DPST Contrlling Hot and Neutral Question

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Jim M426

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I have a Ryobi drum sander. It suddenly stopped working. It has a DPST On-Off switch that controls the hot and the neutral. The neutral side remains open when the switch is closed. I'm looking at bypassing the switch and tying the neutrals together. Everything is 120v.

The H & N from the cord run straight to the DPST switch. On the load side, the H & N run to an outlet that controls the drum motor and to a printed circuit board. The PCB controls the conveyor belt speed. The conveyor belt motor is fed off the PCB.

Does anyone see any reason why the neutral needs to be open when the sander is not in use? In other words, any reason I can't splice all the neutrals together? FWIW, the switch is no longer made.
 
Jim M426 said:
I have a Ryobi drum sander. It suddenly stopped working. It has a DPST On-Off switch that controls the hot and the neutral. The neutral side remains open when the switch is closed. I'm looking at bypassing the switch and tying the neutrals together. Everything is 120v.

The H & N from the cord run straight to the DPST switch. On the load side, the H & N run to an outlet that controls the drum motor and to a printed circuit board. The PCB controls the conveyor belt speed. The conveyor belt motor is fed off the PCB.

Does anyone see any reason why the neutral needs to be open when the sander is not in use? In other words, any reason I can't splice all the neutrals together? FWIW, the switch is no longer made.
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I don't see a technical problem at all. Of course you will void the UL or NRTL seal, but it's your property, right?
 
Ryobi sells a fair amount of product in Australia. The 120V there is actually center tapped ground so each leg is 60V to ground. maybe it was made that way so it could be used in Australia and the US.

It is your property. i don't see why you can't modify it in any way you see fit.
 
That makes sense, Bob. Thanks.

The only thing that made me question bypassing the switch on the neutral was the PCB. While I can't see how a closed neutral on the PCB could cause any problems, I don't have a schematic to run through so I'd know for sure. But if I fry the PCB, the drum sander becomes an anchor.

Oh well, here goes nothing...
 
There may have been a good reason TO isolate the neutral (i.e. the Australia issue, which I was unaware of, so thanks), but there is nothing here saying that you CAN'T switch the neutral. So they probably decided that it meant fewer different versions.
 
Jraef said:
There may have been a good reason TO isolate the neutral (i.e. the Australia issue, which I was unaware of, so thanks), but there is nothing here saying that you CAN'T switch the neutral. So they probably decided that it meant fewer different versions.
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And may be carryover on designs for different systems (and tools) to just switch all poles of the supply - so all are about the same. Might even use same switches for multiple tools even if they exceed the need on some of them.
 
kwired said:
And may be carryover on designs for different systems (and tools) to just switch all poles of the supply - so all are about the same. Might even use same switches for multiple tools even if they exceed the need on some of them.
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Also a high possibility. Parts are cheap, having to maintain nearly duplicate inventory and different assembly processes is what ultimately costs money in the manufacturing game. When I was in manufacturing design, we looked for every angle we could find to make things as uniform as possible, even to the point that in a few cases different model numbers were different only by the number itself, and the price because for the higher price you got another “feature”, which was actually there anyway. Case in point: for most breaker manufactures, the difference between a breaker labeled for 35kAIC and one labeled for 65kAIC is the label and the price. They will defend their opposing argument to the death (because they are paid to do so), but they can’t deny it to anyone who was an insider at any point in their career. Once you know, you can’t in-know it... of course if you want to USE it at the higher rating, you need that label so you are stuck and it doesn’t matter in the long run that you know you are getting screwed...
 
Switch would be usable for 240 units if so rated....cuts down on inventory.
 
petersonra said:
Ryobi sells a fair amount of product in Australia. The 120V there is actually center tapped ground so each leg is 60V to ground. maybe it was made that way so it could be used in Australia and the US.

It is your property. i don't see why you can't modify it in any way you see fit.
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HMMMM!!!

All consumer appliances sold in Australia are 240 VAC. Residential service drops only have two wires plus the messenger cable.

A homeowner can request service for a high demand load for say a welding machine or for a machine shop for example. . . and POCO will provide a separate service drop with a separate metering.

Yup, we do share the language but not their voltage.

Sorry for the audacious impertinence.:ashamed1:
 
myspark said:
HMMMM!!!

All consumer appliances sold in Australia are 240 VAC. Residential service drops only have two wires plus the messenger cable.

A homeowner can request service for a high demand load for say a welding machine or for a machine shop for example. . . and POCO will provide a separate service drop with a separate metering.

Yup, we do share the language but not their voltage.

Sorry for the audacious impertinence.:ashamed1:
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Yes I questioned that too. I have engineered some article 645, 60-0-60v balanced power systems in studios but I don't think that's standard anywhere in the world.

Now the North American split phase system is actually a balanced 240v system when you draw it out. And AFAIK, the European 240v wall outlet voltage is a service grounded neutral just like North America?
 
Andy Delle said:
Yes I questioned that too. I have engineered some article 645, 60-0-60v balanced power systems in studios but I don't think that's standard anywhere in the world.

Now the North American split phase system is actually a balanced 240v system when you draw it out. And AFAIK, the European 240v wall outlet voltage is a service grounded neutral just like North America?
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Those European systems are 415/240 (or 400/230) volt wye systems. Individual single phase customers only have one phase and a neutral brought to them. Remote areas may be only two wire single phase source - but is 240 volts with one conductor grounded. Either way you get one grounded and one ungrounded with 230-240 volts between them. If you have need for three phase or need higher capacity in general - then you get all three phases plus neutral.
 
Andy Delle said:
... AFAIK, the European 240v wall outlet voltage is a service grounded neutral just like North America?
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The circuits may be grounded, but I seem to recall that receptacles in Germany are non-polarized, so a DPST switch might still be needed to assure that the hot wire is switched.

Or maybe they don't care which wire is switched as long as the case is either grounded or non-conductive. Maybe assuring that the hot wire is switched is a purely-American quirk?
 
drcampbell said:
Maybe assuring that the hot wire is switched is a purely-American quirk?
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Sort of. With a two wire load the load stops operating if you open either supply conductor.

Things like screw shell lampholders isn't a bad idea to connect the grounded conductor to the shell, and to open the ungrounded conductor for some additional safety.

If you have a two wire appliance, tool, etc., don't have a polarized plug, and only a single pole switch in the item - you have 50-50 chance of switching the ungrounded conductor. Most users won't know or care, it still turns on/off when you operate the switch.
 
Dispensing with a DPST and connecting neutrals together may not be a good idea because a surge could access more readily.
 
Sahib said:
Sorry, kwired. I was just trying to justify DPST design of OP.
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Which best reason IMO mentioned so far is less parts to have to stock for the manufacturer. Though even if you have something with two ungrounded conductors - a single pole switch still opens the circuit and stops operation.
 
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