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What's wrong with this (subpanel) picture?
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| Jeff Miller 2005-06-17, 11:28 pm |
| Hi, I have an EE background, have wired up a few new homes, and worked
for a short period as a journeyman for a large electical company.
But it's been many years, I'm a little rusty, and because I've only
wired new homes where I had the opportunity to optimize from the start
I'm less familiar with old work and exceptions. So I thought I'd run my
idea by here for a sanity check. My latest NEC is dated 1984. My
terminology is probably a little off sometimes.
I've got an 1884 two-unit building with lots of knob and tube. A
contractor "updated" the electrical in the mid 70's, but the work was
poorly planned and mostly done plain wrong. Lots of reversing hots and
neutrals, some 3 prong outlets totally ungrounded, some 3 prong outlets
grounded with what looks like 20 gauge steel wire... the usual, though
obviously some of the errors could have been made by homeowners after
the update. The service panels are only 50 amps for each flat. Most of
the circuits thread their way through multiple rooms: if you're making
toast in the kitchen and have a space heater plugged in virtually
anywhere, you'll trip a breaker and half the lights will go out.
Actually it really seems like 2 20 amp circuits supply virtually
everything, though there are 7 or 8 circuits wired in at the panel.
Notorious Federal Pacific breakers, of course.
So here's the proposal. I want to put in an addtional subpanel,
eventually for each flat but for now just the top. The exisiting 50A
panel I'll reserve for the kitchen and laundry room, which are the two
rooms closest to the panel and have the most special requirements. I
_hope_ to be able to replace all of the knob-and-tube by using it to
pull romex. Access is good in the attic.
The service entrance is at the botton of the rear stairs, in an enclosed
porch. Meter boxes and breaker boxes are surface mount and joined by
offsets. I'll tap into the service conductors in the meter housing
(after the meter of course) with splice block taps: I have (hmm, only
two come to think about it) IPL 1/0-4 blocks. There may be extra lug
positions inside the meter box already, I dunno. I'll come out with 3X 6
AWG THHN stranded (ebay buy) though EMT (perhaps an offset) and attach
these to the main lugs of a small 70 amp, 2 pole surface mount box. I'll
put a 60 or 70 amp 2 pole breaker in there, and use that to feed the
mainlugs of the subpanel. I'll bring the load side out with 6 AWG
through EMT, about 60 feet into a surface mount, 6-12 circuit two-pole
breaker box to be located in the kitchen pantry. I may have to penetrate
the roof of the porch and the roof gable to bring the feed through the
attic: I can't remember if the porch roof hits higher than the ceiling
joists of the top unit: the back porch is like a "lean-to". The pantry
is 5 feet wide by 3 feet deep, and I thought I'd put the box on the
narrower side so it's not so visible when you look straight on into the
pantry... and besided there are shelves on the longer back wall. They
are about 12 inches deep so I'll have about 8-9 inches on each side of
the breaker panel. The surface of the panel will about about 12" from
the side of the doorjamb of the pantry door, which opens out into the
kitchen.
I hadn't thought about it much but I guess I'd run a bunch of romex back
out of the breaker panel and into the attic through some more EMT to
emerge in the attic. I'll tack it up to the a-frame members near the
lower edge and run branches alongside the ceiling joists, so that if I
ever want to finish the attic I won't have to move anything.
One of the goals is to have all the lights on one or two circuits all
their own so that if a breaker is tripped, the lights stay on.
Two questions: can I use the EMT as the ground fault current conductor
to the subpanel? If not, do I have to use a bare copper conductor of 6
AWG in the same conduit, or can I use another (4th) 6 AWG THHN conductor
in the conduit: THHN is cheaper, it seems. If EMT will suffice, can I
run another 6 AWG THHN, 6 AWG bare, or 12 AWG insulated or bare wire
inside as a supplemental ground? I've seen too many situations where a
discontinuity in the EMT opens the protective ground. I'm thinking 12 GA
might be OK as a supplement becasse the chances of a fault in one of the
20 amp circuits is high relative to the chances of a fault in the feed
to the subpanel.
Do I shunt the fault ground (breaker box frame) to neutral using a
shorting bar at the 60/70 amp panel feeding my subpanel? I remember
somthing about the shunt only being in the main panel or fist disconnect
means... something like that... but as this 70 amp panel will
essentially be in parallel with the existing panel I'm not sure. The
main panel seems to be shunted with a piece of 12 or 14 AWG wire, BTW,
which seems undersized: but those shorting bars have alwasy looked
undersized to me, too.
Any other obvious problems? Thinking about it here's some red flags.
First of course tapping the service condctors, this seems to be
permissible in the meter box. Then, feeding through the little 2 pole, 4
position main lug panel: I've always gone to panels fitting with main
breakers but these are more expensive. I've seen what I propose done in
commercial buldings, I think, and I don't see a problem with it but I
wanted to make sure. By the way, while we're on the subject, the
exisitng Federal Pacific breaker panel appears to be a main lug panel,
too, and it's fed from the meter box via the load side of a 50 amp
breaker installed in the panel. Is that common? Legal? Another red flag
would be the subpanel in the kitchen pantry. I know clothes closets are
prohibited, and placing near flammable materials is prohibited. Would
cereal boxes and the like be too flammable to be located 8-9 inches
away? Deos the fact that someone might lean broom and mop handles
against the panel violate the access requirements.
