SMA Combi-Switch questions about UL rating [RE-wrenches]

[Larry Crutcher, Starlight Solar]

I should have started my own thread on this so here it is again...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I was looking at the SMA combiner last week and I am a little puzzled.

They are using a Square D HU361 disconnect to build the combiner. SMA 
rates the disconnect at 40 amperes. However, Sq D has issued a data 
bulletin, Document Number 3110DB0401, that has specific UL limits when 
used as a PV system disconnect.

Page 2 has the specifications for PV use. At the top of page 2 is this 
note, "Heavy duty safety switches may be used on photovoltaic systems 
with a grounded feed. Refer to Figures 1B, 1D and 2." There is a limit 
of 11.5 ampere per leg in table 1 Limitations when wired according to 
figure 1B, 1D and 2.

Figure 1B is of the HU361. According to this only 11.5 amperes can be 
connected through this entire disconnect. Figure 2 shows each pole 
individually connected to inverters or charge controllers. 

The SMA combiner is not wired according to any figure on this data 
sheet. They have landed two legs on the two outer poles and then 
combined the DC before it feeds the load. I asked the SMA rep and he 
told me it was approved by UL. So how can this be a UL listed 40 amp 
disconnect when it conflicts with the OEM's UL approval?

see Sq D document here: 
http://ecatalog.squared.com/pubs/Electrical%20Distribution/Safety%20Switches/Heavy%20Duty/3110DB0401.pdf


Larry Crutcher
Starlight Solar
Yuma, AZ
Renewable Energy Products Powered by STARLIGHT


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