Connection in exterior concrete pad

In article <j4g90h$v2$2@speranza.aioe.org>, nowhere@here.com says...
> 
> Hi Dennis,
> 
> On 9/9/2011 10:26 PM, Dennis wrote:
> > "Robert Adsett"<sub2@aeolusdevelopment.com>  wrote in message
> > news:120490fb-ba6c-43b3-87b4-cfb63eeac3e1@c29g2000yqd.googlegroups.com...
> >> A company I'm working with is developing an application the needs to
> >> connect power and data (standard 110V/60Hz and RS485 type data)
> >> on a flat exterior concrete pad.
> 
> -------------^^^^^^^^^^
> 
> >> We have connectors that we think will do the job (IP68 with power
> >> and data) but we are looking for a connection box that can be cast
> >> in place in the concrete for the pad side of the connection.  It has
> >> to be flush with the concrete so there is no trip hazard when
> >> unplugged and have a cover (ditto).  The cover can certainly be one
> >> that is removed and replaced as needed.  Obviously it needs to
> >> prevent water entering the cable conduit, the receptacle we are
> >> looking at has a bulkhead seal option so  some sort of divided
> >> box might suit. The climate includes freezing weather, the worst
> >> appears to be -31.  I suspect the ground is more temperate than
> >> the air.
> 
> > Take a walk and see what is used in shopping malls and convention centre
> > floors pehaps they use a suitable housing. Often used for kiosks etc which
> > are moved around in malls.
> 
> I don't think they are considered "wet/damp locations"

That would be clased as normally inside a commercial premises or 
industrial premises. 

Definitely not external wiring. Which is conisdered over here outside 
the Earth Zone as well as being wet/damp and many other things..

-- 
Paul Carpenter          | paul@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/>    PC Services
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Hi Paul,

On 9/10/2011 5:00 PM, Paul wrote:
>>>>> Running mains power in a "wet location" brings on a whole lotta pain
>>>>> (re: Code).  Could you, possibly, consider running "low voltage" power
>>>>> to the box, instead?
>>>>
>>>> That was the first thought.  The panels use DC internally. Unfortunately
>>>> it's only 24V.  Would have been better at 48V but not enough time to
>>>> get the internal components re-designed.  We need around 1kW peak and
>>>> running 70m or so of cable we are looking at a fair voltage drop.
>>>>
>>>> Still might be worth revisiting to see if the components can
>>>> withstand say 28V and deal with the voltage drop.
>>>
>>> Ever thought of box in building to "combine" power and data for
>>> the run to your unit, then run 48V AC to the unit, with suitable
>>> trips for leakage, thermal, shorts, water flooding. Then the conduit run
>>> can also be lower than the box inside the building to allow drainage at
>>> that end as well.
>>
>> You'll never get a ~200 ft pipe to drain unless one end is
>> on the top of a small *hill*!  :>
>
> Yes I meant the point at which the outlet leaves the building is below
> the box in height to allow that end to drain as well. Draining from both
> ends means less slope required and actually small amounts are more
> likely to evaporate.

200 ft of pipe.  Not much air circulating through there.

And, no mention of where that 200 ft *runs* (e.g., if outdoors,
you have to expect some amount of ground heave *or* parts of it
will be significantly lower than the outlet to get below frost line)

>>> Alternatively you could have an isolation transformer to supply
>>> 55-0-55, common on building sites and similar places for a mains
>>> supply that is 'safer'.
>>
>> No longer considered "low voltage".
>
> AFAIR especially in UK/EU for power wiring anything LESS than 1000V
> (1kV) is Low Voltage would need to check my regs, 55-0-55 is Reduced Low
> Voltage (RLV) anything below ABOUT 40V AC is Extra Low Voltage (ELV).
>
> This sort of wiring is commune on building sites for portable power
> tools, nominally specified as 110V.

Here (US -- as Robert used "inches" as a term of measurement, I
assumed that a reasonably safe guess?), 50V is "low voltage".
The next big change in regs comes at 600V (though I think there
is another category at 250V)

There are also things like "power limited" circuits, etc.