Next can I go in through conduit (as ground) and come out with a conduit
stub to protect the romex up into the attic, or am I missing a
restriction about romex in EMT.
Finally, I remember something to the effect that a subpanel of 50A or
more can't supply lighting circuits. Deos this apply when the lighting
circuits are protectd by 15 or 20 amp breakers in the subpanels? I don't
see the problem, unless the subpanel was dedicated to serving an AC unit
or something.
I'm also thinking of using heavier gauge wire to the subpanel (and
perhaps a subpanel with more than 6/12 circuits) in anticipation of the
day when the back porch is demolished, at which time I hope to make the
bottom portion into a garden area (no back yard at present). At that
point I may well want to remove the existing panel entirely. Is there a
restriction on the distance of the breaker panel from the meter box?
Deos that circuit have to be fused on the meter end?
Thanks for listening and any good points you might make!
And if anyione's tempted to say "you should hire a contractor", don't
bother. I was in the industry long enough to know that's no guarantee
anything's done right. Nothing beats review in a public forum like this.
-Jeff
| |
| Roy Q.T. 2005-06-17, 11:28 pm |
| You sound like you do your job well.
The 2 circuit 50 A panel is obvious insufficient for the present
electrical needs of the apartment., Rather than spend on adding another
one I'd give greater consideration to upgrading the entire system up &
down the entire dwelling through the old runway.
I think you could do better than 70 A with a 6 Awg riser from the meter
pan.
You also sound like your not in the US, I seldom hear tenants or owners
use the term Flat, when talking about housing property around here.The
reason I say this is: I have two copies of the current NEC one of them
could go to someone, if I am inclined to forward it somehow.
RQT
| |
|
| 1. get your local Electrical Inspector out there and got thru all of this
with him. After all, his word will, after all is done, be 'law'.
2. You would, IMHO, be best to replace the backfed FPE 50/2 under the meter
with a new 100amp (minimum) panel with a main breaker. The you can add
whatever branch breaker you want (70 amp) to feed your new subpanel. Why?
Well, it is difficult to tell for sure from what you describe, but note that
you can have a maximum of six main disconnects serving a structure. If you
anticipate more subpanels for your other floors, you could exceed the six
disconnect rule before you are done. Also remember that all service
disconnects must be 'grouped'. So you cannot relocate one far away from the
others.
Paying for a one day consult with an electrician experienced in remodeling
may also be cost effective.
"Jeff Miller" <cornheadorama@hotmail.com> wrote in message
news:JuyVd.10931$Pz7.917@newssvr13.news.prodigy.com...
quote:
> Hi, I have an EE background, have wired up a few new homes, and worked for
> a short period as a journeyman for a large electical company.
>
> But it's been many years, I'm a little rusty, and because I've only wired
> new homes where I had the opportunity to optimize from the start I'm less
> familiar with old work and exceptions. So I thought I'd run my idea by
> here for a sanity check. My latest NEC is dated 1984. My terminology is
> probably a little off sometimes.
>
> I've got an 1884 two-unit building with lots of knob and tube. A
> contractor "updated" the electrical in the mid 70's, but the work was
> poorly planned and mostly done plain wrong. Lots of reversing hots and
> neutrals, some 3 prong outlets totally ungrounded, some 3 prong outlets
> grounded with what looks like 20 gauge steel wire... the usual, though
> obviously some of the errors could have been made by homeowners after the
> update. The service panels are only 50 amps for each flat. Most of the
> circuits thread their way through multiple rooms: if you're making toast
> in the kitchen and have a space heater plugged in virtually anywhere,
> you'll trip a breaker and half the lights will go out. Actually it really
> seems like 2 20 amp circuits supply virtually everything, though there
> are 7 or 8 circuits wired in at the panel. Notorious Federal Pacific
> breakers, of course.
>
> So here's the proposal. I want to put in an addtional subpanel, eventually
> for each flat but for now just the top. The exisiting 50A panel I'll
> reserve for the kitchen and laundry room, which are the two rooms closest
> to the panel and have the most special requirements. I _hope_ to be able
> to replace all of the knob-and-tube by using it to pull romex. Access is
> good in the attic.
>
> The service entrance is at the botton of the rear stairs, in an enclosed
> porch. Meter boxes and breaker boxes are surface mount and joined by
> offsets. I'll tap into the service conductors in the meter housing (after
> the meter of course) with splice block taps: I have (hmm, only two come to
> think about it) IPL 1/0-4 blocks. There may be extra lug positions inside
> the meter box already, I dunno. I'll come out with 3X 6 AWG THHN stranded
> (ebay buy) though EMT (perhaps an offset) and attach these to the main
> lugs of a small 70 amp, 2 pole surface mount box. I'll put a 60 or 70 amp
> 2 pole breaker in there, and use that to feed the mainlugs of the
> subpanel. I'll bring the load side out with 6 AWG through EMT, about 60
> feet into a surface mount, 6-12 circuit two-pole breaker box to be located
> in the kitchen pantry. I may have to penetrate the roof of the porch and
> the roof gable to bring the feed through the attic: I can't remember if
> the porch roof hits higher than the ceiling joists of the top unit: the
> back porch is like a "lean-to". The pantry is 5 feet wide by 3 feet deep,
> and I thought I'd put the box on the narrower side so it's not so visible
> when you look straight on into the pantry... and besided there are shelves
> on the longer back wall. They are about 12 inches deep so I'll have about
> 8-9 inches on each side of the breaker panel. The surface of the panel
> will about about 12" from the side of the doorjamb of the pantry door,
> which opens out into the kitchen.
