LumberJocks

Extension cord for Unisaw

  • Advertise with us

« back to Power Tools, Hardware and Accessories forum

Forum topic by cabbie posted 07-03-2018 12:28 AM 503 views 0 times favorited 18 replies Add to Favorites Watch
View cabbie's profile

cabbie

68 posts in 2029 days


07-03-2018 12:28 AM

Topic tags/keywords: electrical saw extension cord tablesaw

Guys-
I’m experiencing some chattering on start-up of my 1997 Delta Unisaw. Motor is 220V 1Ph, 11 amp rating. I know that there is an instantaneous start-up draw of considerably more than 11amps (I’ve seen estimates of almost 3X label stated amp draw). Panel is 30 amp breakers. I’m running it on a 25ft. 10ga. heavy duty extension cord. I’m thinking that there may be enough voltage drop in the 25 ft cord that start-up performance is compromised.
-Should I shorten the 25ft cord (I only need about 10 or 12 feet)?
-Should I hard-wire the 10ga. cord directly into the motor, and not run it thru the pig-tail that comes from the saw switch box?(thus eliminating another connecting point)
-Should I increase the gauge of the extension cord to 8ga? (seems excessive) I’m doing this to avoid having to replace a faulty starter capacitor (expensive, and possibly not necessary).
What say you??
Any help would be appreciated. Also—I’m not an electrician, so “keep it simple, please”.
Thanx!!

-- Jim, Altadena, CA


18 replies so far

View MrUnix's profile

MrUnix

6829 posts in 2254 days


#1 posted 07-03-2018 12:45 AM

I’m doing this to avoid having to replace a faulty starter capacitor (expensive, and possibly not necessary).

10ga is way more than sufficient. As for your start capacitor… is it bad or not? Did you test it (simple multimeter will do). If it is bad, they are not all that expensive… around $10 or so depending where you get it from.

Maybe a better explanation of the problem would help.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View AlaskaGuy's profile

AlaskaGuy

4254 posts in 2364 days


#2 posted 07-03-2018 12:50 AM

Watch this

https://youtu.be/v0hNKt6kByc

I did something similar when I made the molding for my hybrid bonnet top Highboy.

-- Alaskan's for Global warming!

View TheFridge's profile

TheFridge

9711 posts in 1541 days


#3 posted 07-03-2018 02:21 AM

10 is overkill.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View Knockonit's profile

Knockonit

406 posts in 257 days


#4 posted 07-03-2018 02:41 AM

mines on a 50ft 10 gauge,and works fine, also serves as a ext. cord for one of the welders.

can’t go wrong, bigger is better,

View coxhaus's profile

coxhaus

93 posts in 949 days


#5 posted 07-03-2018 03:14 AM

Have you tried the motor without the belts on? If it still does it then its the motor. If not you need to look at the arbor or the belts. The cord should be fine. My 3hp Unisaw runs fine on a 20 foot cord.

I just thought of something. The belts can take a set if you have not used it for a while.

View Fred Hargis's profile

Fred Hargis

5016 posts in 2548 days


#6 posted 07-03-2018 10:33 AM

Whatever problem you think you have, it isn’t that extension cord.

-- Our village hasn't lost it's idiot, he was elected to congress.

View CaptainKlutz's profile

CaptainKlutz

318 posts in 1549 days


#7 posted 07-03-2018 10:35 AM

Not enough information?

+1 Wiring seems like perfect install.
30A breaker installed to code should be protecting 10Ga wire from panel to out let in shop. Unless the total wiring length (breaker to outlet plus extension cord) is over 250-300 feet, voltage drop will be within spec for ~30A starting current. Removing 10-15 feet of wire is not going to make much difference in voltage drop for 220VAC.

Chattering can be result of many issues:

+1 Check motor without belts attached. Bad start capacitor with cause motor to have sluggish start. Although I would be surprised if it was capacitor. My experience with start capacitors typically causes power/toque loss, slow speed spin up, and/or overheating? Bad motor bearings can cause chattering, will also make saw much louder than normal quiet hum when running unloaded.

