module connection arrangement [RE-wrenches]

[Drake Chamberlin]

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Hi Jay,

At 04:12 PM 5/20/02 -0700, you wrote:

>I sure dont' like to put fuses on the roof.  I put my combiner boxes on the
>ground.  If there is going to be  problem, this is probably the place.

This may depend on the series fuse rating of the particular module used, as 
well as the style of junction box.

With Siemens SP 75 modules, with their excellent junction boxes and 15 amp 
series fuse rating, I think we can safely use a 15 amp series fuse on each 
string, in the j box, without concern.

With a real world charging current of 4.4 amps and a closed circuit 
amperage of 4.8 amps, I don't think we would ever blow a fuse unless a 
serious fault condition occurred.  Even given the multiplier of 1.25 X 
1.25, we are still only talking about 7.5 amps.  This is 1/2 of the 
allowable series fuse rating on an inherently current limited system.

So long as the j box with the fuse is clearly labeled, trouble shooting the 
system should not be rendered particularly difficult.  Problems that could 
blow a fuse would be

1) severely damaged module

2) miswired battery bank with no reverse current protection

3) a condition where a large number of modules were in full sun, forcing 
current backward through a miswired module.

4) a ground fault in the series connection between two modules, where open 
cable methods were used instead of conduit.

Fuse replacement would seem to me to be a relatively minor issue in any of 
these situations.

Does anyone know of any code reason to not put the series fuses in junction 
boxes?

Thanks,

Drake 

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