>
> I hadn't thought about it much but I guess I'd run a bunch of romex back
> out of the breaker panel and into the attic through some more EMT to
> emerge in the attic. I'll tack it up to the a-frame members near the lower
> edge and run branches alongside the ceiling joists, so that if I ever want
> to finish the attic I won't have to move anything.
>
> One of the goals is to have all the lights on one or two circuits all
> their own so that if a breaker is tripped, the lights stay on.
>
> Two questions: can I use the EMT as the ground fault current conductor to
> the subpanel? If not, do I have to use a bare copper conductor of 6 AWG in
> the same conduit, or can I use another (4th) 6 AWG THHN conductor in the
> conduit: THHN is cheaper, it seems. If EMT will suffice, can I run another
> 6 AWG THHN, 6 AWG bare, or 12 AWG insulated or bare wire inside as a
> supplemental ground? I've seen too many situations where a discontinuity
> in the EMT opens the protective ground. I'm thinking 12 GA might be OK as
> a supplement becasse the chances of a fault in one of the 20 amp circuits
> is high relative to the chances of a fault in the feed to the subpanel.
>
> Do I shunt the fault ground (breaker box frame) to neutral using a
> shorting bar at the 60/70 amp panel feeding my subpanel? I remember
> somthing about the shunt only being in the main panel or fist disconnect
> means... something like that... but as this 70 amp panel will essentially
> be in parallel with the existing panel I'm not sure. The main panel seems
> to be shunted with a piece of 12 or 14 AWG wire, BTW, which seems
> undersized: but those shorting bars have alwasy looked undersized to me,
> too.
>
> Any other obvious problems? Thinking about it here's some red flags. First
> of course tapping the service condctors, this seems to be permissible in
> the meter box. Then, feeding through the little 2 pole, 4 position main
> lug panel: I've always gone to panels fitting with main breakers but these
> are more expensive. I've seen what I propose done in commercial buldings,
> I think, and I don't see a problem with it but I wanted to make sure. By
> the way, while we're on the subject, the exisitng Federal Pacific breaker
> panel appears to be a main lug panel, too, and it's fed from the meter box
> via the load side of a 50 amp breaker installed in the panel. Is that
> common? Legal? Another red flag would be the subpanel in the kitchen
> pantry. I know clothes closets are prohibited, and placing near flammable
> materials is prohibited. Would cereal boxes and the like be too flammable
> to be located 8-9 inches away? Deos the fact that someone might lean broom
> and mop handles against the panel violate the access requirements.
>
> Next can I go in through conduit (as ground) and come out with a conduit
> stub to protect the romex up into the attic, or am I missing a restriction
> about romex in EMT.
>
> Finally, I remember something to the effect that a subpanel of 50A or more
> can't supply lighting circuits. Deos this apply when the lighting circuits
> are protectd by 15 or 20 amp breakers in the subpanels? I don't see the
> problem, unless the subpanel was dedicated to serving an AC unit or
> something.
>
> I'm also thinking of using heavier gauge wire to the subpanel (and perhaps
> a subpanel with more than 6/12 circuits) in anticipation of the day when
> the back porch is demolished, at which time I hope to make the bottom
> portion into a garden area (no back yard at present). At that point I may
> well want to remove the existing panel entirely. Is there a restriction on
> the distance of the breaker panel from the meter box? Deos that circuit
> have to be fused on the meter end?
>
> Thanks for listening and any good points you might make!
>
> And if anyione's tempted to say "you should hire a contractor", don't
> bother. I was in the industry long enough to know that's no guarantee
> anything's done right. Nothing beats review in a public forum like this.
>
> -Jeff
| |
| jeff miller 2005-06-17, 11:28 pm |
| rieker5.nospam.ever@hotmail.com wrote:
quote:
> 1. get your local Electrical Inspector out there and got thru all of this
> with him. After all, his word will, after all is done, be 'law'.
>
> 2. You would, IMHO, be best to replace the backfed FPE 50/2 under the meter
> with a new 100amp (minimum) panel with a main breaker. The you can add
> whatever branch breaker you want (70 amp) to feed your new subpanel. Why?
> Well, it is difficult to tell for sure from what you describe, but note that
> you can have a maximum of six main disconnects serving a structure. If you
> anticipate more subpanels for your other floors, you could exceed the six
> disconnect rule before you are done. Also remember that all service
> disconnects must be 'grouped'. So you cannot relocate one far away from the
> others.
>
> Paying for a one day consult with an electrician experienced in remodeling
> may also be cost effective.
>
> "Jeff Miller" <cornheadorama@hotmail.com> wrote in message
> news:JuyVd.10931$Pz7.917@newssvr13.news.prodigy.com...
>
>
>
>
Unfortunately in my area the inspectors acknowledge their own
incompetence by requiring all work be performed by licensed contactors,
which is not economically feasible, therefore having the inspector over
is not feasible either. The contractors are thus essentially
self-policing, which leads to a lot of shoddy work. So houses burn down
right and left, but the city deosn't care: they've washed their hands of
responsibility by putting it on the contractors. Lose lose situation if
you ask me.
