Going to install a generator tranfer sub-panel.. I'm getting a permit, but I
wonder if there is anything obvious here that I plan on doing that would be
amiss before i get that permit....

I have a 8-place Square D subpanel with a 70A switch and a 30A breaker wired
with one of those mechanical interlocks that prevent both from being on at
the same time.

So I'll run the 30A breaker via 10/4 romex to an outside plug, which is
where I'll connect my approx 5500W portable generator.

Then I'll run the 70A switch (2 hots) and a neutral via some 6ga wire in a
conduit to a 60A 2-pole breaker in my main panel. Including a 8ga ground in
the same conduit, being sure that the ground and neutral are not tied
together in the sub-panel.

Then I'll load the remaining 4 spots in the subpanel up with the QOT tandem
breakers. One of these is for a 240 circuit (water pump), and i'll tie two
adjacent breakers together with a tie pin from Square D to make a 2-pole
breaker. This leaves 6 circuits for 120V service.

Two things I want to make sure about:

If I add all the breakers in the subpanel up, I'll have 70A (2x20, 2x15) per
leg, which exceeds the 60A subpanel feed breaker and certainly the 30A
generator feed breaker, and even more so, the 5500W generator capacity. But
I don't think the feed breaker will ever trip, and I'll just have to be
careful when on genny. Is there anything not kosher about this setup?

I need to transfer a handful of circuits from the main panel to the sub
panel. Can I do this the easy way.. by leaving each circuit run in the main
panel, and splicing the hots ONLY with a wire nut to feed to the subpanel
via wire of the appropriate guage in a conduit? Anything to be aware of
here, especially if it is OK to leave the ground and neutrual for these
transferred circuits terminated in the main panel? I could run those to,
but not if I don't need to...


Thanks!!
Tman.

It would seem to me the easiest way to accomplish what you want is to buy a
six or ten circuit transfer panel kit from HD or similar place. This has a
ready made panel with multiple switches built in and a cable with a pile of
wires you connect right into your main panel, takes just a couple of hours
and you're done. The way you're going about it is fine, you don't add up the
size of the breakers, but the loads attached to them and I believe you
cannot use a panel as a junction box the way you planned and need to remove
the cables from your main panel and install them into the generator sub
panel.



"Tman" tman9_ at _comcast.net (remove underscores) wrote in message
...
Going to install a generator tranfer sub-panel.. I'm getting a permit, but
I wonder if there is anything obvious here that I plan on doing that would
be amiss before i get that permit....

I have a 8-place Square D subpanel with a 70A switch and a 30A breaker
wired with one of those mechanical interlocks that prevent both from being
on at the same time.

So I'll run the 30A breaker via 10/4 romex to an outside plug, which is
where I'll connect my approx 5500W portable generator.

Then I'll run the 70A switch (2 hots) and a neutral via some 6ga wire in a
conduit to a 60A 2-pole breaker in my main panel. Including a 8ga ground
in the same conduit, being sure that the ground and neutral are not tied
together in the sub-panel.

Then I'll load the remaining 4 spots in the subpanel up with the QOT
tandem breakers. One of these is for a 240 circuit (water pump), and i'll
tie two adjacent breakers together with a tie pin from Square D to make a
2-pole breaker. This leaves 6 circuits for 120V service.

Two things I want to make sure about:

If I add all the breakers in the subpanel up, I'll have 70A (2x20, 2x15)
per leg, which exceeds the 60A subpanel feed breaker and certainly the 30A
generator feed breaker, and even more so, the 5500W generator capacity.
But I don't think the feed breaker will ever trip, and I'll just have to
be careful when on genny. Is there anything not kosher about this setup?

I need to transfer a handful of circuits from the main panel to the sub
panel. Can I do this the easy way.. by leaving each circuit run in the
main panel, and splicing the hots ONLY with a wire nut to feed to the
subpanel via wire of the appropriate guage in a conduit? Anything to be
aware of here, especially if it is OK to leave the ground and neutrual for
these transferred circuits terminated in the main panel? I could run
those to, but not if I don't need to...


Thanks!!
Tman.

I think this site might help you out in some of your
decisions:
http://www.nbmc.com/emergen/index.html

Offhand it sounds OK but it's fuzzy in a couple of
areas (to me). The single most important thing is to
not allow the generator, under any normal "fault'
conditions, to feed the power lines.

