Re: [RE-wrenches] ASP Inverters

[Dave Click]

Jason, I think they were re-branded Eaton inverters. Unlike the modules, 
they were actually UL listed...


On 2014/6/30, 16:13, Jason Szumlanski wrote:
Does anyone know who manufactured the PV250 inverters from ASP before 
they went under? Are they private labeled inverters manufactured by 
others, or is ASP considered the OEM? I was able to find a manual 
online at least.


Any experience out there with faults in these inverters? I have a 
feeling our first service call is going to be the first of many in our 
area. We're implementing a policy that we won't work on the inverters 
if the system has the fraudulent UL labels on the PV panels. That 
should be interesting...


Jason Szumlanski

Fafco Solar



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[RE-wrenches] ASP Inverters

[Jason Szumlanski]

Does anyone know who manufactured the PV250 inverters from ASP before they
went under? Are they private labeled inverters manufactured by others, or
is ASP considered the OEM? I was able to find a manual online at least.

Any experience out there with faults in these inverters? I have a feeling
our first service call is going to be the first of many in our area. We're
implementing a policy that we won't work on the inverters if the system has
the fraudulent UL labels on the PV panels. That should be interesting...

Jason Szumlanski

​Fafco Solar​
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Re: [RE-wrenches] Combining Multiple Inverters

[Glenn Burt]

What am I missing here?

In the 2014 NEC, 705.21 seems to indicate that every inverter needs to have its 
own AC disconnect. Most inverters only have integrated DC disconnects (SMA, 
Power One, Fronius) as I recall. Or has this been interpreted to only apply to 
the DC side of the system?

 

Since NYS is still on the 2008 NEC, and the handbook has a note in 690.64B)1:

The outputs of utility-interactive inverters may not be connected directly in 
parallel without first being connected to the required dedicated circuit 
breaker or fusible disconnecting means.

 

Further, I believe it can be interpreted that each inverter source circuit 
connection “shall be made at a dedicated circuit breaker or fusible 
disconnecting means” as directly quoted from 690.64(B)1.

 

I see a dedicated OCPD being required for each inverter output, unless the 
manufacturer has installation instructions which have been approved by UL 
indicating that more than one can be paralleled and retain its listing (ala 
microinverters).

 

-Glenn

 

From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf 
Of Corey Shalanski
Sent: Monday, June 30, 2014 2:38 PM
To: re-wrenches@lists.re-wrenches.org
Subject: Re: [RE-wrenches] Combining Multiple Inverters

 

Thank you to all who responded to this thread - particularly Jason/Dave/Jay for 
pointing out the maximum OCPD requirements.

 

Getting back to my original question.. I would like to use Dave's "extremely 
small subset" example of two SB5s operating at 277V. In this case, if we were 
to parallel the output of each inverter onto a 50A OCPD (#6 wire), could we 
downsize the wire to #10 from the split going back to each individual inverter? 
or would we be better served (required?) to run #6 all the way back to each 
unit? Since we are dealing with current-limited devices I would tend to think 
we can downsize but wanted to get Wrenches' feedback on this.

 

--

Corey Shalanski

Joule Energy

New Orleans, LA

  

 ᐧ

 

On Fri, Jun 27, 2014 at 12:41 PM,  
wrote:


Message: 5
Date: Fri, 27 Jun 2014 11:32:02 -0400
From: Dave Click 
To: re-wrenches@lists.re-wrenches.org
Subject: Re: [RE-wrenches] Combining Multiple Inverters
Message-ID: <53ad8e72.4080...@fsec.ucf.edu>
Content-Type: text/plain; format=flowed; charset=ISO-8859-1

This is an interesting conversation, but I'm not sure it's going to
really impact anything.

When an inverter is listed, it is tested with some "maximum output
overcurrent protection" as part of its rating per UL 1741. Typically
inverter manufacturers set this to be just above the inverter's max
current + 25%. As you know, many inverters can work at more than one
voltage, so for the SB5s their max current ratings at 277/240/208V are
18/20.8/24A, respectively. The max overcurrent protection is 50A. This
figure often appears in the manual but not in the data sheet. For SMA,
it's in the manuals. For some manufacturers, it's only available from
tech support.

