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Old 03-15-2018, 05:07 PM   #1
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Default Need to understand wiring designations on drawings

I have a 25k sqft machine shop facility that's in its final stages of construction. Location is Houston, TX. We are trying to make the final decisions on transformer size, placement location, whether or not to pair machines, etc. I'm trying to get a better understanding of the wiring designations on the plans themselves.

On the panel schedule next to each CNC machine the wire size is listed as 3#1 and next to "via transformer" it says 1#6G. Below those two it says 1-1/2 deg c.

Are wire sizes not single number sizes?
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Old 03-15-2018, 06:50 PM   #2
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Not sure what you mean 3-#1 means 3 pieces of 1 awg wire
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Old 03-15-2018, 06:52 PM   #3
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I have no idea what 1 1/2 degree C means--

1 1/2" is a pipe size and temp rating is usually 75C or 90C
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Old 03-15-2018, 08:28 PM   #4
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Not sure what you mean 3-#1 means 3 pieces of 1 awg wire
Are you not sure what 3#1 means? or does it mean 3 pieces of 1 awg wire? "3 pieces" doesn't seem specific enough to be on a set of building plans.
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Old 03-15-2018, 08:34 PM   #5
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Are you not sure what 3#1 means? or does it mean 3 pieces of 1 awg wire? "3 pieces" doesn't seem specific enough to be on a set of building plans.
It does to Electrician's. It's just EE shorthand. EE stands for Electrical Engineer ( see what I did there). 3 #1 means 3 pieces of #1 awg wire, 1 #6 in an 1 1/2 " conduit.

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Old 03-15-2018, 08:38 PM   #6
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it says 1#6G
One wire, #6 for the Ground.
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Old 03-15-2018, 08:46 PM   #7
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Three #1's and a #6 ground (copper) in a 1-1/2" conduit. The degree thing is a typo. In 1-1/4" conduit it's 35% fill. They must have gone next size higher.

A better plan would would show the transformers listed as T-1 or T-2 etc... and have a transformer schedule for the primary, secondary and electrode conductor size as well as fuse size, conduit sizes etc... Much simpler. Although some information would be repeated on the panel schedule.
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Old 03-15-2018, 09:50 PM   #8
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After 18 more posts I can post a screenshot of the panel schedule.

The plans have been drawn up already, the engineers designed for the use of 480v on the machines, each machine has it's own individual transformer at 75 kva. I guess the benefit to individual transformers is if one goes down, only one machine sits idle. We're just wondering if it would be more economical to have a larger transformer with several machines hooked up to it. Although, I'm assuming you can wall mount the 75 kva but you can't a bigger transformer? Floorspace is expensive, also limits access for floor polishing machines. We could install a larger transformer outside, but would require a longer run of wire, would the size change? I guess, I just need to get an idea of at what point does it make sense to go one route over the next? How do you determine what's most economical? Are there some online resources you can refer me to?
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Old 03-15-2018, 09:54 PM   #9
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After 18 more posts I can post a screenshot of the panel schedule.

The plans have been drawn up already, the engineers designed for the use of 480v on the machines, each machine has it's own individual transformer at 75 kva. I guess the benefit to individual transformers is if one goes down, only one machine sits idle. We're just wondering if it would be more economical to have a larger transformer with several machines hooked up to it. Although, I'm assuming you can wall mount the 75 kva but you can't a bigger transformer? Floorspace is expensive, also limits access for floor polishing machines. We could install a larger transformer outside, but would require a longer run of wire, would the size change? I guess, I just need to get an idea of at what point does it make sense to go one route over the next? How do you determine what's most economical? Are there some online resources you can refer me to?
Sounds like it would be a hell of a lot cheaper to put in a 480v service to handle the machines and then either a)use a transformer for the 120/208 loads or have a separate 120/208v service. That's assuming I am understanding you correctly.
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Old 03-15-2018, 10:06 PM   #10
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Sometimes the transformers are meant for harmonics. Drives like you have in a CNC can be dirty power. A couple is fine but if you have a lot or it's the majority of the power, that's the reason.

