O/T Contactor Wiring Convention Are there hard and fast rules on direction?

[gbradley]

I was working with a licensed electrician in another state.
He had a 220 contactor wired with the supply coming up through the bottom, and his leads coming out the top of the contactor going to his controller.
I told him that it wasn't right, and he should have the supply power enter the contactor from the top.
He said "what difference does it make?"

Have you ever seen this written down as gospel as to what the convention should be?

 

[bce123]

It makes it harder for the electrons to flow up hill !!!!!

 

[chavak]

He said "what difference does it make?"

Have you ever seen this written down as gospel as to what the convention should be?

It makes a lot harder to troubleshoot, when all your system is the other way around.

Never seen the rules, - but in general, industry standard is 'input on top'

 

[The Plc Kid]

There is no rule that states it has to go in the top just a good practice.

Many OEM's do wire contactors on the bottom. Many newer screw type compressors like our kaeser units have contactors that are supplied frpm the bottom as power to the cabinte comes in the bottom and motors leads are through the bottom of the cabinet.

I don't like it and really could not ever see myself doing it but it is not illegal.

Just a crappy practice in my book IMHO.

 

[Eric Nelson]

If the contactor is labeled L1, L2 L3, and T1, T2, T3, then maybe you can argue that he connected the line to the (clearly marked) load terminals? I'd be interested to see how he wires a starter...

As everyone else said, there is no requirement, just standard practice. Much like the orientation of a receptacle. Ground up, or ground down? I feel it's 'safer' with the ground at the top, but then what do you do with a 4-Plex receptacle? No matter how you orient it, the 'hot' slot is at the top...



-Eric

 

[Saffa]

I've seen both, especially with circuit breakers where the bus bar gets connected on the bottom and the load wiring out the top. residential sparkies do this because more often than not, the installation wiring is going up into the roof cavity.

Having said that, when we're building cabinets I do as most other people do in that line goes in the top, load out the bottom.

Certainly doesn't work the other way around for VSDs and Soft Starters!

 

[JeffKiper]

Eric It is an "optical contusion" as one old timer would say. Not an illusion but a contusion.
You have to install them backwards. That way they neutral is In the outside and the hot is in the middle.
If you invert negative logic that is wired incorrectly does that make it a positive negative?


There are several devices that are marked with line and load on them. Think about if you have a type E starter and wire it from the bottom. Your starter can still get pulled in even when the load is disconnected. I am not a big fan of that setup.

 

[gbradley]

...No matter how you orient it, the 'hot' slot is at the top...
-Eric

I think that you need to buy this style.

 

[Tharon]

I feel it's 'safer' with the ground at the top.

Why do you feel this?

I always feel it safer with the ground at the bottom. The idea being that if the plug ever sags down (gravity, weight of the cord, etc) the ground would be the last prong to be removed.

With the ground up, it would be possible for the cable/plug to sag, and disconnect the ground while the hot and neutral remain connected. Now you have a device that is ungrounded that was designed to operator with a ground.

Plus, it seems that all of the transformer plugs are designed to be plugged into a receptacle oriented with the ground down.

 

[Ned_Flanders]

Why do you feel this?

I always feel it safer with the ground at the bottom. The idea being that if the plug ever sags down (gravity, weight of the cord, etc) the ground would be the last prong to be removed.

With the ground up, it would be possible for the cable/plug to sag, and disconnect the ground while the hot and neutral remain connected. Now you have a device that is ungrounded that was designed to operator with a ground.

Plus, it seems that all of the transformer plugs are designed to be plugged into a receptacle oriented with the ground down.

I feel it's safer living in the Uk where the earth is physically longer than the line conductors in any plug/socket arrangement!

 

[Tharon]

It's longer in the US too. But metal bends, and I guarantee I could push down on the plug enough to bend the ground out of the top and keep the hot/neutral prongs connected.

In industrial use, pulling down on cables from high mounted receps, or pushing down on low mounted receps, has been fairly common. I'd much rather have the ground be pushed in always than have a chance to pull out from a safety point of view.

 

[Eric Nelson]

Why do you feel this?

For many of the reasons stated in the first part of this discussion...

http://www.mikeholt.com/technical.p...ptacles - Ground Up or Ground Down? (9-23-99)

To be fair, the second part of the discussion promotes your method...

There is a valid argument on both sides, which I guess is why it's not in the code book...



-Eric

 

[MikeW]

Label the Contactor When It's "Backwards"...

I have come across a few of these installations over the years and the first thing I do is label it as "POWERED FROM BOTTOM" or a directionaly arrow so the next guy (or myself when I come back years later and am having a senior moment) thats placed in an appropriate location.

 

[OkiePC]

As for household receptacles, I have always preferred them ground down...just because...

About 4 years ago, at home, I had a metal wall plate fall off and land on the hot wire and let some smoke out of the wiring...The plate fell off because of a missing screw from two years earlier when I painted the room... So, now, I agree that ground up would be safer, no matter how upside down looking it is. Metal wall plates might be a no-no too, though...

I really don't like power contactors being wired upside down though. There are times when it is better but agree with comments about labelling those that are done that way.