[RE-wrenches] Mixing Outback FM100 CC with Fm80 or 60.

Fri Jan 21 12:39:08 EST 2022

Ahh the can of worms get opened.
In our conversation Willian brought up the same points.
All true, but the white paper was required by legal (CYA).
I think getting the new unit listed also came into play.

From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> On Behalf Of Maverick Brown
Sent: Friday, January 21, 2022 9:29 AM
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Subject: Re: [RE-wrenches] Mixing Outback FM100 CC with Fm80 or 60.

CAUTION: This email originated from outside of the Company. Do not click links or open attachments unless you recognize the sender and know the content is safe.

Using that logic, wouldn’t the inverters and batteries also be exposed to 300Vdc? And the MX60 would also be at risk for exposing the inverters and batteries to 150Vdc under similar failures?

If that’s the only limiting factor, I’d like to take back a couple AC Coupling arrangements I have made for past Radian expansions. ;-)
Maverick Brown
Off-Grid Solar Commander since 2006
Maverick Solar Enterprises, Inc.
 • Solar Commander Remote Power
 • SunFlow Systems Cathodic Protection
maverick at mavericksolar.com<mailto:maverick at mavericksolar.com>
512-460-9825

On Jan 21, 2022, at 11:15 AM, Tuss, Lones <lones.tuss at enersys.com<mailto:lones.tuss at enersys.com>> wrote:

Hi William
Thank you for taking my call.
I believe the reason we do not recommend mixing the FM100 and the fM60/80 is.
If the FM100 were to short out pv input to output you could expose the 150 volt rated dc breakers on the
FM60/80 to 300 vdc.

From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org>> On Behalf Of William Miller
Sent: Thursday, January 20, 2022 10:54 PM
To: RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>>
Subject: [RE-wrenches] Mixing Outback FM100 CC with Fm80 or 60.

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Friends:

I am sure many of you are familiar with the somewhat new Outback FM100 charge controller.  It allows PV input at up to 300 volts and battery feed at up to 100 amps.  It has a built in GFDI fuse, much like the old XW--now branded I think Conextant-- charge controller.

Outback recommends against installing an FM 100 in an installation with FM60s or FM 80s.  Here is the tech note<https://protect2.fireeye.com/v1/url?k=31323334-501d2dca-31313abf-454455534531-4df62a772b14c6eb&q=1&e=d5f26548-4212-48c3-91e9-e4b3dde4c8e7&u=https%3A%2F%2Foutbackpower.com%2Fdownloads%2Fdocuments%2Fappnotes%2Ffm100_fm80_app_note.pdf> that gives that recommendation.  Below is one paragraph from that tech note.

There is little benefit to mixing an FM100 with an FM60/80. If circumstances require it, this application
note will explore an option.

Note the language is pretty dang squirrely.  Let’s parse the above paragraph:

Sentence 1:  I submit there may be many scenarios where there is significant benefit:  Like if you already have an FM60/80 and you want to add more PV and you want to enjoy the benefits of an FM100, such as higher input voltage or higher output amperage, and not have to fork out an extra $1000 to replace a working FM60/80.  Or you installing more than one PV array,  one array nearby and/or smaller and one further away or larger, and you don’t want to spend close to $1,000 to charge control the nearer array.

Sentence 2:  They are offering “an option,” not the only option.  I believe there are multiple options. In a mixed installation, the FM100 can rely on its internal GFDI fuse and the FM60 or 80 can rely on the old familiar GFDI breaker with the 1 or 0.5 amp pole connected between the negative and equipment grounding system.  Alternatively, Midnite sells a 300 volt rated, multi-pole GFDI breaker that could be shared by an FM100 and an F60/80.  It says right in the FM100 manual that you can use external GFDI devices (page 14).

I am not at all clear as to what problem there is to mixing the two generations of charge controllers.  I reviewed the NEC.  There is no indication that thou shall not mix GFDI styles.

If anyone has a definitive reason why or why not to mix these models of Outback charge controllers, I would be most interested.

Most Sincerely,

William Miller

Miller Solar
17395 Oak Road, Atascadero, CA 93422
805-438-5600
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