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Worth it to convert Delta 36-725 table saw to 220v?

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Forum topic by Amphigory posted 12-29-2015 06:28 PM 1812 views 0 times favorited 16 replies Add to Favorites Watch
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Amphigory

8 posts in 348 days


12-29-2015 06:28 PM

I just got a delta 36-725, and I just blew a fuse cutting through 4×4 fir for my “I’m too cheap to buy hardwood” dining table. Right now, I’ve got two 15a, 110v circuits in the garage. Both are shared with the rest of the house. For what it’s worth, I’m very comfortable with electrical work (electrical engineer and worked my way through college, among other things, as an electrician/plumber’s helper.) I’m mostly asking for opinions on what would be more useful long term as I’m planning to get back into woodworking in a pretty big way. The panel is in the garage and has plenty of capacity (about 10 slots available, 200amp service with only 140amp wired up without overloading right now), so whatever would be best is pretty easy to implement.

As I see it, there are two plans:

Plan 1: 2 20amp 110v circuits, one dedicated to table saw

Pro’s: everything stays 110v, no need for special extension cords, can plug anything anywhere. Have two dedicated circuits for other benchtop and portable tools as needed.

Cons: If I ever get that welder, no place to plug it in.

Plan 2: 1 10amp 220v circuit for table saw, maybe go ahead and run 1 or more 110v circuits too

Pro’s: ??? from what I understand, there’s not a huge advantage for the table saw to convert it to 220. I’d have a plug for that welder. Also, a plug to attach a generator to the house if I ever need to in a power outage.

Cons: More wiring, have to rewire table saw with a long enough cord to actually reach the center of my shop (not practical to drop power in the center), etc.

Plan 2.5: Do the 220v circuit while I have the box open, but leave the table saw running on 110v.

Con: Cost, more wiring, redundant unless I get that welder.

Plan 3: do a subpanel, all surface mount conduit, so that I can implement plans 1 or 2 without having to open up the walls.

Pro: Future expansion is easy. Eventually, I want to air condition the place so that would make it easy to wire for that.
Con: Cost, time.

Anybody with more experience care to comment? The only gotcha is my space is already drywalled, so I’d rather only do this once. It’s a fairly small garage (14×24) so I don’t know how much more equipment I can pack in anyway.

Thanks for your thoughts.


16 replies so far

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MrUnix

4234 posts in 1665 days


#1 posted 12-29-2015 06:36 PM

Read page 7 of your manual, where it states:

A separate electrical circuit should be used for your machines. This circuit should not be less than #12 wire and should be protected with a 20-amp time lag fuse.

Any of your options would be better than your shared 15A circuit currently being used, and you are the best to determine which way you would like to go. And you are correct, you will not get any extra power by converting to 240v – internally, that motor is 120v regardless of how you wire it.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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716

502 posts in 382 days


#2 posted 12-29-2015 06:38 PM

If you have 10 slots available why bother installing a subpanel ?

-- It's nice!

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Amphigory

8 posts in 348 days


#3 posted 12-29-2015 06:43 PM



If you have 10 slots available why bother installing a subpanel ?

- 716

Because then I could do conduit directly from the subpanel and not have to tear into the wall again if I needed more. I’m thinking about just putting an access plate in the wall under the current panel though. I don’t mind the electrical, but I HATE messing with drywall.

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MrUnix

4234 posts in 1665 days


#4 posted 12-29-2015 06:50 PM

I’m thinking about just putting an access plate in the wall under the current panel though. I don t mind the electrical, but I HATE messing with drywall.

- Amphigory

That is what I did… added a 50A 240V outlet and 20A 120v duplex outlet about a foot under the panel. No need to tear up the wall – just cut the hole for the box(es) and run the wire straight up into the breaker box. Total cost was something like $50 IIRC.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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716

502 posts in 382 days


#5 posted 12-29-2015 06:54 PM

And you are correct, you will not get any extra power by converting to 240v – internally, that motor is 120v regardless of how you wire it.
Cheers,
Brad
- MrUnix

Close but not exactly. With 220V you have twice less loss in the extension cable which might turn critical if the saw in not positioned just next to the outlet.
For example if you want to roll your table saw on the driveway and need about 50ft of 18AWG extension cord you will get 10 Volts drop which I would estimate results in 20% power loss. With 220V in the same conditions you will get 5.5V drop which is only 5% power loss. So in that case running 220V circuit increases the power of your motor by 15%.
Also if the outlet is far from the panel the circuit would add its own losses too.

-- It's nice!

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MrUnix

4234 posts in 1665 days


#6 posted 12-29-2015 07:10 PM

For example if you want to roll your table saw on the driveway and need about 50ft of 18AWG extension cord you will get 10 Volts drop which I would estimate results in 20% power loss. With 220V in the same conditions you will get 5.5V drop which is only 5% power loss.

Well.. first off, trying to run a 120v@13A machine with 18ga extension cord is not really a good idea :)
Second – 120v@13A running 50ft through 18ga wire would result in about 6.92% voltage drop (not 20% as you indicated), or 110.7v at the end.
Using the correct sized wire, such as the 12ga specified in the manual, results in only 1.72% voltage drop, or 117.94v at the end.
Using 18ga wire for a 50 foot run at 240 volt will get you the same 1.72% (actually, 1.73%) drop as you would get using 12ga for 120v.

