[RE-wrenches] Best practices for conduit penetration on roof

Tue Nov 27 06:30:04 PST 2012

We're pretty fortunate that a roof mounted readily accessible disconnect
has not been a sticking point locally. I would argue that the AC disconnect
is still the trunk cable connector, which can be not readily accessible.
The AC breaker carrying the combined circuit output in the main
distribution panel or the fusible disconnect switch if performing a supply
side connection would qualify as the readily accessible disconnect. If you
install Enphase I'm sure you are familiar with the manufacturer's excellent
white paper on this issue.

I hear what you are saying about the temperature concerns, but there are
many installations that have far fewer than 17 inverters per string. A
typical residential installation can be split into two or three branch
circuits (thank you, Andrew, for keeping me accurate on the string/circuit
thing!) The temp concern is definitely something to explore further. There
is also the thermal interference factor to take into account for multiple
breakers that Gary did not mention. The full datasheet is here:

http://www05.abb.com/global/scot/scot209.nsf/veritydisplay/11d7d0032b466358c125712400340107/$file/2CDC002052D0203_UL489.pdf

As for the "interior rated" breaker comment, typical AC branch circuit
breakers (i.e. Sq D QO) are mounted in wet location NEMA 3R boxes all the
time on the exterior of a building. I'm not sure I understand this concern.
The temperature derating curve is also similar for ABB and QO breakers. QO
Datasheet here:

http://static.schneider-electric.us/docs/Circuit%20Protection/Miniature%20Circuit%20Breakers/QO-QOB%20Circuit%20Breakers/0730CT9801R108.pdf

I definitely want to be 100% sure the SolaDeck and breakers are
appropriately rated before proceeding. Any comments welcomed...

*Jason Szumlanski** *

*Fafco Solar*

On Mon, Nov 26, 2012 at 6:37 PM, Gary Willett
<gary at icarussolarservices.com>wrote:

>  JASON:
>
> I talked to Steve Capozzi of SolaDeck and he sent me additional info about
> the circuit breakers:
>
> *Manufacturer*:  ABB
>
> *Terminal Temp Rating*:  75C / 167F
>
> *Reference Temperature*: 20C / 68F
>
> *Ambient Temp Derating*:
>
> 30C/86F = 18.7A
> 40C/104F = 17.3A
> 50C/122F = 15.8A
> 60C/140F = 14.1A
> 70C/158F = 12.2A
>
>  My concern is that we may be attempting to use an interior rated AC
> breaker in a roof-deck-mounted NEMA3-R enclosure.
>
> In an Enphase application, with the maximum of 17 inverters per AC Source
> Circuit, the continuous current will be 0.9A x 17 x 1.25 = 19.1A. This
> exceeds the 30C/86F trip current of 18.7A.
>
> The interior temperature of the SolaDeck could very likely approach the
> 60C/140F trip current of 14.1A.
>
> It seems to me that "nuisance trips" could be a high probability event.
>
> Does anyone have any field experience using this Soladeck option for a AC
> Source Circuit Combiner Box (SCCB)?
>
> Another issue, at least in some jurisdictions, is the requirement for a
> roof-top AC Disconnect.
>
> The SolaDeck, when used as an AC SCCB, may not meet the NEC Article 100
> requirements in some jurisdictions for "readily accessible" because a tool
> is required to open it.
>
>       Regards,
>
>
> Gary Willett, PE
> Icarus Engineering LLC
>   Icarus Solar Services LLC
>
> ****
>  On 11/26/2012 2:21 PM, Jason Szumlanski wrote:
>
> I did get some pictures and info from Soladeck. Here are some links:
>
>  Pics:
>
> https://docs.google.com/open?id=1BpiL-1SdSNNsj4wPMQrFCLHH7JT2dek_KftSJl06QLqc0yhJ_1t5oij0aEA6
>
> https://docs.google.com/open?id=1cVuhZGeQNHL1IvGvNBa7v93oZyGBvjxCv5yq4AmoyJeDAITxvgMqgECR2yTv
>
> https://docs.google.com/open?id=1umslTplnFyZG1eNCZE-MMi_OqrSeirFCPRBl9mFNZJ2gQkBjM5LEXnaPKy2l
> Specs:
>
> https://docs.google.com/open?id=13KLAuxUHOR9al7-36reDSJJ7IMnqV3ANPnJILPnrj2xcAi0ksRj67ifKIe7R
>
> https://docs.google.com/open?id=1kvPFcDc1vruS3W_aONlXyIHm1T8-qi4vTpTwGGJ7H0eIwuZ-5e6zrM1CcND5
>
> https://docs.google.com/open?id=1lM8FtYl9HiYohru32UA_Gb1tXZKZ5iw-8tnSu1Un6g4vcklLL-DK1qLPMdsB
>
>  I was told Soligent can source the combiners for you (and me).
>
>   *Jason Szumlanski** *
>
> *Fafco Solar* <http://www.wisestamp.com/apps/wordpress?utm_source=extension&utm_medium=email&utm_term=wordpress&utm_campaign=apps>
>
>
> On Mon, Nov 26, 2012 at 1:50 PM, Jason Szumlanski <jason at fafcosolar.com>wrote:
>
>> I just called Soladeck and they are sending me some more info on
>> availability. I'll pass it along when I get it. I didn't realize they made
>> an AC roof mounted string combiner solution. That's a huge help for 2 or 3
>> string Enphase installations (they make both combiners).
>>
>>  While on the subject, we recently started using the Enphase cable
>> couple with Type TC-ER cable to extend cabling to junction boxes when
>> necessary... No more wasting trunk cable connectors! I suppose Type TC-ER
>> could be used all the way to the main distribution panel, thereby
>> eliminating junctions on the roof, but I haven't looked into the
>> cost/benefit of that idea.
>>
>>    *Jason Szumlanski*
>>
>> *Fafco Solar*
>>
>>
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