Point being:  make sure you talk to someone who knows what local
ordinances will apply lest you come up with a solution that can't
be installed (*sold* but not installed).

Most folks see the Code et al. as a "nuisance".  I, OTOH, figure
there is *some* reason, there -- even if it isn't spelled out
explicitly (though the annotated code books try to put some
explanation behind each requirement).

Also leads to some interesting implementations!  E.g., we looked
into using a pneumatically actuated switch for the garbage disposal
to work around some of the "wet location" and "face up" requirements.

On Sep 10, 4:29=A0am, Paul <p...@pcserviceselectronics.co.uk> wrote:
> Also consider what is used for what is classed as street furniture for
> power signs, and other roadside units as the safety situations are
> similar. These often have forms of isolation trips so that when idiots
> drive into them the power is cut off quick.

That's an interesting thought.  Certainly a place to take a look.

Robert

On Sep 10, 2:47=A0am, Don Y <nowh...@here.com> wrote:
> > Yes, some convention boxes are close but way too large.
>
> Huh? =A0You said 5" -- I assume "diameter" (or, "across a diagonal")?
> <http://www.lewelectric.com/wp-content/gallery/1101-series/6304-be.jpg>
> should be almost exactly 5 inches diagonally...

Convention center box a-la

http://www.graybar.com/documents/hubbell-wdk-convention-center-boxes.pdf

It's got the depth to accommodate a sealed connector but it is too
large.

> Of course, that just gives you *one* connector (power)

Yes and unsealed when connected.  That seems to be the hard part.

> =A0From your followup to this post, it seems like you could afford
> a *second* box nearby that houses your data/signal connector?
> This would get around the prohibition against mains and signals
> in the same box -- and, the 5" limit on the (first) box...

Perhaps.

> Yikes! =A0At 1kw, even 48V would require #10AWG wire. =A0I'd have to
> look up the ohms/foot to figure what sort of a hit you'd take
> at 200+ ft...
>
> At 24V it would probably be impractical (wire sizes).

Yeah, why make it easy on ourselves?

> [You probably *really* want to talk to a Master Electrician and/or
> local inspector in your jurisdiction just to =A0make sure you don't come
> up with a solution that is too clever for the Code Police =A0:> =A0]

Yes, first job is to make it as safe as practical, second is to meet
code requirements.  Finding an existing solution would make both
easier.

Consultations will take place.  I've started making contact.

>
> > Still might be worth revisiting to see if the components can
> > withstand say 28V and deal with the voltage drop.
>
> (without knowing your application, ) is there anything that you can
> *rationalize* bringing power *with* to the site? =A0E.g., a pair of
> lead acid batteries wired in series?
>
> Or, any "easy" (i.e., "it's just money" =A0:> ) way to cut power
> consumption in the devices used?

Haven't figured out any so far.  Unfortunately the power draw
will last for hours.

> Please keep us appraised of how this sorts itself out!

I'll try to do that.

And thanks to everyone for the suggestions so far.

Robert

Hi Robert,

On 9/11/2011 9:55 AM, Robert Adsett wrote:
> On Sep 10, 2:47 am, Don Y<nowh...@here.com>  wrote:
>>> Yes, some convention boxes are close but way too large.
>>
>> Huh?  You said 5" -- I assume "diameter" (or, "across a diagonal")?
>> <http://www.lewelectric.com/wp-content/gallery/1101-series/6304-be.jpg>
>> should be almost exactly 5 inches diagonally...
>
> Convention center box a-la
>
> http://www.graybar.com/documents/hubbell-wdk-convention-center-boxes.pdf
>
> It's got the depth to accommodate a sealed connector but it is too
> large.

How deep do you *need* to go?  Perhaps you can fit an extension
onto the box.  Or, stack one atop the other (bottom removed)
to gain the additional depth -- since the sides will be continuous
concrete...

Can you consider using an "unsealed" connector and counting on the
box -- when closed -- to be "water/rain-tight"?  I.e., when IN USE,
does it still need to meet those requirements?

