Home UPS / Generator Setup

Discussion in 'The Projects Forum' started by jazzpilot56, Mar 2, 2012.

  1. jazzpilot56

    Thread Starter New Member

    Mar 2, 2012
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    0
    I know this has been covered to some extent and I've read the other posts so I hope I'm not being redundant.

    I'm considering buying a backup generator with Automatic Transfer Switch for my house (a Kohler 20KW unit) and thought it would be a great opportunity for me to install a larger UPS in the basement that could power critical circuits on it until the generator kicks in (8-12 seconds).

    My thought was rather than having 10-12 small UPS's for each PC, stereo, home alarm system, and other power sensitive devices I could just install one large (maybe 3KVA) UPS in the basement and plug directly into the circuits thereby eliminating the small UPS's scattered all around the house.

    Actually, I already own a couple of these APC 3KVA units because I run some file/web/email servers in my basement and they can be bought on ebay cheap.

    The reason for the larger generator is because i have a 5-ton A/C, larger refrig and freezer, oven, washer/dryer, etc. Plus the rack of servers I mentioned previously. Besides, it seems like 1/2 the cost of installing a home backup gen is the installation costs, so over spec'ing the unit doesn't add much to the total cost.

    Anyway, my thought was to wire the UPS's between the generator / ATS and the individual circuits - i.e. split my one 200-amp CB panel two smaller ones (say two 100-amp panels) and have one panel wired for critical circuits (the electronics stuff plus some lights so they stay on until the gen fires up) and one for non-critical (A/C, refrig, oven, washer / dryer, etc.).

    Question is - can this be done? Safely? Has anyone done it? Sample circuit diagram?

    Thoughts, input, feedback would be appreciated.
     
  2. JMW

    Member

    Nov 21, 2011
    88
    8
    Yes, it can be done. As you pointed out you will need to add an additional circuit breaker panel. Let's call them sub panels B, C and D. You will have to add an outlet from the original panel to power the UPS, 25 amps 125 VAC. Your problem will be getting power from the UPS to sub panels Panel B, C and D. There are 6-10 amp outlets on the back of my 3kva APC, powered by 3 circuit breakers, I imagine you have the same. You should wire sub Panels B,C and D so that each is fed by one UPS circuit breaker. Then remove the house circuits from Panel A and install them in the appropriate sub panel.
    If you have never done this, I would hire an electrician. You are going to need a lot of stuff, which will entail numerous trips to your local supplier.
    As the sub panels are not "hardwired" to the UPS there may be a code problem.
     
  3. jazzpilot56

    Thread Starter New Member

    Mar 2, 2012
    2
    0
    Everything you said makes sense and was easy to follow. The only additional question is about the potential code issue and hardwiring the circuits to the UPS. Some APC units have nema 15, 20 and even 30 amp recepticles in both locking (i.e. L6-30R) and non-locking 3-prong outlets.

    My thought was to buy one that has the L6-30R recepticles (usually a couple of them) and then cut one end of the 30 amp connecting cable and actually hard wiring it into the circuit breaker box with the other end locking into the L6-30R recepticle.

    Not sure if that would meet code but I'll ask the town inspector.

    My other approach, if the above doesn't fly, is to get a UPS that only has a hard wire panel on the back. I believe APC has that configuration and I know Tripp-lite can be configured like that. Hopefully this would be acceptable by code.

    I agree on the hardware, tools and contractor expertise. I'm bold, but not that bold to attempt an installation of this magnitude by itself.

    I appreciate the feedback. And if / when I complete the project I'll post pictures, wiring diagrams, and feedback on local code.
    ___________________________

    JMW, wanted to clarify with another quick question: my approach would be to wire the 30-amp circuits into 30 amp breaker panels, and then further sub-divide the 30 amps between 15-amp circuits using 15 amp breakers. I assume I could only put two 15 amp circuits on each 30 amp feed from the UPS? I guess this is where my home wiring knowledge tops out, because ideally I'd want to put 3 or 4 circuits on the 30 amp feeds (with the theory that one would never turn everything on at once thereby overload the 30 amp circuit). Well, additional details I'll have to sort out. Again, I appreciate it.
     
    Last edited: Mar 2, 2012
  4. JMW

    Member

    Nov 21, 2011
    88
    8
    The only reason I suggested 3 sub panels is that is how mine is configured. If you only have 1 CB on your unit, then of course you can use 1 30amp panel. Combining 3-10 amp outputs to give you 1-30 amp is considered bad form. First it won't fly code wise, second, no two CB's are exactly the same. So if you draw a 30 Amp load, 1 CB is going to trip, then the other two will follow. I imagine you could open the UPS and find a common output and make a hardwire connection at that point.
     
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