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DPDT Switch - Electrical nerds please assist

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Forum topic by KelleyCrafts posted 05-13-2017 08:09 AM 1524 views 0 times favorited 17 replies Add to Favorites Watch
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KelleyCrafts

2680 posts in 579 days


05-13-2017 08:09 AM

Ok I’m a nerd but not electrical. I do have general electrical knowledge but I don’t do it for a living so it’s not second nature for me.

What I’m doing you ask? I’m a loser at the moment and need to share my dryer outlet with my garage tools. It’s the only 240V plug I have and the expense of a new panel will be too much right now. I’ve already had issues with plugs because of switching them out too often, these things aren’t made to plug in and out often at all. So, I’m putting in a Leviton 1288 DPDT switch (center off) and an outlet for the 240 V I need. The problem, I wired it up and have 120 V at each input (line) on the switch and when I test each output side of the switch I get 120 V on one side but like 43 V on the other. I’m either starting to think the switch is broken or I read the specs wrong on it and it’s not truly ready to dump 240 V out?? I did just read while getting the link that it’s for 2 HP motors and mine are 5 HP but shouldn’t it still show a full 240 V at the switch line out parts?

http://www.leviton.com/en/products/1288

Please assist. The specs are at the link below so you don’t have to search but I would appreciate the knowledge transfer on this. I’m open to any questions, yes I know I should have it to the panel…etc. I’m being as safe as possible under the circumstances so let’s leave the safety police out of this yeah? I appreciate it.

-- http://kelleycrafts.com/ - pen blanks - knife scales - turning tools


17 replies so far

View Gilley23's profile

Gilley23

395 posts in 222 days


#1 posted 05-13-2017 10:32 AM

Flip the switch and take a reading off the load side of the switch. If you get voltage off of the load side then the switch is good.

If the switch is good then you need to check your wiring from point a to point B.

Good luck don’t die.

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Carloz

989 posts in 431 days


#2 posted 05-13-2017 10:54 AM

Did you wire it correctly ?

View mrg's profile

mrg

786 posts in 2839 days


#3 posted 05-13-2017 11:31 AM

Post a pic of the wiring because we are speculating what your doing. Also grab a book on basic electrical wiring at one of the home stores.

-- mrg

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pontic

505 posts in 448 days


#4 posted 05-13-2017 11:56 AM

Switch may be bad. I think you have it wired wrong. 48v is bleed from the other leg. We need a picture of what you did.

-- Illigitimii non carburundum sum

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KelleyCrafts

2680 posts in 579 days


#5 posted 05-13-2017 01:50 PM

I’ll get a pic in a little bit although not sure that would help.

I have the hot wires going to L1 and L2 on the diagram. Then an outlet for the dryer goes to A1 A2 and then the other outlet for the garage goes to B1 B2. All the grounds are tied together at the ground pull. So unless that part is wrong and they are supposed to be different, then something else is wrong.

-- http://kelleycrafts.com/ - pen blanks - knife scales - turning tools

View hhhopks's profile

hhhopks

650 posts in 2217 days


#6 posted 05-13-2017 02:03 PM

Always tough to troubleshoot remotely.
So it is all speculation.

Make sure your meter is on Volt AC when taking measurements.
L1-L2 should be approximately 240 V. L1 or L2 to ground should be approximately 120 V.

The switch diagram doesn’t show a neutral.
How did you measure to get 120 Vac? You should only get that value if you measure L1 to neutral, L1 to ground, L2 to neutral and L2 to ground.

As Gilley suggested, flip the switch (loads not connected) to one side and perform measurement (Let’s say A).
Measure the load side of the switch to ground. You should have 120 Vac for both (A1 & A2).
Also check the B side (don’t change the switch position). B1 & B2 should be near 0. If not, you most likely have miss wired (you got the wires going out to the the load mixed (Example: A1 w B1 and A2 with B2).

Taking volt reading of a “hot wire” to a reference that is floating (un-grounded) can result in wacky reading.

Hope this helps.

-- I'll be a woodworker when I grow up. HHHOPKS

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MrUnix

6017 posts in 2039 days


#7 posted 05-13-2017 02:32 PM

Where is the neutral for the dryer?

IMO, that is absolutely the wrong switch to be using… particularly since you say you have a 5hp load that will be using it. What you should be using is a manual transfer switch (3PDT w/center off), like this one at the BORG.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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TheFridge

8333 posts in 1326 days


#8 posted 05-13-2017 02:35 PM

If you ran a 5hp motor through a 2ho switch there is a good chance the contacts could be toast.

