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Old 07-24-2019, 08:11 AM   #1
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Problems installing outdoor electrical outlet box


Ran into a few issues while installing a standard 2-gang metallic outdoor outlet box. Link to box here

1) The screw heads for the box mounting tabs stick out back the rest of the dimples on the back of the box. Consequently, this makes the top-right and bottom-left diagonals where the mounting tabs are tight to the wall, but then leaves a big enough gap behind the other two diagonals to allow the box to "rock".



I'm close to drilling out these dimples on the inside and ditch the mounting tabs altogether.



2) The threaded holes are too close to the back of the outlet box to accommodate the typical 1/2" liquid tite straight box connector. When mounted to the wall, there's no way to slide the conduit on and screw the compression nut down. Sure, I could attach the conduit and secure the nut BEFORE the box is tight to the wall, but then this 1/2" liquid tite connector is pressed hard against the wall after tightening the box back down. Is this normal?


3) My original plan was to run two 1/2" conduit runs from the house into the box with each carrying a 12/2 NM wire on different 20A circuits that run back to double pole 20A in the breaker panel. Would it be better to just run a single 3/4" conduit run from house to outlet box to carry both 12/2 NM cables?

Last edited by dtbingle; 07-24-2019 at 08:14 AM.
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Old 07-24-2019, 08:41 AM   #2
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Re: Problems installing outdoor electrical outlet box


Add screws and washers to the other 2 holes so all 4 screws protrude equally.??
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Old 07-24-2019, 08:43 AM   #3
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Drilling holes inside the box is fine, but do not drill out the dimples. That would make the box even closer to the wall. Put a dab of caulking on the screws inside the box to make it watertight.
You might use metal flex connectors instead of the plastic ones. They may be slightly smaller.
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Old 07-24-2019, 09:05 AM   #4
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Re: Problems installing outdoor electrical outlet box


Quote:
Originally Posted by Nealtw View Post
Add screws and washers to the other 2 holes so all 4 screws protrude equally.??
This could work.....I was thinking a composite shim on the bottom unsupported corner, but I like that screw idea better if I keep the mounting tabs.

Quote:
Originally Posted by Wiredindallas View Post
Drilling holes inside the box is fine, but do not drill out the dimples. That would make the box even closer to the wall. Put a dab of caulking on the screws inside the box to make it watertight.
You might use metal flex connectors instead of the plastic ones. They may be slightly smaller.
Sorry, my description was misleading about drilling out the dimples. The locations pointed out in the picture actually line up with these flat circle sections on the back - not the little spacing dimples that stick out of the back.


This works though! Planning to drill out the back then and make sure it's silicone'd up. We'll see if HD has smaller/metal flex connectors, otherwise I'll just install the conduit and nut first, then screw outlet box to wall and leave the connector nut tight against the wall.


As far as the number of conduit runs, should I continue with 2x runs of 1/2" liquid tite conduit from outlet box through separate 1" holes in brick wall into house OR buy a new box with a 3/4 inlet and just use a single 3/4 liquid tite run for the two 12/2 cables?

The main driving factor is my SDS+ rotary hammer only accepts up to 1" bit and the 3/4" liquid tite runs a hair over 1" (like 1.040"). I suppose my local HD has a 1 1/4 diamond hole saw or I could try boring out the hole a little with the 1" bit.

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Old 07-24-2019, 09:11 AM   #5
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Re: Problems installing outdoor electrical outlet box


Quote:
Originally Posted by dtbingle View Post
This could work.....I was thinking a composite shim on the bottom unsupported corner, but I like that screw idea better if I keep the mounting tabs.



Sorry, my description was misleading about drilling out the dimples. The locations pointed out in the picture actually line up with these flat circle sections on the back - not the little spacing dimples that stick out of the back.