The whole thing makes me hopping mad. Came as quite a shock that a guy
with an EE degree can't wire (or plumb, for that matter) his own house.
I do remember reading that 6 disconnect rule, now that you mention it. I
may well hit my head on that one, as I'm thinking of adding a subpanel
in the basement too.
Meanwhile, no red flags on what I propose per se?
-Jeff
| |
| jeff miller 2005-06-17, 11:28 pm |
| Roy Q.T. wrote:
quote:
> You sound like you do your job well.
>
> The 2 circuit 50 A panel is obvious insufficient for the present
> electrical needs of the apartment., Rather than spend on adding another
> one I'd give greater consideration to upgrading the entire system up &
> down the entire dwelling through the old runway.
>
> I think you could do better than 70 A with a 6 Awg riser from the meter
> pan.
>
>
> You also sound like your not in the US, I seldom hear tenants or owners
> use the term Flat, when talking about housing property around here.The
> reason I say this is: I have two copies of the current NEC one of them
> could go to someone, if I am inclined to forward it somehow.
>
> RQT
>
Yep. I'd love to replace that panel. Two problems, one is it's all
plumbed in with conduit, I wouldn't look forward to moving it. The other
is I don't think I could afford it right now, though I hadn't given it a
whole lot of thought: actually I have a few extra panels and one might
be suitable. But ultimately I'd like to (re)move it entirely, the whole
rear porch will probably be demolished pretty soon. I've always liked
indoor panels on th same floor, anyway.
Actually it's a 100 amp panel, but last time I checked the price of a
100 amp breaker for it was prohibitive. I'll check again. I suppose I
could use the 50 amp breaker in there to feed my subpanel.
The time and $$$ budget are both limited, the project has to come in at
~$200 and before the new renters move in. Preferrably well below $200, I
do have a number of parts on hand: and finding more in th basement every
day 
Probably the best I could do is spring for 4 or 2 awg at this point, and
use one of my larger panels in the kitchen pantry in anticipation of
making it the only panel in future.
I'm in the US, when I first heard the term "flat" in the context of
apartments around here I latched right onto it, as a valuable
distinction versus several "apartments" on one floor which is more common.
Sure, I could use an updated NEC, I tend to assume not much has changed
but I hear it is a lot bigger, the extra words must mean _something_
I can send you a postal money order to cover expenses and what not.
-Jeff
| |
| Adrienne Hendrickson 2005-06-17, 11:28 pm |
|
"jeff miller" <cornheadorama@hotmail.com> wrote in message
news:CF6Wd.11495$Pz7.10198@newssvr13.news.prodigy.com...
quote:
> rieker5.nospam.ever@hotmail.com wrote:
>
> Unfortunately in my area the inspectors acknowledge their own incompetence
> by requiring all work be performed by licensed contactors, which is not
> economically feasible, therefore having the inspector over is not feasible
> either.
The work you propose to do should require an electrical permit. You need to
check with the local authority having jurisdiction (AHJ). As the previous
poster said, they are the law with regards to what is done. You also need a
later edition of the NEC than 1984. Find out from your AHJ what the legal
edition is for your area. It varies from state to state and city to city,
but is most likely the 1999, 1996 or 2002. Major changes were made to the
code in 1999 and 2002.
As to an EE being able to wire their own house, an EE degree is fairly
broad. Should an EE with a background in computers or semiconductors be
given a free pass?
My recommendation is to talk to you AHJ. If you present a sketch of what you
want to do, you may not need a licensed contractor. I don't know where you
are or what the law is there. Here, what you describe would require a
building permit and inspection and approval by the local AHJ.
quote:
> I do remember reading that 6 disconnect rule, now that you mention it. I
> may well hit my head on that one, as I'm thinking of adding a subpanel in
> the basement too.
The 6-disconnect rule is still in effect. Also, you mentioned tapping at the
meter enclosure. I'd definately talk about this with your utility company as
that is theirs.
Adrienne
| |
| Roy Q.T. 2005-06-17, 11:29 pm |
| As Adrienne suggests, you must contact your Utility Company, they are
the only ones Authorized to open your Meter., they may open it for you,
if you have credentials to schedule the job with them, they are very
helpful, at some point you will need contact & papers from the AHJ in
your local buildings dept.'s electrical division..... it is tedious
enough that it is better to hire a Licensee., but if you own the
property in some states it is not that complex to get {like getting your
C.of O} the electrical inspection required to complete & have the
Utility seal the job when it's done.Hopefully up-to-code.
Sorry about the Code Book, I'll keep looking to see if it is still here.
don't feel too intimidated, I've seen a few jobs recently performed by a
fully lic. electrician on bedrock, that did not meet the Codes & was
rejected by both the AHJ & The Utility.,(Panel Mount was wrong & he
Kinked the Conduit) I saw the problem immediately but was there just for
the Neon & Access Control. it's a matter of Professional Taste, Safety &
Skilled Craftsmanship.
do it like one of your new jobs, ask if you need to know any specific
code requirement, and detail the type of situation & particulars of the
job as you go.
=AEoy
| |
|
| jeff miller wrote:
quote:
>
> So here's the proposal. I want to put in an addtional subpanel,
> eventually for each flat but for now just the top. The exisiting 50A
> panel I'll reserve for the kitchen and laundry room, which are the
> two rooms closest to the panel and have the most special
> requirements. I _hope_ to be able to replace all of the knob-and-tube
> by using it to pull romex. Access is good in the attic.