A Transfer Switch panel is the easiest way to do it,
IMO, and the most reliable. Lots of companies make
them. Yours almost, not quite sounds like a transfer
switch, so I'm not making too many judgements on the
validity of your plans here.

HTH
Pop

"Tman" tman9_ at _comcast.net (remove underscores)
wrote in message
...
Going to install a generator tranfer sub-panel.. I'm
getting a permit, but I wonder if there is anything
obvious here that I plan on doing that would be amiss
before i get that permit....

I have a 8-place Square D subpanel with a 70A switch
and a 30A breaker wired with one of those mechanical
interlocks that prevent both from being on at the
same time.

So I'll run the 30A breaker via 10/4 romex to an
outside plug, which is where I'll connect my approx
5500W portable generator.

Then I'll run the 70A switch (2 hots) and a neutral
via some 6ga wire in a conduit to a 60A 2-pole
breaker in my main panel. Including a 8ga ground in
the same conduit, being sure that the ground and
neutral are not tied together in the sub-panel.

Then I'll load the remaining 4 spots in the subpanel
up with the QOT tandem breakers. One of these is for
a 240 circuit (water pump), and i'll tie two adjacent
breakers together with a tie pin from Square D to
make a 2-pole breaker. This leaves 6 circuits for
120V service.

Two things I want to make sure about:

If I add all the breakers in the subpanel up, I'll
have 70A (2x20, 2x15) per leg, which exceeds the 60A
subpanel feed breaker and certainly the 30A generator
feed breaker, and even more so, the 5500W generator
capacity. But I don't think the feed breaker will
ever trip, and I'll just have to be careful when on
genny. Is there anything not kosher about this
setup?

I need to transfer a handful of circuits from the
main panel to the sub panel. Can I do this the easy
way.. by leaving each circuit run in the main panel,
and splicing the hots ONLY with a wire nut to feed to
the subpanel via wire of the appropriate guage in a
conduit? Anything to be aware of here, especially if
it is OK to leave the ground and neutrual for these
transferred circuits terminated in the main panel? I
could run those to, but not if I don't need to...


Thanks!!
Tman.

Why are you screwing around with this, when real transfer switches are
available? I would be reluctant to buy a house that contained what you are
describing; fearing you had done equally odd things elsewhere.

If you chose to design your own. just be sure that the net current going
though any metal hole must be zero. It was not clear if you were doing
that.

If you try to draw more than 5500w from you generator it will let you know
quickly by stalling. Hopefully you will not burn anything out in the
process.

"toller" wrote in message
...
Why are you screwing around with this, when real transfer switches are
available? I would be reluctant to buy a house that contained what you
are describing; fearing you had done equally odd things elsewhere.

If you chose to design your own. just be sure that the net current going
though any metal hole must be zero. It was not clear if you were doing
that.

If you try to draw more than 5500w from you generator it will let you know
quickly by stalling. Hopefully you will not burn anything out in the
process.

The thing he has is a UL approved double breaker system with mechanical
interlock made by Square D for the purpose he is using it. It's not "odd" or
Rube Golberg, just not the easiest way to do the job


"toller" wrote in message
...
Why are you screwing around with this, when real transfer switches are
available? I would be reluctant to buy a house that contained what you
are describing; fearing you had done equally odd things elsewhere.

If you chose to design your own. just be sure that the net current going
though any metal hole must be zero. It was not clear if you were doing
that.

If you try to draw more than 5500w from you generator it will let you know
quickly by stalling. Hopefully you will not burn anything out in the
process.

The thing he has is a UL approved double breaker system with mechanical
interlock made by Square D for the purpose he is using it. It's not "odd"
or Rube Golberg, just not the easiest way to do the job

I don't doubt you are correct, but to anyone who is unfamiliar with this
item, it will look odd. So unless there is a compelling reason to do it
that way...

"toller" wrote in message
...
If you chose to design your own. just be sure that the net current going
though any metal hole must be zero. It was not clear if you were doing
that.
ahh so I need to run both the hot and neutral (and ground also?) from the
subpanel, through the conduit, then splice in the main panel. This makes a
lot of sense... I suppose a net current in the conduit could induce a
current in the conduit itself.

If you try to draw more than 5500w from you generator it will let you know
quickly by stalling. Hopefully you will not burn anything out in the
process.
The generator breaker actually pops before the voltage or frequency gets out
of bounds enough to fry something...

