# Explosion proof



## MikeFL (Apr 16, 2016)

As in CO2? 
Like the stuff we put in our sodas?
The stuff plants take from the air to make sugar?


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## kb1jb1 (Nov 11, 2017)

CO2 is used to put out fires. 
Three things are needed. 1. Oxygen. 2. An ignition source. 3. Fuel or something that burns


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## micromind (Aug 11, 2007)

I don't see why it would be, CO2 is an inert gas........it doesn't burn and can't explode.....well, I guess it could if the pressure went too high......lol.


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## WronGun (Oct 18, 2013)

MikeFL said:


> As in CO2?
> Like the stuff we put in our sodas?
> The stuff plants take from the air to make sugar?


I suppose except its in a pressurized tank about 50’ tall, not that it should matter. 


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## gnuuser (Jan 13, 2013)

it wouldn't be needed providing that co2 is the only gas that would be stored in the place and it would be suitably dust /particulate free.
but we all know that rule is rarely ever followed


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## WronGun (Oct 18, 2013)

I have a lot to figure out on this job. 

I powered the interior equipment that uses the carbon dioxide a couple years ago. 

Now I’m moving the equipment and the massive tank to another building. So now I will not only need to re-power the equipment but also the entire tank containment area. 

I was wondering about explosion proof for pressurized tanks but it may not be required. 

I have (1) 500’ run of 480v/50a and (1) 480v/30a
And 2 runs of 500’ 120v/20a circuits 

Voltage drop calcs show I may need to run a panel for the 20a circuits.

It’s a very intense move as we are on a tight schedule and switchover. Moving from 1 plant to another plant. Production has a 72 hr shutdown max between the entire process. 

More questions to come, don’t you guys worry. Lol

No serious your help is always appreciated...


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## LEVY (Jan 28, 2021)

WronGun said:


> Is an explosion proof installation required for carbon dioxide ? Currently the existing installation is Rigid without exposition proof fittings .
> 
> 
> Sent from my iPhone using Tapatalk


What do you mean by explosion proof?

You mentioned fittings.

When we install explosion proof equipment on the oil fields, we mean no sparks on the open.

This is an electrician oriented forum, so most of us think about the electrical side of the "explosion proof".

You might be talking about the pressure side, I don't know.


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## WronGun (Oct 18, 2013)

I mine as well start off if anyone would like to help. 

1. Finding mixed info on 120v/240 single phase and 480v 3ph. power in same raceway. 

2. Grounding of exterior equipment. Tank will sit on a newly poured pad next to building Im figuring this this needs to be grounded back to the main building steel. In picture you can see ground come up and lug to the exterior frame supports. Bottom left of pic. 




















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## WronGun (Oct 18, 2013)

LEVY said:


> What do you mean by explosion proof?
> 
> You mentioned fittings.
> 
> ...


Yes I mean fittings, enclosures, sealing procedures like I’ve done at gas stations, propane filling stations which I understand are a far different than carbon dioxide


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## splatz (May 23, 2015)

I can't think of anything in the NEC that would require explosion proof equipment in the vicinity of pressurized non-combustible gas. All the hazardous location rules involve something combustible - flammable - explosive. 

However maybe you could put something in your proposal that requires the customer have it reviewed by an engineer. There's an engineer somewhere that's responsible for the pressurized gas system.


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## splatz (May 23, 2015)

WronGun said:


> I mine as well start off if anyone would like to help.
> 
> 1. Finding mixed info on 120v/240 single phase and 480v 3ph. power in same raceway


What did you find? As long as ALL the conductors have insulation higher than the highest voltage in the raceway, you can mix. AFAIK.


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## WronGun (Oct 18, 2013)

splatz said:


> What did you find? As long as ALL the conductors have insulation higher than the highest voltage in the raceway, you can mix. AFAIK.


That’s the info I have. If all conductors rated 600V im good. Is insulation color a factor or will tape suffice?


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## gnuuser (Jan 13, 2013)

splatz said:


> What did you find? As long as ALL the conductors have insulation higher than the highest voltage in the raceway, you can mix. AFAIK.


with exception of communication conductors unless they are properly shielded and isolated


WronGun said:


> Yes I mean fittings, enclosures, sealing procedures like I’ve done at gas stations, propane filling stations which I understand are a far different than carbon dioxide
> 
> 
> Sent from my iPhone using Tapatalk


exactly but theres a misnomer here!
explosion proof is preventing the circuit from igniting exterior flammable or explosive vapors,
in the oil and fuel industries the fittings are liquid, oil, and vapor tight to prevent the inclusion of the flammables inside the conduits and fixtures
while they may seem like the same there is actually quite a difference.
that being oil, liquid tight use solvent impervious seals while simple explosion proof use rubber or silicone gaskets.