For the Sunny Boy line, the only way you could have more than one
inverter on a shared OCPD is if you have two SB5s operating at 277V
(18.1A rated current each, so 2x18.1x1.25 < 50A). The SB6, SB7, and SB8
all have currents too high to make this work, as they share the 50A max
OCPD. The SB3/3.8/4 have a max OCPD of 30A, which is too low to
double-up since each SB3 requires an OCPD of at least 20A. The TLs don't
work either, as the max for any unit is too low. I don't see it in the
SMA manual, but I know that in other manuals I've seen a manufacturer
requirement for a dedicated OCPD. The only inverters I know of that have
a max OCPD rating far beyond their rated current are micro-inverters.

As for the shared disconnect, since at least the 2005, 690.15 has noted,
"A single disconnecting means in accordance with 690.17 shall be
permitted for the combined ac output of one or more inverters or ac
modules in an interactive system." That being said, the NEC requires ac
modules and micro-inverters to have ac disconnects (connectors,
typically) per 690.6 and 690.15(A). 690.15 notes that an inverter be
able to be disconnected from all sources, but if doubling up these SB5s
you could argue that this shared disconnect accomplishes that via the
anti-islanding protection... so I agree now that this is a grey area.

Anyway, it comes down to whether it's worth worrying about this for what
is an extremely small subset of compatible inverter configurations, when
you can just do something like install a $50 Eaton BR24L70RP (70A bus,
240V, 4 spaces) with two 30A breakers and be on your way.

DKC

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Re: [RE-wrenches] Combining Multiple Inverters

[Jason Szumlanski]

Bill,

I would be happy to contribute.

Regarding the 120% rule, I'm not sure I agree. There can be panelboards
connected in series in a supply side connection, and there can be loads in
PV inverter aggregation panels used in supply-side connections.​ For
example, it is common to install a dedicated outlet circuit for monitoring
gateways in microinverter system aggregation panels.

This below is compliant, and would have the same need for the 120% rule as
a load side connection if I understand the rationale correctly
(notwithstanding the way each code cycle is organized):

Supply<-->Fusible Disconnect<-->Aggregation Panel<-->Sub-Aggregation
Panels<-->PV Inverters and Loads


​I'm not up to speed on the 2014 changes, so I'm really just talking about
the changes from 2008 to 2011, which seem to have moved in the direction of
applying 705.12(D)(1)-(7) to both load- and supply-side ​interconnected
systems in 2011, whereas 690.64(B)(1)-(7) in 2008 clearly applied to
load-side connections only.

Are you saying 705.12(D)(1)-(7) in 2011 apply to load-side connections
only? That's not the way I interpret it.


Jason Szumlanski

​Fafco Solar​





On Fri, Jun 27, 2014 at 8:12 PM, Bill Brooks  wrote:

> Jason,
>
>
>
> It sounds like you want to get involved with the PV industry forum. We
> have about 30+ active members this year so your input would be welcome.
>
>
>
> I think your idea about organization needs to be informed about some
> details. First of all, you need to read the new, very different, 705.12(D).
> SolarPro has a nice article about code updates.
>
>
>
> Secondly, rules on the supply side are very different than load side.
> Supply side connections, by definition have no loads connected to them. It
> is simpler and does not need any 120% rule. The 120% rule is a very
> conservative restriction. No such restriction exists on the supply side.
>
>
>
> Too much to cover all the issues now—suffice it to say there are many,
> many reasons to keep supply-side and load-side connections separate.
>
>
>
> Bill.
>
>
>
> *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On
> Behalf Of *Jason Szumlanski
> *Sent:* Friday, June 27, 2014 5:45 AM
> *To:* RE-wrenches
>
> *Subject:* Re: [RE-wrenches] Combining Multiple Inverters
>
>
>
> It depends on your applicable code. In the 2008 code, 690.64(B) was
> specifically titled "Load Side" and the provisions of that section in full
> were not applicable to supply side connections. That was probably not the
> intention (i.e. the 120% rule and OCPD requirements should have applied to
> aggregation panels). In the 2011 code, 705.12(D) is the similar section,
> but it has been titled "Utility Interactive Inverters." This section now
> "allows" load side connections, but the requirements (1) through (7) of
> this section still apply to supply side connections (my interpretation).
>
>
>
> The better code organization IMO would be:
>
>
>
> 705.12 (A) Allow supply side connections
>
> 705.12 (B) Allow load side connections
>
> 705.12 (C) Integrated Electrical Systems
>
> 705.12 (D)(1)-(7) The requirements for all interconnection methods
>
> 705.12 (E) Greater than 100kW
>
>
>
> ​
>
> A bit off-topic, but we recently had a utility reject a plan to install a
> 320A meter socket with a 200A main distribution panel and a 100A solar
> aggregation panel (with four 20A backfed breakers). The two panels were to
> be fed from double lugs in the meter can. They said this was not allowed -
> they didn't want solar in their meter can. When I pointed out that dual
> 200A load panels are commonly fed this way and this was no different
> because I could just backfeed each 200A panel with two 20A breakers, my
> comment was met with blank stares.
>
>
>
> Jason Szumlanski
>
> ​Fafco Solar​
>
>
>
>
>
>
> On Thu, Jun 26, 2014 at 6:11 PM, Corey Shalanski <
> cshalan...@joule-energy.com> wrote:
>
> ᐧ
>
> Perhaps I should've been more specific with my scenario. I was imagining a
> supply side connection, as this would more commonly be the case when
> combining multiple inverters. In this case it seems like the provisions of
> 705.12(D) for load side conections don't even apply, no? Rather 705.12(A)
> becomes the relevant section, and I see very few restrictions there.
>
>
>
> Even with a load side connection I would tend to agree with Jason's
> interpretation: Does the "source interconnection" in 705.12(D)(1) refer to
> each individual inverter, or can it refer to an aggregated "source"?
>
>
>
> I am interested in pursuing this idea, mainly to understand how/where the
> NEC forbids it. In lieu of a clear Code reference against it, how is this
> any different from a branch circuit (in reverse)? ie, as with
> microinverters.
>
>
>
> --
>
> Corey Shalanski
>
> Joule Energy
>
> New Orleans, LA
>
>
>
> On Thu, Jun 26, 2014 at 9:20 AM, <
> re-wrenches-requ...@lists.re-wrenches.org> wrote:
>
>
> Message: 11
> Date: Thu, 26 Jun 2014 09:10:07 -0400
> From: Jason Szumlanski 
>
>
> To: RE-wren

