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Sawmill

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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
This is going to be fun, customer bought a sawmill, and whoever wired it is running all of the motors off one breaker. Sizes from 5 hp all the way up to 150, I think he said!
 

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augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Other than a rats nest it may not be as bad as it looks on 1st glance. I believe the 3 larger starters are a wye-delta arrangement for the largest motor and the would be on that one breaker.
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
I’ve got to go to Ohio and disconnect all of it, don’t know what the rest of it looks like, but the customer wants to save as much of the conduit and wire as I can. All of it is ran by a 260 kva generator.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Sounds like a PIA job.....
Most likely he will want to to save the wirenuts also :)
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
hillbilly1 said:
It’s about 45 minutes from my favorite Ohio state park, Hocking Hills.
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We stay in cabins at Lake Hope State Park Wednesday through Sunday the first weekend of June when my motorcycle forum group ST-Owners has one of their events.

The other one I regularly attend, also Wednesday through Sunday, is at Backwater Falls State Park, WV the first weekend of October. Great fall colors in the mountains!

We usually ends up with around 50 to 60 people, many couples and some singles, around 40 bikes, mostly Honda ST1100s and ST1300s, a few Goldwings, BMWs, etc.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Not at all unusual in older sawmills. I was told by the old gaffers the idea was that if any one motor goes down, everything needed to shut down anyway. The lack of short circuit protection for the smaller motors (usually oilers or feed motors) was generally tolerated in the mill environment, where production is king.

Nowadays I would just slap on some of those IEC style Motor Protection Switches ahead of the existing starters. Fuses and fuse holders are cheaper, but they suck when it comes to keeping things running or getting them back on line in a hurry. I would open panels with fuse blocks in them like that and there would be boxes of fuses in the bottom, almost always too big so that they wouldn't blow. What's the point of that?
 
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garbo

Senior Member
Recommend that you get a shoe horn out ( after neatening up rats nest of wires ) to squeeze in fuse blocks to feed each motor starter. Use the short fuse blocks that are rated for use up to 600 volts.If they are worried about if one motor trips out and other motors continue to run you can wire in all of the overload contacts in series.
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
garbo said:
Recommend that you get a shoe horn out ( after neatening up rats nest of wires ) to squeeze in fuse blocks to feed each motor starter. Use the short fuse blocks that are rated for use up to 600 volts.If they are worried about if one motor trips out and other motors continue to run you can wire in all of the overload contacts in series.
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Yeah, wouldn’t be hard to interlock everything. Once I get up there to disconnect everything, I will have a better plan of attack.
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
ptonsparky said:
Looks similar to what ended up being my first PLC project at a small cattle feedlot.

Enjoy.
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I had a project many years ago that I wanted to go that route, but plc’s were still pricey then. It was for a Home Depot Expo store. They had an actual shower display with working shower heads and body sprays in an enclosed room with full height glass viewing windows. The engineers were concerned with too many showers being activated, and overflowing the drain system. I designed and built a controller that would not allow more than one shower display at a time to be activated. It would also limit the amount of time the heads ran. I wish I still had pictures of that. All mechanical relay logic.
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
It’s worse than I thought! This is the control “fuse” Cabinet is not grounded, pvc from generator, no ground pulled. At least they bonded the neutral.
 

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gadfly56

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
hillbilly1 said:
It’s worse than I thought! This is the control “fuse” Cabinet is not grounded, pvc from generator, no ground pulled. At least they bonded the neutral.
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I meant to ask, is the customer relocating the equipment, or is it staying in place?
 
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Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Jraef said:
Not at all unusual in older sawmills. I was told by the old gaffers the idea was that if any one motor goes down, everything needed to shut down anyway. The lack of short circuit protection for the smaller motors (usually oilers or feed motors) was generally tolerated in the mill environment, where production is king.

Nowadays I would just slap on some of those IEC style Motor Protection Switches ahead of the existing starters. Fuses and fuse holders are cheaper, but they suck when it comes to keeping things running or getting them back on line in a hurry. I would open panels with fuse blocks in them like that and there would be boxes of fuses in the bottom, almost always too big so that they wouldn't blow. What's the point of that?
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POCO view here.

I hate it when they do that. Upsizing the fuses instead of fixing the issue.
The problem on our end is upsizing that fuse now throws the overcurrent to our side. We have a few family owned mills on our system and a couple of them were blowing primary fuses when the motors jammed. 56kW PD, we have a 75 kVA bank, with fuses sized at about 125kW, blowing primary 14.4kV fuses
 
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