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## gpop (May 14, 2018)

You have Nec is the minimum then you have site specs to follow. I have been on jobs where the site specs called for gas seals on all conduit that enter's a air conditioned space from a non air conditioned space.
I do not think co2 is corrosive but that could be another reason for the gas seals. i would rather ask if they require them because reworking conduit with wire as it would not be a easy fix later.

As others have said you can mix different voltage wires as long as they are rated at the higher voltage. You can also mark with tape (depending on gauge) but its poor craftsmanship. I have seen 120v wires (no power) in a 480v conduit capable of pulling in a magnetic relay. It would take a lot less to active a solid state relay.


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## Kevin (Feb 14, 2017)

WronGun said:


> That’s the info I have. If all conductors rated 600V im good. Is insulation color a factor or will tape suffice?
> 
> 
> Sent from my iPhone using Tapatalk


I'd probably pull 2 different colors so you don't accidentally mix up the 2 voltages to the wrong devices.

I don't know what the NEC says... but that's what I would do... well, I'd run teck but I digress.


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## MikeFL (Apr 16, 2016)

Now's your opportunity to set it up how you like it.
If any of these conductors/ cables are data you may want a separate raceway in the interest of signal quality. 
Sounds like you're under pressure. I wish you success with that and I mean that sincerely.


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## splatz (May 23, 2015)

WronGun said:


> That’s the info I have. If all conductors rated 600V im good. Is insulation color a factor or will tape suffice?


You have to use different color schemes for different voltage systems but 210.5(c)(1)(a) allows tape.


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## WronGun (Oct 18, 2013)

The actual switchover is under pressure, but I have 2 -3 weeks to get the interior pipe installed and prepped, exterior panel installed, exterior pipe installed, I will run a measure tape and get colored cuts. After all this work is done I have 72 hrs to check my work and perform a switchover. 

Until then I need to get more questions answered about grounding, design the install, rent a 35’ lift and buy a full tugger package, lol. 

And they need to take this massive freezer from -20 degrees to 45 degrees so I don’t freeze my balls off.










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## WronGun (Oct 18, 2013)

This also brings me to my next question. Can you mount strut supports to the lower truss steel like they did coming up from electric room ? This is my pipe run

I’ve never done it this way, but it looks much easier than full racks. 





















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## splatz (May 23, 2015)

WronGun said:


> This also brings me to my next question. Can you mount strut supports to the lower truss steel like they did coming up from electric room ? This is my pipe run
> 
> I’ve never done it this way, but it looks much easier than full racks.


It's perfectly fine as long as you have a clear path.


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## MikeFL (Apr 16, 2016)

Get an engineer to bless the added load on the trusses. 
Any idea how much weight that is? Someone needs to do all that math.


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## splatz (May 23, 2015)

MikeFL said:


> Get an engineer to bless the added load on the trusses.
> Any idea how much weight that is? Someone needs to do all that math.


That may very well be true if it's a really heavy rack but I have to say I have never heard of anyone checking that. 

It's loading the trusses the same whether you hang trapezes from threaded rod or put the strut directly on the trusses.


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## splatz (May 23, 2015)

WronGun said:


> The actual switchover is under pressure, but I have 2 -3 weeks to get the interior pipe installed and prepped, exterior panel installed, exterior pipe installed,* I will run a measure tape and get colored cuts*. After all this work is done I have 72 hrs to check my work and perform a switchover.


Where would the colored cuts come in?


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## 460 Delta (May 9, 2018)

splatz said:


> What did you find? As long as ALL the conductors have insulation higher than the highest voltage in the raceway, you can mix. AFAIK.


While I mix voltages myself, I always feel a little dirty doing it. It’s much easier to run one conduit to a pump or compressor or such with the power and control together, but for some reason I feel bad for doing it, even if it’s perfectly fine.
At a plant we have, an auger power wire and a limit switch finally crossed up after 40 years in the same conduit. The 277 volt blast to the 120 volt limit input Opto relay set the Alkon control panel on fire right beside the plant operator. The 10’x8’ control room looked like someone had set a tire on fire in it, greasy black soot on everything.


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## WronGun (Oct 18, 2013)

splatz said:


> Where would the colored cuts come in?


Where would they come in? In our pipe at the electrical room and 500’ feet away...

Maybe I will give them an option for a separate pipe and explain it’s not required. I don’t want to automatically include it if it’s not necessary as it’s going to jack up costs. 