>
> The service entrance is at the botton of the rear stairs, in an
> enclosed porch. Meter boxes and breaker boxes are surface mount and
> joined by offsets. I'll tap into the service conductors in the meter
> housing (after the meter of course) with splice block taps: I have
> (hmm, only two come to think about it) IPL 1/0-4 blocks.
Splicing in the meter enclosure is a bad idea. The meter box is not
designed to have enough space to make splices.
Splcing service wires is a bad idea. Remember the service wires, in
effect, have no overcurrent protection.
Likely will also violate NEC.
quote:
>There may be
> extra lug positions inside the meter box already, I dunno. I'll come
> out with 3X 6 AWG THHN stranded (ebay buy) though EMT (perhaps an
> offset) and attach these to the main lugs of a small 70 amp, 2 pole
> surface mount box. I'll put a 60 or 70 amp 2 pole breaker in there,
> and use that to feed the mainlugs of the subpanel.
#6 wire has a 60° ampacity of 55 amps. Lugs under? 100 amps are limited
to the 60° ampacity to avoid heating problems (unless lugs at both ends
of the wire are listed for a higher temperature). The useable rating of
your wires is 55 amps.
Why would you use a main-lug pannel instead of main-breaker. Main lugs
allow more breakers which are likely to overload your #6 wire.
quote:
>If EMT
> will suffice, can I run another 6 AWG THHN, 6 AWG bare, or 12 AWG
> insulated or bare wire inside as a supplemental ground?
#6 OK, #12 not a good idea - if the EMT opens it is way too small.
quote:
>
> Do I shunt the fault ground (breaker box frame) to neutral using a
> shorting bar at the 60/70 amp panel feeding my subpanel?
"Main onding jumper" only at service disconnects, which this is. Without
looking it up, the size is the same as the "grounding equipment
conductor" (to "groundng electrode" - water pipe) unless furnished by
the manufacturer of the panel, in which case the panel listing covers it.
You do, in addition, have to connect the neutral/ground to a "grounding
electrode".
The EMT from the meter can to the panel requires grounding other than
EMT connectors, typically a ground clamp on the EMT with the "grounding
electrod conductor" running througn it.
quote:
> Is there a restriction on the distance of the breaker panel from the
> meter box?
If this has a service disconnect it has to be at the closest position
inside the house. Again, service wires have no effecive overcurrent
protection.
Services, as you should be aware, have requirements that are unique
because of the potential hazards, from shock and fire, that they can
create. Advice through a newsgroup may not be adequate, there are so
many considerations.
What is the ampacity of the service wires? Are they going to be
protected by the multiple over current devices in this installation?
Having a single main-breaker panel has major safety advantages.
There have been a lot of changes since 1984. As you probably also know
having a current code book is not enough. You have to be able to find
the applicable requirements, which is not always easy for an
electrician. A current, really good, wiring-for-dummies-type book might
be good - but it has to be good for services. Multiple service
disconnects are likely beyond such a book.
bud--
| |
| Jeff Miller 2005-06-17, 11:29 pm |
| Bud wrote:
quote:
> jeff miller wrote:
>
>
>
> Splicing in the meter enclosure is a bad idea. The meter box is not
> designed to have enough space to make splices.
> Splcing service wires is a bad idea. Remember the service wires, in
> effect, have no overcurrent protection.
> Likely will also violate NEC.
>
>
> #6 wire has a 60° ampacity of 55 amps. Lugs under? 100 amps are limited
> to the 60° ampacity to avoid heating problems (unless lugs at both ends
> of the wire are listed for a higher temperature). The useable rating of
> your wires is 55 amps.
> Why would you use a main-lug pannel instead of main-breaker. Main lugs
> allow more breakers which are likely to overload your #6 wire.
>
>
>
> #6 OK, #12 not a good idea - if the EMT opens it is way too small.
>
>
> "Main onding jumper" only at service disconnects, which this is. Without
> looking it up, the size is the same as the "grounding equipment
> conductor" (to "groundng electrode" - water pipe) unless furnished by
> the manufacturer of the panel, in which case the panel listing covers it.
> You do, in addition, have to connect the neutral/ground to a "grounding
> electrode".
> The EMT from the meter can to the panel requires grounding other than
> EMT connectors, typically a ground clamp on the EMT with the "grounding
> electrod conductor" running througn it.
>
>
> If this has a service disconnect it has to be at the closest position
> inside the house. Again, service wires have no effecive overcurrent
> protection.
>
> Services, as you should be aware, have requirements that are unique
> because of the potential hazards, from shock and fire, that they can
> create. Advice through a newsgroup may not be adequate, there are so
> many considerations.
>
> What is the ampacity of the service wires? Are they going to be
> protected by the multiple over current devices in this installation?
> Having a single main-breaker panel has major safety advantages.
>
> There have been a lot of changes since 1984. As you probably also know
> having a current code book is not enough. You have to be able to find
> the applicable requirements, which is not always easy for an
> electrician. A current, really good, wiring-for-dummies-type book might
> be good - but it has to be good for services. Multiple service
> disconnects are likely beyond such a book.
>
>
> bud--
Hmm... well in the 1984 NEC splicing is allowed in and only in the
service box... but that may be a significant change in later editions.
