Wiring a replacement pool automation center

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Old 08-19-16, 03:29 PM
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Question Wiring a replacement pool automation center

Hello. I'm upgrading my pool automation center this weekend. The current install has 3 separate 20a 240v circuits and a 15a 120v running from the main panel to the automation center. It's a 60+ ft run in 1/2" EMT, about 40 ft of which is underground. In that 1/2" EMT they ran: 9 12awg wires (2 red, 2 blue, 2 black, 1 light red for 110, white and green).

The new panel has a built-in 10 space load center / subpanel. I would really like to use this. I've been thinking about pulling new wires back to the main panel and wiring this as a 50A subpanel with each pump on it's own branch circuit. This would also serve as a GFCI and disconnecting means.

The issue is -- I can't figure out how to get 50A through 1/2" conduit without exceeding the 40% fill numbers.

Alternatively, I may not need 50A, but my calculations say I do unless I'm missing something:

3 HP VS filter pump (16 amps)
2 HP waterfall pump (10.2 - 11 amps)
1.5 HP therapy jet pump (8.8 - 9.6 amps)
Misc 110v stuff (7 amps)

This adds up to 45 amps. However, this is worst case scenario with all pumps, salt cell, heater, and landscape lighting running simultaneously and at full speed (unlikely).

A) Is there any way to get 50A through the existing 1/2" conduit?
B) Is there a way I can get by with only a 40A sub panel breaker?

I really don't want to use the existing 3 separate circuits as then I can't utilize the sub panel feature of the new panel and have to maintain separate switches for disconnects. I also would rather not run new conduit below ground, either...

Any other suggestions are much appreciated! TIA!
 

Last edited by Justin Horne; 08-19-16 at 04:23 PM.
  #2  
Old 08-19-16, 03:52 PM
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It's a gray area if your current installation is even code. For detached structures you can only have one circuit. If there is no shed then a gray area. Subpanel is a great idea and is what you should do.

I also would rather not run new conduit below ground, either...
Please tell us why. Burying new conduit and using individual wires is the best solution like it or not. You could also use direct burial cable no conduit. A third option would be conduit with individual wires secured to a fence if there is a fence near by.

Note your voltages are 120v and 240v not 110v and 220v.
 
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Old 08-19-16, 04:22 PM
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It's a 60+ ft run in 1/2" EMT, about 40 ft of which is underground.
EMT should NEVER be used underground. For this reason alone you really need to run new conduit.

You CAN use #8 copper conductors and get a full 50 amperes at the sub-panel. You CAN use a smaller neutral conductor since the 120 volt load is so low and the equipment grounding conductor only needs to be a #10.
 
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Old 08-19-16, 04:26 PM
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Interesting -- I hadn't thought about the multiple runs in the same conduit already being out of compliance.

Burying new conduit isn't easy. The landscape is rocked and we have cliche to dig. It's a big job...

So, are you saying that 50a is not doable? Looks like 40A isn't an option as this would still require 8ga as 10ga is only good to 30a.
 
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Old 08-19-16, 04:29 PM
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I used the term EMT, but that may be incorrect. It's metal conduit wrapped with black tape.
 
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Old 08-19-16, 04:35 PM
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As for the smaller neutral conductor, can I still connect it to the neutral bar? What if in the future someone adds another 15a 120 breaker? Would this still be to code?
 
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Old 08-19-16, 04:45 PM
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Is the conduit threaded at the joints? EMT is too thin to thread and uses compression couplings. IMC (Intermediate Metallic Conduit) is usually threaded but can also use compression fittings. 1/2 inch nominal IMC has an internal diameter of 0.660 and at 40% fill is 0.137 square inches. Using two #8, one #10 and one one #12 copper with THHN/THWN insulation would require 0.1076 square inches so could be run through IMC.

If you have RMC (Rigid Metallic Conduit the 40% fill would be 0.125, still enough room for the aforementioned conductors.

