[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>
>
> _______________________________________________
> List sponsored by Redwood Alliance
>
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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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