The point about the meter box being owned by the power co is a good one:
I think I'll have to take a different approach, namely replacing the 50
amp main breaker with 100 amps and using the existing 50 amp to feed my
subpanel. I'll double check but I'm quite sure it is a 100 amp panel.
I wanted to use a main lug panel as opposed to a main breaker panel in
case of the remote possibility that the feed lines to the breaker panel
shorted near the panel, and to keep the disconnects near the
meters/service drop so that the fire company could de-energize the
building from one spot. Deos that make any sense? To clarify let me
re-iterate that the idea was to put a small box near the meter, and run
close to 100' of #6 to the subpanel. 100' of unprotected #6 makes me
nervous.
Very good point about the panels limiting the application temperature of
the wires. Mine are rated 75 C but I'll look into that more carefully in
the latest NEC. The old FPE panel may be rated 60 C.
I haven't measured the gauge of the service wires but they look plenty
big, I'd guess 200 amps. But that would be shared by both flats, so I'll
have a 100 amp ceiling per flat. And of course I have to double chck on
their sizes.
I'll spend some time down at the library looking through the new NEC,
and some commentary and tutorial books. I always do but I figured it
would be good to get some pointers here too, so I know where to focus.
There's a few calcs I have to make yet, such as voltage drop through
that #6 wire.
-Jeff
| |
| Roy Q.T. 2005-06-17, 11:29 pm |
| He Jeff: it sounds like you bought some loose no. 6 awg and now you will
need greenfield (empty armoured flexible conduit) or pipe to run it
through oh well., i hope everything works out ok., sorry about the book,
but happy to hear you've got one @ your library. =AEoy
| |
| Jeff Miller 2005-06-17, 11:29 pm |
| Roy Q.T. wrote:
quote:
> He Jeff: it sounds like you bought some loose no. 6 awg and now you will
> need greenfield (empty armoured flexible conduit) or pipe to run it
> through oh well., i hope everything works out ok., sorry about the book,
> but happy to hear you've got one @ your library. ®oy
>
Yep. But pipe was in the picture anyway because most of the main run is
surface/exposed. Not looking forward to that, one thing I hate it's
pipe. All in all I wish I had the extra couple grand to permit and
contract and... essentially do all the things I'll have to do in 5
years anyway when I demolish the back porch. Unfortunately I don't see
my cash flow situation turning around for about a year... though now
that the cold season is mostly over and space heaters are out of the
picture I might be able to squeak by with the existing wiring this year.
It sucks soooo bad though... it really sunk in for the first time only
last night when I was checking the rating of the exisiting panel that
the whole house is run off 2 X 20A and 3 X 15A breakers. And even those
are run in the worst possible way: I dunno where 4 of them go because it
really seems that %80 of the house runs off one of them. I think when it
was originally knob-and-tube'd there was only 1 or 2 circuits, and the
"update" just coupled up to them and added a dedicated here and there
for laundry and what not.
-Jeff
| |
| Jeff Miller 2005-06-17, 11:29 pm |
| Bud wrote:
quote:
> jeff miller wrote:
>
>
>
> Splicing in the meter enclosure is a bad idea. The meter box is not
> designed to have enough space to make splices.
> Splcing service wires is a bad idea. Remember the service wires, in
> effect, have no overcurrent protection.
> Likely will also violate NEC.
>
>
> #6 wire has a 60° ampacity of 55 amps. Lugs under? 100 amps are limited
> to the 60° ampacity to avoid heating problems (unless lugs at both ends
> of the wire are listed for a higher temperature). The useable rating of
> your wires is 55 amps.
> Why would you use a main-lug pannel instead of main-breaker. Main lugs
> allow more breakers which are likely to overload your #6 wire.
>
>
>
> #6 OK, #12 not a good idea - if the EMT opens it is way too small.
>
>
> "Main onding jumper" only at service disconnects, which this is. Without
> looking it up, the size is the same as the "grounding equipment
> conductor" (to "groundng electrode" - water pipe) unless furnished by
> the manufacturer of the panel, in which case the panel listing covers it.
> You do, in addition, have to connect the neutral/ground to a "grounding
> electrode".
> The EMT from the meter can to the panel requires grounding other than
> EMT connectors, typically a ground clamp on the EMT with the "grounding
> electrod conductor" running througn it.
>
>
> If this has a service disconnect it has to be at the closest position
> inside the house. Again, service wires have no effecive overcurrent
> protection.
>
> Services, as you should be aware, have requirements that are unique
> because of the potential hazards, from shock and fire, that they can
> create. Advice through a newsgroup may not be adequate, there are so
> many considerations.
>
> What is the ampacity of the service wires? Are they going to be
> protected by the multiple over current devices in this installation?
> Having a single main-breaker panel has major safety advantages.
>
> There have been a lot of changes since 1984. As you probably also know
> having a current code book is not enough. You have to be able to find
> the applicable requirements, which is not always easy for an
> electrician. A current, really good, wiring-for-dummies-type book might
> be good - but it has to be good for services. Multiple service
> disconnects are likely beyond such a book.
