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Joined: Apr 2002
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Reno:
Maybe for 2017? It may be difficult to arrive at 'wording', but...let's think about it starting with good old common sense (which is not within the NEC defs)



John
Joined: Jul 2004
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I think the biggest impediment to "back to back" installations is the basement. The meter has to be eye high at grade so you are either running the SE inside the home or you are punching a hole in the wall below grade, directly into the main panelboard enclosure. That may work in the desert but anyplace where it rains can be a problem.

Maybe we could remove "where subject to physical damage" from 230.50(B)(1) where it is inside the building and assume any SE cable inside the home is subject to physical damage (an undefined term anyway).
At least that would get it in pipe.
Personally I would say rigid/intermediate metal pipe but that may be a bridge too far. Maybe add EMT.
The problem with RNC, even sch80, is, a drywall screw goes right through it. It feels like wood to an 18v screw gun.


Greg Fretwell
Joined: Apr 2002
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The basic 'unwritten rule' that is followed around here for the panel in basement scenario is:
Drill in above sill plate; turn straight down, and enter the panel. This works for even the high ceiling basements.

This seems to work for 'mostly' everyone. Yes, we get the occasional, drill in, turn left for xx' then down into the panel. That don't work!

Commercial jobs, specially the older ones that opted for the good ol' 6 switch rule is where it gets interesting. Bring on the concrete!!


John
Joined: Jan 2005
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Cat Servant
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Wording? Have the 'six throws' rule specify that the disconnects will be part of, or immediately next to, the meter enclusure.

With 'tamper resistant' meter rings now the norm, we cannot rely upon pulling the meter as a disconnecting means.

Joined: Apr 2002
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Reno:
Yes, pulling the meter is getting to not be an option. We have a variety of rings, barrel locks, larger brass 'ghetto' locks, etc., all property of the POCO.

I've seen quite a few very interesting attempts by people to 'get it open', some of which are really scarry.

I have to find some time to look thru my pic scrapbook for some of the really interesting ones!


John
Joined: Jun 2006
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M
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The issue here is related to the fact that most of we canuks see outdoor locations for OCD as rust prone. OC devices are also not temperature compensated. If it is hot the breakers trip early if the panel is in a high ambient. (think Death Valley) but if it is below 0C or 32 F the trip time goes up and can increase OL trips by a lot of time.
For locations where outdoor services are accepted like saw services or traffic controlers there is no building to put the panel inside. A pedistal service for a motor home and such are exceptions. The CEC has adopted a rule that will permit an outdoor main but the branch circuits and even another main inside the building may be required to deal with overload. This allow the protected conductors to run inside the building where a panel migh have a better location than an exterior wall.

Joined: Jul 2004
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Overload protection could be handled by the main in the load side panel in the house. You are basically only looking for short circuit protection from the outside service OCP.
If the inside panel was MLO I can see your concern about the trip curve when the feeder was sized by 310.15(B)(6).
I suppose the answer would be in the breaker trip curve graph.

As for rust, We have a far worse problem with that here. That may be why plastic enclosures are becoming so popular.


Greg Fretwell
Joined: Jan 2005
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Cat Servant
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I guess this is what you might call the 'discussion' or 'negotiation' stage.

As a bare minimum, I want to be able to turn off the power at the meter- manually, automatically, or both. I don't care. I just want you to be able to do SOMETHING when Granny bangs a picture-hanger into those high-amp wires ... besides cooking marshmallows for arriving firefighters, as you wait on the PoCo.

Trip curve? Ambient compensation? In nearly every instance, I don't really care how accurate the breaker is. It's powering a feeder, with far smaller branch circuit protection downstream.

FWIW, some of the hottest parts of the USA are also the places where ALL of the breakers are mounted outside the house. High-ambient nuisance tripping does not seem to be an issue.

Rust? I see no reason for the disconnect box to rust any faster than the meter pan. As wet as Canada may be, I defy them, or anywhere else, to compete with the industrial cities of the North when it comes to corrosion. The "rust belt" don't go through Florida (though Toronto is pretty close).

Also, bear in mind that the UL standard was changed, perhaps as long as ten years back, to require additional rust protection. The older boxes you see rusting away often had no protection beyond the grey primer coat of paint.

I have not seen plastic enclosures, though I am aware of some RV pedestals like that. Might be a good thing - IF the plastic is a decent one. "Sun rated" PVC conduit doesn't impress me; the stuff seems to self-destruct after about eight years.

Let's not let the 'best' become the enemy of 'good enough.' Just give me a way to turn the house 'off.'

Joined: Apr 2002
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I agree with Reno on the rusting out of 'older' items that I see. In a few of the 'older' resi developments (20+ yrs old) there are numerous meter pans that have corrosion issues, & a lot that were replaced already. All are UG services, with the load side exiting thru the back of the meter pan to the panel.
The POCO BUD transformers also are showing rusting. Guess it was a bad period for paint back then!

Ambient temps here swing 100+, and I have not heard of any temp related issues with any exterior main cbs. Meter/main units are very scarce here.

Non-metalic enclosures? Sq D had a 'plastic' pull out HVAC type disco a while back, but I have not seen any recently. A few pool equipment rooms have SS enclosures, and I once had a non-metalic 40 circuit, 120/208, 4 wire panel enclosure fabricated. Pricey....heck yes!

With the newer standards, I feel the 'corrosion' issues for a new install, in a 'normal' atmosphere will be a moot point.






John
Joined: Apr 2002
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Reno:

One issue that nobody brought out yet against exterior mains is the joker that turns the power off & runs. A local solution is a 'breakaway' padlock, which is OK with the first responders.


John
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