Re: [RE-wrenches] Combining Multiple Inverters

[William Miller]

Corey:

I think what you are proposing is a bad idea and false economy. 

It is good practice to provide disconnecting and over-current protection 
devices to all discrete components in any system. This applies to power systems 
as well as signaling systems. This provides capability to isolate sub-systems 
for troubleshooting and temporary operation in case of partial failures. The 
cost of a small sub-panel is a minimal, necessary part of this type of 
installation.

Now that we have seen that very few cases support the math needed to comply 
with code, further discussion seems purely academic.

William Miller

Miller Solar

> On Jun 30, 2014, at 11:50 AM, Brian Teitelbaum  
> wrote:
> 
> Corey,
>  
> The wire ampacity has to be sized for the OCPD, as this is potentially a 
> bidirectional wire in a fault. While the inverter is current limited, the 
> grid it’s connected to is only limited by the Service Main, and that 50A 
> OCPD, which would exceed the ampacity of #10 wire.
>  
> Brian Teitelbaum
> AEE Solar
>  
>  
>  
> From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On 
> Behalf Of Corey Shalanski
> Sent: Monday, June 30, 2014 11:38 AM
> To: re-wrenches@lists.re-wrenches.org
> Subject: Re: [RE-wrenches] Combining Multiple Inverters
>  
> Thank you to all who responded to this thread - particularly Jason/Dave/Jay 
> for pointing out the maximum OCPD requirements.
>  
> Getting back to my original question.. I would like to use Dave's "extremely 
> small subset" example of two SB5s operating at 277V. In this case, if we were 
> to parallel the output of each inverter onto a 50A OCPD (#6 wire), could we 
> downsize the wire to #10 from the split going back to each individual 
> inverter? or would we be better served (required?) to run #6 all the way back 
> to each unit? Since we are dealing with current-limited devices I would tend 
> to think we can downsize but wanted to get Wrenches' feedback on this.
>  
> --
> Corey Shalanski
> Joule Energy
> New Orleans, LA
> ᐧ
>  
> 
> On Fri, Jun 27, 2014 at 12:41 PM,  
> wrote:
> 
> Message: 5
> Date: Fri, 27 Jun 2014 11:32:02 -0400
> From: Dave Click 
> To: re-wrenches@lists.re-wrenches.org
> Subject: Re: [RE-wrenches] Combining Multiple Inverters
> Message-ID: <53ad8e72.4080...@fsec.ucf.edu>
> Content-Type: text/plain; format=flowed; charset=ISO-8859-1
> 
> This is an interesting conversation, but I'm not sure it's going to
> really impact anything.
> 
> When an inverter is listed, it is tested with some "maximum output
> overcurrent protection" as part of its rating per UL 1741. Typically
> inverter manufacturers set this to be just above the inverter's max
> current + 25%. As you know, many inverters can work at more than one
> voltage, so for the SB5s their max current ratings at 277/240/208V are
> 18/20.8/24A, respectively. The max overcurrent protection is 50A. This
> figure often appears in the manual but not in the data sheet. For SMA,
> it's in the manuals. For some manufacturers, it's only available from
> tech support.
> 
> For the Sunny Boy line, the only way you could have more than one
> inverter on a shared OCPD is if you have two SB5s operating at 277V
> (18.1A rated current each, so 2x18.1x1.25 < 50A). The SB6, SB7, and SB8
> all have currents too high to make this work, as they share the 50A max
> OCPD. The SB3/3.8/4 have a max OCPD of 30A, which is too low to
> double-up since each SB3 requires an OCPD of at least 20A. The TLs don't
> work either, as the max for any unit is too low. I don't see it in the
> SMA manual, but I know that in other manuals I've seen a manufacturer
> requirement for a dedicated OCPD. The only inverters I know of that have
> a max OCPD rating far beyond their rated current are micro-inverters.
> 
> As for the shared disconnect, since at least the 2005, 690.15 has noted,
> "A single disconnecting means in accordance with 690.17 shall be
> permitted for the combined ac output of one or more inverters or ac
> modules in an interactive system." That being said, the NEC requires ac
> modules and micro-inverters to have ac disconnects (connectors,
> typically) per 690.6 and 690.15(A). 690.15 notes that an inverter be
> able to be disconnected from all sources, but if doubling up these SB5s
> you could argue that this shared disconnect accomplishes that via the
