Sub Panel Feeder Run


I just purchased a home built in 1905 and as I've gone through it I found a number of surprises. One in particular is puzzling me. The home has 100 amp service, and the wiring has been updated. There is a detached garage with a subpanel. The subpanel in the garage is fed by a 2-2-2 al feeder cable that makes a run of about 90 feet, back to the main panel in the house and connected with a 100 amp double pole circuit breaker. It looks fairly new but it seems to be a long run for a cable of that size. Theres not much to power in the garage typical lights and outlets. Is this a typical and when I say typical I mean safe situation? Thanks. -Mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
bigpete50 wrote:

In Canada, if it's got 90C insulation then #2 cable is good for 100A as a subservice.
By my calculations pulling 100A on that cable would give a bit over 5V drop, or about 2%.
However...it is not reasonable to pull that much off the main panel. The exact amount that would be reasonable to supply to the subpanel would depend on the details of the house load.
Are you sure the service isn't coming to the garage, and the house being fed via that cable?
Chris
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

A 100a sub panel on 2ga al is technically a violation but the realiity is, if the service is also 100a I can't see how you could ever get 100a in that feeder unless everything in the house was turned off.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I don't see this as likely to cause a problem since your not using anything near 100 amps in the garage but if you are concerned just change the breaker that feeds the subpanel to smaller one, 50 or 60 amps say. Plenty of power for your garage and no chance ( however unlikely) of overloading the cable that feeds the sub panel.
--

Mike S.

< snipped-for-privacy@aol.com> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
How do you figure the 2ga is a violation?
--
Steve Barker



< snipped-for-privacy@aol.com> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 18 Nov 2006 22:08:01 -0600, "Steve Barker LT"
310.16 You did see "aluminum?"
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The OP doesn't specify any type of cable. According to 310.16 - #2 (90 degree) is good for 100 amps
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 19 Nov 2006 08:15:05 -0500, "RBM" <rbm2(remove

The problem is most breakers are only rated for 75c
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Is there a code reference that disallows you from connecting a 90 degree conductor, and using it a full value? I checked with Square D, and while they describe it the same as you, they don't indicate that you can't do it, and only mention that you may have nuisance tripping as a result
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
RBM wrote:

110.14-C generally limits 100A or less terminations to 60C ampacity (75C if rated for over #1 wire). This was a UL requirement, and thus enforcable, before it appeared in the NEC a few code cycles ago. It appeared in the UL Green book, which I'm sure everyone reads. One could splice a larger wire with a 60C ampacity of 100A to the end before landing it on the breaker.
Cable to a detached garage is not likely rated 90C so the cable itself is probably not rated 100A.
-- bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yes, and 4ga cu is good for 100a and one size bigger al is what it normally accepted. So 2ga al should be fine.
s
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Steve Barker wrote:

#4 Cu is rated 100A only for residential services. This is a feeder.
-- bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yes, and it is RESIDENTIAL. duh.
--
Steve Barker



"Bud--" < snipped-for-privacy@isp.com> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 20 Nov 2006 08:30:27 -0600, "Steve Barker LT"
The "residential" exception 310.15(B)(6) is only for the mian feeder or service to the dwelling. It does not include feeders to sub panels. As I said in my first response this is probably not important since the whole house is running on a 100a service but technically it is a violation.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It is important to me however, since I'm doing exactly that. Running a 100a sub off a 200a main. My electrician has told me 3 fours and a bare 8 will be fine. Could you cite the section pertaining to "it does not include feeders to sub panels" please?
--
Steve Barker




< snipped-for-privacy@aol.com> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It's in 310.15(6). The glitch is more in the temperature rating of the circuit breaker as #4 copper is good for 95 amps if it's 90c wire. I've scoured Google about this and have found that some jurisdictions accept the service feeder table for sub panel feeders as well, so your electrician may be right in that regard
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 20 Nov 2006 14:10:06 -0600, "Steve Barker LT"

The #4 for 100a comes from the table referenced here
310.15(B)(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For dwelling units, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service lateral conductors, and feeder conductors that serve as the main power feeder to a dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboard(s). The feeder conductors to a dwelling unit shall not be required to be larger than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.22, and 230.42 are met.
Notice it says "For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboard(s)."
In the case of the other poster, if his service was #4cu or #2al he could use that size for his sub panel.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.