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## splatz (May 23, 2015)

WronGun said:


> Where would they come in? In our pipe at the electrical room and 500’ feet away...
> 
> Maybe I will give them an option for a separate pipe and explain it’s not required. I don’t want to automatically include it if it’s not necessary as it’s going to jack up costs.


That's what I was wondering, if it was just for feeders, I was thinking how much chance for confusion is there for confusion, is it that bad to just tape them. (Of course you're going to buy the multiple colors for the branch circuits.) 

I agree that two conduits for two feeders would be money well spent. 

Would a transformer in the new location for the 120/208 loads make sense?


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## gpop (May 14, 2018)

WronGun said:


> This also brings me to my next question. Can you mount strut supports to the lower truss steel like they did coming up from electric room ? This is my pipe run
> I’ve never done it this way, but it looks much easier than full racks.


As long as you do not drill the truss. On some trusses there's a small gap between the angle iron's that you can use a bolt and washer. On others a beam clamp bolted to unistrut works. 

Keep a eye out for what looks like a cat 5 cable that may be tie wrapped to the trusses as that may be a thermal sensor for the fire alarm and watch the sprinker heads when you are swinging conduit around and you should be fine.


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## WronGun (Oct 18, 2013)

splatz said:


> That's what I was wondering, if it was just for feeders, I was thinking how much chance for confusion is there for confusion, is it that bad to just tape them. (Of course you're going to buy the multiple colors for the branch circuits.)
> 
> I agree that two conduits for two feeders would be money well spent.
> 
> Would a transformer in the new location for the 120/208 loads make sense?


A transformer is definitely a possibility. I definitely have some design work and options to lay out for the plant managers. The only engineers on the job are site engineers who are overseeing the transport of the tank and the actual design of the new containment area. The electrical, telecom, and alarm work is on me. I’m never lucky enough to have things designed for me. I suppose when you are bigger company you employ your own engineers. 

The good news is this company has never shown any worries about saving money, they always seem to want to go top notch and cover all Basis. I think if I lay out a comprehensive design they will be all about it. 

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## micromind (Aug 11, 2007)

300.3(C)(1). 600 volts nominal or less. Conductors of circuits rated 600 volts, nominal, or less ac circuitsand dc circuits shall be permitted to occupy the same equipment wiring enclosure or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable or raceway.


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## WronGun (Oct 18, 2013)

So I’ve pretty much designed the job and have a few more checkpoints to cover. 

I calculated for voltage drop according to distance do I need to figure additional calculations for multiple conductors ? 

8 current carrying conductors 
1 neutral 
3 grounds 

I will spend a few more days looking this over and making necessary changes


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## WronGun (Oct 18, 2013)

I already found my first error this calls for 2 1/2” EMT to the first junction, unless I can eliminate or downsize grounding conductors 

If I can’t get this down to 2” emt, it’s 2 pipes to first junction. 


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## gpop (May 14, 2018)

Be careful trying to save money on materials as that can bite you hard. If they want a quality job then use quality parts. If they want cheap and cheerful then bring everything to code limits and hope you can struggle through.

The last thing you need is a tight conduit on a long pull. The extra money you save in material will normally get wasted in labor or a nicked cable.


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## WronGun (Oct 18, 2013)

gpop said:


> Be careful trying to save money on materials as that can bite you hard. If they want a quality job then use quality parts. If they want cheap and cheerful then bring everything to code limits and hope you can struggle through.
> 
> The last thing you need is a tight conduit on a long pull. The extra money you save in material will normally get wasted in labor or a nicked cable.


You’re right, I think I’m going to revise it to include 2 pipes from the main electrical room to first junction. 


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## micromind (Aug 11, 2007)

Why 4X4s, 4X6s and 4X1s? If it's a simple 3Ø circuit, it doesn't need a neutral. If the 4th wire is a ground, only one ground is needed and it needs to be sized to the largest breaker.


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## WronGun (Oct 18, 2013)

micromind said:


> Why 4X4s, 4X6s and 4X1s? If it's a simple 3Ø circuit, it doesn't need a neutral. If the 4th wire is a ground, only one ground is needed and it needs to be sized to the largest breaker.


So I could eliminate (1) #6awg 

But the 4x1AWG includes a neutral for a 240V/70A sub panel 


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## micromind (Aug 11, 2007)

WronGun said:


> So I could eliminate (1) #6awg
> 
> But the 4x1AWG includes a neutral for a 240V/70A sub panel
> 
> ...


If it's single phase, why 4 conductors?