Thirdly, the comment was that – provided the proper power supplied – the motor will still produce the same amount of power regardless of how it’s wired. Using an extension cord alters that equation, but it is insignificant as long as you use the proper sized cord. Similar to how an outlet on the other side of the house, when wired correctly, will be just as usable as one next to the breaker box. As mentioned, a dual voltage motor still only sees 120v across it’s windings, regardless of how it is wired.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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WhyMe

615 posts in 1027 days


#7 posted 12-29-2015 07:11 PM

If it was me I’d do Plan #3. Put in at least a 60A feeder and breaker from the main panel and use at least a 100A 20 space main breaker panel for the sub-panel. Then you can go crazy with outlets from there.

I wouldn’t worry with changing the saw to 240V.

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knotscott

7216 posts in 2841 days


#8 posted 12-29-2015 09:19 PM

If you decide to run any wire, I’d definitely install a 240v circuit. Your current saw has a 13 amp 120v 1.5hp motor, but if you ever get a tool with a larger motor, whether a TS, DC, BS, planer, jointer, or welder, you may wish you had 240v capability.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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rwe2156

2198 posts in 947 days


#9 posted 12-29-2015 11:25 PM

Well, I’ll be the lone ranger and agree with option 3.

I think you’ll be further ahead with future expansions.
I would surface mount the subpanel and run armor flex cable or emt externally on walls.
You will have a huge amount of freedom in running/adding/changing circuit runs.

Need a dedicated circuit for that dust collector? No problem.

This is what I did in my shop and it worked out great.

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

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HerbC

1592 posts in 2325 days


#10 posted 12-29-2015 11:48 PM

One thing you said makes me wonder whether you are as “experienced” as you state…

” ... Also, a plug to attach a generator to the house if I ever need to in a power outage.”

You must NOT attach a generator to the house’s wiring system by plugging into an outlet socket that is wired directly into the house wiring. Instead you must use a properly designed disconnect switch arrangement that will not allow the generator power to be fed to the house without properly disconnecting the system from the main power grid. Doing this wrong can be very dangerous and/or cause a lot of damage to the home or even to the power grid system.

Be Careful!

Herb

-- Herb, Florida - Here's why I close most messages with "Be Careful!" http://lumberjocks.com/HerbC/blog/17090

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hotbyte

844 posts in 2441 days


#11 posted 12-30-2015 12:24 AM

I’d say get saw on a 20amp circuit and be sure for rips of that size to use a thin kerf rip blade.

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716

502 posts in 382 days


#12 posted 12-30-2015 12:29 AM


For example if you want to roll your table saw on the driveway and need about 50ft of 18AWG extension cord you will get 10 Volts drop which I would estimate results in 20% power loss. With 220V in the same conditions you will get 5.5V drop which is only 5% power loss.

Well.. first off, trying to run a 120v@13A machine with 18ga extension cord is not really a good idea :)

Agreed. But in fact running an induction motor on inappropriate circuit is the most common reason of electrical damage.

Second – 120v@13A running 50ft through 18ga wire would result in about 6.92% voltage drop (not 20% as you indicated), or 110.7v at the end.

I did not indicate 20% voltage drop, I indicated 20% power loss and stand by it. I said 10 volts drop. ( see above).

Thirdly, the comment was that – provided the proper power supplied

Sorry the comment was different. See your own post.

Similar to how an outlet on the other side of the house, when wired correctly, will be just as usable as one next to the breaker box. As mentioned, a dual voltage motor still only sees 120v across it s windings, regardless of how it is wired.


It will not be just as usable. I mentioned it will be close but not the same. 15A circuits are wired with 14ga wire because the builders are usually very greedy. I am not aware of any code enforcement on the length of the circuit as I saw pretty long (more than 150 ft circuits put in by the original builder) but I could be wrong here. On these circuits the power loss will be significant to the point you cannot ignore it.

Cheers,
Brad

- MrUnix


In two words a 220(240V) circuit does provide more power at the blade of a table saw. How much more depends on other factors as you noted but always more than a 110V(120V) circuit

-- It's nice!

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MrUnix

4234 posts in 1665 days


#13 posted 12-30-2015 12:36 AM

Sorry the comment was different. See your own post.

I did… it was about what the motor sees internally… you were the one who brought up providing an under powered power source. A 240v motor is still just a 120v motor internally. Watts are watts.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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Amphigory

8 posts in 348 days


#14 posted 12-30-2015 03:38 PM



One thing you said makes me wonder whether you are as “experienced” as you state…

” ... Also, a plug to attach a generator to the house if I ever need to in a power outage.”

You must NOT attach a generator to the house s wiring system by plugging into an outlet socket that is wired directly into the house wiring. Instead you must use a properly designed disconnect switch arrangement that will not allow the generator power to be fed to the house without properly disconnecting the system from the main power grid. Doing this wrong can be very dangerous and/or cause a lot of damage to the home or even to the power grid system.

Or, perhaps I”m experienced enough to know how to obviate those possibilities? Wouldn’t it be wonderful if there were a simple way to completely disconnect the home from the grid in an emergency situation?

(For the record, Herb is correct that this can be dangerous if you don’t know what you’re doing. It can be dangerous to linemen working to restore power (who are expecting a wire to be dead) and if the power comes back on you’ll almost certainly be out of phase with the grid, which can do lots of Bad Things. You should only even consider this sort of jury rig if you know EXACTLY what you’re doing. And I would only consider it in an emergency situation.)

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Amphigory

8 posts in 348 days


#15 posted 12-30-2015 03:45 PM

When I opened up the box, it turned out that it was really easy to just drop some wire from the bottom of the box to an OB in the wall. It was so easy that it just didn’t seem worth the expense at this time to “overbuild”. Being lazy and cheap, I just added 2×20amp dedicated circuits—one for the TS and one for my dust collector… ahem … shop vac. If I ever need to adda 220volt circuit, I can do so in probably less time than it would take to run conduit from a subpanel.

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