Extension cord use?

[byeilts]

Just coming back after a couple of years of inactivity w/ the BT. Just wanted to verify if one can use an approp. guage extension cord for the BT3100. A couple of years ago I thought I read that it was a no-no. Just getting my shop set up in the garage, have a very supportive wife that wants to learn woodworking w/ me. Any help would be appreciated. thanks Brent

[Bruce Cohen]

Brent,

If you keep it short (10' or less) and use 12 ga. 3 strand, you should have no problems. I have mine hooked up to a dedicated 20A. circuit though.

Bruce

[tjr]

I've seen these extension cord discussions before and have to admit I'm a bit confused. IIRC, a regular 15 amp household circuit uses 12ga wire from the breaker box to the outlet. In our house, the wire from the breaker box to the outlet in our garage must be at least 50' long. Some people with bigger houses must have longer. So would adding a 25' 12ga extension make a difference? Or is the wire in flexible extension cords different from the solid copper wire used for house wiring?

[LCHIEN]

I've seen these extension cord discussions before and have to admit I'm a bit confused. IIRC, a regular 15 amp household circuit uses 12ga wire from the breaker box to the outlet. In our house, the wire from the breaker box to the outlet in our garage must be at least 50' long. Some people with bigger houses must have longer. So would adding a 25' 12ga extension make a difference? Or is the wire in flexible extension cords different from the solid copper wire used for house wiring?

you have a couple of issues. One the stranded wire is a little more resistive than solid, not hugely so, though. The other is the presence of more friction based contacts - e.g. plugs. Also can be lossy.

Overall, extension cords can be used. You have to keep them in good order and properly sized, that is hard for the average Joe to do. Hence the recommendations against them in general discussions.

[vaking]

I am using my BT in combination with a small dust collectors connected with Sears autoswitch. That means BT3100 and 3/4 HP dust collector are plugged to the same 15 amps circuit and are being turned on together. Works without any issues even with a short extension cord from the autoswitch.
In fact, a 12" CMS connected without any dust colectors creates a bigger load and sometimes pops the breaker. What I am saying is that BT3100 is probably not the biggest load you have.

[JimD]

Universal motors, like the BT3100s, draw more amps when under load. I am pretty sure you can trip a breaker with a BT3100 alone, let alone one plus a DC. On the other hand, I have no problem believing it works provided you do not cut thick (>1 inch) material.

I use a short extension cord - maybe 15 feet - but I think it is 14 or possibly even 16 gauge wire. I am on a 20 amp circuit and it is always the only load. I have never flipped the breaker with the BT3100. I have flipped the breaker when I was in the garage where the house wiring was much longer. My shop is very close to the breaker box and the outlet I use for the BT3100 is less than 8 feet from it.

Jim

[master53yoda]

The electrical code uses 100ft distance from the panel to load in its calculations. They are #14 wire up to 15 amps, #12 wire up to 20 amps, #10 wire up to 30 Amps. These calcs are based on a max of 60 degree C rise. You should never load a circuit more then 80%.

You can use extension cords in the same sizes but bear in mind the distance from the panel. That is why my shop has a sub-panel installed, feed from the main panel with #6 wire . It allows me to us a 50 to 75 'ft cord sized for the load. For table saws etc. no cord should be less then #12. I also have a 100' #10 cord if I must go long distances from the panel.

[LarryG]

Art already mentioned what I was going to say, but I'll say it anyway to reinforce it: since the BT has a 15A motor, it should ideally be plugged into a 20A circuit.

[Ed62]

since the BT has a 15A motor, it should ideally be plugged into a 20A circuit.

There's a good chance that I'm not remembering this correctly. But I thought Loring said, in an older post, that the BT would be better served with a 15 amp breaker. Now I'm confused. Wouldn't a 20 amp breaker be more likely to allow the motor to be fried? Can someone educate me please?

