[RE-wrenches] Remote battery disconnects

Sat Jan 28 17:14:50 PST 2023

James:

Your on-grid home or business already has a quick and efficient means of
disconnecting power by a random person: If you have a non-CT meter it’s a
matter of clipping the meter tag and pulling the meter. If there is a CT
meter,  there will be a switch to flip.

Fortunately off-grid homes do not usually have random people on the
premises.

I have always felt it beyond my expertise to second-guess what first
responders require  to perform their jobs safely.

Most code requirements do add expense and inconvenience. However most
requirements seem well founded in logic. When I travel in third world
countries or read about building system failures, I personally appreciate
the codes we have.

William

On Sat, Jan 28, 2023 at 4:58 PM James Jarvis <jj at aprsworld.com> 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
>> _______________________________________________
>> List sponsored by Redwood Alliance
>>
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William Miller
Miller Solar.com
895-438-5600
www.millersolar.com
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