# Design build machine shop- derating nameplate?



## 460 Delta (May 9, 2018)

Will they be running every tool simultaneously at capacity? Usually machines aren’t all ran at the same time.


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## Coach529 (Sep 20, 2016)

460 Delta said:


> Will they be running every tool simultaneously at capacity? Usually machines aren’t all ran at the same time.


No. Of course some will be, but not all and not to 100% full load.


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## MDShunk (Jan 7, 2007)

Even if all machines are running, seldom do machines draw full nameplate horsepower. You run a 5hp mill or a 15 hp lathe and you're only doing "ordinary" work, you might only be using 2hp's worth of work on each machine. Same story with welders. Are they welding pop cans together with a big 200 amp tig machine or are they welding armor plate? 

This is why the NEC lets you do about anything you want under engineering supervision. 

For my own comfort level with situations like this, I prefer to calculate near full size. You don't know what machines will show up later, be swapped out, or how many new employees will be hired in the future. If it's a one or two man shop, and will likely stay that way, I'd be more inclined to calculate based on the continuous load plus the ability to start the two largest motors. 

You're unlikely to find any fantastic guidance in the NEC.


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## cdslotz (Jun 10, 2008)

If the service is existing @400A, you still need to provide a load calc to what this customer is using the space for....if it shows he needs a 600A or 800A service.....so be it.


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## 460 Delta (May 9, 2018)

Can they give you an idea of what machines will be running simultaneously? I don’t think you need to size the service to every machines nameplate rating. 
This sounds like a high leg delta in an older building am I correct? Try to watch putting a large single phase load on the B phase. Lights can be ran off the other phases also to even the load up.


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## Coach529 (Sep 20, 2016)

The local inspector was little help.....he referred me to article 220 and offered no advice.


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## Helmut (May 7, 2014)

You can put 1000A of machine shop stuff on a 400A service, if it's not all on at the same time, which it usually isn't.

If it's like most folks moving into a new space, budgets determine what gets done upfront, and what will have to wait a while. I doubt they would want to upgrade the incoming service, if what is existing will work somehow.

Install what they got, and sell them a new service upgrade down the road if they feel the need to expand in the future.


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## Coach529 (Sep 20, 2016)

Helmut said:


> You can put 1000A of machine shop stuff on a 400A service, if it's not all on at the same time, which it usually isn't.
> 
> If it's like most folks moving into a new space, budgets determine what gets done upfront, and what will have to wait a while. I doubt they would want to upgrade the incoming service, if what is existing will work somehow.
> 
> Install what they got, and sell them a new service upgrade down the road if they feel the need to expand in the future.


OK, but what about the inspection?


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## Helmut (May 7, 2014)

Coach529 said:


> OK, but what about the inspection?


What about it?

Tell the inspector you're only puting in 300A worth of machine stuff.
Add more later


The service is existing and code compliant correct?


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## paulengr (Oct 8, 2017)

If it’s existing Code let’s you monitor it for a period of time to get the real load data. Usually if I can do that much then I can look at what’s changing and estimate that at full load to be conservative.

If it’s new whether there’s an engineer or not you ask questions and estimate diversity factors.


Sent from my iPhone using Tapatalk


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## Coach529 (Sep 20, 2016)

It is an existing machine shop, running currently in Southern California.

The customer is going to move it to Northern Idaho.


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## MDShunk (Jan 7, 2007)

Coach529 said:


> It is an existing machine shop, running currently in Southern California.
> 
> The customer is going to move it to Northern Idaho.


Perfect! Get the last year's worth of utility demand data printout from the existing service from their poco.


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## paulengr (Oct 8, 2017)

MDShunk said:


> Perfect! Get the last year's worth of utility demand data printout from the existing service from their poco.



Agreed IF the utility has it. Not all do. Most of the ones that charge real time pricing take the average of the 3 peaks (15 minute averages) for the month or some similar calculation and they give you all the data pretty much for free.


Otherwise you can monitor it yourself for 30 days and take the highest 15 minute average. This Fluke advertisement/article talks about it:
http://www.fluke.com/fluke/uses/com.../articlecategories/electrical/loadstudies1735


Of course if you don't have one of those meters laying around (who does...), you can rent a decent one for a fairly reasonable price. Just keep in mind for 3 phase you'll be strapping 3 CT's and 3 voltage probes to a line. It's no big deal to do it with a pair of rubber (voltage insulated) rubber gloves especially with flexible CT probes where you can wrap them around almost anything. The voltage clips are usually the more irritating since it's often hard to find a good spot where they stay where they are clipped on. Put them on the conductor, NOT the bolt heads. If you have to use iron core CT's try to find a nice perfectly round conductor to clip them around...you get erroneous readings a lot on bus bars. The software side of these things is designed for just about any kind of power study you can think of, which is a nice way of saying it's WAY overly complicated and hard to navigate but for such a simple study usually you can get through it fairly quickly. Also make sure you have the charger plugged into it and good batteries because once everything is up and running (check in a couple hours just to verify), you're going to close the door and walk away for a month...


That's by Code and in a machine shop you might have to actually do this. With most industrial customers in reality you can pretty much figure out what their peak demand is in a couple hours or maybe a couple days with a little sleuthing. Walk through the electrical room and ask a bunch of questions about startups and operating conditions and they can pretty much tell you everything you need to know. A couple spot tests are usually all it takes to figure out their peak load. Technically you should still measure 30 days worth of data but I've never been asked for it


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## 460 Delta (May 9, 2018)

One other thing, if the existing machine shop is on a 480 volt system, you’ll have some changes to make on the machine tools to accommodate the lower voltage and higher current, motor connections and possibly wire upsizing and starter upsizing. 
Just another thing to keep in mind.


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## brian john (Mar 11, 2007)

Coach529 said:


> The local inspector was little help.....he referred me to article 220 and offered no advice.


What you wanted from him was not in his job description.

Monitor the load OR get the utility bills and see if they show peak demand.


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## MDShunk (Jan 7, 2007)

For industrial customers, I've generally found the plan reviewers (inspectors) much less fussy about a new service size than the power company's lines engineers.  It wouldn't be unreasonable to submit a permit application that said, simply, this equipment has been running on an XXX amp service for XX years with no overloads to note. In fact, I've done just that in a couple few jurisdictions. The worst thing that will happen is that it will get bounced back for more information.


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## Cow (Jan 16, 2008)

MDShunk said:


> Perfect! Get the last year's worth of utility demand data printout from the existing service from their poco.



This is what we'd do.

The printout can be sent in with the plan review. Super simple here in Oregon.


Have the customer get you the meter # and call their power company if you need to.


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## Coach529 (Sep 20, 2016)

Thanks for all the info guys.


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