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Electrical Wiring in the Home/Bypass/secondary power to a subpanel


kbenton wrote at 2014-05-15 17:49:41
Hello Bob,

Thanks again for the clear and concise answer.  After reading your response I went back and reviewed the manual for my UPS.  It is an older model APC Matrix 5000 made up of two units... an Isolation Unit (IU) and an Electronics Unit (EU)(along with battery packs of course). The IU contains the isolation transformer, EMI/RFI filtering, surge suppression circuits, and bypass circuits.  The EU contains the microprocessor, inverter, battery charger, transfer and tap changing circuits, and various interfaces.

In normal operating mode the UPS acts just the way you described in your reply, however when the system is in Bypass mode only the IU is in use and the EU is taken out of the circuit. The IU will continue to condition the input/output load but will not provide any protection from sags, swells, or blackouts.  In fact the UPS system is designed so the EU can be placed in Bypass mode and then separated from the IU for repair/replacement.  Of course the flaw in this is if you need to work on the IU then you still need to shutdown the load running through the IU and to the mission critical system.

What I would like to do is place the UPS in Bypass mode (cutting the inverter and batteries out of the circuit), bypass the load at the subpanel via the 30 amp breaker in the main panel and then de-energize the whole gen/ups circuit so I can do maintenance on the components in the circuit (and perhaps reconfigure the whole circuit to make it easier to maintain).



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Electrical Wiring in the Home

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Licensed Master Electrician (32 years) 6165B Contractor in Closter New Jersey with 40 years total experience in Residential - Commercial - Industrial work. Emergency Service - General trouble shooting and repair work - ONAN & GENERAC generator installation - Paddle fans - Kitchen & Bath exhaust fans - AC lines - Smoke detectors - Telephone lines - Cable TV lines - Computer network cabling - Exterior lighting - Recessed lighting - Security lighting - (200 - 150 - 100 amp service up grades) - Electric Heat - New circuits - New appliance hook ups - and more ! FREE ESTIMATES 201-358-1552 Fully Insured


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"The Frank Williams School of Electrical Construction". My dear old boss is 100 ! and still going God Bless him. I started working for "Tenafly Electric" right out of high school at 19. He was tough but I learned more working for him in 8 and half years than most guys. We did mostly industrial work while doing some commercial and residential so I was fortunate to be exposed to all 3 areas of electrical construction. The guys I worked with were all good guys and I stay in touch with some of them still. Most of us went into our own buisness's which says something about the caliber of the guys I worked with. We had some interesting clients : Wella Corp. of shampoo fame, Farah Fawcett etc, I didn't buy shampoo for 10 years. It was a great place to work. Pan Am the former airline just before they went under, another great place to work, nice clean environment. C&C Metals, the largest button manufacturer in the US at that time, a not so clean environment but a very interesting place to work, lots of machine's cranking out buttons of all kinds but you had to be on your toes, it was a potentially dangerous place to be . All kinds of action going on around you.

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