I’m in the process of adding 220V service to my shop and now have to rewire my DW746 tablesaw. The actual rewiring is no problem – it’s about a 5 minute job. My question is if I rewire the motor to 220V do I have to replace the switch? I’ve looked all over the internet, through the manual, and on the switch itself, but I can’t seem to find anything. On page 1 of the manual it says you should replace the switch, if necessary. Great. That’s really helpful. Well, FWW Folks, anyone out there know if it’s necessary?
Aaron
Replies
First question I would ask is why are you re-wiring the machine for 220 if it is currently wired for 110?
Lee
I'm going up to 220 from 110 because I now have 220 service in the shop and my 110 circuits are getting close to maxed. Switching over would free up some 110 amps to be used for other things. Also, because the circuits are about maxed I get a small brownout during the start up load that I'm sure is not good for the motor. My shop setup is fairly temporary, so I don't really want to do any more wiring.
Aaron
What type of switch is on the saw now? Is it a magnetic type switch or is it more like a toggle switch, similar to a common light switch?
Does the manual show how to rewire the motor (from 110 to 220)? If not, many times there is a plate attached to the motor that may have a wiring diagram.
I would consider buying a new magnetic switch. I think Woodcraft or any other woodworking supply place may carry a third party switch.
Are you comfortable installing the switch yourself? If not, I suggest getting help. Being shocked doesn't seemed conducive to woodworking.
Did you install the 220 service or did you hire someone?
Good luck,
Bill
I just got back from the shop where I pulled the switch off an opened it up. The reason that I didn't see any markings on the outside is it is just a casing. Inside, I found a toggle-type switch rated for 220 (actually, i think it said it would up to 277V. I also saw markings for 2hp in 220 and 1.5hp in 120.), so I think I'm set and probably explains why I can't find any info anywhere on the internet about changing out the switch.
As for the motor wiring, there was a plate on the motor and a few posts on the internet describing it. I got that finished and it was no problem. Tomorrow, i'll get a new plug for it and see how we did. Cross your fingers! Thanks for all the help guys.
Sounds like you have plenty voltage capacity but be sure it is two pole or you will have a shock hazard. I'm with Mapleman on changing from 110v to 220. A smaller motor like that would gain little advantage in voltage drop by going to 220 volts and for every 220 volt circuit you use, you are tieing up two 110 volt circuits. You do not save 110 volt circuits by using a 220 volt circuit, instead you lose one. In fact, the 110 volt breakers can be doubled up so you can actually put four 110 volt circuits in the space of one 220 volt breaker. You should not be getting brownout if you use a dedicated 110 circuit unless you have an awful long lead - like 150 feet or so. Another cause of brownout is if the supplier is not giving you enough voltage. Check both legs to the neutral.
Edited 1/9/2009 11:08 pm ET by Tinkerer3
I'm pretty sure it is a double-post as both the hot and neutral wires (or, 2 hots in 220) go through the switch. I imagine in a single post the neutral would bypass the switch.
As for the discussion on 110 v. 220. I'm aware of the loss of a potential circuit by going to a double pole breaker. The problem isn't so much space in the box as getting wire out to the shop. Getting additional wire pulled to the shop would be a bear, and it is a temporary set up, so i'm hesitant to spend the money to get it set up in the most efficient manner. The 220 circuit was already there, so it was just a matter of hooking it up. My thought in going to 220 was to take advantage of some additional, unused capacity. If I don't convert to 220 then I lose a circuit and have less overall power in the shop.
Aaron
"I'm pretty sure it is a double post." If that is the case - no problem. A neutral is never switched as far as I know unless all the legs are shut off simultaneously as in "pulling the plug."
aaron,
Look carefully at the switch and see if there is a voltage rating on it. There may, or may not be. If it's marked as rated for 220 V, then no prob.
If it's not marked I'd try my local Dewalt service shop. Ask them for the HP and voltage rating of the switch.
Don't settle for an amp rating. A motor is an inductive load and the switch must be rated to interrupt that current. It's different than switching a lightbulb.
Good luck
Fred
Fred,
I pulled the switch apart and inside it had a volt range on it. i can't remember the low end (somewhere around 110), but I believe it said it would handle to 277V. It also appeared to be rated for 2hp motors at 220 and 1.5hp motors at 110. The motor on the saw is 1.75hp, so I think I'm set. I'm going to go get a plug tomorrow and fire it up. Thanks for the help.
Aaron
Often the reason for replacing the switch is not the voltage rating but rather that they like a dpst in order to interrupt both legs of the 220. 120v only requires a spst.
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Men will never be free until the last king is strangled with the entrails of the last priest.~ Denis Diderot
Standard switch is fine. Saw runs better on 240.
Why would it run better on 240? Assuming adequate wiring there should be no difference in the performance of the tool.
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Men will never be free until the last king is strangled with the entrails of the last priest.~ Denis Diderot
To be sure I don't know why! Mine just has, Maybe starting volt drop?
Solid saw no regrets. Standard blade is very sweet, most stock blades are where they cut corners.
I think he said he was having brown-out problems on startup before. If so, this would be the situastion where the switch makes a lot of sense.
The person claiming the tool ran better on 220 was not the person that said he had a brownout problem.
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Men will never be free until the last king is strangled with the entrails of the last priest.~ Denis Diderot
I just reread the thread and the OP was having a brownout problem and you are right the switch will be a good thing for him.
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Men will never be free until the last king is strangled with the entrails of the last priest.~ Denis Diderot
No problem at all with present switch. I rewired my 746 to 240v. and it runs fine. They wouldn't say it could be done if the switch wasn't rated for it.
Actually my saw has never seen 120v. I changed it over to 240v. right out of the box.
Work Safe, Count to 10 when your done for the day !!
Bruce S.
Edited 1/10/2009 10:10 pm ET by BruceS
Well, I got the last bit of wiring done today and got the saw all hooked up. Everything works perfectly. The saw runs much better on 220, but that may have to do with the way I had it hooked to 110. Now, the saw spools up to speed in a fraction of a second and actually seems to have more power.
Thanks to all who gave advice. I appreciate the help.
I have had 3 tablesaws in my shop (detached garage feeding thru 50' of #6 cable) over the years & have always rewired the motors to run on 220v. They come up to speed instantly & work much better ripping 2" hardwood. It's just Ohm's Law - double the voltage, 1/2 the current in the line = 1/2 the line loss. If the hydro came directly from the pole with the transformer to the shop directly, there might not be such a noticeable difference. All motors in both my shops over 3/4 hp are wired 220v.
Dw746
How is the 220 conversation going. Did it work out. I have the same saw and can stop the blade pushing hard maple and burn cherry. Think the 220 might help. Any thoughts
220V conversion
Ye mate, you made the right choice, and yes, I know this is an old post - but the facts hold as true today as they did when the OP first broached the topic.
We run workshops in UK, Australia, Canada and USA and we HATE 110V for ANY power tools.
Once you go 220/240V or 3 phase - you simply never go back.
In fact, I'd rather run cordless than run 110V these days.
Well done mate!
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