I’d check resistance from each common to their respective poles. If it’s not in neighborhood of 1/4 to 1/2 an ohm or less you have a problem.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View rwe2156's profile

rwe2156

2716 posts in 1320 days


#9 posted 05-13-2017 02:42 PM

Curious as to why you think you need a switch?

I’ve seen the suggestion of make a pigtail with dryer plug on one end and 240V recept on the other. This also ensures the dryer can’t be run while the machines are in use. I don’t like this because 40 or 50A (or whatever your dryer is) will be an amperage mismatch to the extension cord and will not protect the wiring. Even if the motor has an overload switch sh*t can happe. What if a piece of sheet metal dropped and cut through your wire (how do I know that?)

The best solution is find a couple slots in your panel and put in a dedicated 240v circuit for your machines. Even better that that, put in a subpanel.

20A breaker and 12G wire is rated up to 3HP. Use metal clad wire and surface mount on your shop wall. Its really quite simple but if you’re not comfortable with it, get an electrician.

Once you’ve done that, daisy chain several outlets in the circuit so you don’t have all that pluggin /unplugging ;-)

Its really well worth the expense to wire your shop properly.

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

View KelleyCrafts's profile

KelleyCrafts

2680 posts in 579 days


#10 posted 05-13-2017 03:46 PM

Hhhopks that’s exactly what I did. I measured L1 and L2 to ground, each 120V. With switch on A I measured A1 to ground 120V and A2 to ground is not 120V. Same thing for B1 and B2 I was expecting 120V on both like you say but I’m not getting it. I am however on L1 and L2.

It’s a 30A outlet by the way.

Unix my dryer only has 3 wires. Two blacks and a ground. I’ll possibly pick that switch up today instead. Although the outlet is only 30A.

Fridge I’ll check resistance when I get back to the project but I didn’t run anything off the switch yet. I was putting it in and the readings just weren’t right. Figured the switch wasn’t working right (it’s not) and wanted to double check my work since it was late.

-- http://kelleycrafts.com/ - pen blanks - knife scales - turning tools

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KelleyCrafts

2680 posts in 579 days


#11 posted 05-13-2017 04:14 PM

Well Unix, it looks like I’ll have to order that one it’s not available in store. I checked Amazon and didn’t find one as cheap or cheaper that was prime and didn’t see any at Lowe’s so maybe my search wasn’t good. After reading HHH’s reply I think the switch has a problem because what he said I should get I’m not getting and it’s wired as it should be.

I guess I’ll place an order for what Unix suggested unless someone chimes in today with a better option. Thanks for the input fellas.

-- http://kelleycrafts.com/ - pen blanks - knife scales - turning tools

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KelleyCrafts

2680 posts in 579 days


#12 posted 05-13-2017 04:29 PM

Actually MrUnix, the switch youinked shows you can control two power sources for one item. I assume that would be for a generator or street power going to one appliance of some sort for power outages or whatever. Am I missing something?

-- http://kelleycrafts.com/ - pen blanks - knife scales - turning tools

View Carloz's profile (online now)

Carloz

989 posts in 431 days


#13 posted 05-13-2017 08:48 PM

The right switch costs more than a panel. Installation is a bit easier than the panel, but regardless you must to get a permit to install it the same as with a panel. At the end of the day you are left with either sorry setup with two half useful outlets or a properly wired circuit with enough outlets for all present and future tools.

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MrUnix

6017 posts in 2039 days


#14 posted 05-14-2017 12:02 AM

Actually MrUnix, the switch youinked shows you can control two power sources for one item. I assume that would be for a generator or street power going to one appliance of some sort for power outages or whatever. Am I missing something?
- ki7hy

That is what transfer switches are typically used for… but it’s still just a switch and the electricity doesn’t really care one way or the other :)

(ground/neutral connections omitted for clarity)

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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KelleyCrafts

2680 posts in 579 days


#15 posted 05-14-2017 01:21 AM

Sorry Unix, since I posted I looked up some schematics on how that switch works. I’ll just wire it “backward” and it should be good. It’s ordered. You are seriously a go to on this forum for stuff like this. I think you directly or indirectly because of past replies to other schmucks like myself have helped me a ton with things like my makita 2030, PM72 with phase converter, etc. thanks a bunch man. I should be ok from here.

For the record however, I still think the first switch had a problem. I never ran any tools off of it, never even plugged one in. It definitely wasn’t feeding 120V off the one side of output lines. The other output lines on the opposite side had 120V so I was a little over half way there. But something wasn’t right. Hopefully the next switch does the job.

-- http://kelleycrafts.com/ - pen blanks - knife scales - turning tools

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