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Need help with wiring for a Powermatic 72

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Forum topic by SweetTea posted 09-17-2019 03:14 PM 569 views 0 times favorited 21 replies Add to Favorites Watch
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SweetTea

463 posts in 1173 days


09-17-2019 03:14 PM

I have a 3 phase 7.5hp Powermatic 72 that I am getting ready to run the line for getting power to it. I have a RPC that is driven by a 25hp motor. The only thing is that the Powermatic 72 is wired for 440v. Would I need to change the wiring over to 240v before connecting it to my RPC? If so, is this done at the switch? Star/Delta type thing? I have an industrial electrician coming to run my lines. I am sure he is more than capable of switching it over. I am just curious. I am using 10/3 mc for the wiring and running it on a 40amp 3 pole breaker at my load center.


21 replies so far

View ibewjon's profile

ibewjon

1007 posts in 3306 days


#1 posted 09-17-2019 04:26 PM

7 1)2 HP should draw 22 amps on 230/240 volt system 10 awg is good, but code shows a 45 amp breaker, and the proper heater element overloads in the starter. Just a switch or disconnect to turn it on or off without overload protection will not protect the wire and can be dangerous. Many people do not want to spend the money for a starter, but without a starter you need to put 10 awg on a 30 amp breaker, no larger. Or upgrade to 8 awg wire. And don’t forget the ground wire, 10 awg, not 12 or 14. Rotation is changed at the motor connection box, the diagram is on the motor.

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clagwell

41 posts in 306 days


#2 posted 09-17-2019 06:58 PM

... Powermatic 72 is wired for 440v. Would I need to change the wiring over to 240v before connecting it to my RPC?

Yes. (Well, actually it only has to be done before you turn it on but you eliminate a chance for error if it’s done first.)
.. is this done at the switch?

No, it’s done at the motor.
Star/Delta type thing?

No, more like a series/parallel type of thing. There should be a wiring diagram on the motor or inside the connection cover that shows the proper way to do it.

The more difficult problem may be the switch. Assuming it’s actually a contactor with overload protection there are two things to look out for.

First, the contactor coil voltage. If it’s 480V it will need to be replaced. If it’s low voltage with a transformer the transformer will need it’s primary changed to 240V.

Second, the overload sensing will need changed since the motor requires twice the current at 240V. You may need to change heaters or adjust the current setting depending on exactly what you have.

-- Dave, Tippecanoe County, IN

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SweetTea

463 posts in 1173 days


#3 posted 09-18-2019 09:05 AM



7 1)2 HP should draw 22 amps on 230/240 volt system 10 awg is good, but code shows a 45 amp breaker, and the proper heater element overloads in the starter. Just a switch or disconnect to turn it on or off without overload protection will not protect the wire and can be dangerous. Many people do not want to spend the money for a starter, but without a starter you need to put 10 awg on a 30 amp breaker, no larger. Or upgrade to 8 awg wire. And don t forget the ground wire, 10 awg, not 12 or 14. Rotation is changed at the motor connection box, the diagram is on the motor.

- ibewjon

Will take your advice into consideration. I am planning to use the stock switch that came on the saw from Powermatic.

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ibewjon

1007 posts in 3306 days


#4 posted 09-18-2019 11:23 AM

Add on…I meant to say voltage motor runs on is changed at the motor box, and rotation can also be changed there. Does the switch operate a starter mounted on the saw? And yes, the coil voltage or transformer wiring is another thing you will have to deal with.

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SweetTea

463 posts in 1173 days


#5 posted 09-19-2019 12:12 PM



... Powermatic 72 is wired for 440v. Would I need to change the wiring over to 240v before connecting it to my RPC?
Yes. (Well, actually it only has to be done before you turn it on but you eliminate a chance for error if it s done first.)
.. is this done at the switch?
No, it s done at the motor. Star/Delta type thing?
No, more like a series/parallel type of thing. There should be a wiring diagram on the motor or inside the connection cover that shows the proper way to do it.

The more difficult problem may be the switch. Assuming it s actually a contactor with overload protection there are two things to look out for.

First, the contactor coil voltage. If it s 480V it will need to be replaced. If it s low voltage with a transformer the transformer will need it s primary changed to 240V.

