ECN Forum Forums General Topics of the Trade General Discussion Area In over my head again...

Hey Guys...

I've got an upcoming project with a lumber mill (of sorts) that has moved to a building with an existing 480V Delta Service with three 50KVA cans, one per phase (obviously)...

The 480V goes Directly into a 75Kva Dry Type Xformer and gets converted to 120/208V Wye before going to a 225A three phase 120/208V panel.

There is no 480V Panelboard, of which I will have to add one...

Anyway...

In a nutshell, does three 50Kva cans give the same power as a single 150Kva can? In other words, can I get 180 Amperes at 480V outta this thing or just 60A?

The motor load is going to be HUGE.

Nameplates are largely unavailable, except on individual motors... Most are 460V or 230V, only a few are rated for 208V...

1> 40HP Blower
2> 10HP Blower
3> 5HP Tablesaw
4> 5HP Band Saw
5> 220V 3 Phase 145A Moulder
6> 5HP Router
7> 15HP Planer
8> 15HP Planer
9> 150HP Sander (not a typo) with 50HP Conveyor
10> 15HP Unknown Machine
11> 15HP Unknown Machine
12> 3HP Unknown Machine
13> 2HP Unknown Machine
14> Various Fractional HP tools and machines.

The Moulder will only operate on 220 3 phase... I asssume that 208 will not work and it will require a Xformer for 240V 3 Phase at 150A.

Just how big a service will they need?

Any and all help appreciated.

Virgil,

Let me tell you that I have never personally met an electrician or electrical contractor who ever made any money in West Virginia wiring a sawmill for a lump sum. Keep that in mind when you put a price on this.

The capacity of the transformer bank is the sum of the 3 pole pigs, so 180 amps is the answer.

Service size is = humongous & it is shown on page 335 of Allegheneys "Rules for Customer Service."

Actually, this is a small sawmill. I did some power factor correction up in Bartow at Interstate Hardwoods & they had a connected load in excess of 1000 hp if I remember right.

Let's take a crack at this, assuming everything is 480

largest motor 150 hp 180 amps
25% of largest motor 45
40 hp blower 52
10 hp blower 14
5 hp tablesaaw 7.6
5 hp bandsaw 7.6
moulder (about 60 hp) 77
5 hp router 7.6
two 15 hp planers 42
50 hp conveyor 65
two 15 hp loads 42
3 hp unknown 4.8
2 hp unknown 3.4

comes to about 548 amps & doesn't consider those minor loads or any lighting or any future growth.

I'd go with an 800 amp service. For economy's sake, it would might be cheaper to go with two 400 amp mains rather than an 800.

Good luck.

Tom

[This message has been edited by Tom (edited 09-28-2004).]

I think I'd look at 1200 amp service, to accomodate machines they haven't told you about, machines they will buy in 6 months, and for various heating, ventilation, lighting and miscellaneous loads. We've done a couple of specialty mill shops, that all 3 cases we had to upgrade the service AFTER the project started.

Thanks guys,

Fortunately, this is T&M, but if there's any way to lose money on a job... I'll find it.

Thanks again, fellas.

I have a feeling said customer will say no thanks and continue his search for those with a better control over the laws of physics than me... I'm sure he'll find someone who can make all this run on the existing service without a hitch... I mean, he "...has a 480V service already!" (his words)...

Virgil,

If the cheapskate won't hire you, keep your eye on this place. You may get called back after the POCO gives him grief about firing up a 150 hp motor with their dinky 150kva bank.

If you do get this work, make sure you check with the POCO about starting those 50 HP & larger motors with across the line starters, you may need to go to reduced voltage starting, especially on the 150 hp.

Tom

Now, he's willing to get rid of the big sander and go with a smaller, say, 25 HP unit.

largest motor 40 hp 52 amps
25% of largest motor 13
25 hp sander 35
10 hp blower 14
5 hp tablesaw 7.6
5 hp bandsaw 7.6
moulder (about 60 hp) 77
5 hp router 7.6
two 15 hp planers 42
two 15 hp loads 42
3 hp unknown 4.8
2 hp unknown 3.4

330 amps roughly without incidental, lighting, HVAC and misc loads.

The 150 KVA bank will pump out 312.5 A.

He's going to want to keep what he's got and make me work miracles with it...

Should I bail?

Thanks again!

In last post you said 150 kva will pump out 312.5??? I get the 180 u posted in your orginal post??

Heh... Yup..

Uh.. Well Uh, I Uh...

Hmmmm... How did I do that?



Guess I left out the /1.73 part...

Monday morning math... (grumble grumble)

Which illustrates perfectly that I'm in over my head...

"mayday! mayday! we're going down!!!!"

Geez... (shaking head ruefully at self)

[This message has been edited by sparky66wv (edited 11-01-2004).]

Will these all be running at the same time? How many guys in the shop? Would there be some way to isolate some of the loads with a transfer switch that will not allow the bigger loads to run unless all of the smaller loads are taken offline? That of course will depend on if he can run his business that way. He may just need a miracle.

That's up to you. I would, but we live and work in different enviornments. It sounds a little tougher out there, and you might have to try to turn it into a decent job. But then again that may take a miracle too.

Virgil,

If the 3 transformers belong to the power company, then that end of the deal is their problem.

I re-read your original post, but I don't see that you mentioned the size of the existing service. If it is not at least as big as your calculations for the motors indicate it should be, I'll just mail you the red sticker.

If the owner does not want to upgrade service to adequate capacity, I think I'd want a downpayment, T&M or not. You may not have to trash the whole service, you might be able to just add on another 200 or 400 amp disconnect, provided that you have CT metering & have not already hit the 6 disconnect limit.

You may still have a problem with the larger motors. Presuming you're dealing with Allegheny, they require you to consult them about any 3 phase motor over 19.9 hp. So you should prepare you customer for sticker shock if you need to get reduced voltage starters.

This thing is starting to smell bad. Either convince your customer that you know best or let him go the DIY route.

Tom