Back feed thru a fusible disconnect

[Zee]

but how are you connecting in the MAIN PANEL, w/o a breaker?

And why fusible?
Just put a 2p60 brkr. in the main and use a non-fusible disco.

[Zee]

On another forum, I was following a thread about the back fed breaker heating up
under load.

My Utility requires a lockable OFF AC disconnect, so I am considering using a fusible type
disconnect with a couple of 60 amp fuses for the back fed OCPD and avoid using
a back fed breaker altogether.


I never see any examples of connecting that way --- is there a problem with doing this?

I should add my Utility Service entrance is on the outside of a detached garage and from
the meter/ base enclosure goes to a Siemens #WB2225 Outdoor Circuit Breaker Enclosure
with a 225 Amp max Rating and a 200 AMP breaker installed. This then feeds a Midwest
T1220 Terminal box which I will also be feeding from the fusible AC disconnect.

Planning on using a Fronius 11.4-1 inverter with a Max continuous rating of 47.5 Amps.
Any problems with doing it this way?

You will need to connect to the MAIN panel. The rating of the breaker that feeds the subpanel, for CODE reasons, will block subpanel tie-in.

You do not need to do a line tap. ====>

NAptown: 120% x 225A bus > 200A + 60A breakers
Should be fine.

You do not sound like someone qualified to do a line tap in any case, i agree 100% with NAPTOWN.

[Dakota]

No, that should meet the NEC 120% rule --- that Siemens #WB2225 Outdoor
Circuit Breaker Enclosure has a 225 AMP Bus rating, so 225A X 1.2 = 270 Amps
and with a 200 AMP breaker installed could go to a 70 A OCPD.

The inverter has a Max continuous rating of 47.5 Amps so should be OK with
60 amp fuses.

I'm still a little uncertain if it's kosher to back feed thru that fusible AC disconnect
because I can't find any examples of doing that. I can't see a problem with that
method as long as the Utility is on the Line input and the inverter on the Load terminal
so that when the AC Disconnect is in the OFF position the fuse terminals are not hot.

You are actually a bit above what you could backfeed and will need to do a line tap which in your case is fairly easy since everything is outside.
The issue in your original question is some manufacturers of breakers do not work well with backfeeding. Specifically if the circuit breaker is marked with line and load designations on the terminals they may not be backfed.
A line tap is something that should be performed by a licensed electrician who is familiar with the procedure

[inetdog]

...The issue in your original question is some manufacturers of breakers do not work well with backfeeding. Specifically if the circuit breaker is marked with line and load designations on the terminals they may not be backfed.

You may ask what difference it makes which way the power is flowing, since AC alternates the direction of both current and voltage anyway.
An oversimplified answer is that it makes no difference when the breaker is closed (unless it is a GFCI or AFCI breaker, which we will ignore as not appropriate for this use.) The problem arises while the breaker is opening and after it has opened. Those two situations are not symmetric between forward and back feeding.
Backfeeding from GTI is inherently different from backfeeding from a source such as a generator which can operate independently, but the NEC does not make any distinction between the two types of backfeeding.

[Naptown]

You are actually a bit above what you could backfeed and will need to do a line tap which in your case is fairly easy since everything is outside.
The issue in your original question is some manufacturers of breakers do not work well with backfeeding. Specifically if the circuit breaker is marked with line and load designations on the terminals they may not be backfed.
A line tap is something that should be performed by a licensed electrician who is familiar with the procedure

[Dakota]

On another forum, I was following a thread about the back fed breaker heating up
under load.

My Utility requires a lockable OFF AC disconnect, so I am considering using a fusible type
disconnect with a couple of 60 amp fuses for the back fed OCPD and avoid using
a back fed breaker altogether.


I never see any examples of connecting that way --- is there a problem with doing this?

I should add my Utility Service entrance is on the outside of a detached garage and from
the meter/ base enclosure goes to a Siemens #WB2225 Outdoor Circuit Breaker Enclosure
with a 225 Amp max Rating and a 200 AMP breaker installed. This then feeds a Midwest
T1220 Terminal box which I will also be feeding from the fusible AC disconnect.

Planning on using a Fronius 11.4-1 inverter with a Max continuous rating of 47.5 Amps.
Any problems with doing it this way?