>
>
> bud--
BTW, I'm well aware that I should be pulling permits for this stuff, and
I'd like nothing more than to do so. But, as I was flabbergasted to find
out _after_ buying the house, the homeowner is not permitted to work on
his own building in this jurisdiction. Seems like that should be against
the State Constitution. What do I pay my propety taxes for, what does
the Building Department exist for if not to inspect electrical work? And
if they are competent in their job, what should it matter if I'm a
contractor or not? Basiclly the Department relies on contractors for
on-the-job training of Department employees: size of and reputation (for
which read size) of the contractor determines the level of scrutiny a
job receives. I've seen TV exposes (not that I watch much TV, or believe
much of what I see) of this sort of thing with regard to general
construction in other parts of the US, but it's especially disturbing to
see it happen with respect to electrical.
And this isn't idle speculation, I worked for the largest "fast food"
style electrical house in my area for a while. You know, the guys with
three full pages of YP ads. A real eye opener. Despite the fact that I
had no credentials I quickly became the "answer man" responsible for
training the new kids, and I do mean kids. I'll never forget explaining
the difference between an amp and a volt to a guy who'd been there for
more than a year. "So your saying it's the AMPS, not the VOLTS that tell
you it's undersized..." Uh, yeah. He got hired based on his experience
as a cable TV installer. And he was doing jobs with no supervision, as a
rule.
I don't relish breaking the law (at least not consciously) but the way
the law is mis-structured here I don't have a feasible alternative.
Hey man, I'm a victim of, like, SOCIETY!
-Jeff
| |
| Jeff Miller 2005-06-17, 11:29 pm |
| Hmmm, I kinda missed this part when i first read your response.
Bud wrote:
quote:
>"Main onding jumper" only at service disconnects, which this is.
>Without looking it up, the size is the same as the "grounding
equipment >conductor" (to "groundng electrode" - water pipe) unless
furnished by >the manufacturer of the panel, in which case the panel
listing covers >it.
Interesting. I assumed it had to be sized to carry any conceivable fault
current, IE: be the same ampacity as the service conductors into the
box, or at least as the biggest conductors out of the box. But I suppose
the size of the grounding electrode is dictated by considerations
like that and so it follows the bonding jumper is in essence dictated
likewise.
I really need to brush up on the basic theory of grounding. If only I
could find a good theorhetical treatment, the practical implications
should logically follow.
quote:
>You do, in addition, have to connect the neutral/ground to a
"grounding >electrode".
Hmmm. I'll look into this also.
quote:
>The EMT from the meter can to the panel requires grounding other than
>EMT connectors, typically a ground clamp on the EMT with the
"grounding >electrod conductor" running througn it.
Hmmm. This contradicts my (vague) memory to some extent. What I remember
is something about a grounding conductor being optional, inside the
conduit, bare, and something about "in continuous contact with it's
length". Now, how the heck you can ensure that a conductor inside a
piece of EMT is in continuous contact with it is beyond me... but what
you describe sounds to me like a "parallel grounding scheme" which has
it's own special requirments.
Well, I very much appreciate your points, this kind of thing (pointing
out where I should focus when I read through the codes again) is exactly
what I was looking for. But at this point I'm feeling like I'm abusing
your time and looking a whole lot dumber than I actually am because I've
been too lazy thus far to pick up the book and pour through it the way I
always do when it's been a while since I've done a job. Of course now
I've changed the plan to a staigtforward subpanel job, for superior
stealth factor. I knew the power co. owns the meter, and I've seen
cunstruction power taps much as I described, but someone here said the
power co. owns the meter box, too: and in any case I'm thinking now,
given the fact I'm off permit, what the heck was I THINKING doing
unusual things in the box?
I just so badly wanted to decrease my reliance on that old Federal
Pacific box rather than increase it. But I checked it out more carefully
and it's not the _most_ notoriously designed FPE model.
-Jeff
| |
|
| Jeff Miller wrote:
quote:
> Bud wrote:
>
> Interesting. I assumed it had to be sized to carry any conceivable fault
> current, IE: be the same ampacity as the service conductors into the
> box, or at least as the biggest conductors out of the box. But I suppose
> the size of the grounding electrode is dictated by considerations like
> that and so it follows the bonding jumper is in essence dictated likewise.
The "grounding electrode conductor" carrys current temporarily and is
normally bare. IMHO "main bonding jumpers" are shockingly small, usually
a machine screw.
(For non-service parts of the system, grounding and bonding conductors
are also reduced in size at larger sizes from the size of the circuit
conductors - using a different table.)
quote:
> I really need to brush up on the basic theory of grounding. If only I
> could find a good theorhetical treatment, the practical implications
> should logically follow.
I'm not sure the theory-to-application logic is always obvious, but the
application-to-theory logic usually is. The NEC is to a considerable
degree a pragmatic code of correcting problems based on experience.
quote:
>
> Hmmm. This contradicts my (vague) memory to some extent. What I remember
> is something about a grounding conductor being optional, inside the
> conduit, bare, and something about "in continuous contact with it's
> length". Now, how the heck you can ensure that a conductor inside a
> piece of EMT is in continuous contact with it is beyond me... but what
> you describe sounds to me like a "parallel grounding scheme" which has
> it's own special requirments.
Because of the high potential fault currents (because service wires are,
in effect, not fused) the service entry metal enclosures have to be
bonded together by greater-than normal means, see 250.92.
