# high HP (250-400 HP) motor installation



## erics37 (May 7, 2009)

crashprone said:


> Hi guys,
> 
> Long story short, I'm looking at getting a 250-300 HP motor set up, and I'm specing out my panel. Unfortunately I've never actually used a 250 HP motor before. What kind of wiring is available in the box? Is it like the smaller HP motors that just have wire leads to ring terminal on? Pretty sure I don't have a wire nut that big! Could I do two wires per terminal? It seems a lot easier to run a pair of 2/0 wires than 1 400 kcmil wire per phase.
> 
> ...


What voltage is it operating at?


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## Nick0danger (Aug 19, 2012)

big motors have big pecker heads, and most have terminals, and are very nice to terminate, no rubber tape or shrink.


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## xlink (Mar 12, 2012)

Maybe thermal protection connections in the jb if you want to go that route.


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## mbednarik (Oct 10, 2011)

Nick0danger said:


> big motors have big pecker heads, and most have terminals, and are very nice to terminate, no rubber tape or shrink.


Rubber tape and shrink are things of the past, try a burny bit-4 sometime.


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## micromind (Aug 11, 2007)

Most motors that size are single voltage and have either 6 or 12 leads. They also have huge knockouts, usually threaded, sometimes one, sometimes more than one. You'll almost certainly need to use reducing bushings. 

Most of the time, you're better off using two parallel conductors rather than one big one. 

A lot of big motors have lugs crimped on the leads. 

I just connected a 400HP motor today, it had 12 - 3/0 leads. I had two parallel 350 copper in two 3" sealtites. I used 6 hole Polaris blocks, similar to the ones shown above. 

If you plan your wire layout, it's not too hard to connect all those wires. 

If I use split bolts or crimp lugs and bolts, I start with a layer of cheap black tape applied sticky side out. Then I use a ton of 130C followed by a couple of wraps of 88 or 33. Some guys use Cambric, I don't. When (not if; when) the splices need to be taken apart, just slit them open and they peel right off. If you start sticky side in, it'll be next to impossible to get the tape off. 

The main key is to plan your wire layout before you start. Otherwise, you'll be fighting it all the way.


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## glen1971 (Oct 10, 2012)

Depending on the motor terminal box configuration, it may be nexessary to replace and install a NEMA rated junction box..We did 2 - 600 hp, 480 volt motors on one job and had to redo it 3 times, cuz the engineer didn't like the junction box he was specifying... Fortunately (and rarely) he was changing his mind to larger boxes and had no problems at all in signing the extras to do the work..

I've never used the connectors shown above.. Are they CSA'd? In the past I've either used: Ring connectors and MSC boots or with 88 and 130 taped as as stated above with the first layer sticky side out.... Or using stnad-offs and set screw connections (usually with higher voltage motors..


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## JRaef (Mar 23, 2009)

Most big motors I have seen lately do not have terminal blocks, they have crimped lugs. The "official" way I was trained in IBEW school waaaay back when was to crimp on ring terminals to your leads, bolt the terminals together using grade 5 hex bolts and lock washers, cover with 2 layers of varnished cambric tape so that it doesn't stick to the bolted connection, followed by 3-4 layers of fusing rubber tape like 88 to protect against it wearing through by vibrating against the sides, covered by 2-3 layers of good black vinyl tape like 33+ to keep the rubber tape in place intil it fuses. Using 33+ sticky side out I suppose will do the same thing as the varnished cambric, unless the connection gets hot, in which case it might melt and make a mess. I know, it's not supposed to get that hot... I'm just talking about reality here. We all make mistakes sometimes.:blink:

All that said, more recently I too have been seeing people who know they will have to remove and service the motor regularly, replace the peckerhead box with a bigger Hoffman style box and mount a connection block in it, either stud to stud for crimp lugs on both sides or stud to mechanical lug if they don't want to crimp onto their lead cables. If the connection block is mounted down, there is no need to worry about rubbing through the insulation, but mounting it down means having to meet wire bending space requirements, which means a bigger box.


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## ampman (Apr 2, 2009)

micromind said:


> Most motors that size are single voltage and have either 6 or 12 leads. They also have huge knockouts, usually threaded, sometimes one, sometimes more than one. You'll almost certainly need to use reducing bushings.
> 
> Most of the time, you're better off using two parallel conductors rather than one big one.
> 
> ...


what type of starter did you use for that


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## Big John (May 23, 2010)

I had one this morning I wish I'd taken a picture of: 250HP 480V. Opened up the peckerhead and saw tape-balls the size of cantaloupes. Fought my way though the layers of 33 and mastic and eventually found a damn Polaris connector at the center of the ball. :wallbash:

Apparently someone was really used to using split-bolts.