I don't know all the details so I could be a bit off here but I'd run 3X4s for the 50A, 3X6s for the 30A and 3X1s for the 70A plus 1X6 for the ground. 

If the 70A is fed from a single phase source, then 3X1s is good though I'd likely run 2X1s and 1X2 for the neutral. If it's 2 legs of a 120/208Y, I'd run 3X2s plus 1X4 for the neutral and set a 3Ø panel.


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## WronGun (Oct 18, 2013)

micromind said:


> If it's single phase, why 4 conductors?
> 
> I don't know all the details so I could be a bit off here but I'd run 3X4s for the 50A, 3X6s for the 30A and 3X1s for the 70A plus 1X6 for the ground.
> 
> If the 70A is fed from a single phase source, then 3X1s is good though I'd likely run 2X1s and 1X2 for the neutral. If it's 2 legs of a 120/208Y, I'd run 3X2s plus 1X4 for the neutral and set a 3Ø panel.


It’s from an entirely different panel so I was figuring it’s own ground, I could be wrong here though. 


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## splatz (May 23, 2015)

micromind said:


> If it's single phase, why 4 conductors?
> 
> I don't know all the details so I could be a bit off here but I'd run *3X4s for the 50A, 3X6s for the 30A and 3X1s for the 70A plus 1X6 for the ground.*
> 
> If the 70A is fed from a single phase source, then 3X1s is good though I'd likely run 2X1s and 1X2 for the neutral. If it's 2 legs of a 120/208Y, I'd run 3X2s plus 1X4 for the neutral and set a 3Ø panel.


Southwire has a conduit fill calculator, it's pretty good ... it's showing a pretty low fill in a single 2" conduit. It will rattle around like a BB in a boxcar with 2.5" conduit.

I might be wrong but I would think, if possible, I'd prefer to build one conduit set up for an easy pull, not too far / minimum bends between pull points. If the layout of the site doesn't allow that, then yes two conduits.

(edit - had 3 x #4, 4x #6, and 3x #1 before...)


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## WronGun (Oct 18, 2013)

splatz said:


> Southwire has a conduit fill calculator, it's pretty good ... it's showing a pretty low fill in a single 2" conduit. It will rattle around like a BB in a boxcar with 2.5" conduit.
> 
> I might be wrong but I would think, if possible, I'd prefer to build one conduit set up for an easy pull, not too far / minimum bends between pull points. If the layout of the site doesn't allow that, then yes two conduits.
> 
> View attachment 153781


Looks good but if I were pulling one ground if acceptable I think it would be a #1 

If I need to pull 2 it would be (1) #1 and (1) #4


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## splatz (May 23, 2015)

WronGun said:


> Looks good but if I were pulling one ground if acceptable I think it would be a #1
> 
> If I need to pull 2 it would be (1) #1 and (1) #4


Good catch, but here's a third answer 
Someone else could check my work but...

If you look at 250.122, the EGC for up to 100A OCPD is #8 Cu.

BUT, you increased the size of the minimum #4 (42 kcmil) for a 70A circuit to a #1 (84kcmil) - you doubled it.

So, you have to increase the size of the EGC proportionately - #8 (17 kcmi) and I had #6 (26 kcmils) so that's too small, #5 (35 kcmil) would work but for practical purposes you'd need #4 (42 kcmil).

(I edited the last post to fix the conduit fill calculation.) 

Of course you don't even have to run the EGC with EMT. But one thing I am not sure about, IF you do use a wire type EGC, do you still have to satisfy 250.122?


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## Sberry (Jan 11, 2021)

Personally like 2 pipes if no one is fussing over cost but,,, C02 isnt really inert and it isnt corrosive. But if it is going to separate equipment or panels a separate pipe couldnt hurt. Sometimes simplifies it with smaller pipe.


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## WronGun (Oct 18, 2013)

splatz said:


> Good catch, but here's a third answer
> Someone else could check my work but...
> 
> If you look at 250.122, the EGC for up to 100A OCPD is #8 Cu.
> ...


I don’t see anything about over sizing the EGC in 250.122 it only says it shall not be undersized according to table 250.122 and is not required to be oversized. I increased the size of the current carrying conductors due to VD% on a 450’-500’ run.


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## WronGun (Oct 18, 2013)

WronGun said:


> Looks good but if I were pulling one ground if acceptable I think it would be a #1
> 
> If I need to pull 2 it would be (1) #1 and (1) #4
> 
> ...


