[RE-wrenches] Remote battery disconnects

Sun Jan 29 11:41:09 PST 2023

James, Brian and others:

Thank you all for the lively discussion.  I am always interested in my
colleague’s perspectives and this has been illuminating.

It appears to me the discussion has forked:  One topic is how to deal with
the reality of the new code regarding a very narrow scenario: ESS inside of
a residence.  The other topic is: has the NEC evolved to be overly
restrictive without factual basis?

Regarding the first topic, it’s in black and white that we must provide
battery disconnecting means for energy storage systems located in one or
two family homes if the battery voltage exceeds 60 VDC.  There are very few
areas that do not adopt the NEC.  If you install ESS you will eventually
have to deal with this code requirement one way or another.

Due to lax enforcement or unfamiliarity on the part of local building
departments, some of you may be able to skirt this requirement.  This is
great until something happens.  If your non-compliant installation causes a
loss, you will end up in the defendants chair, not the building inspector.

Here is how I approach these compliance conundrums:  If I could argue the
code does not apply or there is a good reason to waive the requirement; if
the building official agrees; if I feel the installation is really and
truly safe without meeting the  requirement—only then could I proceed
without the disconnect.  Otherwise I am going to have to find a way to
comply.

As contractors, each of you makes those decisions every day:  What is safe
enough for my clients?  If any of you think you know more than the people
who write the codes, then install what you can get away with and keep your
fingers crossed.  I am not willing to live like that.

Regarding the second topic: Are we being picked on by an overly
scare-mongering NFPA?

What is interesting here is that while most electrical codes are trying to
prevent house fires, this particular section is trying to protect fire
fighters after a fire starts (or an earthquake happens or a dump truck runs
into your house, etc.).

When California first adopted roof clearances for fire fighters, I got my
feelings hurt because I was losing business and I did not understand what
it takes to fight a house fire.  I spoke with a few fire fighters and
learned about roof and wall venting and how it is affected by prevailing
winds.  I came around to appreciate there is a real need for rooftop fire
setbacks.

It is self-evident why firefighters would not want to cut into a wall with
a demo saw if there are energized, high amperage conductors in or on that
wall.  This code requirement for battery disconnecting means is
fundamentally sensible.  That ends the discussion for me.

Oh, yeah, the charge controller blowing up thing:  Does anyone have any
factual data to share on this?  Regardless of that, does it really matter
if the charge controller is saved but the house burns down?

The islanding thing:  To be compliant, all ungrounded battery conductors
need to be disconnected.  This includes the charge controller circuit(s).
With the charge controllers and inverters disconnected from the batteries
and from each other there cannot be DC “islanding”.

The house flooding thing:  At the surface, it appears you have a choice of
disasters:  flood or fire.  I submit that fire is more destructive (I don’t
think many people have died from a ruptured water pipe).  I don’t think it
has to be either or:  Find a way to provide emergency power to freeze
protection devices with that disconnect waived or under key in cooperation
with the fire department.  This may mean the batteries need to remain
connected.  Put those leads in metal raceway and mark their locations from
the outside.  Work with building and fire officials.  Limit your liability.

Thanks again to all of you for the discussion.  I know what I need to do.

William Miller

Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com

CA Lic. 773985

*From:* James Jarvis [mailto:jj at aprsworld.com]
*Sent:* Saturday, January 28, 2023 7:03 PM
*To:* Brian Mehalic
*Cc:* RE-wrenches; william at millersolar.com
*Subject:* Re: [RE-wrenches] Remote battery disconnects

Brian and William,

With all due respect, I think your geographical location of California may
be limiting in your understanding of the implications of local power
security.

Where I am in Minnesota and where I work in Alaska, loss of power and
backup power can have very expensive consequences. When it is -30F outside
and howling wind, buildings only have a matter of hours before their
interiors will drop below freezing. A few hours after that pipes start to
freeze and break. Pressurized water then starts to spray everywhere and
then things can very quickly run into six-figure dollars amounts of damage.
So one way of reducing this risk is by installing an ESS.

Around here, prior to the latest NEC, we didn't have exterior disconnects
available for anyone to shut off power. We still don't for businesses.

My point is that NEC is mandating that there be zero security of a
buildings electrical systems by requiring publicly accessible disconnects
on backup systems. And if NEC wasn't so prescriptive, there could be
slightly more secure alternatives such as a KNOXBOX or access controlled
disconnects.

William: I also disagree with your premise that you'll test the battery
disconnect system after dark. That's not a test; that's just cheating. You
had a knowledge person tell you that the MPPT controllers can and do blow
up when they lose their voltage reference (battery) under load. And
removing the battery from the circuit does allow the charge controllers to
island with the inverter and DC loads and do other damage. I know of a
telecom customer that had hundreds of thousands of dollars of damage when
their battery became disconnected. If you are unwilling to test it at full
load, I'd guess you know that the whole concept is a dumb idea.

-James Jefferson Jarvis
APRS World, LLC
+1-507-454-2727

http://www.aprsworld.com/

On Sat, Jan 28, 2023 at 7:35 PM Brian Mehalic <brian at solarenergy.org> wrote:

Every single house I’ve looked at in my town has a breaker panel with a
main service disconnect on the outside of the house already. So in many
cases we are well beyond worrying about someone “flicking your switch!”

In fact, in addition to the emergency disconnect requirement for stationary
standby batteries [480.7(B)] and ESS [706.15(B)] in one- and two-family
dwellings, also added in 2020 was the requirement for an emergency
disconnect for services on those same one- and two-family dwellings
[230.85].

Brian Mehalic

On Jan 28, 2023, at 5:58 PM, James Jarvis via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

It would be nice if the decision was up to the owner / occupant of the
property. I, for one, do not want any random person to be able to turn off
my house or business with the flick of a switch. I feel strongly that there
is far too much fear mongering in NEC with relation to renewable energy.

-James Jefferson Jarvis
APRS World, LLC
+1-507-454-2727

http://www.aprsworld.com/

On Sat, Jan 28, 2023 at 6:22 PM William Miller via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

Esteemed wrenches:

Well if my house is on fire and the entry of fire responders is delayed for
lack of a disconnect, I choose having the disconnect. I can worry about the
charge controllers later.

Others may prioritize their charge controller over their homes…

Put a cable-tie lock in the closed position to discourage kids from messing
with it. Test it only after dark.

William

On Sat, Jan 28, 2023 at 2:32 PM William Bryce <wlbryce at pineridgeproducts.com>
wrote:

All

One thing that no one is talking about is what happens to the MPPT charge
controllers when the Battery Disconnect trips when the charge controllers
are under full load.

Many will blow up. Try turning off the battery breaker on a SolaArk  when
the charge controllers are maxed, and see if you get lucky.

On Sat, Jan 28, 2023 at 3:27 PM William Miller via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

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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-- 

William Miller
Miller Solar.com
895-438-5600
www.millersolar.com

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