I need a 600V/ 60A DC disconnect for my PV system. I've realised that there two available Square D disconnects in your website.
What's the difference between H362NRB and H362RB ?
https://www.greentechrenewables.com/product/square-d-h362nrb?qty=1
https://www.greentechrenewables.com/product/square-d-h362rb?qty=1
They seem to be exactly the same.
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13 years 5 months ago
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The "N" in H362NRB stands for Neutral.
When photovoltaic panels convert the sun’s energy into electricity, the power generated is direct current (DC). Typically, the systems are designed with DC system voltages in the 400–600V range. This is much higher voltage than typically found in building systems. The higher voltage, when combined with the lack of a current sine wave with zero crossings, creates a number of challenges in wiring, particularly when switching circuits on and off.
DC can arc real bad! DC circuits consist of two wires—a positive and a negative. In mostPV systems, one of these wires is grounded (like a neutral in an AC system). Which of the two wires is grounded is specified by the solar panel manufacturer. The more common application is a negative ground, and the location of this bond is usually found at the inverter. Per the National Electrical Code Section 690.5(A), only the current-carrying ungrounded conductor should be switched. Thus, in a negative-grounded system, only the positive wire is switched. Unlike AC systems that possess a current sine wave with zero crossings, the interruption of higher voltage DC circuits requires an increased air gap to safely and quickly interrupt and break the arc. The increased gap is accomplished by wiring multiple poles of a single switch in series for safe arc interruption. All switch manufacturers require the use of multiple poles at 600 Vdc to maintain the ULT listing. For this reason, a switch should only be used to switch one circuit. The UL listing of these products does not permit multiple circuits to be switched by one switch. Installers may need to add jumpers to a two- or three-pole switch, add a neutral, and add labels to meet this requirement.The "N" designated switches have an insulated terminal block in which to connect the (usually negative) conductor instead of pulling it all the way to the inverter, where there is usually a connection to ground.
Some switches also have a bonding lug which would allow for direct connection to a ground rod or other equipment ground.
Here is the Square D disconnect installation manual
So: NRB = Isolated terminal block equipped switch and RB = No terminal block.
The DC disconnect can be configured in whatever manner suits your installation!
That really clears it up for folks. Thanks! You know, it would be great to see pictures or drawings along with the product listings that show the benefit / use of an isolated terminal in the DC disconnect - or simply an accurate picture depicting the NRB and RB models. Since the different amp ratings all look roughly the same, there could be just two pictures for the full amperage range of DC disconnects...