>> Of course, that just gives you *one* connector (power)
>
> Yes and unsealed when connected.  That seems to be the hard part.

If it has to be sealed while in use, then the risk of liquids
entering the box, etc. increases dramatically.  I had assumed
you only needed to be able to seal it up when *not* in use.

>> From your followup to this post, it seems like you could afford
>> a *second* box nearby that houses your data/signal connector?
>> This would get around the prohibition against mains and signals
>> in the same box -- and, the 5" limit on the (first) box...
>
> Perhaps.

No doubt not as elegant as a "one box" solution.  But, constraints
may preclude that approach.

>> Yikes!  At 1kw, even 48V would require #10AWG wire.  I'd have to
>> look up the ohms/foot to figure what sort of a hit you'd take
>> at 200+ ft...
>>
>> At 24V it would probably be impractical (wire sizes).
>
> Yeah, why make it easy on ourselves?

Perhaps a few square yards of PV's?  :-/

<frown>  Well, at least you don't have to *also* make it "inexpensive"!

On Sat, 10 Sep 2011 22:33:53 -0700, Don Y <nowhere@here.com> wrote:

>Most folks see the Code et al. as a "nuisance".  I, OTOH, figure
>there is *some* reason, there -- even if it isn't spelled out
>explicitly (though the annotated code books try to put some
>explanation behind each requirement).

They are, and they aren't, a nuisance.

Wiring codes - for the most part - are minimum guides for trade
electricians.  Particularly at low voltages they routinely permit
installations that no safety conscious engineer (or sane person) ever
would approve.  

But then periodically the regs change for no apparent reason other
than to stimulate business for electricians and suppliers.  You
compare the old and new regs and it's obvious that the new is not
safer in any way - it's just different enough that existing
installations have to be "fixed".

George

Hi George,

On 9/11/2011 1:48 PM, George Neuner wrote:
> On Sat, 10 Sep 2011 22:33:53 -0700, Don Y<nowhere@here.com>  wrote:
>
>> Most folks see the Code et al. as a "nuisance".  I, OTOH, figure
>> there is *some* reason, there -- even if it isn't spelled out
>> explicitly (though the annotated code books try to put some
>> explanation behind each requirement).
>
> They are, and they aren't, a nuisance.
>
> Wiring codes - for the most part - are minimum guides for trade
> electricians.  Particularly at low voltages they routinely permit
> installations that no safety conscious engineer (or sane person) ever
> would approve.

What the Code calls Low Voltage, AFAICT, *requires* close to nothing!
I wanted to relocate the transformers for the landscape lighting to the 
back of the garage.  This adds ~40 wire feet (each way) of conductor
to the circuit.  I figured I could just run a pair of 12's for each
conductor (let's drive IR losses into the mud :> ) and satisfy *my*
needs.

Of course, those 12's were going to come from some extra ROMEX I
have lying around.  "Hmmm... how will an electrician know that *this*
ROMEX is carrying 12-24VAC while *that* ROMEX (a few inches away)
is carrying mains voltage?"

And, what if there's a short or partial short.  Granted, it's only a
few hundred watts, but...

<frown>

> But then periodically the regs change for no apparent reason other
> than to stimulate business for electricians and suppliers.  You
> compare the old and new regs and it's obvious that the new is not
> safer in any way - it's just different enough that existing
> installations have to be "fixed".

I don't know how "real" that scenario is.  I.e., as a kid, I recall
hearing (I hung around with lots of tradesmen) that any wiring that
was NOT up to the latest code had to be upgraded *to* that code.
It struck me, then, as silly:  "Who the hell will ever hire an 
electrician to install an extra receptacle if that electrician is
then going to turn around and say, 'I'm sorry, sir, but I have
to remove all this K&T wiring and replace it with _______'?"

I suspect the practical effect is that these things just get
conveniently ignored.  OTOH, its hard to see writing a reg
where you deliberately *allow* "bad practices" to remain in
place...

