Using #10 Supply Lines

[Skeezix]

From Mr. Chien's FAQ (which, BTW, is a real piece of work - one of the best written I've seen in a long time):

What power and wiring do I need for my BT3x?

The saw only uses 120V, it may be AC 50 Hz or 60 Hz. It is rated at 15 amps. It is recommended that the BT3x have a dedicated grounded line with a circuit breaker of 15 or 20 amps (not larger!) and branch wiring of 14 or 12 gage.

I am going to install a dedicated line from my breaker box to my garage. Total length will be 80 feet from the breaker box to the BT3100 receptacle. To minimize line losses, I planned to use #10 wire on a 30-amp breaker but Mr. Chien indicates that is not recommended. Is this to protect the saw from excessive current draw?

[Black wallnut]

Yes! The saw has no built in thermal protector (circuit breaker or fuse) and running it on a 30 amp breaker will guarentee that you will most likely never blow the breaker but instead you will fry your motor in case of an overload. IMHO for an 80' run a 15 amp breaker wired with awg 12 would be sufficient. Just do not use any other devices on the same circuit as the saw. If you are already planning on using 10 guage(if that is the correct wire size for a 30 amp run of 160 feet? I'd have to look it up) you could wire in a 30 amp sub-panel and branch off that with a 15 amp breaker for the saw leaving room for other devices on seperate circuits.

BTw see my reply to the other topic.

[rbfunk]

Just a quick calculation shows me that for a 1% max voltage drop you would need number 6 at 80 feet. 2.5% drop with #10 and 5% with #12.
I used the calculator at http://www.vihon.com/Vihon_Calculato...alculator.html

If you are going to dedicate this outlet to your saw then use a 15 amp breaker to protect the saw. If you want to use a 30 amp breaker you may want to use a 30 amp receptical. Either way make sure you lable the breaker and the outlet since it will handle a higher current if you need it in the future.
Bob

[Tom Slick]

why are you running a 30 amp circuit? you can still use 10 awg wire (#10 is incorrect nomenclature) with 20 or 15 amp circuit parts. the amperage rating is not how much amperage is available from it's source, it's how much amperge the circuit can use before it is overloaded, damaging the circuits components.

[maxparot]

Using the #10awg wire isn't going to be a problem. Nothing in electrical code or theory prevents you from doing so. Increasing wire size has only 2 problems. The first is the increased expense of the heavier conductor. The second possible problem is if the wire doesn't fit the terminals you need to connect it to.
As for the breaker if you are looking to optimize the circuit for your BT3xxx then go with a 15 amp breaker it provides maximum protection for the saw's motor. If what you want is a maximized dedicated circuit for use with 120v tools up to 20 amps go for the 20 amp breaker. If you need a 30 amp 120 volt line yes you can run the saw on it but if you want to protect the saw you may want to add a 15 amp breaker to the saw.

[LCHIEN]

From Mr. Chien's FAQ (which, BTW, is a real piece of work - one of the best written I've seen in a long time):

What power and wiring do I need for my BT3x?
The saw only uses 120V, it may be AC 50 Hz or 60 Hz. It is rated at 15 amps. It is recommended that the BT3x have a dedicated grounded line with a circuit breaker of 15 or 20 amps (not larger!) and branch wiring of 14 or 12 gage.

I am going to install a dedicated line from my breaker box to my garage. Total length will be 80 feet from the breaker box to the BT3100 receptacle. To minimize line losses, I planned to use #10 wire on a 30-amp breaker but Mr. Chien indicates that is not recommended. Is this to protect the saw from excessive current draw?

Thanks for the compliment and welcome.

You have several requirements here.
1) lomg run of wire, you are going to 10 AWG to reduce voltage drop on this long run. That makes sense.
2) 10 AWG can be used with a 30Amp branch circuit in normal applications, I assume that's why you are thinking about putting it in.
3) as pointed out, a 30Amp breaker will protect the wiring, but not the saw. That's a danger.

My suggestion would be to put a sub panel at the garage, the wiring to the garage protected by the 30Amp breaker. At the sub panel put a 15A breaker to a single outlet for protecting the saw. Put another 15A breaker for general outlets.

This is perfectly safe but it does have one minor flaw. If using both the general circuit and the saw it is possible to go over 15A and have too great a drop. 10 ga wire is about 1 milliohm/ft, or 2 milliohms both ways. An 80-ft run will have 160 milliohms. At 15 amps then we're talking about ~2.5 volts loss, at 30 amps we're talking ~5 volts loss.

I don't think that's really terrible, it's about 4% with your saw running as hard as possible and the general line fully loaded, too. Considering that equipment is generally designed to work with bare minimum a range of 110-120V, and often as low as 105 allowing for line drops and stuff,
I don't think you'll have a real problem unless your line voltage is low to start with. (if it is low all the time sometimes the power company can adjust it, you know, with a transformer tap change). In general, you won't really notice a 5% loss of power in your saw from one day to another. Usually your house input will be 115-120V.

You will want, as you get more equipment and stuff, some additional circuits in your garage shop for dust collector or vac, compressor, lights, fans etc. that all need to be able to run simultaneously, so maybe if you plan well ahead you can put 8 ga to a sub box and three 15A circuits in the garage.

HTH and Good luck.