> anti-islanding protection... so I agree now that this is a grey area.
> 
> Anyway, it comes down to whether it's worth worrying about this for what
> is an extremely small subset of compatible inverter configurations, when
> you can just do something like install a $50 Eaton BR24L70RP (70A bus,
> 240V, 4 spaces) with two 30A breakers and be on your way.
> 
> DKC
> ___
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> List Address: RE-wrenches@lists.re-wrenches.org
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Re: [RE-wrenches] Combining Multiple Inverters

[Chris Mason]

You are not dealing with current limited devices, you are dealing with the
grid which is infinite. This is why you put the OCPD at the grid end of the
wiring, not the inverter end.


On Mon, Jun 30, 2014 at 2:38 PM, Corey Shalanski <
cshalan...@joule-energy.com> wrote:

> Thank you to all who responded to this thread - particularly
> Jason/Dave/Jay for pointing out the maximum OCPD requirements.
>
> Getting back to my original question.. I would like to use Dave's
> "extremely small subset" example of two SB5s operating at 277V. In this
> case, if we were to parallel the output of each inverter onto a 50A OCPD
> (#6 wire), could we downsize the wire to #10 from the split going back to
> each individual inverter? or would we be better served (required?) to run
> #6 all the way back to each unit? Since we are dealing with current-limited
> devices I would tend to think we can downsize but wanted to get Wrenches'
> feedback on this.
>
> --
> Corey Shalanski
> Joule Energy
> New Orleans, LA
> ᐧ
>
>
> On Fri, Jun 27, 2014 at 12:41 PM, <
> re-wrenches-requ...@lists.re-wrenches.org> wrote:
>
>>
>> Message: 5
>> Date: Fri, 27 Jun 2014 11:32:02 -0400
>> From: Dave Click 
>> To: re-wrenches@lists.re-wrenches.org
>>
>> Subject: Re: [RE-wrenches] Combining Multiple Inverters
>> Message-ID: <53ad8e72.4080...@fsec.ucf.edu>
>> Content-Type: text/plain; format=flowed; charset=ISO-8859-1
>>
>>
>> This is an interesting conversation, but I'm not sure it's going to
>> really impact anything.
>>
>> When an inverter is listed, it is tested with some "maximum output
>> overcurrent protection" as part of its rating per UL 1741. Typically
>> inverter manufacturers set this to be just above the inverter's max
>> current + 25%. As you know, many inverters can work at more than one
>> voltage, so for the SB5s their max current ratings at 277/240/208V are
>> 18/20.8/24A, respectively. The max overcurrent protection is 50A. This
>> figure often appears in the manual but not in the data sheet. For SMA,
>> it's in the manuals. For some manufacturers, it's only available from
>> tech support.
>>
>> For the Sunny Boy line, the only way you could have more than one
>> inverter on a shared OCPD is if you have two SB5s operating at 277V
>> (18.1A rated current each, so 2x18.1x1.25 < 50A). The SB6, SB7, and SB8
>> all have currents too high to make this work, as they share the 50A max
>> OCPD. The SB3/3.8/4 have a max OCPD of 30A, which is too low to
>> double-up since each SB3 requires an OCPD of at least 20A. The TLs don't
>> work either, as the max for any unit is too low. I don't see it in the
>> SMA manual, but I know that in other manuals I've seen a manufacturer
>> requirement for a dedicated OCPD. The only inverters I know of that have
>> a max OCPD rating far beyond their rated current are micro-inverters.
>>
>> As for the shared disconnect, since at least the 2005, 690.15 has noted,
>> "A single disconnecting means in accordance with 690.17 shall be
>> permitted for the combined ac output of one or more inverters or ac
>> modules in an interactive system." That being said, the NEC requires ac
>> modules and micro-inverters to have ac disconnects (connectors,
>> typically) per 690.6 and 690.15(A). 690.15 notes that an inverter be
>> able to be disconnected from all sources, but if doubling up these SB5s
>> you could argue that this shared disconnect accomplishes that via the
>> anti-islanding protection... so I agree now that this is a grey area.
>>
>> Anyway, it comes down to whether it's worth worrying about this for what
>> is an extremely small subset of compatible inverter configurations, when
>> you can just do something like install a $50 Eaton BR24L70RP (70A bus,
>> 240V, 4 spaces) with two 30A breakers and be on your way.
>>
>> DKC
>>
>
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>
>
>