I have finalized 

240V/70A 1AWGX4 
480V/30A 6AWGX3
480V/50A 4AWGX3

2” EMT 


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## splatz (May 23, 2015)

WronGun said:


> I don’t see anything about over sizing the EGC in 250.122 it only says it shall not be undersized according to table 250.122 and is not required to be oversized. I increased the size of the current carrying conductors due to VD% on a 450’-500’ run.


250.122


> (B) Increased in Size. Where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation, wire-type equipment grounding conductors, where installed, shall be increased in size proportionately, according to the circular mil area of the ungrounded conductors.


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## WronGun (Oct 18, 2013)

splatz said:


> 250.122



Looks like I need to run a number 8. 


So would it be code to run an 8 from my 240 panel, splice with another number 8 from the 480 panel in a can above both panel and run 1 #8 for the entire run. I normally would just carry 2 grounds in this situation, but maybe I’m wrong. 












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## splatz (May 23, 2015)

This is what I was trying to do in post #41 above
Let me try it again...
And again if anyone wants to check my work that would be great

The largest OCPD for the three circuits in the pipe is 70A
The minimum Cu size wire for that circuit is #4 per Table 310.16
That #4 41.740 kcmils per Chapter 9 Table 8
You upsized that to #1 to reduce voltage drop
That #1 is 83.690 kcmils per Chapter 9 Table 8
You upsized the wire by a factor of 
( 83.690 / 41.740 ) = 2.00503114518 
(in other words, you about doubled it)
The minimum ground for a 70A circuit is #8 per 250.122
That #8 is 16.510 kcmils per Chapter 9 Table 8
Upsizing it proportionall, the minimum kcmil for the EGC is
(16.510 * ( 83.690 / 41.740 ) ) = 33.103064207 kcmils
The minimum size greater than 33.103 kcmils in Chapter 9 Table 8 is #4
Therefore, the minimum wire for the single EGC for this circuit is #4

And of course, since you're running EMT, it's all academic,
you don't need a wire for the EGC at all. 




WronGun said:


> Looks like I need to run a number 8.
> 
> 
> So would it be code to run an 8 from my 240 panel, splice with another number 8 from the 480 panel in a can above both panel and run 1 #8 for the entire run. I normally would just carry 2 grounds in this situation, but maybe I’m wrong.


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## WronGun (Oct 18, 2013)

splatz said:


> This is what I was trying to do in post #41 above
> Let me try it again...
> And again if anyone wants to check my work that would be great
> 
> ...


I get this, but that is a minimum correct ? What is wrong with going bigger? 


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## splatz (May 23, 2015)

WronGun said:


> I get this, but that is a minimum correct ? What is wrong with going bigger?


Well, I'd say that bigger is better only in that you won't attract the inspector's scrutiny, and you don't have to do your math. Smaller on the other hand saves money, space, time, and energy - costs less and easier to pull. 

In this case, since the EMT is perfectly acceptable as the EGC anyway, I think I'd go smaller and save a buck and save some effort. .


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## WronGun (Oct 18, 2013)

splatz said:


> Well, I'd say that bigger is better only in that you won't attract the inspector's scrutiny, and you don't have to do your math. Smaller on the other hand saves money, space, time, and energy - costs less and easier to pull.
> 
> In this case, since the EMT is perfectly acceptable as the EGC anyway, I think I'd go smaller and save a buck and save some effort. .


On this particular run being 500’ I agree with you. Normally if it was a shorter run I would pull the #4 larger EGC. Reason is I’m likely to use #4 THHN far more often than #8 so I would be ordering a 500’ reel and have leftover #4. 

I don’t know about you but I rarely ever use #8. 


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## DHF (Oct 12, 2020)

WronGun said:


> Is an explosion proof installation required for carbon dioxide ? Currently the existing installation is Rigid without exposition proof fittings .
> 
> 
> Sent from my iPhone using Tapatalk


wrongun: you do not need explosion proof fitting in an atmosphere of CO2. C02 is used for a fire suppressant in many cases, look in the NFPA code under class l, ll, and lll hazardous it will tell of the different properties of surrounding atmosphere. sir I spent 12 years in a paint/chemical plant that was all class l hazardous, as a side note explosion proof fittings are not water proof, also do not use the couplings that come with ridgid pipe as couplings and use proper thread cutting dies for the rigid conduit. hope this helps.