+1 Check belts. Glazed surfaces, dents, chunks missing, flat spot that doesn’t smooth out after a few minutes of saw running,; all point to a need for replacement belts.

Check belt tension. Too loose, too tight; both can create chatter.

Check different saw blade. Missing tooth, or other damage to blade can create chatter.

Last, and probably most time consuming to fix:
Check for arbor run out, and/or bearing wear. Remove belts, remove blade, check for noisy bearings Goal is zero noise, as cabinet table saw typically has low noise level, unless cutting wood.
Then use dial indicator on arbor flange and shaft looking for excess movement. There are rebuild guides for vintage Unisaw arbor assembly on owwm.org site. There are also past LJ posts on unisaw arbor issues, and tolerances.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View rwe2156's profile

rwe2156

3003 posts in 1535 days


#8 posted 07-03-2018 02:27 PM

Cabbie,

#12 wire and a 20A circuit is plenty for that motor. To my knowledge, the start up spike is to quick it isn’t an issue. AFAIK, you wire motors based on FLA, not theoretical startup draw.

So I don’t think your issue is electrical. I would go with what CaptainKlutz said.

I elected to run wire to box mounted directly to the side of the machine cabinet. I run the flex conduit alongside the DC pipe.

-- Everything is a prototype thats why its one of a kind!!

View Fresch's profile

Fresch

269 posts in 1975 days


#9 posted 07-03-2018 04:46 PM

Clean the starter.

View cabbie's profile

cabbie

68 posts in 2029 days


#10 posted 07-03-2018 04:49 PM

Thanks for the help, guys. Re: more info—the “chatter” on start-up is a banging sound as soon as I hit the On button , and the blade will only turn slowly. If I quickly turn the unit off, then turn it back on again while the blade is turning slowly it will (most of the time) start normally. It’s as if it needs a bit of help to get the blade moving from a dead stop.
I hope this helps. Let me know any other thoughts you have.
PS—how do I test a capacitor?? I’ve got a meter.

-- Jim, Altadena, CA

View MrUnix's profile

MrUnix

6829 posts in 2254 days


#11 posted 07-03-2018 05:13 PM

Bad cap or centrifugal switch for sure. Testing with a multimeter is easy using your highest resistance range. Rather than explain it here, there are a zillion tutorials out in the wild – follow this google search.

If the cap tests ok, then you will need to open the motor up and check the centrifugal switch for sawdust/crud stuck between or otherwise dirty contacts, mis-adjustment or improper operation.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View splintergroup's profile

splintergroup

2153 posts in 1277 days


#12 posted 07-03-2018 05:20 PM

My 3hp Unisaw has a 12 foot, 12 AWG cord running to a 220V dedicated socket which is connected by 30 feet of 12 AWG romex to a 20 Amp breaker.

Nary a hint of voltage drop issues.

View cabbie's profile

cabbie

68 posts in 2029 days


#13 posted 07-05-2018 04:23 PM

Brad-
Thanks for the lead on the centrifugal switch. I didn’t even know that it had one. I’ll pull it apart and see if a good cleaning helps.
Jim

-- Jim, Altadena, CA

View TheFridge's profile

TheFridge

9711 posts in 1541 days


#14 posted 07-06-2018 01:24 AM

I’ve had way more problems with centrifugal switches than with capacitors. A lot easier to check the cap first though :)

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View clin's profile

clin

882 posts in 1051 days


#15 posted 07-06-2018 03:15 PM

Just to put stone numbers on this extension cord. #10 wire has 1 mOhm per foot of resistance. So a 25’ foot cord will have 50’ of round trip wire. So that’s a total of 50 mOhms of resistance. For every 10 A of current that will drop 0.5 V.

So even if you had say 40 A of start current, you’d only drop 2 V or less than 1% of your 240 V supply. Of course there is much more wiring in your walls. A 25’ of extension, though not trivial, is not going to create much of a voltage drop.

-- Clin

showing 1 through 15 of 18 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com