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Running Conduit Through Wall Outside for Electric Car Charging Station

Running Conduit Through Wall Outside for Electric Car Charging Station

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  #1  
Old 05-22-15, 10:50 AM
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Running Conduit Through Wall Outside for Electric Car Charging Station

Hello. I am looking to add an electric car charging station to my house for my new Chevrolet Spark, and am looking for opinions on my plan to accomplish this.

Background
I live in Portland, Oregon. Our winter temperatures typically do not drop below 20F. Summer temperatures typically don't spend much time above 90F or so.

The car charger that I (already) have is a Bosch Power Max 30A / 18ft cord (Power Max™ 30A / 18ft cord | Bosch Electric Vehicle Solutions). The documentation for this charger recommends a 40A, two pole breaker.

Rough Plan Overview
My electrical panel is located on a wall that is not adjacent to my garage and (I believe) makes the installation much simpler if I go out the exterior wall and run down the side of the house to where the charger will be installed. This conduit run would be located on the north side of the house and would thus never receive direct sunlight. My floor plan and proposed run is shown below:
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I currently have an existing run of conduit doing something similar for a heat pump behind our house:
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A picture of the outside wall where the run would be made (note the window on the right edge as a reference to the previous image):
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Wire Sizing and Type
Due to the 40A breaker, it looks like the minimum wire gauge that will be acceptable for me is 8 AWG. Doing a rough estimate, I believe my total run will be approximately 50-55 feet in length. I remember seeing somewhere that it can be a good idea to upsize the conductors one size when running in conduit. Does this seem necessary? I'd rather spend the extra money on larger conductors now than in the future.

As for wire type, due to this being an exterior conduit run I am planning on using THHN/THWN-2 wire. I plan on purchasing one length of black, one of red, and one of green (all cut to length). This is an example of what I am looking at:
Wire link: https://www.platt.com/platt-electric...spx?zpid=99633
Wire datasheet: https://www.platt.com/CutSheets/Mult...nded-8-750.pdf

Conduit Sizing and Type
I am currently planning on using EMT over PVC conduit. Are there any compelling reasons as to why I should not do this?

Looking at my Ugly's handbook, regardless of whether I use 6 AWG or 8 AWG THHN/THWN, it looks like I should be using 3/4" EMT.

Going From the Panel to the Exterior Wall
It looks like when the existing heat pump conduit was installed they used metallic flexible conduit inside the walls. I would imagine that this would make pulling and/or re-pulling the wire much simpler and am therefore planning on doing this as well. Are there any issues with this?
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Looking at this it appears that I could probably add my wires (8 or 6 AWG) to the existing flexible metal conduit and not overfill the conduit. This would let me avoid a bunch of drywall work. I would then have to change the exterior LB to something else (to go the other direction). Looking through the Home Depot website I didn't see anything that would be a direct replacement. Would I be using a junction box at that point? Something like this perhaps: Wiegmann 6 in. x 6 in. x 4 in. NEMA 3R Screw Cover Box-RSC060604RC - The Home Depot

Connection From Conduit to Charging Station
The charging station documentation recommends using a flexible final connection to the charging station itself (so that it can be mounted and removed easier). As such, I am planning running the final loop using 3/4" liquidtight. Would there be a benefit/requirement to put a junction box or disconnect handle at the junction between the liquidtight and the EMT?

Summary
Is there anything that I am missing or making a drastic mistake on?

Thanks in advance for any assistance!
 
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  #2  
Old 05-22-15, 11:11 AM
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Your plan all looks good with a few notes. I prefer EMT for long horizontal runs because PVC will eventually sag and look bad unless you screw it down every 6". There's no need to use larger than #8 copper THHN -- it's rated for 50A in conduit. Also 1/2" EMT is ok for two #8 and 1 #10 ground.

Don't re-use the flexible metal currently used by the heat pump. Install a new piece just for this run. If you feed through the hole from the outside, you might be able to get it to the panel without removing drywall beyond the panel cover.

The final junction box / disconnect is not required unless the charger manufacturer requires a local disconnect. A pull box or "C condulet" at the transition would be a good idea, because there's no way you'll get the wires through the flex without one.

Make sure to seal up both ends of the conduit with duct sealant once you get everything installed to prevent condensation in the pipe.
 
  #3  
Old 05-22-15, 11:47 AM
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ibpooks - thank you for the response and the comments.

I will stay with the EMT as the outside of my house does not need anymore screw holes in it.

May I ask why you don't recommend that I re-use the existing flexible metal in there and put something like this (KILLARK Conduit Body,T,3/4 In,Malleable Iron - Conduit and Outlet Bodies - 2NB53|OT-2M - Grainger Industrial Supply) on the exterior? I'm not sure how I would manage to run wire from the outside to the panel while going past three or four studs. I guess that I just got hopeful for a few minutes that I would be able to avoid the additional penetration in the exterior wall and all that drywall work!

For the 90 corner transitioning from the horizontal conduit run to the vertical, would you recommend using a pre-bent sweep or doing it as a hard 90 with a LB or pull elbow?

For the duct sealant, would that be used at the charger end of the liquidtight and where it leaves the house?

Thanks again.
 
  #4  
Old 05-22-15, 12:07 PM
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May I ask why you don't recommend that I re-use the existing flexible metal in there
Running two high-power circuits through the same pipe requires derating for heat, which ultimately requires larger wires and therefore larger pipe. It would end up requiring the single pipe be replaced with a larger one which is the same wall damage as just running a new one with the additional complication of disturbing the heat pump.

I'm not sure how I would manage to run wire from the outside to the panel while going past three or four studs.
Ahh, I didn't realize it was that far. Looks like you will need to do a little drywall work. Do you have attic or basement access in that area?

For the 90 corner transitioning from the horizontal conduit run to the vertical, would you recommend using a pre-bent sweep or doing it as a hard 90 with a LB or pull elbow?
Either is ok. You could also buy or borrow a pipe bender and make the 90 yourself.

For the duct sealant, would that be used at the charger end of the liquidtight and where it leaves the house?
Correct on both.
 
  #5  
Old 05-22-15, 12:14 PM
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Thank you for the explanation on the second conduit reasoning.

I did buy a bender but I was wondering that for the single corner it might be cheaper to just buy a fitting and return the bender.

Do you have a recommendation for a duct sealant?
 
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Old 05-22-15, 12:27 PM
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It's sold in a 1 lb brick for like $1, essentially generic from any of the electrical supply brands.
 
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Old 05-22-15, 08:40 PM
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I have a few more questions.

Since I am going to be running this conduit on the side of my house, am I required to use rain tight fittings?

Similarly, am I required to have a drain point at some point in the system? My original thought was to end the EMT and then use liquidtight in a "U" shape to connect to the charger. This would result in the bottom of the liquidtight loop being the lowest point in the system and thus collect the water. I'm assuming that drilling a drain hole in the liquidtight isn't a super plan. Am I better off putting a tee fitting at the lowest point, connecting one end to the EMT, and come out the side (and up) to the bottom of the charger?
 
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Old 05-22-15, 09:14 PM
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Raintight fitting are required for the EMT.
 
  #9  
Old 05-24-15, 09:46 AM
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Just wondering, why are you putting the charger on the outside of your home? It would be just as easy to put it on the inside wall of the garage and would certainly look a lot better.
 
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