Also with arc flash concerns if the transformer is under 125 kVA and the output voltage is 208 or less, no PPE needed. So that's a great reason for several smaller transformers instead of one big one.

It does save money to have fewer big transformers but there are goid reasons to have more small ones.

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Old 03-15-2018, 10:10 PM   #11
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I don't know about the Carolinas, but around here a line reactor is a hell of a lot cheaper than a full sized dry transformer to feed a piece of equipment.
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Old 03-21-2018, 05:41 PM   #12
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Sounds like it would be a hell of a lot cheaper to put in a 480v service to handle the machines and then either a)use a transformer for the 120/208 loads or have a separate 120/208v service. That's assuming I am understanding you correctly.

My mistake, the service going in is 480v. We are using transformers to step down from 480v to 208 or 220 for each piece of equipment.

It's my understanding that it's best to have the transformers within 10' of the machine. Reduced wiring cost, fewer disconnects required, etc.

We don't want the transformers on the ground next to the machine, makes it hard to work on the machine and keep the machine area clean, also might make it difficult to space the machines closer together.

We're willing to spend a marginal difference in wiring cost to put the transformers up on the wall away from the machines.

If Transformers are further than 10' away from the machine, I'm guessing that would mean there will need to be a disconnect on the secondary side of the transformer? Then we will have to run the required wire size all the way to the machine.

What I want to figure out now is what combination of transformers we should get. I doubt we would get anything larger than 125kva, they would all be 45, 75, or 125 kva. I'm not sure how heavy a 480 to 208 transformer would be, I know the 45 kva are like 380 lbs.

I want to figure out what breaker size and wire size would be required on primary side and on secondary side. On secondary side the wire size is also dependant on length of run.

I want to figure out the best way to mount the transformer on the wall to save on floorspace.

Here's a list of the machines and their rated capacity:

Asset # Description Rated Capacity KVA
1 Doosan 300LC CNC Lathe 44.43
2 Doosan DMV 3016L CNC Mill 32.12
6 Doosan DMV 4020 CNC Mill 39.52
7 Doosan DMV 4020 CNC Mill 35.8
8 Doosan 240B CNC Lathe 32.62
9 Doosan 300LC CNC Lathe 45.14
10 Doosan 300C CNC Lathe 45.14

12 Mori Seike NL3000Y 56
13 Mori Seike NL2500 39
14 Mori Seike NL2500 39
15 Mori Seike NL2500Y 50
16 Mori Seike NL2500Y 50

I need to find out how many taps can be made into a single transformer. Our total KVA is 508.77. The most cost efficient one seems to be the 150kva. We could go with (4) 150's and that would give us 600 kva and would give us some spare capacity.
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Old 03-22-2018, 05:56 AM   #13
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How many (secondary) taps? Get an Ilsco or similar catalog. They make transformer lug kits with near on infinite holes; just need to match the hole pattern on the transformer. Secondary protection is what you should more rightly be concerned about- six disconnect rule.

I really feel in my gut you're screwing up by not doing a separate transformer for each machine. In the machine tool world, it's as much for stepping down the voltage as it is for isolating transients. Plus, do you want one transformer failure (or appurtenances associated with that transformer) to really bring down 4 machines? You're talking about bringing down nearly a million dollars worth of VMC's to save a few thousand on the initial install. I'm not sure if you're the electrician employed by the machine shop or if you work for a contractor, so your motivations may be different, but it's something to think about.

Oh, and I agree that flying the transformers is the only thing to do in a machine shop. Chips, coolant, compressed air... all are incompatible with floor or skid mounted transformers. You can fab up some crap from Kindorf, buy a transformer wall bracket from the catalog, or make something from welded angle iron. It's done every day, so it's a pretty simple affair that shouldn't require much thought.
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Old 03-22-2018, 06:26 AM   #14
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On the line reactors vs. transformer comment I distribute and install both. If you need a transformer anyway, no reason do use line reactors instead. Plus it isolates all ground faults and all even harmonics, and converts voltage. So if you already need a transformer use it. If you don't the line reactor does OK.

