New Jet 708100 -- Lights Dim When I Turn It On

  • Advertise with us

« back to Power Tools, Hardware and Accessories forum

Forum topic by nellie posted 11-14-2007 09:28 PM 7152 views 0 times favorited 16 replies Add to Favorites Watch
View nellie's profile


20 posts in 4119 days

11-14-2007 09:28 PM

I just bought a new Jet 708100 and set it up in my garage. When I turn it on the lights in the garage momentarily dim and then seem to come back to full brightness. I also tried turning it on with my Shop Van running and that slowed down when I turned on the saw. Obviously my garage’s electricity is not what it should be, but I’m wondering whether there’s any danger—to the electrical system and/or the saw—indicated by the dimming lights. I’m concerned that the saw isn’t going to cut at full power because of the electrical drain on the system, or that I’ll trip the circuit while cutting. I haven’t actually cut anything yet as I want to make sure this is going to work for me in terms of its size and power needs first. If it doesn’t, then I’ll have to return it. BTW, this is a rented house so I don’t have any plans to upgrade the electrical system.

Thanks for any input.

16 replies so far

View Nils's profile


141 posts in 4104 days

#1 posted 11-14-2007 11:15 PM

I’m glad you asked this question, because the exact same thing happens to me when I turn on my lathe. I was also wondering if I’m endangering myself or my family when doing this. Putting new electrical service out to the garage will not be happening any time soon, unfortunately.

-- Nils Davis, Menlo Park, CA

View knothead's profile


163 posts in 4188 days

#2 posted 11-14-2007 11:58 PM

If your saw is like mine it has an inductance (sp?) motor on it that requires more energy (amperage) to start the motor than it requires to operate. I have my General saw on a 20 amp circuit and the saw always causes the overhead lights to dim slightly as I start it up. I have pushed my saw thru some 2 5/8” maple and have only tripped the breaker once under a load and that was because I forgot to momentarily shut off the window airconditioner that is in my shop that is plugged into the same circuit before I began. I have stalled the saw on 2 occasions completely and have not blown the breaker. Also I generally can operate the saw and A/C at the same time for “normal” cuts. I would think unless your circuit is totally inadequate (Low aperage) or misswired you will be just fine. I too have dreams of dedicated 30 amp branches in my shop. Maybe someday…. Still wouldn’t hurt to have an electrician check for you.

-- So Much Wood - So Little Time! --

View Bob #2's profile

Bob #2

3810 posts in 4262 days

#3 posted 11-15-2007 12:03 AM

This is caused by too light a wire carrying the electricity to the plug.
It’s no likely the cord on your tools is a problem.
I would seriously consider having an eletrician take a look for you and tell you what is the best route to take.
You will have to chck the guage of wire feeding the garage and the breaker in your main electrical box to see what you have.
A betting man would guess 16 guage wire to a 15 amp fuse.
Tools draw almost all that capacity when starting.

Short of that, I cant’ help you that much.
Don’t burn the guys house down.

p.s. I just looked up Jet 708100 and find that it is a model of power tablesaw.
It might me a good idea to add that to you postings as most of us are not up to date with the model number game.
That type of motor will draw 13 – 18 amps when starting on 110 volts.


-- A mind, like a home, is furnished by its owner

View gene's profile


2184 posts in 4124 days

#4 posted 11-15-2007 12:28 AM

You are probably going to need a dedicated 20 amp circuit with 12-2 wire, just for your shop tools. I’m guessing that your receptacles and lights are on a 15 amp circuit with 14-2 wire. Definitely consult an electrician, it can’t hurt. You can burn the starting windings out in your tools. Your breaker should kick out before it harms the house, but I would not take the chance. The lights should not dim
God bless

-- Gene, a Christian in Virginia

View che's profile


123 posts in 4266 days

#5 posted 11-15-2007 12:36 AM

A small amount of dimming is OK, a lot is not. Sorry I can’t say what a “Lot” is. Motors can draw over 6X as much current when starting up. This high current draw will cause a temporary voltage drop which is seen in the lights. It doesn’t take much of a drop in voltage to reduce the light output.

