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Tradeoffs in Balance of System Materials

Although there are many non-standard electrical components that go into the wiring of a residence with a Photovoltaic system, there are additional questions that must be asked regarding the wiring of a sustainable home. The most important characteristics of these components are safety, reliability, sustainability, energy efficiency, and cost. To make the example of how options will be weighted, the conduit used in a house will be considered. In most residences either a metallic or plastic conduit is used. In regions where the NEC isn’t enforced as strictly entire homes may be wired with romex(Insulated 3 Wire containing a hot, neutral, and a ground). The NEC states that some form of conduit must be used, and for additional protection any Plastic conduit must have a ground wire fed through it. Many times metallic conduit doesn’t require this ground wire as the conduit itself is bonded to the panel and thus grounded. However, when installing outlets on the outside portion of the house, questions start popping up. This metallic conduit may act as a thermal bridge compromising the seal of the house. If a PVC conduit is used or “smurf tube”, the sustainability of the material has to be questioned even though it may do a better job maintaining the thermal envelope. So a question arises: Does metallic conduit with its additional safety and potential for being recycled outweigh the additional cost of the pipe and the energy losses through heat or does a plastic conduit with better heat savings and ease of installation outweigh the additional cost of a ground wire and its environmental impact?


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