[RE-wrenches] Remote battery disconnects

Sat Jan 28 19:02:31 PST 2023

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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