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How to add a 3 phase sub panel to a balanced 3 phase main panel?

How to add a 3 phase sub panel to a balanced 3 phase main panel?

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  #1  
Old 02-26-16, 06:14 AM
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How to add a 3 phase sub panel to a balanced 3 phase main panel?

Members location is France.

Hey everybody!

My house has a 3 phase power supply. Each phase is separated at the main panel into three different sections of the house. For example, one phase powers the downstairs, one the upstairs and one a sub panel in the basement. Through my investigation I found out this could be called a "balanced 3 phase system". Is this accurate?

I want to install an instant hot water heater that requires a 3 phase 415V supply. How should I make the connection at the main panel to divert a 3 phase supply to a small sub panel which only supplies the hot water heater, without disturbing the current setup of the balanced system? Should I split the main supply before it enters the main 3 phase differential or split each individual phase after the differential? Or is there a better solution that I am not seeing? I have a fairly good knowledge of electricity but 3 phase mixed with sepereate single phases is a bit over my head.

Thanks!
 

Last edited by ray2047; 02-26-16 at 08:11 AM.
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  #2  
Old 02-26-16, 06:49 AM
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Why do you want to add a panel? Why not just add a breaker to an existing panel.


What do you mean by 3 phase differential? Are you talking about a Residual Current device (GFCI) ?

I'm assuming you live somewhere with 240v power, so your electric codes may vary. Where I live you can't have gfci in another panel than the first downstream breaker

Don't worry about "disturbing the balance" I'm pretty sure a 3 phase heater draws current equally from each phase.
 

Last edited by Esand1; 02-26-16 at 07:16 AM.
  #3  
Old 02-26-16, 08:25 AM
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You would need to power the new device with a triple pole breaker that draws from each of the phases. The balance is not relevant in this case, although three-phase heaters are usually balanced due to their design of three equal heating elements.
 
  #4  
Old 02-26-16, 09:55 AM
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Ipbooks- I'm not sure of the French name and strangly Wikipedia (my normal resource for translation) doesn't have a link from its article on RCDs to a French article, but in Spanish gfci breakers are called differential interruptors

What I think Sha Yne is asking is if he should splice the wires before or after the GFCI breaker in his main panel. I guess in theory it wouldn't matter except for nucience tripping, but at least here, the code is that you can't have the gfci protection in a different box than the CB.

Here is one of my subpanels
 
  #5  
Old 02-26-16, 04:41 PM
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What I think Sha Yne is asking is if he should splice the wires before or after the GFCI breaker in his main panel. I guess in theory it wouldn't matter except for nucience tripping, but at least here, the code is that you can't have the gfci protection in a different box than the CB.
Yes this is correct. Sorry I forgot to mention that I live in france. I am from the states but most of my electrical work had been here. The power here is 240V.

Should I add a terminal like this after the GFCI?
[ATTACH=CONFIG]63345[/ATTACH]

After, connect all my old setup to the terminal, then run from each pole to a breaker like this? [ATTACH=CONFIG]63346[/ATTACH]

Also could you please elaborate on nucience tripping?

For the wires and connections, I will check local code and buy wire and install accordingly.

The heater is a Siemens DE 4152427 24-27 kW. This is a translation of the energy supply demands
Electrical connection 3 ~ / PE, 400 V, 24/27 kW protection 40 A
Does all of this together sound like it would work?
 
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Last edited by Sha Yne; 02-26-16 at 05:00 PM.
  #6  
Old 02-26-16, 05:48 PM
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Yes.... it sounds like it will work.

As far as that terminal block..... that looks like overkill. It's pretty hard for us to advise you as things are done differently here in N. America and we have no idea what your system looks like there. A picture or two would be really helpful so that we can see what you are working with.

I'm not sure if you need to connect before or after the GFI protection. That would be dependent on your code there as well as the manufacturers recommendation.

http://www.doityourself.com/forum/el...-pictures.html
 
  #7  
Old 02-26-16, 06:09 PM
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I'm not sure about what the codes are for installing a subpanel over there. I know that here you can't have the downstream breakers protected by a GFCI in another Panel. Here's how one of my sub panels is wired FWIW.

https://lh3.googleusercontent.com/-v...2/IMG_6204.JPG (Big Image)

If you zoom in on the diagram on the cover you can see that everything in the panel is projected by the GFCI breaker, and then is split between the 3p and 1p loads. You can also see that the lines coming from the main continue on to another panel without out passing through the GFCI breaker. That subpanel has its own GFCI devices. That is due to code according to my electrician. I don't know if its the same there. All though most of our electric code is copied from euro norm so it could be.

You originally posted that you wanted to add another subpanel, personally if you have space in your main panel I'd just add the breaker there.

Also 27kw is one hell of a powerful heater. Double check the amperage rating for your GFCI breaker.
 
  #8  
Old 02-28-16, 05:34 PM
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The whole panel, with the GFCI on top with a breaker for a sub panel with a dedicated phase, next row down is the upstairs circuit with its own phase and the last row is the downstairs circuit and last phase. The main supply is at the bottom.
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GFCI, supply on top
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Main supply
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I notice that your R2 has a neutral and the R3 not. Would I need to run a neutral, from the neutral terminal directly to the heater, or buy a 4 pole breaker instead and pass the neutral through there?

I have the space in my panel and I like your advice, just gonna put the breaker in the main panel.

The amperage rating for my GFCI reads 40A. The heater is very powerful but extremely efficient.

I was checking the local online shops for 4-5 pole terminals and almost all of them are the same type. Just wondering where would be a good place to put it.
 
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  #9  
Old 02-28-16, 06:49 PM
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You don't need a neutral for the 3 phase heater.

27 KW @ 415v is 60 amps. You can't put it behind that GFCI breaker. If the local electric code requires GFCI protection you'll need another GFCI device.

You might have a bigger problem though. What size are the main supply wires? It's hard to tell in the photo but they look about 6mm.

You need to check to see if adding the heater won't overload those supply wires.
 
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