Second, the overload sensing will need changed since the motor requires twice the current at 240V. You may need to change heaters or adjust the current setting depending on exactly what you have.

- clagwell


Add on…I meant to say voltage motor runs on is changed at the motor box, and rotation can also be changed there. Does the switch operate a starter mounted on the saw? And yes, the coil voltage or transformer wiring is another thing you will have to deal with.

- ibewjon

Here are the pics of the stock Powermatic switch and cut off box.

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ibewjon

1007 posts in 3306 days


#6 posted 09-19-2019 02:24 PM

This could be a problem. I know the heater elements are too small as on 240 you draw twice the amps, so you need the proper size. I am going to guess that the coil is 480 since I do not see a control transformer to give you a 120 control voltage. Hopefully the 120 coil is still available. And the fuses in the disconnect will also need to be replaced. I can post code chart fuse size later. The 600 volt rating of the disconnect is ok, just get the proper time delay to match the rated voltage of the disconnect.

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clagwell

41 posts in 306 days


#7 posted 09-19-2019 03:17 PM

What ibewjon said except I think you will need a 240V coil not 120V.

-- Dave, Tippecanoe County, IN

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ibewjon

1007 posts in 3306 days


#8 posted 09-19-2019 03:32 PM

Force of habit. Any control voltage over 120 has not been used in many years. Any place we worked, we changed over to 120 for safety. Or add a 240/120 control transformer to use 120 control voltage. The deciding point is what starter coil is available. You may need a new starter, or a vfd instead of the rpc. Or use a separate 120 circut for controls. Yes, it can get complicated. But you will still need new coil, new heaters, and new fuses. A vfd may be less expensive, or not much more.

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ibewjon

1007 posts in 3306 days


#9 posted 09-19-2019 06:00 PM

You will need 30 amp time delay fuses

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SweetTea

463 posts in 1173 days


#10 posted 09-20-2019 11:44 PM



Force of habit. Any control voltage over 120 has not been used in many years. Any place we worked, we changed over to 120 for safety. Or add a 240/120 control transformer to use 120 control voltage. The deciding point is what starter coil is available. You may need a new starter, or a vfd instead of the rpc. Or use a separate 120 circut for controls. Yes, it can get complicated. But you will still need new coil, new heaters, and new fuses. A vfd may be less expensive, or not much more.

- ibewjon

This is quickly going over my head. I am not familiar with what the coil, heater and starter are with regards to my 72. Are these items in the switch components?

Would it still require these modifications if I used a static phase converter? Could I just mount a SPC on the side of the saw and use a toggle switch? I do have a SPC on hand that is rated to the appropriate HP rating on this saw and the loss of 1/3 power will not affect the intended usage of this setup.

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CaptainKlutz

1898 posts in 2007 days


#11 posted 09-21-2019 01:03 AM

+1 on the above intelligent electrical posts. Let a dummy, dummy it up for you:

Bottom line:
4 things have to change to get from 440v to 220v, regardless of your 220v 3PH source (RPC or SPC).

- If you keep the fuses in disconnect box (which are not required with proper sized breaker in the circuit, and overload on motor starter), they have be doubled.

- The coil on the contactor/relay in motor starter needs to be changed

- The overload heaters in the motor starter also need to be changed.

- The motor wiring connections down at motor will need to change from series (440v) to parallel (220v) configuration.

The suggestions for using a VFD might be confusing, until you realize the VFD would use your 220V input and generate 440V to run the machine. There are even some VFD that will take single phase 220v and generate 440v 3PH.

Note1:
With VFD supplying 3PH 440v, possibly none of wiring on machine needs to change. But you would lose the VFD control capability, such as soft start, adjustable frequency, adjustable overload, etc.

Note2:
The old ITE/Gould/Telemecanique company no longer exists. Various brands where sold to other companies, and some parts are still available. Finding coil and heater parts will probably have to use NOS (new old stock). Due to costs for NOS parts, it might be cheaper to replace entire motor starter with new IEC motor starter, or use a 220v to 440v VFD.

I don’t mess with 440v 3PH much any more.
Will leave this in hands of our resident electricians for help.

#IAMAKLUTZ and hope i got the summary right.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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ibewjon

1007 posts in 3306 days


#12 posted 09-21-2019 01:03 AM

If you don’t know what the various parts are, it is time to hire professional help.

