Intercept

[mstrlucky74]

Scenario, have existing 30A feeder from MCC to motor(blue line). Now they want to add VFD( highlighted in red) in middle of run and utilize extg. feeder. They are also replacing moto. Not 100% sure best way to do this. Would you pull back extg. conduit/wire to where about the VFD is and use that point as the intercept and run new from intercept point to VFD and from VFD to motor? Or would you leave existing run in place and just cut/ intercept the pipes at aprox the VFD location so you don’t need as much pipe/wire. Just not sure how you get the pipe off and have enough wire to splice.

Hope that makes sense. Thanks.

 

[PaulMmn]

What kind of distances are we talking about from the VFD to the motor?

You're going to have to cut the pipe at the location of the VFD; probably insert elbows and new pipe to the VFD.

I don't think there's much you can do to cut into an existing pipe and remove a section... wasn't there a thread around here not long ago about a 'clamshell' "T" for just such a circumstance? You'd have to open up enough length to splice in wires to the VFD and back. Probably no slack in the pipe!

What kind of shape are the existing wires in?

Looks like the VFD is closer to the MCC than the motor. Gently cut the pipe at the VFD, pull existing wires towards the motor far enough to get clean ends at the motor, new pipe to connect the old pipe to the VFD (snaking the old wire to the VFD). New pipe to the other end of the gap in the old pipe; new wire to the MCC.

 

[iceworm]

There have two or three recent threads about feeding VFDs. You may wish to look those up.

You didn't ask, however:

• Check the MCC feeder. If it is a Mag-only (MCP) breaker, you may wish to change that out to a TM CB
• Check the VFD name plate FLC. 430, Part X says the feeder to the VFD must be 125% the VFD input rating - doesn't matter what size the motor is.
• Most AHJs I have dealt with consider the VFD as the controller. And the disconnect has to be in sight of the controller. There is no forgiveness as there is with the motor. If the vfd contains a disconnect - you're good. If not and MCC mounted disconnect is not sight of VFD, you will need a disconnect at the VFD.

 

[mstrlucky74]

There have two or three recent threads about feeding VFDs. You may wish to look those up.

You didn't ask, however:

• Check the MCC feeder. If it is a Mag-only (MCP) breaker, you may wish to change that out to a TM CB
• Check the VFD name plate FLC. 430, Part X says the feeder to the VFD must be 125% the VFD input rating - doesn't matter what size the motor is.
• Most AHJs I have dealt with consider the VFD as the controller. And the disconnect has to be in sight of the controller. There is no forgiveness as there is with the motor. If the vfd contains a disconnect - you're good. If not and MCC mounted disconnect is not sight of VFD, you will need a disconnect at the VFD.

Ok I will and thanks but what does your info have to do with my question about best way to intercept feeder?

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[iceworm]

Ok I will and thanks but what does your info have to do with my question about best way to intercept feeder?..

Not a freaking thing. Which is why I said:

You didn't ask, however:

 

[mstrlucky74]

Not a freaking thing. Which is why I said:

Aaaahhhhhh...ty

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[sameguy]

If the wire is correct for the VFD then cut the pipe towards the motor so the wire will make it to the VFD, rework the pipe accordingly. New wire from VFD to motor, need new pipe for controls too.

 

[oldsparky52]

Sounds like this conduit is exposed and accessible. Cut the conduit and wiring in two. Modify both conduits so they are about 1' shorter each and install a 2' junction box (shallow is better) or better yet a 4x4x2' wireway. Pipe from here to the VFD and anywhere else you need to go. You'll have 1' of wire to splice into. If that's not enough, install a longer wireway.

This assumes there is room to do this.

But, I would want to pull new wire.

 

[PaulMmn]

Sounds like this conduit is exposed and accessible. Cut the conduit and wiring in two. Modify both conduits so they are about 1' shorter each and install a 2' junction box (shallow is better) or better yet a 4x4x2' wireway. Pipe from here to the VFD and anywhere else you need to go. You'll have 1' of wire to splice into. If that's not enough, install a longer wireway.

This assumes there is room to do this.

But, I would want to pull new wire.

Don't forget- the leads at the new motor won't be long enough (unless you stretch them).

 

[oldsparky52]

Don't forget- the leads at the new motor won't be long enough (unless you stretch them).

Hum, I believe we are speaking of two different scenarios.

 

[PaulMmn]

Hum, I believe we are speaking of two different scenarios.

No, you said cut the conduit, insert a wireway, add extra conduit and hook up the VFD. But you assumed that the wires at the new motor would be long enough as they are. I assume they won't be (they never are).

 

[oldsparky52]

No, you said cut the conduit, insert a wireway, add extra conduit and hook up the VFD. But you assumed that the wires at the new motor would be long enough as they are. I assume they won't be (they never are).

There would be 12" of wire that came from the motor in the wireway for splicing purposes. New conduit and wire from the controller to the wireway would extend the wires coming from the mcc and extend the wires that went to the pump. I don't understand what you are talking about the wires at the motor as far as what I'm talking about.

Now, the way I would do it is to remove the existing wiring, cut the conduit that was just cleared, turn them and run two conduits to the controller (if it's not a problem for the controller, you could just run one conduit and put a junction box where the original conduit was cut). Depending on the number of bends, you probably should just plan on putting a junction box where you cut the original conduit and then pull all new wire. But then, I might not get the job, huh?

 

[sameguy]

Mixing line with load on a VFD normally isn't good.

 

[oldsparky52]

Mixing line with load on a VFD normally isn't good.

So two conduits it is.

 

[PaulMmn]

There would be 12" of wire that came from the motor in the wireway for splicing purposes. New conduit and wire from the controller to the wireway would extend the wires coming from the mcc and extend the wires that went to the pump. I don't understand what you are talking about the wires at the motor as far as what I'm talking about.

Now, the way I would do it is to remove the existing wiring, cut the conduit that was just cleared, turn them and run two conduits to the controller (if it's not a problem for the controller, you could just run one conduit and put a junction box where the original conduit was cut). Depending on the number of bends, you probably should just plan on putting a junction box where you cut the original conduit and then pull all new wire. But then, I might not get the job, huh?

I thought you were talking about using the existing wiring. Since they're replacing the motor/pump, the existing wires would probably not reach. I was proposing pulling the existing wires far enough towards the motor to make sure they'd reach the motor, use new conduit to the VFD and back to the existing conduit, and new wire back to the MCC.