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## crashprone (Feb 21, 2013)

Guys! Thanks for all the help! This'll make it a lot easier to get my wiring laid out ahead of time. Also gives me some great advice on the connectors! Thank again, Gents!


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## Cow (Jan 16, 2008)

Big John said:


> I had one this morning I wish I'd taken a picture of: 250HP 480V. Opened up the peckerhead and saw tape-balls the size of cantaloupes. Fought my way though the layers of 33 and mastic and eventually found a damn Polaris connector at the center of the ball. :wallbash:
> 
> Apparently someone was really used to using split-bolts.


What....the....****?

I cut the splices apart on a 200HP the other day, it still makes me mad when people don't use varnished cambric!

I use insulated taps on motors as much as possible. I don't have a problem cutting factory crimped ring terminals off.....:whistling2:


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## Jlarson (Jun 28, 2009)

JRaef said:


> All that said, more recently I too have been seeing people who know they will have to remove and service the motor regularly, replace the peckerhead box with a bigger Hoffman style box and mount a connection block in it, either stud to stud for crimp lugs on both sides or stud to mechanical lug if they don't want to crimp onto their lead cables. If the connection block is mounted down, there is no need to worry about rubbing through the insulation, but mounting it down means having to meet wire bending space requirements, which means a bigger box.


Polaris or a new box and blocks for me, split bolts or back to back crimps and tape as an extreme last resort only, hate taping stuff.


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## Jlarson (Jun 28, 2009)

Big John said:


> I had one this morning I wish I'd taken a picture of: 250HP 480V. Opened up the peckerhead and saw tape-balls the size of cantaloupes. Fought my way though the layers of 33 and mastic and eventually found a damn Polaris connector at the center of the ball. :wallbash:
> 
> Apparently someone was really used to using split-bolts.


:laughing: Somebody went full ****** on that one.


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## Big John (May 23, 2010)

Jlarson said:


> ...Hate taping stuff.


 For some stupid reason, I enjoy making multi-layer tape splices.

But I will admit that they are almost always more fragile than a manufactured insulated term, and it consumes a ton more labor.

In my defense, I did not retape the Polaris lugs.... :whistling2:


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## John Valdes (May 17, 2007)

Cow said:


> What....the....****?
> 
> I cut the splices apart on a 200HP the other day, it still makes me mad when people don't use varnished cambric!
> 
> I use insulated taps on motors as much as possible. I don't have a problem cutting factory crimped ring terminals off.....:whistling2:


I hear you loud and clear on the varnish cambric.
I come from an age where there were no Polaris taps and I had to use ring lugs with bolts and washers or split bolts (bugs/kearny's).

Then insulating with three different (3) materials.

Varnish - _Wrap varnish tape sticky side up for the first layer._
Rubber Tape (Scotch)?
Plastic Tape Scotch 33
Friction Tape

Way back, the varnish tape had no glue. No sticky side.
We never let the varnish tape sticky side to come in contact with the connection. Wrap first few turns with sticky side up. Then rotate to finish sticky wrapping. Tight.
Then a good layer of rubber (The wide thick rubber) soften all corners. Finish with several wraps of Friction tape. 

The friction tape is old school and I am not sure they even make it anymore. It has little if any dialectic strength/rating.
But, it is tough and a provides very good mechanical protection.


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## micromind (Aug 11, 2007)

ampman said:


> what type of starter did you use for that


Soft start with a bypass contactor.


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## sparky970 (Mar 19, 2008)

We just did a 500hp, 480v motor and drive fed with parallel 500's. Motor had 3 wires per phase in the peckerhead, which was about the size of a toaster. We ended up putting. A 24" x 24" NEMA 4x j-box on it. Mill spec is lug and tape. Double half lap of VC, 130c, and 33


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## Cow (Jan 16, 2008)

sparky970 said:


> We just did a 500hp, 480v motor and drive fed with parallel 500's. Motor had 3 wires per phase in the peckerhead, which was about the size of a toaster. We ended up putting. A 24" x 24" NEMA 4x j-box on it. Mill spec is lug and tape. Double half lap of VC, 130c, and 33


You have to wonder if the people who design motors have ever actually wired them? I've wired a bunch of motors with small peckerheads at 480v, I have no idea how they expect you to ever be able to wire them for 240V!!!! Thank god it's almost all 480 3 phase around here!


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