[RE-wrenches] Insurance and rapid shutdown

Fri Apr 3 12:54:22 PDT 2026

Below is a message I received off-line a while ago re: AP Smart, along with
photos.

I thought I’d contact you off list.  You have been asking about RSD units,
I wanted to pass along my experience with the AP Smart RSD unit.  I’ll let
the pictures do most of the talking - see below.  Bottom line, APSmart is a
nice little easy piece of plastic junk to install and commission.  However,
when something goes wrong it can be a real pain to ID the fault.  They have
a little gadget that you have to wave over the conductors to listen for a
pulse (not always easy on a roof!  I went thru 2 inverters about 6 hrs on
the phone with SMA (I got ALL sorts of weird errors, but only 1 arc fault),
2 weeks of back and forth with AP Systems/Smart.  After I finally got the
arc fault, in an act of desperation, I started tearing the array apart at
significant expense and much frustration by my client (he totally lost
faith in solar and had been wanting it for years) I finally found the
problem.  Luckily this one was on a new install on a metal roof and not on
a system that had been through a few seasons with build up of leaf detritus
under the array on an asphalt shingle roof.  I’ve been at this for 17yrs
now and have never had a piece of equipment fail this catastrophically -
especially a piece of unnecessary safety equipment.  Their tech support
engineer, while well meaning, is extremely difficult to understand due to
language barrier and completely failed to take any responsibility for this
failure which could have resulted in a house fire and who knows what else….
My strong recommendation is to limit the use of any RSD unless pressed to
do so by an AHJ.  It’s my opinion that these units should be at least in
metallic enclosures.  I worked at Tigo back before RSD was a “thing” and do
see the advantages, but I just think (like BB) that there are more
downsides than up at this point in time given the available tech.  I keep
this unit in my van and show every AHJ then ask them to tell me what they
want me to do in writing.  I am not going to be on the hook the
consequences of such a catastrophic failure.

William Miller

Miller Solar

www.millersolar.com

CA License C-10 77398

*From:* Tyrone Houck [mailto:tyronehouck at gmail.com]
*Sent:* Friday, April 3, 2026 10:17 AM
*To:* william at millersolar.com
*Subject:* Re: [RE-wrenches] Insurance and rapid shutdown

Thanks for sharing. I've asked this group multiple times for any anecdotes
or pictures of APSmarts failing and never recieved any response. Tigo
failures are mentioned often. Personally, I've installed upwards of 1000
APs  with no issue(I don't make a habit of stress testing them by
repeatedly hitting the switch during peak production though). All that
said, I wouldn’t bother installing them in a situation that didn't warrant
RSS.

On Fri, Apr 3, 2026, 10:06 AM William Miller <william at millersolar.com>
wrote:

I have seen photos of one AP Smart RSD that had melted and burst into
flames.

The job they are required to do : open a high voltage, arc sustaining
circuit under load is a difficult task to accomplish, especially in a small
package in an extreme environment.

William Miller
Miller Solar.com
805-438-5600
www.millersolar.com

On Fri, Apr 3, 2026 at 10:00 AM Tyrone Houck <tyronehouck at gmail.com> wrote:

If considering retrofitting rapid shutdown I would recommend APSmart. I
have never had any failures or heard of anyone else who has.

On Fri, Apr 3, 2026, 8:05 AM William Miller via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

If he wants to be more assured of filing an insurance claim he should
install RSS.

Seriously, the equipment has a bad safety record. I would recommend a
safety inspection and a modern charge controller with arc flash and ground
fault detection over RSS.

William Miller
Miller Solar.com
805-438-5600
www.millersolar.com

On Fri, Apr 3, 2026 at 7:46 AM Drake Chamberlin via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

Hello All,

A client, for an off grid system, is in an area with no code requirements
nor inspections. He is concerned that if he does not get rapid shutdown, it
could affect his ability to get an insurance claim paid, if ever needed.

The array is on a separate utility building that houses a water pump and
tank as well as the inverter and batteries. Since there is more in the
building than just solar related equipment, RS is technically required.

Has anyone ever had to deal with this issue?

Thank you,

Drake

-- 

*Drake Chamberlin*

*Athens Electric LLC*

*Ohio Electrical Contractor’s License 44810*

*NABCEP Certified PV Installation Professional*

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