This works though! Planning to drill out the back then and make sure it's silicone'd up. We'll see if HD has smaller/metal flex connectors, otherwise I'll just install the conduit and nut first, then screw outlet box to wall and leave the connector nut tight against the wall.


As far as the number of conduit runs, should I continue with 2x runs of 1/2" liquid tite conduit from outlet box through separate 1" holes in brick wall into house OR buy a new box with a 3/4 inlet and just use a single 3/4 liquid tite run for the two 12/2 cables?

The main driving factor is my SDS+ rotary hammer only accepts up to 1" bit and the 3/4" liquid tite runs a hair over 1" (like 1.040"). I suppose my local HD has a 1 1/4 diamond hole saw or I could try boring out the hole a little with the 1" bit.

You could keep adding washers (spacers) under all 4 screws to give the conduit room to the wall.
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Old 07-24-2019, 03:20 PM   #6
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Re: Problems installing outdoor electrical outlet box


Quote:
Originally Posted by dtbingle View Post
This could work.....I was thinking a composite shim on the bottom unsupported corner, but I like that screw idea better if I keep the mounting tabs.



Sorry, my description was misleading about drilling out the dimples. The locations pointed out in the picture actually line up with these flat circle sections on the back - not the little spacing dimples that stick out of the back.


This works though! Planning to drill out the back then and make sure it's silicone'd up. We'll see if HD has smaller/metal flex connectors, otherwise I'll just install the conduit and nut first, then screw outlet box to wall and leave the connector nut tight against the wall.


As far as the number of conduit runs, should I continue with 2x runs of 1/2" liquid tite conduit from outlet box through separate 1" holes in brick wall into house OR buy a new box with a 3/4 inlet and just use a single 3/4 liquid tite run for the two 12/2 cables?

The main driving factor is my SDS+ rotary hammer only accepts up to 1" bit and the 3/4" liquid tite runs a hair over 1" (like 1.040"). I suppose my local HD has a 1 1/4 diamond hole saw or I could try boring out the hole a little with the 1" bit.

for block like that, I would use a hammer and star bit, or use the drill and wallow the hole.

MN-B can not be used in a wet location.

I would use a XXX/3 cable before I used 2 2 cable wire.

Best bet is to use PVC and individual conductors.
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Old 07-24-2019, 04:58 PM   #7
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Re: Problems installing outdoor electrical outlet box


Larger bits are available for SDS+ drills.
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Old 07-25-2019, 09:56 AM   #8
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Re: Problems installing outdoor electrical outlet box


I ended up just using the 1" SDS+ masonry bit and wallowing the hole out a little. Went much quicker/smoother than expected.

Ended up forgetting the mounting tabs and drilling through back of box. Each screw got a blob of duct seal underneath the head and then a blob of silicone on the outside of the back of the box.



Quote:
Originally Posted by jbfan View Post
MN-B can not be used in a wet location.

I would use a XXX/3 cable before I used 2 2 cable wire.

Best bet is to use PVC and individual conductors.
I don't disagree that technically per NEC, any raceway above ground and exterior to the home is a "wet" location and therefore using NM-B is against code.

However, I'm pretty confident that I won't have any problems due to the fact that NM-B was used for the short distance it extends into a "wet" location.
Personally I think it's a better install then running individual wires inside to a junction box and then converting to NM-B through the house. If "This Old House" does an almost identical install with NM-B, it's good enough for me haha.

Yes, a 3 conductor wire could have been used, but the advantage of a MWBC (1 less wire to run / cost) to save over running a 4th conductor is not worth the disadvantages of a MWBC. If anything, I should have just picked up a 12/4 w/ ground NM-B cable.

Quote:
Originally Posted by brric View Post
Larger bits are available for SDS+ drills.
True, but only up to 1" SDS+ are carried local in store. Looks like you can order up to 1-1/4" in SDS+ before it switches to the SDS-Max shank. Or get SDS+ core bits, which are expensive and not available locally either. Basically, not patient enough to order online haha.
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