Added:

Yes, you would connect the neutral, regardless of conductor size, to the neutral buss. Remember that the neutral only carries the unbalanced load of the 120 volt circuits. Using a #12 allows that unbalanced load to be as high as 20 amperes. Using a #10 conductor instead of the #12 for the neutral would bring the total required space to 0.1154 square inches, still less than the maximum for 1/2 inch RMC and also allow a maximum of 30 amperes unbalanced load on the 120 volt circuits. It will be a very tight pull and require lots of lubricant.
 
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Old 08-19-16, 05:00 PM
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The landscape is rocked and we have cliche to dig. It's a big job...
IMC or RMC can be burried in as little as 6" so even with rocks might not be as hard as you think.
 
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Old 08-19-16, 05:06 PM
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Hmm...any idea what size this is? I'm actually going to re-measure...this could be 3/4" ...

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Old 08-19-16, 05:15 PM
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Pull the cover off the box and get the camera right down on the ground so I can see the connectors. It does look like EMT that someone wrapped with tape. That tape is meant to protect steel piping for water and fuel gas, not electrical conduit. It may have done an okay job protecting the conduit but you won't know until you try to pull the existing conductors.
 
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Old 08-19-16, 05:32 PM
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Pics below. I really expected to find some wire nut in there, not a loop of conductors!

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Old 08-19-16, 06:12 PM
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It looks like your lucky day. The center conduit, the one going underground, is threaded into the box. That means it is probably IMC. The conduit on the right is using a compression connector and is probably EMT.

The box is obviously being used just as a "pull point" and the big loop of wires is a good sign that the person who did the work really did know what they were doing.

Unless one of the real electricians finds fault with what I previously suggested it looks like you are good to go with the #8 and #10 conductors. The only snag I can foresee is if the present conductors are stuck tightly in the conduit and can't be pulled out.
 
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Old 08-19-16, 06:16 PM
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Thanks Furd -- great news! I'm going to pull 3x 8ga wires (black, red, and white) with a 10ga ground (green). That will work, correct? My calculations show that with 3/4 IMC I should be good to code, assuming I can get them all pulled. This will be a fun weekend!
 
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Old 08-19-16, 06:19 PM
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You may have to pull one wire at a time to get them out. If you can, leave one wire to use as a pull wire to pull in your new conductors.
 
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Old 08-19-16, 06:20 PM
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Furd, assuming continuous conduit couldn't he use the 10 for neutral instead of ground and not use a ground?
 
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Old 08-19-16, 06:30 PM
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Theoretically, IF the conduit was contiguous AND had tight joints it could be used for equipment grounding. I prefer to have a separate equipment grounding conductor to be absolutely certain it is a low impedance connection.

With the limited amount of 120 volt equipment I see no reason to pull a full-sized neutral conductor as long as the 120 volt load is more-or-less balanced across the two "hot" leads.

Did you confirm that it is indeed 3/4 inch conduit? I admit it looks like it in the pictures but pictures can be deceiving.
 
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Old 08-20-16, 12:36 AM
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This is a "pool" power center. It will require an insulated ground.
 
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Old 08-20-16, 12:46 AM
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Ooops I forgot the insulated ground so forget my suggestion.
 
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Old 08-20-16, 03:15 AM
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Good catch, Pete. Thank you. This is why I normally defer on questions concerning pools, too far from my areas of expertise.
 
  #20  
Old 08-20-16, 01:30 PM
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Update:

It was 3/4" conduit so I was able to pull 3 8ga (red, black, white) and 1 10ga (green). But now, I'm thinking I may need to install grounding rods. Do I?

The new subpanel/load center is installed on an exterior wall away from the house. Does this require 2 grounding rods because it is now a subpanel? Also, I assume I leave the neutral bar separate from the ground?

I'm also having an issue finding the bonding from the pool itself. There was a ground clamp around one of the 1/2" conduits that fed one of the light switch boxes, and that was used to bond the pumps, heater, etc. BUT when I took the old panel off I found that it was only about 12" of conduit buried underground and pulled right up. I have no idea then where the "proper" bonding wire is going back to the pool...
 
 

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