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## schreib (Apr 30, 2020)

WronGun said:


> Is an explosion proof installation required for carbon dioxide ? Currently the existing installation is Rigid without exposition proof fittings .
> 
> 
> Sent from my iPhone using Tapatalk


NO. the answer is NO. You do NOT need explosion proof electrical equipment for CO2 associated equipment. Explosion proof and Intrinsically safe would be the keywords to search for IF you were powering equipment meant for combustible gases or explosive particles. 
Examples:
-- combustible / explosive gases: Hydrogen, gasoline mixed with air above the LEL(Lower Explosive Limit), naphtha, MEK, THF, MIBK and other highly flammable organic solvents higher than the LEL.
-- particles: Flour dust, grain dust(as in grain elevators in the farmland), carbon dust.

To understand this better search under NFPA, National Fire Protection Association and "nfpa explosion proof requirements"
Explosion Proof Electrical is very expensive from a number of points of view:
-- seals must be placed and filled in conduit at entry to all boxes
-- boxes are huge and heavy and all exposed switches expensive

If you have NOT done this before you should not walk but run from that job. Let a pro do it like Egan Contractors.


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## crwilliams (Oct 26, 2012)

WronGun said:


> Is an explosion proof installation required for carbon dioxide ? Currently the existing installation is Rigid without exposition proof fittings .
> 
> 
> Sent from my iPhone using Tapatalk





WronGun said:


> Is an explosion proof installation required for carbon dioxide ? Currently the existing installation is Rigid without exposition proof fittings .
> 
> 
> Sent from my iPhone using Tapatalk


explosion proof is to stop the electrical systems from causing explosions in flammable atmospheres. It’s not about protecting the electrics from something else exploding.


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## WronGun (Oct 18, 2013)

This job is turning me into a stress ball, lol. 

We’ve changed things around. They added a 480V/30A bailer. And moved all the equipment closer to 250’ via Main. 

Now I’ve decided to run (1) 208V/70A load center and (1) 480V load center to the equipment area. 

I don’t know how many amps to pull for the 480v load center. Do I figure full rating which would be 110amps in which I would need to upsize to 480V/150amp load center? I would like to get away with 480V/100A if possible. 


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## Mikeith (Mar 6, 2014)

WronGun said:


> Is an explosion proof installation required for carbon dioxide ? Currently the existing installation is Rigid without exposition proof fittings .
> 
> 
> Sent from my iPhone using Tapatalk





WronGun said:


> Is an explosion proof installation required for carbon dioxide ? Currently the existing installation is Rigid without exposition proof fittings .
> 
> 
> Sent from my iPhone using Tapatalk





WronGun said:


> Is an explosion proof installation required for carbon dioxide ? Currently the existing installation is Rigid without exposition proof fittings .
> 
> 
> Sent from my iPhone using Tapatalk





WronGun said:


> Is an explosion proof installation required for carbon dioxide ? Currently the existing installation is Rigid without exposition proof fittings .
> 
> 
> Sent from my iPhone using Tapatalk


I would think you wouldn't be concerned about explosions in your conduit run as much as oxygen deprivation. If your conduit runs were piping a leak of CO2 (heavier than air ) and displacing the air in an area then maybe seal offs would be in the design So if there is a conduit say to the electrical room or to an area where the air is at a different pressure I'd use seal offs


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## micromind (Aug 11, 2007)

WronGun said:


> This job is turning me into a stress ball, lol.
> 
> We’ve changed things around. They added a 480V/30A bailer. And moved all the equipment closer to 250’ via Main.
> 
> ...


If they've already added stuff, they're going to add more. 

If it were me, I'd install a 200 amp 480 panel maybe 3Ø 3 wire or 4 wire with a small neutral. 

I'd also lay out the pipe supports so I could add another 2" fairly easily. 

I'd also consider running 100 amps to the 120/208 panel. If the source is 3Ø, I'd most certainly pull all 3 phases plus a neutral.


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## WronGun (Oct 18, 2013)

micromind said:


> If they've already added stuff, they're going to add more.
> 
> If it were me, I'd install a 200 amp 480 panel maybe 3Ø 3 wire or 4 wire with a small neutral.
> 
> ...


The 120/208 is coming from a 3 phase source. The extra wire will require larger pipe or 2 pipe runs. So I figured just pulling L1, L2, N, G

I made it clear at the meeting today now is the time to tell me all of your needs. Considering the time crunch do I keep making this job bigger or take it as it is and wait for the second job, lol. 

They are on a tight schedule and I’m currently balls deep in another very large commercial fit up. 

In this situation I feel like covering their needs I have (2) 12 space panels figured which is a little bigger than their requirements and calling it a day. I’ll be back in 2 months 


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## splatz (May 23, 2015)

WronGun said:


> This job is turning me into a stress ball, lol.
> 
> We’ve changed things around. They added a 480V/30A bailer. And moved all the equipment closer to 250’ via Main.
> 
> ...