If the startup doesn’t trip the breaker it is unlikely that “normal” operation will. I get a little dimming on startup and normal cutting is no problem. I have tripped the breaker a couple of times making full deepth cuts in some really hard walnut. You can do some troubleshooting to determine the severity and location of the problem. The danger is fire from overheating.
1. Lights all over the house flicker.
2. Lights on one phase flicker (about 1/2 of the house).
3. Lights on one circuit flicker.

-- Che.

View Lalaland's profile


44 posts in 4219 days

#6 posted 11-15-2007 02:04 AM

Check the spec plate on the saw itself. It will give you the electrical data you will need. As others have said, there will be a higher voltage at startup. Dimming the lights is a sure sign that your circuit is overloaded. Machines and lights and whatever else is on that circuit don’t mix well. You would be well advised to find a way to get a separate circuit for just the saw, nothing else. If other machines are on the same circuit, don’t get them running at the same time. Continuous voltage drops like this will cause your motor to fail. After 18 years in the electrical trade, I can assure you that you don’t want to push it. Better to be safer and get machines on different circuits than lighting.

View Nils's profile


141 posts in 4104 days

#7 posted 11-16-2007 06:56 PM

Thanks for the comments. I suspect it is the gauge of the wire leading out the garage – it’s not very impressive.

-- Nils Davis, Menlo Park, CA

View Dick, & Barb Cain's profile

Dick, & Barb Cain

8693 posts in 4540 days

#8 posted 11-17-2007 06:19 PM

You better check out the voltage in your shop. You could have a low voltage problem like I had.

The lights in my cabin used to dim when the refrigerator turned on.

Check out my story here.

-- -** You are never to old to set another goal or to dream a new dream ****************** Dick, & Barb Cain, Hibbing, MN.

View Calgirl's profile


188 posts in 4136 days

#9 posted 11-17-2007 09:53 PM

If your saw allows, switching to 230 volts will save your wiring and wear and tear on your saw. It shouldn’t cost too much to wire a 230 circuit if your sub panel is in the garage.

Q & A from Wood Mag Nov. 2007
Q: Watts the difference? I purchased a used tablesaw that has an option to wire it for either 115 or 230 volts. What are the pros and cons for either voltage?
A: Your tablesaw’s motor uses the same amount of electricity measured in watts regardless of the voltage. If you look at the plate on your saw’s motor, you’ll see that as the voltage doubles, the saw uses half as many amps. For example, this contractor-style saw drops from 18 to 9 amps as the voltage doubles. Either way you multiply the combinations—-115 volts times 18 amps or 230 volts times 9 amps—-the power consumption remains 2,070 watts. So why wire for 230 volts? Look at those amp numbers again. If you’re pulling 18 amps on a 20 amp circuit, there’s the chance of tripping a circuit breaker if your saw encounters an especially heavy load, or at startup, when it draws a brief surge of power. By switching to 230 volts, you relieve that strain on the circuit, doing yourself a favor.

-- Forget the health food, I need all the preservatives I can get !

View Karson's profile


35154 posts in 4641 days

#10 posted 11-17-2007 10:52 PM

I would guess that you need to upgrade the power to your workshop. If everything is being fed from one circuit. (air conditioner, saw, lights, dust collector.

It would b smart to upgrade.

I ran a 50Amp 230 Volt circuit to my shop and then I terminated it into a sub panel. From there I branched off into 230 V circuits, 120V circuts etc.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Appomattox Virginia †

View nellie's profile


20 posts in 4119 days

#11 posted 11-17-2007 10:59 PM

How much—ballpark—does it cost to upgrade? Let’s say I just want a dedicated circuit for the table saw, any ideas how much I should expect to spend?