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CaptainKlutz

1898 posts in 2007 days


#13 posted 09-21-2019 01:34 AM


If you don t know what the various parts are, it is time to hire professional help.
- ibewjon

+10

BTW – If I was making the conversion from 440v to 220v, this would be my plan:
- Remove the disconnect switch, not needed for 220v machine using a plug/receptacle power feed.

- Call Powermatic and price conversion parts for changing motor starter to go from 440v to 220v. Assuming its original OEM starter. If less than $100, buy parts. If more than $100, buy a new IEC starter like this one:
https://www.amazon.com/Big-Horn-18837-220-240-Volt-18-26-Amp/dp/B002LVUWIQ

- Reconfigure and rewire existing motor starter for twice the current & half voltage,
or install new starter.

- Rewire the motor connections to 220v.

Plug it in, check voltages with meter. The hit power button, and run the smoke test.

Reason: The 220v to 440v 7.5HP VFD is $400+.
If I already have RPC with 220v 3PH power, it is cheaper to get new starter, larger wire, and new plug/receptacle; then cost of adding the VFD.
Not having the 1PH to 3PH PRC/SPC, it would be cheaper to use VFD instead, and remove all the extra stuff.

Cheers!

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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SweetTea

463 posts in 1173 days


#14 posted 09-21-2019 01:01 PM


If you don t know what the various parts are, it is time to hire professional help.
- ibewjon

+10

BTW – If I was making the conversion from 440v to 220v, this would be my plan:
- Remove the disconnect switch, not needed for 220v machine using a plug/receptacle power feed.

- Call Powermatic and price conversion parts for changing motor starter to go from 440v to 220v. Assuming its original OEM starter. If less than $100, buy parts. If more than $100, buy a new IEC starter like this one:
https://www.amazon.com/Big-Horn-18837-220-240-Volt-18-26-Amp/dp/B002LVUWIQ

- Reconfigure and rewire existing motor starter for twice the current & half voltage,
or install new starter.

- Rewire the motor connections to 220v.

Plug it in, check voltages with meter. The hit power button, and run the smoke test.

Reason: The 220v to 440v 7.5HP VFD is $400+.
If I already have RPC with 220v 3PH power, it is cheaper to get new starter, larger wire, and new plug/receptacle; then cost of adding the VFD.
Not having the 1PH to 3PH PRC/SPC, it would be cheaper to use VFD instead, and remove all the extra stuff.

Cheers!

- CaptainKlutz

So I can purchase that $74 starter and reconfigure the wiring at the motor end for parallel instead of series then just remove the disconnect box and be good to go? With all of the talk I was afraid this would get very expensive very fast. That is not actually too bad.

Oh and I do have a professional that will be doing the work. I just needed to have an understanding of what and how this would all be done.

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SweetTea

463 posts in 1173 days


#15 posted 09-21-2019 01:10 PM



Force of habit. Any control voltage over 120 has not been used in many years. Any place we worked, we changed over to 120 for safety. Or add a 240/120 control transformer to use 120 control voltage. The deciding point is what starter coil is available. You may need a new starter, or a vfd instead of the rpc. Or use a separate 120 circut for controls. Yes, it can get complicated. But you will still need new coil, new heaters, and new fuses. A vfd may be less expensive, or not much more.

- ibewjon

I priced a VFD from Jack Forsberg a while back and for him to make one capable of running a 7.5hp motor it would have cost $500 then $58 shipping. This will be significantly cheaper with replacing the starter, switching the motor connections to parallel and removing the disconnect box. So far I am $600 deep in my 3 phase setup. I already had a 25hp 3 phase motor and purchased an American Rotary panel. The industrial electrician that is doing the install for me is a close friend and is taking beer and pizza as payment for helping me with this.

I did seriously consider using VFD’s. I have a lot of 3 phase machines now including a 10HP wide belt and a 10HP dust collector that I am not yet using. The price on a VFD capable of running my 10HP wide belt was $850 + $80 shipping from Canada. That was a bit steep considering how many other 3 phase machines that I have. I plan to purchase another larger RPC down the road. All together I have 10 machines and counting that are 3 phase. I just picked up 2 more 10HP dust collectors at a price that I couldn’t refuse.

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