If you're going to put in a panel, did you reconsider setting a transformer? Just spitballing. But with a 480 panel and a 208/120 transformer and panel, I don't think it would save money, but the cost would be offset quite a bit by running one feeder instead of two, and it's more flexible. One set of 2/0 (175A) or 3/0 (200A) and the optional #4 ground. No need to upsize the conductors for voltage drop at 480V and 500' - and so no need to upsize the EGC.


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## WronGun (Oct 18, 2013)

splatz said:


> If you're going to put in a panel, did you reconsider setting a transformer? Just spitballing. But with a 480 panel and a 208/120 transformer and panel, I don't think it would save money, but the cost would be offset quite a bit by running one feeder instead of two, and it's more flexible. One set of 2/0 (175A) or 3/0 (200A) and the optional #4 ground. No need to upsize the conductors for voltage drop at 480V and 500' - and so no need to upsize the EGC.


Wouldn’t I need to carry a neutral from the main 480 gear in order to install a transformer. 


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## splatz (May 23, 2015)

WronGun said:


> Wouldn’t I need to carry a neutral from the main 480 gear in order to install a transformer.


You'll have to bond the transformer to building steel but the secondary neutral is new, separately derived, no electrical connection to the primary side.


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## WronGun (Oct 18, 2013)

splatz said:


> You'll have to bond the transformer to building steel but the secondary neutral is new, separately derived, no electrical connection to the primary side.


That works out good. So (3) 3/0 w/ #3 EGC


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## splatz (May 23, 2015)

WronGun said:


> That works out good. So (3) 3/0 w/ #3 EGC


I thought #4 EGC but either way, not too bad...


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## micromind (Aug 11, 2007)

WronGun said:


> Wouldn’t I need to carry a neutral from the main 480 gear in order to install a transformer.
> 
> 
> Sent from my iPhone using Tapatalk


No, they're different systems with no electrical connection between them. There's no place to land the 277 neutral on the 120 system.


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## WronGun (Oct 18, 2013)

Well I’m all done with the design. I’ve decided (1) 480V/200A feed with load center with a 30KVA Transformer and a 120V/208V/100A load center. 

300’ of 2” EMT, Multiple cans, large trough over panel area, strut wall buildout, 3 safety bollards, and then we have the exterior tank containment area.

Not the biggest job I’ve done but probably the most mechanical and planned out. I also tagged on an additional $4000 for part of the cost of a new Greenlee UT-10 tugger w/ floor mount kit. 

The only part I’m not sure is if the tank pad needs to also be grounded to building steel and whether I need additional disconnects if the panels are within sight of interior equipment. 


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## micromind (Aug 11, 2007)

I've always grounded tanks, even if they're inert gas. 

The only reason I can think of about needing disconnects when the panel is in sight is the locking means. You might get away with a breaker lock but if I remember, the locking means needs to be part of the equipment, not an add-on. 

I've installed plenty of stuff using the breaker only as the disconnect but sometimes the safety nazi will feel the need to bolster his ego so I have to install the switches..........


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## WronGun (Oct 18, 2013)

micromind said:


> I've always grounded tanks, even if they're inert gas.
> 
> The only reason I can think of about needing disconnects when the panel is in sight is the locking means. You might get away with a breaker lock but if I remember, the locking means needs to be part of the equipment, not an add-on.
> 
> I've installed plenty of stuff using the breaker only as the disconnect but sometimes the safety nazi will feel the need to bolster his ego so I have to install the switches..........


Currently the tank is grounded at the existing location. But I can’t tell if it’s just ground rods or going back into the building steel because the snow is 3’ deep in that area. 


I’ve done a number of industrial jobs where they wanted disconnects 5’ from the panel. I may just install them anyways because we have the existing ones where all this equipment is currently installed. 

The job has a much higher price tag than I figured. I hope it doesn’t scare them. I have close to $20,000 in material on this. 


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## splatz (May 23, 2015)

@WronGun, did you work out the transformer calculations?


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## WronGun (Oct 18, 2013)

splatz said:


> @WronGun, did you work out the transformer calculations?


I haven’t figured out hard calculations just yet. Off the top of my head 30KVA is around 35 amp from 480V panel and feeding a 100A 208V load center. (83 amp). It’s been a while since I’ve done this, isn’t there an OCPD adjustment ?


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## splatz (May 23, 2015)

I'll take a stab at it, see if this adds up for you...