View Dick, & Barb Cain's profile

Dick, & Barb Cain

8693 posts in 4540 days

#12 posted 11-17-2007 11:28 PM

Voltage, & Amperes!

This is a little example about the differences in voltage.

The number one reason the auto industry switched from 6 volts to 12 volts years ago.

They ended up using half as much copper, & they raised the price of there cars.

-- -** You are never to old to set another goal or to dream a new dream ****************** Dick, & Barb Cain, Hibbing, MN.

View Dadoo's profile


1789 posts in 4231 days

#13 posted 11-18-2007 12:04 AM

Obviously you have too many appliances shareing the same circuit. The first thing to do would be to eliminate them, or try the saw in another outlet. (Different circuit). Your saw takes 115/230v single phase to operate.

There are a hundred other items (dead rat lying across the terminals, etc.) that may also affect the circuit, but try elimination first. Let me know how that goes and I’ll try and help you troubleshoot it further, if necessary.

-- Bob Vila would be so proud of you!

View Karson's profile


35154 posts in 4641 days

#14 posted 11-18-2007 06:33 AM

If you only have one circuit from your main to the workshop. you are basicly in trouble.

I do all my own electrical work so I don’t have any idea what it might cost you.

The workshop that I’m in now has it’s own electric meter and own 200 Amp service. But It had only a couple of 22o volt circuits to water pump and water heater, air conditioner.

So I put in another sub panel and i’ve now got 8 220 volt circuits.
Welder, table saw, Dust collector, Air compressor, planer, jointer, bandsaw, Air Conditioner, plus a few more 110 Volt circuits.

In my case the previous owner built the building to store his Motor Home, and he paid $55,000 to have it done. So I didn’t have to do any building work except add electric circuits.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Appomattox Virginia †

View Joshua Howe's profile

Joshua Howe

71 posts in 3714 days

#15 posted 10-30-2009 10:13 PM

Didn’t read all these post so this may already be covered but for anyone that is reading this old post this may help you.
You need to be able to at least get an average amps on a circuit. This page will help if you don’t want to mess with or know the formulas.
So what I use is this:
watts=amps X volts
if this is the case then
so to use this in a project I’m currently working on I have 6 puck lights at 20watts each so I have a total of 120 watts in lights I also am installing a plug in this wet bar. So since this is a wet bar I figure the highest power usage item is a blender so I looked when in Lowe’s one day and the largest power consumer(blender) they had was at 650watts so I said to myself okay lets use the formula.
650w + 120w= 770w
so everything is standard kitchen wiring so it will be 120 volt(110V) power supplied.
770w/120v=6.416 amps
okay so I like to round up and play on the safe side when it comes to electricity
so 7amps
well knowing this I know I can use 14/2 wire(Romex) but being the safe person I am I’m using 12/2wire reason being is I don’t know if some jack-leg is going to plug a power strip in here and try and run 3 or 4 blenders when he throws a party showing off is new wet bar. I would rather throw a breaker than burn down a house.
O by the way 14/2 “UP TO” 15amps at 120volts
12/2 20amps at 120volts
it pretty easy once you now what you are working with
when you talk about 220 your amps start to drop
but what most of you guys are talking about are machinery motors which have a huge start-up draw.
What I did in my shop was to run your lights on a completely different circuit not hard to do just find an open spot in your breaker box and place a breaker and put all your lights on this breaker
I then have plugs for certain machines watch your plug buying they are amp rated also so everything should be rated for more amps than you need and every thing should have the right size wire for the amps your are carrying(this is where fires happen to small of a wire for the amps being pulled) allows play it safe and if you are the least bit unsure than find someone that knows because there is no room for maybes.
Our tools will definitely burn up if they are not supplied with the proper amps and amps are lost in connections and distance okay tired of typing hope this helps

-- Wood,clay,metal, and stone are all just materials, until an artist's hand touches them.--TreeFormDesign

showing 1 through 15 of 16 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