Assuming an EMT service entry raceway, the meter box is commonly bonded
to the neutral, one of the several places this is permitted. The service
riser is connected to the meter box through a "hub" on box which is a
permitted bond. The service panel/ground system is required to be
connected to the neutral (which is then the groundED conductor) with a
"main bonding jumper" (and this combination is required to be connected
to "grounding electrode(s)" by "grounding electrode conductor(s)". This
leaves the pipe from the meter can to the panel. Standard locknuts are
not permitted for the bond so the EMT connector-to-panel connection
can't be used. Commonly a pipe ground clamp is attached to the EMT, and
as the "grounding electrode conductor" leaves the panel it goes through
the lug on the ground clamp. (This is not a ground wire inside the EMT.)
Bud--
| |
| Roy Q.T. 2005-06-17, 11:29 pm |
| There is a grounding or bonding clamp [required by the NEC, that hardly
anyone uses but should use in new work] you can use them at either end
of your emt, placed tightly wire secured over your locknuts, the wire
attaches to each boxed end through the pipe, and that is up to code
bonding for all your pipework., the idea is, if your pipes become loose
the bonding wire will ensure proper ground.The rest is pretty much out
of the inkwell };-)
=AE
you can get a license electrician to over see your plans and file the
job for the permit on commenced work, then when you finish, he comes in
takes a look makes sure everythings cool, gets it inspected and the
utility closes the job after he completes the paperwork for you ....
this may vary from state to state.
I feel like you sometimes: all that matters is that the job be done
right with the codes and good workmanship. In some instances it's not
uncommon for the utility to license a job they deem well done and
approve it for an owner.
=AE
| |
| Andrew Thomas 2005-06-17, 11:30 pm |
| Roy Q.T. wrote:
quote:
> There is a grounding or bonding clamp [required by the NEC, that hardly
> anyone uses but should use in new work] you can use them at either end
> of your emt, placed tightly wire secured over your locknuts, the wire
> attaches to each boxed end through the pipe, and that is up to code
> bonding for all your pipework., the idea is, if your pipes become loose
> the bonding wire will ensure proper ground.The rest is pretty much out
> of the inkwell };-)
> ®
>
> you can get a license electrician to over see your plans and file the
> job for the permit on commenced work, then when you finish, he comes in
> takes a look makes sure everythings cool, gets it inspected and the
> utility closes the job after he completes the paperwork for you ....
> this may vary from state to state.
>
> I feel like you sometimes: all that matters is that the job be done
> right with the codes and good workmanship. In some instances it's not
> uncommon for the utility to license a job they deem well done and
> approve it for an owner.
>
>
> ®
>
I bought a pair of those grounding nuts you mentioned. Becuase this is a
subpanel project it makes sense to me both ends should be grounded this
way. But as much a ensuring good contact despite a loose pipe, would it
be safe to say that ensures good contact despite the epoxy coating on
the boxes?
-Jeff
| |
| Andrew Thomas 2005-06-17, 11:30 pm |
| jeff miller wrote:
quote:
> rieker5.nospam.ever@hotmail.com wrote:
>
>
> Unfortunately in my area the inspectors acknowledge their own
> incompetence by requiring all work be performed by licensed contactors,
> which is not economically feasible, therefore having the inspector over
> is not feasible either. The contractors are thus essentially
> self-policing, which leads to a lot of shoddy work. So houses burn down
> right and left, but the city deosn't care: they've washed their hands of
> responsibility by putting it on the contractors. Lose lose situation if
> you ask me.
>
> The whole thing makes me hopping mad. Came as quite a shock that a guy
> with an EE degree can't wire (or plumb, for that matter) his own house.
>
> I do remember reading that 6 disconnect rule, now that you mention it. I
> may well hit my head on that one, as I'm thinking of adding a subpanel
> in the basement too.
>
> Meanwhile, no red flags on what I propose per se?
>
> -Jeff
By the way if anyone is still listening this project is %95 finished and
going well. The project expanded in scope to include ripping out _all_
knob and tube wiring and replacing with Romex: ripping out _all_ the old
work boxes and replacing with boxes designed to anchor Romex: grounding
all the pendulum light fixtures, previously ungrounded: replacing all
the outlets with nylon-face Hubbles (they are nearly all within 3" of
the floor, and as it happened I had dozens of surplus Hubbles lying
around) and I think I replaced all the light switches while I was at it.
Because I am not confident the service conductors from meter to
primary panel are larger than #6 (the only number I can see is a 6, and
it looks a size bigger than my THHN 6 but I'm not quite sure), I'm
sticking with my 50 A main breaker and 50 A breaker to subpanel for now.
Ridiculous but good for now. Also I was careful to balance the loads on
each line given a worse case scenario of space heaters on in all (3)
rooms without gas heat, 20A in the bathroom, and 20A in the kitchen.
Would like to upgrade main breaker to 100 or at least 70: then all
lights could be incandescent and 20A in laundry room
| |
| HorneTD 2005-06-17, 11:30 pm |
| Andrew Thomas wrote:
quote:
> I bought a pair of those grounding nuts you mentioned. Becuase this is a subpanel project it makes sense to me both ends should be grounded this way. But as much a ensuring good contact despite a loose pipe, would it be safe to say that ensures good con
tact despite the epoxy coating on the boxes?
quote:
>
> -Jeff
If the connections are made up wrench tight as the code requires then
the lock nuts will bight on through the coating and bond the pipe. The
use of bonding bushings or lock nuts is to provide redundant bonding of
the pipe.
--
Tom H
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