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

Tue Nov 27 08:42:14 PST 2012

JASON:

The reference temperature for the Square-D breakers is 40C/104F, as 
opposed to 20C/68F for the ABB breakers. The possibility of a "nuisance 
trip" due to derating would occur sooner for a 20A ABB breaker than for 
a 20A QO/QOB breaker.

I received a follow-up e-mail earlier today from Steve Capozzi of SolaDeck:

    -------- Original Message -------- 

    Subject: 	RE: SolaDeck
    Date: 	Tue, 27 Nov 2012 07:20:17 -0600
    From: 	Steve Capozzi <scapozzi at rstcenterprises.com>
    Organization: 	RSTC Enterprises
    To: 	<gary at icarus-engineering.com>

    Gary,

      I sent ABB engineering an e-mail yesterday to see if they have any
    new items with higher ambient temps.

    The breakers we have were the highest at the time we started into AC
    systems.

    We have never had a issue in the field with these breakers.

      I will keep you posted.

    steve

    Steve Capozzi
    President
    RSTC Enterprises Inc
    2214 Heimstead Road
    Eau Claire, Wi 54703
    866-367-7782
    715-830-9997

  I'll keep you posted with what I find out.

Regards,

Gary Willett, PE
Icarus Engineering LLC

Icarus Solar Services LLC

On 11/27/2012 8:30 AM, Jason Szumlanski wrote:
> 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 <mailto: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 <mailto: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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