-- 
Chris Mason
NABCEP Certified Solar PV Installer™
Solar Design Engineer
Generac Generators Industrial technician

www.cometsolar.com 
264.235.5670
869.662.5670
Skype: netconcepts
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Re: [RE-wrenches] Combining Multiple Inverters

[Brian Teitelbaum]

Corey,



The wire ampacity has to be sized for the OCPD, as this is potentially a
bidirectional wire in a fault. While the inverter is current limited, the
grid it’s connected to is only limited by the Service Main, and that 50A
OCPD, which would exceed the ampacity of #10 wire.



Brian Teitelbaum

AEE Solar







*From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On
Behalf Of *Corey Shalanski
*Sent:* Monday, June 30, 2014 11:38 AM
*To:* re-wrenches@lists.re-wrenches.org
*Subject:* Re: [RE-wrenches] Combining Multiple Inverters



Thank you to all who responded to this thread - particularly Jason/Dave/Jay
for pointing out the maximum OCPD requirements.



Getting back to my original question.. I would like to use Dave's
"extremely small subset" example of two SB5s operating at 277V. In this
case, if we were to parallel the output of each inverter onto a 50A OCPD
(#6 wire), could we downsize the wire to #10 from the split going back to
each individual inverter? or would we be better served (required?) to run
#6 all the way back to each unit? Since we are dealing with current-limited
devices I would tend to think we can downsize but wanted to get Wrenches'
feedback on this.



--

Corey Shalanski

Joule Energy

New Orleans, LA

ᐧ



On Fri, Jun 27, 2014 at 12:41 PM, 
wrote:


Message: 5
Date: Fri, 27 Jun 2014 11:32:02 -0400
From: Dave Click 
To: re-wrenches@lists.re-wrenches.org
Subject: Re: [RE-wrenches] Combining Multiple Inverters
Message-ID: <53ad8e72.4080...@fsec.ucf.edu>
Content-Type: text/plain; format=flowed; charset=ISO-8859-1

This is an interesting conversation, but I'm not sure it's going to
really impact anything.

When an inverter is listed, it is tested with some "maximum output
overcurrent protection" as part of its rating per UL 1741. Typically
inverter manufacturers set this to be just above the inverter's max
current + 25%. As you know, many inverters can work at more than one
voltage, so for the SB5s their max current ratings at 277/240/208V are
18/20.8/24A, respectively. The max overcurrent protection is 50A. This
figure often appears in the manual but not in the data sheet. For SMA,
it's in the manuals. For some manufacturers, it's only available from
tech support.

For the Sunny Boy line, the only way you could have more than one
inverter on a shared OCPD is if you have two SB5s operating at 277V
(18.1A rated current each, so 2x18.1x1.25 < 50A). The SB6, SB7, and SB8
all have currents too high to make this work, as they share the 50A max
OCPD. The SB3/3.8/4 have a max OCPD of 30A, which is too low to
double-up since each SB3 requires an OCPD of at least 20A. The TLs don't
work either, as the max for any unit is too low. I don't see it in the
SMA manual, but I know that in other manuals I've seen a manufacturer
requirement for a dedicated OCPD. The only inverters I know of that have
a max OCPD rating far beyond their rated current are micro-inverters.

