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Whole House - Back up generator

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    #16
    First question is do you want to back up the entire service?

    If so you need a large enough generator for the entire calculated load. You will need either multiple transfer switches or change service equipment so there is a single disconnect and transfer ahead of the feeders.

    If you only want to back up selected loads you could install another feeder to a panel containing the desired loads and then install a transfer switch and appropriate sized generator and transfer switch to supply just the designated backup panel.
    I live for today, I'm just a day behind.

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      #17
      We are backing up the whole service, I already did a load calc and came up with about 54KW demand, so I went with a 60KW generator. We are backing up everything because moving selected loads from the panel to be backed up would be un-reasonable.


      I ended up removing the existing service equipment and installing a service rated ATS to feed the existing panels. Attached is my new partial schematic.
      Attached Files

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        #18
        Looks good. Now the tough part, finding room to fit all the equipment.
        Some people are like slinkies. They serve absolutely no useful purpose. But still put a smile on your face when pushed down a flight of stairs.

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          #19
          lol, I thats the real tough part.


          If I am using a service rated ATS, the GEC would come out of the ATS and I would need a EGC from the generator correct? Article 250 in the handbook doesen't show a service rated ATS.

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            #20
            Originally posted by Npstewart View Post
            lol, I thats the real tough part.


            If I am using a service rated ATS, the GEC would come out of the ATS and I would need a EGC from the generator correct? Article 250 in the handbook doesen't show a service rated ATS.
            A service rated ATS is/contains the service disconnect. The original panel is now supplied by a feeder and you will need separate grounded and grounding conductors to it.

            Not trying to be judgemental but you said "moving selected loads from the panel to be backed up would be un-reasonable".

            Lets say you only need 15KVA for items that are really needed to be backed up.
            Cost of a 16 or 20KVA generator will be considerably different as well as 100 VS 400 amp transfer equipment. Now consider how much fuel the larger generator will use even if it runs with only 20-25% load most of the time when it runs. It will likely run weekly just for 'exercise' with little or no load but will use more fuel doing so.

            Just some things to consider.

            Most of my residential customers that have ever wanted generator want just about the smallest generator possible yet they wonder why it can't run the entire house when it is time to use it. - Most of time is manual transfer (I use transfer term pretty loosley in this situation) and only 5-6000 Kw generator.

            More than once I have had service calls for something not working right while using generator, when I get there they have a double male ended 5-15 cord and are trying to make it energize the entire house panel. The items that don't work right are on the other leg of the panel and are back fed through a 240 volt load such as the water heater.

            I once had a farmer hook up a tractor PTO driven generator (directly) to an auger motor so he could get corn out of his bin to feed cattle during an extended power outage. He miswired the motor and made a dead short between L1 and L2 by the way he connected it.

            The HP of the tractor was well above the generator capability. When he attempted to turn that "short circuit' on one of the universal joints on the PTO shaft just snapped right off.

            Sorry about straying off topic a little there.
            I live for today, I'm just a day behind.

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              #21
              When I said "moving selected loads from the panel to be backed up would be un-reasonable", I was actually thinking of a conversation I had with the owner. They basically wanted everything back up EXCEPT the pool panel, but, they want to run the filter. However, in order to run the filter you need to run the pumps, and they have (3) 1.5 HP pumps, which is the only thing on the pool panel because their heater is natural gas. So basically the only thing they didn't want to run is a fountain, and some landscape lights. In my opinion it wouldn't be worth re-arranging their equipment to avoid powering landscape lights.

              With my experience, when a home-owner that owns a 8,000 or 9,000 square foot house says they want a generator, it means they want EVERYTHING backed up, even when they say they don't.

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                #22
                Originally posted by Npstewart View Post
                When I said "moving selected loads from the panel to be backed up would be un-reasonable", I was actually thinking of a conversation I had with the owner. They basically wanted everything back up EXCEPT the pool panel, but, they want to run the filter. However, in order to run the filter you need to run the pumps, and they have (3) 1.5 HP pumps, which is the only thing on the pool panel because their heater is natural gas. So basically the only thing they didn't want to run is a fountain, and some landscape lights. In my opinion it wouldn't be worth re-arranging their equipment to avoid powering landscape lights.

                With my experience, when a home-owner that owns a 8,000 or 9,000 square foot house says they want a generator, it means they want EVERYTHING backed up, even when they say they don't.
                Hey if they want to spend the money then by all means let them.

                Even if I could afford to do that for my own place I probably would only back up what is necessary, I just am not the kind of person that is wasteful in general.

                A few years ago I was without power for 10 days after an ice storm. My normal monthly electric bill was around $200 at that time. The cost to keep a portable generator running (that could not even run everything that normally runs) was starting to look like it would be around $900 if it were to run for 30 days.
                I live for today, I'm just a day behind.

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                  #23
                  Don't forget not to put your service conductors in the same pipe as your feeders. Sometimes it's easy to think about one large nipple to go from meter to panel etc.... I have fixed situations like these when people retro fit xfer panels into existing situations.
                  Make something idiot proof and someone will make a better idiot.

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                    #24
                    Originally posted by mikeames View Post
                    Don't forget not to put your service conductors in the same pipe as your feeders. Sometimes it's easy to think about one large nipple to go from meter to panel etc.... I have fixed situations like these when people retro fit xfer panels into existing situations.
                    Is that even possible to do if he is doing this:


                    Originally posted by Npstewart View Post
                    We are backing up the whole service, I already did a load calc and came up with about 54KW demand, so I went with a 60KW generator. We are backing up everything because moving selected loads from the panel to be backed up would be un-reasonable.


                    I ended up removing the existing service equipment and installing a service rated ATS to feed the existing panels. Attached is my new partial schematic.
                    I live for today, I'm just a day behind.

                    Comment


                      #25
                      Nope
                      Make something idiot proof and someone will make a better idiot.

                      Comment


                        #26
                        What make and model transfer switch did you or are you installing?
                        remember, there is always a shot on the pool table.....

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                          #27
                          What's fueling the generator?

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