ANYONE HERE AN ELECTRICIAN?

[1958 delivery]

I am about to install a 3 phase lathe in my shop. I have 208/120 service. The lathe is going in about 10 feet from the interior breaker panel. My question is there is a separate fused shut off box installed next to the breaker panel that has the 3 phase wired in with fuses, no load connected. Do I come off that fused box or should I come from the breaker panel it self?

 

[LMBRJQ 60]

If you were in New Zealand i could tell you Mike
But your power is all upside down to me

Steve

 

[61BUBBLE348]

One thing Mike, just make sure your phases are correct otherwise your motor rotation will be reversed. To rectify this you change 2 of the phases over.

As long as you have the sequence, RWB, WBR or BRW, we use Red, White & Blue for Low voltage phase identification.

You will also need to check that the lathe does or does not require a Neutral. could be either star or delta configuration, star uses 3 phases and a neutral, delta uses phases only with the load across phases.

hope it helps.

 

[1958 delivery]

208 is a Y. I'm concerned if the existing fused box is the proper source

 

[Dewman]

I'm concerned if the existing fused box is the proper source

Does the Lathe have a nameplate? If so, the name-plate should have an amp rating or FLA (full load amps) rating. The name-plate may also have a min-fuse/breaker size and a max-fuse/breaker size. You would want the fuses & breaker to fall within the min-max rating.

The disconnect should be fed from a breaker in the breaker panel. Is there a breaker in the panel labeled for the disconnect? If so, what is the breaker size? What are the fuses rated (amps) for in the disconnect.

You should be able to use the 3-phase disconnect if the the fuses, wire and breaker are the right size for what the name-plate on the lathe is calling for.

Make sense? If you want to, you can PM me with your phone number.

 

[1958 delivery]

All the sizing, power, etc I have covered, I was a test tech for a few years for major utility. I don't know electricians stuff, is fused disconnect normal/acceptable. The 3 ph fused box is mounted right next to the panel, it's hot 208. Looks like the easiest way to run wire over to the lathe. The fuse size may be large, wire is definitely adequate, looks like #8. Haven't picked up the lathe until Friday but it's small, probably 2-3 hp so probably down in the 8 amp range. Also things like can I use armor wire exposed interior to the lathe. My thoughts are to use armor wire 12ga. One thing I can't see yet is what size breaker(if any) is connected to this disconnect. Another concern is the box is wired with the 3 phases but no ground (4th) wire?

 

[bobs409]

Well I'm not an electrician but I did stay at a Holiday Inn express last night. (I've been dying to say this one, couldn't stop myself)

 

[Mr Goodwrench]

Mike Pretty sure you can only get 208V from STAR and I kinda doubt your lathe will accept that you will just have to look on the motor and see if they give you a wiring pattern for 208V. If it has control circuits for relays and motor starters you will need to look at re-tapping the control transformer for 208V usually not a big deal. Not to question your intelligence but are you sure you have three phase power being delivered to your breaker box? I'm thinking with STAR you have three legs that will measure 120V to neutral and the 208V comes from phase to phase (square root of 3 = 1.73 X 120V = 207.8V I have re-wired many lathes and Milling Machines even some CNC and am getting ready to do this in my shop at home where I do NOT have three phase power and no way of getting it so I'm using a rotary phase
converter to generate the third phase for me. Hope this helps.

 

[1958 delivery]

Yes, it's 120/208. Yes any phase to neutral is 120V and phase to phase is 208v. The lathe was being run at previous owners shop on 208, pretty common system here. Motors rated at 220 or 240 run on 208. The 208 is close to the min required on those as long as the service is not under min.

 

[Mr Goodwrench]

Sounds like you should be good to go Mike, I would just wire it the way the previous owner did and let the chips start flying! have fun but be careful the end result of getting a part of your body in a rotating chuck aint pretty.

 

[1958 delivery]

Any electricians? Strange service to me. The main feed from the outdoor meter box comes inside and to a box just under the fused box, these cables continue to the breaker box and are the main feed cables. The main cables are spliced in this smaller box and those 3 lines run up into the fused box so the fused box does not come from a breaker. Inside this box is a fourth cable, I suspect the neutral or ground but it comes over from the breaker box and is laying unused in this smaller box, it wasn't run up to the fused box but looks like it could be Any ideas? I would post some pics but I left my camera at the house..

 

[1958 delivery]

Figured out the wires. The breaker panel does not have 3 phase, it has 2 phases and the neutral, so only single phase comes out of the breaker box. The fused disconnect box has all 3 phases to it but no neutral, that is the only source for 3 phase power. I imagine there is a T print for this but that's why I need an electrician, probably have to hire one.

 

[Mr Goodwrench]

Wish I could help you Mike but I'm stumped? I have mostly dealt with full three phase and mostly 460/480 V The 208 V is oddball to me although in industry it seems to be the standard for all the overhead lighting.

 

[1958 delivery]

I have one more question that maybe, just maybe someone can help. My disconnect box has 35 amp fuses that are 3" long. I would like to install 20 amp fuses but when I went to home depot anything less then 30mps is much shorter, like 1.5". Does anyone know if they make a 20-25 amp fuse that is 3" long?

 

[61BUBBLE348]

Mike, the fuse rating is purely for discrimination of the circuit,

in other words it is there to protect the cable going to the machine in an overload or short circuit situation, if your cable is rated at more than 30 amps you are good to go.

an example would be, 1000 amp cable protected by an 800 amp fuse at the transformer, then a 240 amp cable protected by a 200 amp fuse at the street, then a 120 amp cable protected by a 100 amp fuse at the building and a 45 amp cable protected by a 30 amp fuse at the switch board.

hope this helps.

cheers

 

[1958 delivery]

I need 20amp fuses. Does anyone know if they are available in a 3" fuse?

 

[1958 delivery]

OK, found it. Smallest 3" fuse is 35 amps, they make reducers to install the smaller fuses(0-30) in the larger box. Thank you internet.

 

[droptop62ss]

To run a 3 phase piece of equipment on signal phase you will need a phase converter .If you run a 3 phase motor on signal phase you will burn the motor up.
your other option is to change the motor to a signal phase motor .

 

[1958 delivery]

To run a 3 phase piece of equipment on signal phase you will need a phase inverter .If you run a 3 phase motor on signal phase you will burn the motor up.
your other option is to change the motor to a signal phase motor .

I have 3 phase power

 

[droptop62ss]

ok then you must have another panel in the building that feeds the fused disconnect . or is it feed from the panel that it is next to ?