Wire size is first by Code second by voltage drop third by length of conduit (magnetics). Normally it's never a problem unless you have a lot of load going a long way (hundreds of feet). It's a simple exercise for any licensed electrician to do it by Code. The Code book has tables and translating kVA to amperes is a basic calculation that is on the license test.

Second you do NOT go running a hundred "taps " off a transformer secondary without protection. The most common way to do distribution is the same as the one in your house just bigger.

Third by Code the wire size is set by the overcurrent protection. So if I had say a 500 kVA 480 :208 transformer with 10 fused disconnects the cable going to each would have to be sized for around 1400 A which would be bus bars or multiple 500 MCM cables per phase, plus a big junction box at each disconnect to size down to the disconnect terminal size. With a 50 kVA transformer it's around 140 A which is easily manageable with a single conductor per phase but still expensive wire. At 480 V it would be down to 600 A per phase for the same current but a panelboard on the 480 side knocks the 480 V side down to roughly 60 A which is an easily manageable and cheap wire size you could buy at Home Depot if you had a failure in the middle of the night. Plus all the other advantages.

A 500 MCM cable is NOT like pulling house wire. It is about 1" in diameter and only bends with tools. It requires pullers to pull it in. At least cost effectively. I hve done it by hand but its slow and lots of helpers for most runs. The installation labor alone triples. Your $5/foot cost becomes more like $50/foot.

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Old 03-23-2018, 11:29 AM   #15
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If you have one larger 480-208 transformer to feed multiple machines, you then must add a 208V distribution panel, breakers etc., plus local disconnects at the machines. Then if some day a new machine gets installed there and needs 480V, you only have 208 at that spot, so you need to run new 480V circuits to it.

By having a transformer at each machine, there is no need for a 208V distribution panel, just the local disconnect. Then if a future machine needs 480V, it’s already right there at the transformer primary.

So actually, this is someone planning ahead.
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Old 03-23-2018, 11:35 AM   #16
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Originally Posted by jmw_man View Post
I have a 25k sqft machine shop facility that's in its final stages of construction. Location is Houston, TX. We are trying to make the final decisions on transformer size, placement location, whether or not to pair machines, etc. I'm trying to get a better understanding of the wiring designations on the plans themselves.

On the panel schedule next to each CNC machine the wire size is listed as 3#1 and next to "via transformer" it says 1#6G. Below those two it says 1-1/2 deg c.

Are wire sizes not single number sizes?
What is a puzzle to you a j-man electrician can do in his sleep.

1 1/2 " Conduit...

Etc.

Fiddling with this stuff is not going to save you any money -- and is most likely to bring you to grief.
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Old 03-23-2018, 11:37 AM   #17
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Originally Posted by jmw_man View Post
After 18 more posts I can post a screenshot of the panel schedule.

The plans have been drawn up already, the engineers designed for the use of 480v on the machines, each machine has it's own individual transformer at 75 kva. I guess the benefit to individual transformers is if one goes down, only one machine sits idle. We're just wondering if it would be more economical to have a larger transformer with several machines hooked up to it. Although, I'm assuming you can wall mount the 75 kva but you can't a bigger transformer? Floorspace is expensive, also limits access for floor polishing machines. We could install a larger transformer outside, but would require a longer run of wire, would the size change? I guess, I just need to get an idea of at what point does it make sense to go one route over the next? How do you determine what's most economical? Are there some online resources you can refer me to?
Transformers will never 'go down.'

Get real.
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Old 03-23-2018, 05:35 PM   #18
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To be honest, in the 20 years we've been in business, we've never had a transformer failure, which is why we are considering few transformers with higher kva rating. It will also give the shop a cleaner look. I just want to make sure it isn't a problem to fly the 150 KVA transformers.

As for the transients comment, does the MDP not act like a large surge protector?
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