"toller" wrote in message
...
If you chose to design your own. just be sure that the net current going
though any metal hole must be zero. It was not clear if you were doing
that.
ahh so I need to run both the hot and neutral (and ground also?) from the
subpanel, through the conduit, then splice in the main panel. This makes a
lot of sense... I suppose a net current in the conduit could induce a
current in the conduit itself.

If you try to draw more than 5500w from you generator it will let you know
quickly by stalling. Hopefully you will not burn anything out in the
process.
The generator breaker actually pops before the voltage or frequency gets out
of bounds enough to fry something...

toller wrote:
The thing he has is a UL approved double breaker system with mechanical
interlock made by Square D for the purpose he is using it. It's not "odd"
or Rube Golberg, just not the easiest way to do the job


I don't doubt you are correct, but to anyone who is unfamiliar with this
item, it will look odd. So unless there is a compelling reason to do it
that way...



Try cost. Adapting a panel or sub panel for generator transfer service
cost a lot less than stand alone transfer switches or premanufactured
transfer panels. You trade your additional labor for lower material cost.
--
Tom Horne


Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.

Tman wrote:
"toller" wrote in message
...

If you chose to design your own. just be sure that the net current going
though any metal hole must be zero. It was not clear if you were doing
that.

ahh so I need to run both the hot and neutral (and ground also?) from the
subpanel, through the conduit, then splice in the main panel. This makes a
lot of sense... I suppose a net current in the conduit could induce a
current in the conduit itself.

If you try to draw more than 5500w from you generator it will let you know
quickly by stalling. Hopefully you will not burn anything out in the
process.

The generator breaker actually pops before the voltage or frequency gets out
of bounds enough to fry something...



There is no need to run the neutral or each ground to the transfer
panel. You can run just the ungrounded conductor as long as it goes out
and back through the same raceway, cable, and/or knock outs.
--
Tom Horne

Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.

Tman (tman9_at_comcast.netremoveunderscores) said...

I have a 8-place Square D subpanel with a 70A switch and a 30A breaker wired
with one of those mechanical interlocks that prevent both from being on at
the same time.

So I'll run the 30A breaker via 10/4 romex to an outside plug, which is
where I'll connect my approx 5500W portable generator.

Then I'll run the 70A switch (2 hots) and a neutral via some 6ga wire in a
conduit to a 60A 2-pole breaker in my main panel. Including a 8ga ground in
the same conduit, being sure that the ground and neutral are not tied
together in the sub-panel.

So far, so good. I have nearly the same setup, except the panel I have
came with two 30A breakers for the interlock. My connection to the generator
inlet is the same, except I used conduit with three 10 gauge wires for the
two lines and neutral and a 12 gauge grounding conductor (the ground can
be one size smaller, except once you get to 14 ga).

My connection to the main panel used #10 conductors and a #8 ground and
runs off a 40A breaker (sized larger in case I want to upgrade it later,
but the 30A breaker at the transfer panel is ultimately the overcurrent
protector here).

Then I'll load the remaining 4 spots in the subpanel up with the QOT tandem
breakers. One of these is for a 240 circuit (water pump), and i'll tie two
adjacent breakers together with a tie pin from Square D to make a 2-pole
breaker. This leaves 6 circuits for 120V service.

No, it doesn't. Unless Square D has come out with new mini-breakers that
provide a proper 2-pole option (I have seen some other manufacturers that
provide a 2-space mini breaker configuration, where the two outer breakers
are single pole and the two inner are tied together to give a 2-pole
breaker), you will have to use a full-size, two position breaker for your
240 volt circuit (a QO215 or QO220, for instance). This will leave you
with only two full positions on the panel, where you could install two
mini breakers (QOT1515, for instance) to give you four more circuits.

If I add all the breakers in the subpanel up, I'll have 70A (2x20, 2x15) per
leg, which exceeds the 60A subpanel feed breaker and certainly the 30A
generator feed breaker, and even more so, the 5500W generator capacity. But
I don't think the feed breaker will ever trip, and I'll just have to be
careful when on genny. Is there anything not kosher about this setup?

Not really. Have you ever added up all the breakers in your main panel (on
each leg)? It is not unusual for them to exceed the main breaker's rating.

A branch circuit protected by a 15 A or 20 A breaker typically does not
run constantly with that amount of current (forget, for the moment that
breakers are only supposed to be loaded to 80% of their capacity, since
80% of the sum of all breakers compared to 80% of the main breaker's
rating is still relatively the same comparison!).