30kVA = 30,000VA

30,000 / (480*1.73) = 36A primary current
30,000 / (208*1.73) = 83A secondary current

Primary OCPD - 450.3 - 36 * 1.25 = 45A (note that since there will be 2ndary protection you could go up to 250%) 
Primary EGC for 45A OCPD= #10 
Primary phases wire - 36*1.25 = 45A -> #8 AWG (three CCC, no derate)

Assuming you can keep the panel main within 10' ...
Panel main 83*1.25 = 103.75 -> 110A OCPD
Secondary EGC for 110A OCPD = #6
Secondary CCC's - four in conduit, derate 80% - 110/.8 = 137.5 -> 1/0 AWG
note that since this size is the minimum for the ampacity, not need to upsize the EGC
Bonding jumper based on secondary CCC's - (250.66) for 1/0 CCC = #6


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## WronGun (Oct 18, 2013)

splatz said:


> I'll take a stab at it, see if this adds up for you...
> 
> 30kVA = 30,000VA
> 
> ...


I may have to post some pics when done and let you guys roast me since you helped so much with this....


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## splatz (May 23, 2015)

WronGun said:


> I may have to post some pics when done and let you guys roast me since you helped so much with this....


DEFINITELY post pictures, but check my work before you buy anything


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## WronGun (Oct 18, 2013)

splatz said:


> DEFINITELY post pictures, but check my work before you buy anything


Definitely 


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## splatz (May 23, 2015)

> DEFINITELY post pictures, but check my work before you buy anything





WronGun said:


> Definitely


With luck some other voices from the hive mind will weigh in here too...


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## WronGun (Oct 18, 2013)

splatz said:


> I'll take a stab at it, see if this adds up for you...
> 
> 30kVA = 30,000VA
> 
> ...


What did you mean by assuming I could keep the main panel within 10’


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## splatz (May 23, 2015)

WronGun said:


> What did you mean by assuming I could keep the main panel within 10’


I believe if you use a breaker over 125% up to 250% for the primary protection, the secondary protection is required, and it has to be either at the source or according to the tap rules. You'd be safe with a 10' tap for sure, longer would depend. 

But if you keep the primary protection at 125% then you don't have to protect the secondary conductors ahead of the panel, and the 10' / tap rules doesn't matter.


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## splatz (May 23, 2015)

@WronGun, I was in an electrical room yesterday looking at the transformers and thinking about that distance limit. Ten foot conductors is pretty freaking short. 

I looked at 240.21, 240.21(C) is transformer secondaries with a list of six conditions. I think (6) is going to let you go 25', if you can work with that. 



> (6) Secondary Conductors Not over 7.5 m (25 ft) Long.
> Where the length of secondary conductor does not exceed 7.5 m (25 ft) and complies with all of the following:
> 
> (1) The secondary conductors shall have an ampacity that is not less than the value of the primary-to-secondary voltage ratio multiplied by one-third of the rating of the overcurrent device protecting the primary of the transformer.
> ...


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## Viggmundir (Sep 13, 2019)

splatz said:


> I'll take a stab at it, see if this adds up for you...
> 
> 30kVA = 30,000VA
> 
> ...


I don't know the NEC so maybe I'm wrong about this, but up here in Canada we would count the 3 hots and a neutral as only 3 current carrying conductors, as the neutral only carries the unbalanced load, so no need to derate 80%...


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## splatz (May 23, 2015)

Viggmundir said:


> I don't know the NEC so maybe I'm wrong about this, but up here in Canada we would count the 3 hots and a neutral as only 3 current carrying conductors, as the neutral only carries the unbalanced load, so no need to derate 80%...


It depends - the rules for this are in NEC 310.15(B)(5)(a)-(c). With four wire Y circuits you don't always have to count the neutral, but I figured on counting the neutral because of (c):



NEC 310.15(B)(5)(c) said:


> On a 4-wire, 3-phase wye circuit where the major portion of the load consists of nonlinear loads, harmonic currents are present in the neutral conductor; the neutral conductor shall therefore be considered a current-carrying conductor.


​So if the 208/120 panel is mostly lighting and VFDs driving motors, you're going to have to count that neutral and derate.


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## WronGun (Oct 18, 2013)

splatz said:


> I believe if you use a breaker over 125% up to 250% for the primary protection, the secondary protection is required, and it has to be either at the source or according to the tap rules. You'd be safe with a 10' tap for sure, longer would depend.
> 
> But if you keep the primary protection at 125% then you don't have to protect the secondary conductors ahead of the panel, and the 10' / tap rules doesn't matter.


I don’t plan to go over 125% regardless, and the transformer will be smack in the middle of the 2 panels. Still good to know what the allowances are here. 


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