My new table saw calls for a 20 amp 240v time lag fuse. However, the panel box (Square D) in my shop only uses circuit breakers. Does anyone know if I can substitute a 240v, 20 amp double pole, high magnetic trip breaker instead? Thanks.
Carlos
My new table saw calls for a 20 amp 240v time lag fuse. However, the panel box (Square D) in my shop only uses circuit breakers. Does anyone know if I can substitute a 240v, 20 amp double pole, high magnetic trip breaker instead? Thanks.
Carlos
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Replies
I would expect no problems using the circuit breaker rather than the fuses. Just be careful doing the work and follow good trade practices.
Preaching to the choir but it bears repeating: Saving money and being self-sufficient won't mean much if you electrocute yourself or the house burns down. When in doubt call in the professionals.
My 3HP Jet cabinet saw starts up fine with a regular 20A double pole breaker.
"My new table saw calls for a 20 amp 240v time lag fuse."
Carlos,
Just curious, what brand and how many HP?
Jon
It's a 5 h.p. Delta Unisaw.
Thanks to all for your helpful comments.
Carlos
It that a 3 phase motor?
20 amp is too low for 5 ph 240 single phase motor.
Does it have internal overload protection or a motor starter with protection?
Is this new new or just new to you?
According to the owner's manual it's a single phase 230 v motorwith an overload protector. The manual clls for the 20 amp use and the saw is new.
That is way too small.
But is the current rating on the motor name plate?
I called Dewalt technical assistance and they corrected the manual and said I needed a 30 amp time lag circuit breaker (in place of a fuse). I'll try that and if it works I'll post a note. My Norm Abrahms workshop (24'X24') is still under construction so it may be awhile. Thanks to all for your advice and comments.
That sounds better. I believe the FLA for 3HP saws run around 14-16A at 240V and the 5HP are in the 22-25A range. I don't have the NEC handy but you need to stay under 80% of the breaker's rating for continuous use, but also you can't exceed I believe 175% of the motor's rating for a single motor on a dedicated circuit. A woodworking/ big wig EE friend back East told me to put it on a 20A, and that a 30A was technically too big (200% of FLA rating).
I assume you know that in addition to the 30A breaker that you also need to bump up to 10 gauge wire from their recommendation of 12 ga in the manual. I believe you can run a 12 gauge extension cord from the wall to the saw since wire that is in "free-air" has a higher ampherage rating than wire enclosed in a wall or raceway (conduit). My saw came with a short piece of 14 ga cord which I replaced with a longer piece of 12 ga.
Thank you for the suggestion to increase the gauge of the wire. I haven't covered that wall yet so I'll run this suggestion by Delta, see what they say and replace my 12 gauge if needed. Again to all, thank you for the helpful notes - even the funny ones.
Carlos
Could be your right. I had assumed that this was another case of a grossly inflated motor HP rating.
Dyno rating a motor, IMHO, makes little sense as anything other than a marketing ploy. It is like driving a Pinto into a brick wall and recording the energy released in terms of HP. Makes the engine sound very impressive. Like maybe 500HP or such.
A Unisaw will have a brand name motor with standard ratings.
Baldor and Leeson are a couple of brands.
4Lorn1,
I like your Pinto analogy. I too rant about those stupid HP ratings. Sears is the worst. Sears customers are the stupidest? Even if your motor is 100% efficient (not!), amps x volts better be 746 watts for every horsepower you try to sell me.
A Pinto probably does 500 hp dumping the clutch. Hitting a wall at 60 mph would be 1,000s of hp.David Thomas Overlooking Cook Inlet in Kenai, Alaska
Carlos,
Bill is right if the machine is not 3 phase. Their web site:
http://www.deltawoodworking.com/index.asp?e=136&p=743
says they recommend a 40 amp leg with a Slo-Blow fuse if 240V.
My 3HP Delta, on a 25 amp circuit has tripped the [conventional] breaker many a time when it has gotten bogged down.
Hope this helps.
Jon
Mine's 120 volt 2 HP. I'm on a 30 amp two wire service. Even with slow blow fuses, it absolutely blows the main if you just hit the big switch. I had to make a cam and driver to spin it up with an electric drill in order to start it. So far I haven't bogged it down enough to blow a fuse.
-- J.S.
At least with some brands of panels you can get breakers with different time curves. However, the standard breaker has a fairly good time lag built in.
If you have trouble, and can't find motor start breakers for your panel, you can install a subpanel (fed with, say 30A breakers) and install motor start fuses or breakers in the subpanel.
Breaker? We don't need no stinkin' breakers. Just wire it directly into the main panel. Regards, The crew of Trading Spaces.
disclaimer: DO NOT ACTUALLY DO THIS.