Ed

[pelligrini]

Naa, having a bigger capacity breaker would not affect the saw. The saw will pull the amount of current it needs. In the instance of a BT, usually much less than 15 amps under normal loading. Just because a circuit can handle a 20amp load doesn't mean the device is getting 20amps pushed into it. It's more of a function of the voltage. It's more like saying that there is 20 amps there for it to use if needed.

I prefer to have the saw on a dedicated circuit. If it needs the current it will be available, and I don't have to worry about tripping the breaker. I did all the circuits off my shop sub-panel as 20 amp. I already had a box of 12ga wire and the 20amp outlets didn't cost much more. I think a BT would be fine on a dedicated 15amp circuit. It is a 15 amp motor, but it doesn't always pull that much current. The times it does the duration isn't very long.

Another factor against using long, smaller gauge extension cords is the voltage drop. That will also affect the total load on the circuit too. I've got a nice power strip with a 12ga cord. I think the cord is about 10'. It connects to a dedicated circuit, and my 21829 and router plug directly into it.

Before I ran 120' of 6ga wire to my little shop for a sub-panel I had a couple extension cords running to it. One off the back porch outlet, and another off a nearby bedroom circuit. Using some shorter 12ga cords worked better than a normal orange 14ga long one. I still couldn't power up my old window air conditioner. That thing will pull 14.8 amps.

[Richard in Smithville]

My BT is close enough to a plug that I can run with out an XT cord. It's plugged into 15 amps and there is no noticable dimming of lights on the same circuit when I fire it up or run under load.

[master53yoda]

There's a good chance that I'm not remembering this correctly. But I thought Loring said, in an older post, that the BT would be better served with a 15 amp breaker. Now I'm confused. Wouldn't a 20 amp breaker be more likely to allow the motor to be fried? Can someone educate me please?

Ed

The breaker size is to protect the wiring not the motor. the lower the circuit breaker size the smaller the wire and the higher the voltage drop across the wire. this reduces the available voltage to the motor causing a higher current draw in order to deliver the same power. this higher current draw causes more heat in the motor windings and more arcing at the brushes. if the motor is fully loaded and on the BT3000 with a 15 amp motor this would be found when your ripping 2" on a long run. the high current draw on a 15 amp circuit could cause as much as a 10 to 15 volt drop at the motor. the breaker may not trip right away but the heat in the motor windings becomes excessive . the same conditions on a 20 amp circuit would only generate a 2 to 3 volt drop with less current flow and less motor heat. The saw would work just the same and have less heat if it was plugged into any circuit higher then 20 amp when cutting heavy boards. I have ripped many 2 3/4" cuts in 8 ft boards without ever generating enough heat to cause problems with the motor. I also change the brushes once per year because of doing a lot of ripping with my saw. I have recently gotten a good band saw so will no longer do the ripping with the table saw that i used to.

[Daryl]

I ran my shop from about thirty feet of extension cord for a few years. The plug was the weak spot, they would get hot and start to melt.

[Ed62]

Yoda, Larry, and Loring. Thanks very much for the information. I'll have to read it a couple of times so it sinks in. But it will sink in. I do understand about the voltage drop through the wiring. What a great place to get info!

Ed

[LarryG]

The way that breakers are specifed and I went through the specs from makers like Square D, is that a 15A breaker can handle 15A all day and night long.

Loring, once again ... our electrical engineering consultant insists this is not the case. I have discussed this with him several times. He has repeatedly told me that a properly operating circuit breaker will carry only 80% of its rated load indefinitely; above that, any continuous load (as opposed to momentary, like a motor starting) will cause it to trip within three hours; the more the load exceeds 80%, the faster it will trip within that three hour window.

Our consultant is a professional EE, licensed in multiple states, with about 20 years of experience. He is in private practice, specializing in the design of commercial and residential power systems, starting at the utility company's transformer and continuing all the way down to the building's switches and outlets.

He tells me that there ARE breakers that can carry their rated load continuously, but that these are very expensive, special-order items. Perhaps you were looking at the specs for this type of breaker instead of those commonly used in residential and commercial panels.