[RE-wrenches] Remote battery disconnects

Christopher Warfel cwarfel at entech-engineering.com
Mon Jan 30 03:46:33 PST 2023


I don't think the discussion has forked at all.  A solution to this 
problem, and it is the best solution all things considered, including 
firefighter exposure to 10 ft of conductors that I have a hard time 
imaging them being exposed to,  is for the NEC to issue a memo 
IMMEDIATELY indicating that this section of the code is no longer to be 
considered a requirement and that the next Code cycle will eliminate 
this requirement.

The other solutions discussed would only work for a few configurations 
realistically and would introduce more danger. Chris



On 1/29/2023 2:41 PM, William Miller via RE-wrenches wrote:
>
> 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 <http://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 <http://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
>                             <http://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 <tel:805-438-5600>
>
>                             www.millersolar.com
>                             <http://www.millersolar.com/>
>
>                             CA Lic. 773985
>
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>             -- 
>
>
>             William Miller
>             Miller Solar.com
>             895-438-5600
>             www.millersolar.com <http://www.millersolar.com>
>
>             _______________________________________________
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-- 
             Christopher Warfel
                      ENTECH Engineering, Inc.
PO Box 871, Block Island, RI 02807
                                 401-466-8978
<http://entech-engineering.com>

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