[RE-wrenches] Remote battery disconnects

Sat Jan 28 12:16:44 PST 2023

Jeremy:

Thanks for posting the code references for those that had never looked them
up.

Chris:

What do you mean by “a disconnect for AC wiring, not specific to which or
both panel types”?

All:

Code references are handy when receiving edicts from building officials,
but not required, IMHO, for two reasons:  The contractor should already be
versed in the codes and, building departments can mandate their own
requirements above and beyond the code.

It may seem redundant to require an AC disconnect for premise wiring as
well as a DC battery disconnect.  In most cases if you disconnect the
inverter from the batteries the AC power goes off.  However if the
generator is running at the time, some battery inverters can operate when
disconnected from batteries.  So to completely de-energize all components
of an off-grid home you need to disconnect the generator and the battery
leads.

In this case the home is required to have fire sprinklers.  There is
pressure pump to provide flow to these fire sprinklers-- said pump being
powered by the inverter/battery system.  I am going to apply for a waiver
to remove the DC disconnect requirement on the grounds that the pressure
pump is essential fire suppression equipment.  Instead I will propose to
supply an AC disconnect (meeting all requirements for accessibility and
marking) that will disconnect all premise wiring except the pressure pump.

By the way, I will of course be trying to apply the logic that the voltage
specification is for nominal battery voltage and this project having a
nominal 48 volt bank does not require the battery disconnect.

I will let the group know what response I receive.  Regardless of how this
works in this jurisdiction, I think these are both valid arguments worth
trying in any jurisdiction requiring the battery disconnect.  Some
officials are amenable to dialog and negotiation and some are less so.

William Miller

Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com

CA Lic. 773985

*From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
Behalf Of *Jeremy Rodriguez via RE-wrenches
*Sent:* Saturday, January 28, 2023 10:12 AM
*To:* cwarfel at entech-engineering.com; RE-wrenches
*Cc:* Jeremy Rodriguez
*Subject:* Re: [RE-wrenches] Remote battery disconnects

*2020 Code Language:*

*480.7 DC Disconnect Methods.*

*(A) Disconnecting Means.* *A disconnecting means shall be provided for all
ungrounded conductors derived from a stationary battery system with a
voltage over 60 volts dc. A disconnecting means shall be readily accessible
and located within sight of the battery system.*

*N* *(B) Emergency Disconnect.* *For one-family and two-family dwellings, a
disconnecting means or its remote control for a stationary battery system
shall be located at a readily accessible location outside the building for
emergency use. The disconnect shall be labeled “EMERGENCY DISCONNECT”.*

*N **(C) Disconnection of Series Battery Circuits.* *Battery circuits
exceeding 240 volts dc nominal between conductors or to ground and subject
to field servicing shall have provisions to disconnect the series-connected
strings into segments not exceeding 240 volts dc nominal for maintenance by
qualified persons. Non-load-break bolted or plug-in disconnects shall be
permitted.*

Jeremy Rodriguez

Solar Installation / Design

All Solar, Inc.

1453 M St.

Penrose Colorado 81240

Sent by Jeremy's iPhone. Sorry for typos and shorthand.

On Jan 28, 2023, at 7:28 AM, Christopher Warfel via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

Seems confusing that the AHJ is requiring a disconnect for AC wiring, not
specific to which or both panel types, and then a dc disconnect with no
code reference.  Was trying to convey a reasonable, safe approach.  A lot
of bad information from fire department solar consultants making a lot of
money fear mongering, which has led to this type of situation.  Chris

On 1/27/2023 3:35 PM, William Miller via RE-wrenches wrote:

Glenn:

As I wrote, a DC disconnect is required.  Here is an excerpt from the Q&A
with the building official:

4.   Will you be requiring an external disconnect to disconnect the AC
output of the inverter system from premise wiring?

Yes, as required per 230.85

5.   Will you be requiring an external disconnect to disconnect batteries
from the inverters?

Yes

If the DC disconnect was not required I would not be wasting everyone’s
time with my post.  I try to be careful about that, researching on my own
before posting and trying to make my questions very clear.  I also try not
to embarrass myself with dumb questions, but that does happen occasionally…

William

Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com

CA Lic. 773985

*From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
Behalf Of *Glenn Burt via RE-wrenches
*Sent:* Friday, January 27, 2023 11:46 AM
*To:* William Miller via RE-wrenches
*Cc:* Glenn Burt
*Subject:* Re: [RE-wrenches] Remote battery disconnects

Does the AHJ really want the batteries disconnected from conductors, or
does he really just want the inverters to stop operating and producing AC
within the house?

Obviously there is a big difference here and it may be changing as the code
evolves.

-Glenn

Sent from my 'smart'phone, so please excuse typos and spelling errors.

------ Original message------

*From: *William Miller via RE-wrenches

*Date: *Fri, Jan 27, 2023 2:26 PM

*To: *RE-wrenches;

*Cc: *William Miller;

*Subject:*[RE-wrenches] Remote battery disconnects

Friends:

We have a large-ish residential off-grid system install coming up.  The AHJ
has said they will require a remote battery disconnect.  I suspect there
will be fire sprinkler controls and a pressure pump that would become
inoperable if this system were engaged.  In this case we will apply for a
waiver.

The last time this was discussed here as far as I can find was October of
2020.  At that time no one suggested any specific battery disconnect
equipment.

To further clarify my needs:  There will be 4 or 5 Radian 8048 inverters (5
or 6 4/0 battery circuits, ~350A each) and two 175 amp PV recombiner
outputs.  That is 6 poles of high amperage DC disconnects.

The battery array will be either a UnigyII VRLA or a lithium of a brand yet
to be determined.  In the case of lithium we will look for a system that
can remotely enable a BMS shutdown.  In the case of a VRLA lead-acid, we
will not have that luxury.

I have done some considerable research and have not found viable, high
amperage, remotely activated shutdown equipment.

I am wondering what hardware others may be using to achieve remote battery
disconnecting in these types of cases..

William

Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com

CA Lic. 773985
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