As for the shared disconnect, since at least the 2005, 690.15 has noted,
"A single disconnecting means in accordance with 690.17 shall be
permitted for the combined ac output of one or more inverters or ac
modules in an interactive system." That being said, the NEC requires ac
modules and micro-inverters to have ac disconnects (connectors,
typically) per 690.6 and 690.15(A). 690.15 notes that an inverter be
able to be disconnected from all sources, but if doubling up these SB5s
you could argue that this shared disconnect accomplishes that via the
anti-islanding protection... so I agree now that this is a grey area.

Anyway, it comes down to whether it's worth worrying about this for what
is an extremely small subset of compatible inverter configurations, when
you can just do something like install a $50 Eaton BR24L70RP (70A bus,
240V, 4 spaces) with two 30A breakers and be on your way.

DKC
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Re: [RE-wrenches] Combining Multiple Inverters

[Corey Shalanski]

Thank you to all who responded to this thread - particularly Jason/Dave/Jay
for pointing out the maximum OCPD requirements.

Getting back to my original question.. I would like to use Dave's
"extremely small subset" example of two SB5s operating at 277V. In this
case, if we were to parallel the output of each inverter onto a 50A OCPD
(#6 wire), could we downsize the wire to #10 from the split going back to
each individual inverter? or would we be better served (required?) to run
#6 all the way back to each unit? Since we are dealing with current-limited
devices I would tend to think we can downsize but wanted to get Wrenches'
feedback on this.

--
Corey Shalanski
Joule Energy
New Orleans, LA
ᐧ


On Fri, Jun 27, 2014 at 12:41 PM,  wrote:
>
>
> Message: 5
> Date: Fri, 27 Jun 2014 11:32:02 -0400
> From: Dave Click 
> To: re-wrenches@lists.re-wrenches.org
> Subject: Re: [RE-wrenches] Combining Multiple Inverters
> Message-ID: <53ad8e72.4080...@fsec.ucf.edu>
> Content-Type: text/plain; format=flowed; charset=ISO-8859-1
>
> This is an interesting conversation, but I'm not sure it's going to
> really impact anything.
>
> When an inverter is listed, it is tested with some "maximum output
> overcurrent protection" as part of its rating per UL 1741. Typically
> inverter manufacturers set this to be just above the inverter's max
> current + 25%. As you know, many inverters can work at more than one
> voltage, so for the SB5s their max current ratings at 277/240/208V are
> 18/20.8/24A, respectively. The max overcurrent protection is 50A. This
> figure often appears in the manual but not in the data sheet. For SMA,
> it's in the manuals. For some manufacturers, it's only available from
> tech support.
>
> For the Sunny Boy line, the only way you could have more than one
> inverter on a shared OCPD is if you have two SB5s operating at 277V
> (18.1A rated current each, so 2x18.1x1.25 < 50A). The SB6, SB7, and SB8
> all have currents too high to make this work, as they share the 50A max
> OCPD. The SB3/3.8/4 have a max OCPD of 30A, which is too low to
> double-up since each SB3 requires an OCPD of at least 20A. The TLs don't
> work either, as the max for any unit is too low. I don't see it in the
> SMA manual, but I know that in other manuals I've seen a manufacturer
> requirement for a dedicated OCPD. The only inverters I know of that have
> a max OCPD rating far beyond their rated current are micro-inverters.
>
> As for the shared disconnect, since at least the 2005, 690.15 has noted,
> "A single disconnecting means in accordance with 690.17 shall be
> permitted for the combined ac output of one or more inverters or ac
> modules in an interactive system." That being said, the NEC requires ac
> modules and micro-inverters to have ac disconnects (connectors,
> typically) per 690.6 and 690.15(A). 690.15 notes that an inverter be
> able to be disconnected from all sources, but if doubling up these SB5s
> you could argue that this shared disconnect accomplishes that via the
> anti-islanding protection... so I agree now that this is a grey area.
>
> Anyway, it comes down to whether it's worth worrying about this for what
> is an extremely small subset of compatible inverter configurations, when
> you can just do something like install a $50 Eaton BR24L70RP (70A bus,
> 240V, 4 spaces) with two 30A breakers and be on your way.
>
> DKC
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