Disconnects on Fronius [RE-wrenches]

Matt Thompson matt at greenlotusconstruction.com
Fri Oct 20 09:28:43 PDT 2006


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Hello,

In small systems without a fuse combiner box, I install an MC connection 
on each positive DC leg inside the Fronius wiring box.
This is especially a good idea if getting to an MC conn on the roof is 
difficult. When servicing the IG one has to push the MC plugs through 
the knockout one at a time.
To me this solution seems to be a safe alternative to an external DCD.

Matt Thompson

Mark Frye wrote:
> I tend to agree much more with Dan on this issue. Note also that the 
> brand with the X also uses an integrated "DC Disconnect".
>
> Once you have a fused combiner box, you essentially have an external 
> disconnect.
>
> In a small system with just a few strings I don't have a fused 
> disconnect and do have to get to the MC connector which are also "no 
> load" disconnecting means. I always build with plenty of space between 
> the array and the roof deck and home run connectors are always easy to 
> get at.
>
> An electrician is a person who knows the hazards associated with working 
> on electrical systems and knows how to protect themselves from those 
> hazards.  PV systems have their own particular hazards which can be 
> addressed with specific protective actions.
>
> Just like any other aspect of electrical work, you shouldn't work on PV 
> it if you don't know it. I think we should be focusing on disseminating 
> appropriate safety measures for working on PV rather than putting a 
> bunch of bells and whistles on methods that already have the basic 
> protective elements available to the qualified individual.
>
> Berkeley Solar Electric Systems
>
>
> William Miller wrote:
>   
>> Dan:
>>
>> I have to say I think you and Fronius are way off-base on this issue.  
>> You 
>> are encouraging installers to install systems unsafely just to save 
>> themselves a few dollars.  I presume this is to give Fronius some kind 
>> of 
>> market advantage.
>>
>> Here's an analogy for you:  I could not install a roof-top air 
>> conditioning 
>> unit and have the disconnect for it at ground level.  The disconnect has 
>> to 
>> be within line of sight of the unit.  Human nature being what it is, 
>> someone is going to remove a Fronius inverter and fail to get a ladder 
>> and 
>> climb up on the roof just to disconnect the DC feeder to the inverter.
>>
>> If Fronius had remained silent on the issue, that would be one thing, 
>> but 
>> actively encouraging installers to disregard common safety practices is, 
>> in 
>> my professional opinion, unconscionable.
>>
>> As I said, I like your product and I like your people.  I disagree 
>> strongly, for safety reasons alone, on this one issue.
>>
>>
>> Sincereley,
>>
>> William Miller
>>
>>
>>
>>
>>
>> At 12:16 PM 10/19/2006, Fortson Dan wrote:
>>
>>     
>>> Hi William,
>>>
>>> I hope you are recovered from the SP-2006 event. I have read your 
>>> comment 
>>> on wrenches & will respond there as well. My stand on the Fronius 
>>> disconnect & code compliance is somewhat more measured than Fronius 
>>> techs 
>>> in the past as I believe it's ultimately up to the inspector. I 
>>> understand 
>>> Mr. Wiles refuses to commit on the matter. The live wire issue is real & 
>>>
>>> not trivial though. In fact, in the training I just gave at SP2006, I 
>>> emphasized to those in the class, who would likely be the ones 
>>> disconnecting a unit from the wall, that it is neither safe nor 
>>> advisable 
>>> to do so while the wires are hot. I generally recommend pulling string 
>>> fuses or disconnecting one connector in each string, then checking with 
>>> a 
>>> volt meter or on the Fronius display that DC voltage is, in fact, zero. 
>>> This method ensures that there will not be live wires unattended for 
>>> children to play with, etc.
>>>
>>> Your solution of using an external DC disconnect ensures safety but many 
>>>
>>> installers do not feel the trade-off is worth the investment. That's a 
>>> personal decision which must be made by the installer.
>>>
>>> Hope to see you next year at the show,
>>>
>>> Dan Fortson
>>>
>>> Applications Engineer
>>>
>>> Fronius USA
>>>
>>> (810) 220-4414
>>>       
>> __________________________________________________________________
>> William Miller
>> Miller Power and Communications
>> Voice :805-438-5600     Fax: 805-438-4607
>> email: wrmiller at mpandc.com
>> http://mpandc.com
>> License No. C-10-773985
>> _____________________________________________________________
>> Check out our latest project at 
>> http://mpandc.com/case_studies/pv_school/pv_school.html 
>> --
>> [Non-text portions of this message have been removed]
>>
>>     
>
>
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