" circuit breaker. Tom, any idea of what info I need off of the panel. The panel is a Square D Type 1 Catalog # QOC4OU. Any other info I need?
Thanks again.
Bob
Look for "HACR" on the little white label below the lug. I've bought them in HD, single-pole included. The only ones in my QO panel at home with HACR rating also happen to be the only ones with the current rating in white on the end of the handle. The older ones I have don't have it (except for the 2-pole units). Grainger shows a "high magnetic" type in 15 and 20A versions (1995 catalog), but Square D only shows HACR types on their web site.
HACR types, in case you're interested, are intended to be equivalent to dual-element (time-delay) fuses for HVAC equipment installations. The time-current curves for circuit breakers were not consistent amongst manufacturers, as the story goes, so they developed a standard that matched that of the fuses (which were standardized), which is required for installation of listed hermetic compressor powered condensers and such that say as much on the label.
I thought that most small circuit breakers were time-delay (or inverse-time), and that HACR types were even more forgiving, since they need to not trip when the compressor tries to restart and can't after a short power-out condition, allowing it's own overload protection to trip and reset (sometimes repeatedly) until the pressure drops and it lights off. Be seeing you...
On page 432 of the 2002-2003 Grainger Catalog #393 there are Sq D miniature circuit breakers. They show three curve setting B, C and D. The D curve is a magnetic trip between 10 and 14 times the rated current for motor starting.
The Grainger part #6B112. Sq D #MG24525 and cost $41.85. I don't know if this will fit in your panel.
I would take the advise that has been made in previous posts and install a good 220V outlet near the DC. Reconnect your motor for the higher voltage then the line current will drop to 1/2 of what is now is and your problems will be solved.
220V is available in your panel box and will require a 2-Pole breaker rated for the outlet wiring you have or will be installing. You will need a 220V polarized outlet and polarized plug for your DC.
You will not be able to use an extension cord for the 220V unless it has the same polarized plug and socket. However I don't recommend using an extension cord for any permanent setup.
If you have a series of 115 V outlets installed along the wall at waist height as was suggested one of them could be wired with a 220V polarized outlet at the same time. Also check to see if the "Code" requires "Ground Fault" protection where the outlets will be located.
This is how I wired my shop.
Good luck.
Marv
Robbie - the part number you gave is for a flush cover for a 200A Square D QO load center; close enough. You should be able to read the label on the breaker without removing it (use a flashlight and look hard). If it doesn't say HACR, go to the local big box or electrical supply and buy one that does (Square D QO, which is 3/4" wide; not Homeline, which is 1" wide).
When it does start, how long does it take? I don't have that particular DC, but my 1.5 hp takes about 1 to 2 seconds to start on 120V (pulling a max of about 70A), and it will start on a 15A circuit most of the time, and never trips the breaker on a 20A circuit. If yours is taking longer than that, there may be something wrong with the DC itself right out of the box (you did say it did this from day one). Be seeing you...
Tom: I'd say it takes two to three seconds to start up.
Ok, I'm going against the conventional wisdom in this thread, and going to argue that you have a dust collector problem, not a circuit problem.
As I understand it, since you got the machine, a 120V (and thus no more than 15A) dust collector, it has repeatedly tripped a 20A circuit at every other startup. It does this on the same circuit repeatedly, whether or not it is on an extension cord.
So, from this, we can determine that the problem is _not_ the extension cord.
Next test - move the dust collector a completely different circuit, preferably an outlet near the beginning of the circuit, and try it again.
If it doesn't trip the breaker, then by all means, switch to a "time delay circuit breaker". I'll be surprised if this is the case - there is no valid reason (while I recognize that all motors draw higher amounts of current at startup, circuit breakers are designed to handle this. The "time delay" circuits are typically for very large motors, not for 1.5hp dc's) for a device designed to be used in a residential (read, 120V 15A) circuit to require a breaker change.
More likely, you will find the same problem exists on the different circuit. In which case, you will need to promptly return the dc as defective to wherever you bought it, as it has an internal electrical fault of some type. I suspect the switch, but that's just a guess.
Again, assuming this is a 120V, no more than 15A dc, it should start fine every singe time even on a 15A circuit. Putting in a time delay breaker may mask the problem, but it certainly won't fix it, nor will switching the machine over to 240V (unless, of course, the issue was in the cord itself or one of the connections).
d-
Edited 2/16/2003 10:19:45 PM ET by DM_Woodworking
Tom and all:
Update on the dust collector problem. Looks like Delta is buying me a new motor. Took the collector into the local Delta authorized repair shop two weeks ago today. I called back yesterday as agreed and he told me that Delta was sending a new motor.
Good thing. The motor start up circuit was going to be $125 just for the breaker -- before the electrician. Ouch.
Thanks for everyone's great counsel on this one.
Delta did send a new motor to the repair shop and I am picking the DC up tomorrow. Will let you know if it still pop's the breaker or if the motor was the fix.
Bob
Robbie - 2 to 3 seconds sounds like a long start-up time, even for a DC. My 1.5 hp DC starts in about 1 second, maybe slightly more, and peaks at around 65A. Since I don't have the Delta, I don't have any first hand knowledge as to how long it should take, but if you go to the store where you bought it and have them demonstrate a floor model, maybe you can compare. If yours is taking significantly longer, bring it back for an exchange. If it's taking too long to start, it certainly would explain why it trips the breaker. It's been said several times here, and your electrician said it too (in one of your posts), that the breaker should be able to absorb the start-up surge. But 1.5 hp is about the biggest motor you can reasonably expect to run on a 20A circuit, and a dragged-out start-up would explain the breaker tripping problem. Perhaps someone else with the same model can time and post how long it takes to start it.Be seeing you...
Robbie,
Is there a rating plate on the motor? If so what is the running current of the motor at 120 V?
If there is no rating plate, and some of the imported motors do not have rating plates possibly you can find a friend who has a clamp-on ammeter and a line splitter to read the running current. (A line splitter is a one foot long extension cord made of individual insulated wires so a clamp-on ammeter can read the current flowing in one of the current carrying wires.)
I may be wrong but most American made 1 1/2 HP 115 V single phase motors have a running current of 16-17 Amps at 3450 RPM and 18-21 Amps at 1750 RPM. I doubt if the imported motors are more efficient and therefore use less current.
Marv
Tom:
You and DM Woodworking were correct. I got back a repaired dust collector from Delta today. They swapped out the motor. I took it back into the shop and it starts sharply and quickly every single time now. Although he thought it may have been either a switch or capacitor problem, the tech said he didn't waste too much time with it, because it was under warranty and Delta is very good about that. He told them to swap the entire motor out and that is precisely what they did.
The DC also feels as if it is more powerful now. The bags are VERY tight when on.
Thank you again for the solid advice.
Bob
You're welcome.Be seeing you...
Always happy to help and especially pleased to hear you got your problem resolved :)
Doug
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