Has anyone any experience with this from a *business location"
point of view?  I.e., perhaps there they are bigger "sticklers"
for these details?

On Sep 11, 2:06=A0pm, Don Y <nowh...@here.com> wrote:
> How deep do you *need* to go? =A0

With the current connector candidate, 50mm.

> Perhaps you can fit an extension
> onto the box. =A0Or, stack one atop the other (bottom removed)
> to gain the additional depth -- since the sides will be continuous
> concrete...

That's essentially what the convention boxes appear to do.
We have come up with a design we can build ourselves
that uses the same principle but if we can find an
existing solution it would make our life easier.

> > Yes and unsealed when connected. =A0That seems to be the hard part.
>
> If it has to be sealed while in use, then the risk of liquids
> entering the box, etc. increases dramatically. =A0I had assumed
> you only needed to be able to seal it up when *not* in use.

As I said, why make it easy on ourselves?  It is, unfortunately to
situation that needs to be worked to.


> Perhaps a few square yards of PV's? =A0:-/

And the corresponding kWhs of batteries. :)

That was in the original design concept until the implications of
the power requirements were pointed out.  Then I think it failed
on both aesthetic and cost grounds.

> <frown> =A0Well, at least you don't have to *also* make it "inexpensive"!

Thank heavens for small mercies.

Robert

On Sep 12, 10:01=A0am, Robert Adsett <s...@aeolusdevelopment.com> wrote:
> On Sep 11, 2:06=A0pm, Don Y <nowh...@here.com> wrote:
>
> > How deep do you *need* to go? =A0
>
> With the current connector candidate, 50mm.
>
> > Perhaps you can fit an extension
> > onto the box. =A0Or, stack one atop the other (bottom removed)
> > to gain the additional depth -- since the sides will be continuous
> > concrete...
>
> That's essentially what the convention boxes appear to do.
> We have come up with a design we can build ourselves
> that uses the same principle but if we can find an
> existing solution it would make our life easier.
>
> > > Yes and unsealed when connected. =A0That seems to be the hard part.
>
> > If it has to be sealed while in use, then the risk of liquids
> > entering the box, etc. increases dramatically. =A0I had assumed
> > you only needed to be able to seal it up when *not* in use.
>
> As I said, why make it easy on ourselves? =A0It is, unfortunately to
> situation that needs to be worked to.
>
> > Perhaps a few square yards of PV's? =A0:-/
>
> And the corresponding kWhs of batteries. :)
>
> That was in the original design concept until the implications of
> the power requirements were pointed out. =A0Then I think it failed
> on both aesthetic and cost grounds.
>
> > <frown> =A0Well, at least you don't have to *also* make it "inexpensive=
"!
>
> Thank heavens for small mercies.
>
> Robert

I suppose it's too late to consider power over ethernet or, gulp, some
kinda domotics like X10?

On Sun, 11 Sep 2011 19:09:53 -0700, Don Y <nowhere@here.com> wrote:

>> But then periodically the regs change for no apparent reason other
>> than to stimulate business for electricians and suppliers.  You
>> compare the old and new regs and it's obvious that the new is not
>> safer in any way - it's just different enough that existing
>> installations have to be "fixed".
>
>I don't know how "real" that scenario is.  I.e., as a kid, I recall
>hearing (I hung around with lots of tradesmen) that any wiring that
>was NOT up to the latest code had to be upgraded *to* that code.
>It struck me, then, as silly:  "Who the hell will ever hire an 
>electrician to install an extra receptacle if that electrician is
>then going to turn around and say, 'I'm sorry, sir, but I have
>to remove all this K&T wiring and replace it with _______'?"

There now are several states that require inspection for home sales
and where either the seller or buyer *must* agree to fix any code
violations or the home will lose its occupancy permit.

In most states, though, home sales still are caveat emptor.


>Has anyone any experience with this from a *business location"
>point of view?  I.e., perhaps there they are bigger "sticklers"
>for these details?

Business and occupancy permits don't transfer with a commercial sale,
so commercial properties can be sold with code violations because the
new owner will need to get new permits anyway.

George