Certain load assumptions are made when figuring out how many devices are
on a single circuit, and these assumptions are worst-case scanarios.
For instance, when planning a new circuit where general receptacles and
light fixtures are concerned (as oppposed to knowing exactly what will
be there), I tend to use 100 Watts for lights and 200 Watts for
duplex receptacles. Many receptacles in a home are there because code
requires you to be no more than six feet along a wall from an outlet, so
1500 Watts worth of receptacles on a 15 A circuit (1500 Watts is a close
estimate for 80% of 15 A at 120 volts!) may only end up with 200 Watts on
the circuit under normal use.

Some outlets require a dedicated circuit. So a 1200 Watt refrigerator
would use up one full circuit, but not be accounting for any more than
10 A when it was actually running.

I need to transfer a handful of circuits from the main panel to the sub
panel. Can I do this the easy way.. by leaving each circuit run in the main
panel, and splicing the hots ONLY with a wire nut to feed to the subpanel
via wire of the appropriate guage in a conduit? Anything to be aware of
here, especially if it is OK to leave the ground and neutrual for these
transferred circuits terminated in the main panel? I could run those to,
but not if I don't need to...

Hmmm. Something I didn't have to deal with, since mine was new construction
so all the transfer-switch circuits had their home runs to the transfer
switch. What you are essentially doing is running a "switch loop" for each
of these circuits. On the surface, this seems acceptable, but I would run
it past your inspector before getting started.

The cost of your permit actually buys you a bit of a consultant. Inspectors
are generally available for an hour in the morning to answer questions. Make
use of this service (just don't abuse it!).

--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
- Napoleon
-------------------------------------------------------------------------
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Calvin Henry-Cotnam ) said...

Tman (tman9_at_comcast.netremoveunderscores) said...
I need to transfer a handful of circuits from the main panel to the sub
panel. Can I do this the easy way.. by leaving each circuit run in the main
panel, and splicing the hots ONLY with a wire nut to feed to the subpanel
via wire of the appropriate guage in a conduit? Anything to be aware of
here, especially if it is OK to leave the ground and neutrual for these
transferred circuits terminated in the main panel? I could run those to,
but not if I don't need to...

Hmmm. Something I didn't have to deal with, since mine was new construction
so all the transfer-switch circuits had their home runs to the transfer
switch. What you are essentially doing is running a "switch loop" for each
of these circuits. On the surface, this seems acceptable, but I would run
it past your inspector before getting started.

Let me correct what I said here, as I was thinking only about the
non-generator operation.

You will have to run a full cable for each branch circuit that was in your
main panel to the transfer panel. Both its hot and neutral must be terminated
in the transfer panel.

There is part of me saying that the heavy neutral between the main panel
and the transfer panel would handle the neutral current in generator mode,
since it only exists when mains current is cut off, but there's something
nagging me that this is not quite right.

--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
- Napoleon
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HorneTD ) said...

toller wrote:
The thing he has is a UL approved double breaker system with mechanical
interlock made by Square D for the purpose he is using it. It's not "odd"
or Rube Golberg, just not the easiest way to do the job

I don't doubt you are correct, but to anyone who is unfamiliar with this
item, it will look odd. So unless there is a compelling reason to do it
that way...

Try cost. Adapting a panel or sub panel for generator transfer service
cost a lot less than stand alone transfer switches or premanufactured
transfer panels. You trade your additional labor for lower material cost.

The panel in question made by Square D is simply a small panel with eight
breaker positions (4 on each leg), a neutral bus (isolated from the chassis)
and a ground bus.

Power coming into one of these panels is "back-fed" through a 2-pole
breaker that acts as the "main breaker" for the panel.

When the same panel is adapted as a transfer switch, it comes with two
2-pole breakers (mine was a pair of 30A breakers, but the OP mentioned
a 30A and a 70A) along with a mechanical interlock that not only prevents
the two from being turned on at the same time, but also ensure that there
is a break-before-make action (meaning that trying to turn one on will
force the other to be shut off before the first one even comes close to
being on). My inspector did a close check to see that this was the case.

Since 4 positions in the 8 position panel are used up, you only have
four circiuts with full-size single-pole breakers, but can double that
with the use of the QOT mini breakers from Square D.

--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
- Napoleon
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