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Thread: synchronizer for MEP-803A

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    4 Star General Keith_J's Avatar
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    Quote Originally Posted by rhurey View Post
    House takes 400A service... Gen set puts out 52A...

    Skeptical the transfer box is rated for 100kw.
    The switch is sized for the generator. Your house isn't always drawing 400 amperes..that would be a huge power bill every month even in the PNW with cheap hydro power.
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    4 Star General Guyfang's Avatar
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    Quote Originally Posted by rhurey View Post
    House takes 400A service... Gen set puts out 52A...

    Skeptical the transfer box is rated for 100kw.
    If one needs a transfer box rated for 100 KW, one only needs to look for a bigger rated box. The biggest I ever used was rated at 750 KW. The components for the Patriot system, ( rated at 150 KW, and I pushed them to about 200 KW ) are off the shelf components.

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    Quote Originally Posted by Keith_J View Post
    The switch is sized for the generator. Your house isn't always drawing 400 amperes..that would be a huge power bill every month even in the PNW with cheap hydro power.
    Uh... Not from what I understood guyfang to be suggesting.

    To switch from grid to gen using the box to synchronize between grid and generator and then flip over, the grid power would need to come in through the box. Sure the house doesn't always draw 400A, (Nor even close since we've managed to drop the usage by 50% since we bought it) but wiring it up so the feed came in via the box and getting a permit signed off would require the box to be able to carry the full load. (Yes, likely somewhat less if we get out the NEC worksheets and do all the math, but for discussion...)

    If I was feeding a sub-panel I could see this approach working. But I'm feeding the entire house via the panels.

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    Quote Originally Posted by rhurey View Post
    Uh... Not from what I understood guyfang to be suggesting.

    To switch from grid to gen using the box to synchronize between grid and generator and then flip over, the grid power would need to come in through the box. Sure the house doesn't always draw 400A, (Nor even close since we've managed to drop the usage by 50% since we bought it) but wiring it up so the feed came in via the box and getting a permit signed off would require the box to be able to carry the full load. (Yes, likely somewhat less if we get out the NEC worksheets and do all the math, but for discussion...)

    If I was feeding a sub-panel I could see this approach working. But I'm feeding the entire house via the panels.

    Right, a 400A service with one of these boxes that is clearly not rated for 400A would be a problem. All of the equipment in this example would need to be able to support the full rated current, which in this case is 320A (as thats the continuous rating of a 400A service, but lets just say 400A to not muddy the waters))

    From your first means of disconnect (since this box even if modified doesnt count as a service entrance) which is 400A, going to this box, the wires and contactor would need to be 400A. The only way this box (say it was rated at 100A) would be to throw a 100A breaker as your OCPD upstream of this box but then you wouldnt have your 400A service, it would act more like a 100A service.

    Hypothetically I could see half the box (the contactor for the generator side) being safe at 100A size because it wouldnt be surpassed unless a bigger generator would be used, but code wise I dont know if that would even be allowed.
    I doubt that any inspector would sign off on any of this though, using a contactor as a continuous service to be in-line with the grid to me seems unreliable even if it is permissible.

    As others suggested transferring between generators and not grid to generator is the purpose of these boxes, but much beefier and complex hardware exists for grid to generator but the concept is the same. I think this was touched in some cogeneration threads, which also, these generators are not friendly for cogeneration. For all intents and purposes a simple transfer switch with a super low transfer time will prevent computer loads from shutting off and compressors from stalling. Or a closed transition transfer switch does make before break transfers and that transition is under 100ms where both grid and generator would be connected.

    My solution to this whole blip when I transfer is a 20kva UPS at home which will allow me all the grid to generator and back transfers I want without losing a cycle.
    It's not that I have too many generators, it's that I don't have enough room.

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    Quote Originally Posted by Demoh View Post
    ....My solution to this whole blip when I transfer is a 20kva UPS at home which will allow me all the grid to generator and back transfers I want without losing a cycle.
    That was my solution at home except I utilize a 5K UPS (pure sine) coupled with my 17.7 KW solar battery bank.
    Picked up a couple of 5K UPS's for a song a few years back so the 2nd one is a backup. APC Matrix 5000's.
    5K is more that adequate for running essentials during an outage for us.
    It's nice to switch the generator off and have a quiet nights sleep and still have power during an outage.
    Last edited by kloppk; 11-13-2018 at 08:02.
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    Quote Originally Posted by kloppk View Post
    That was my solution at home except I utilize a 5K UPS (pure sine) coupled with my 17.7 KW solar battery bank.
    Picked up a couple of 5K UPS's for a song a few years back so the 2nd one is a backup. APC Matrix 5000's.
    5K is more that adequate for running essentials during an outage for us.
    It's nice to switch the generator off and have a quiet nights sleep and still have power during an outage.
    Oh wow an oldie. I have a 3k FerrUPS (only 120V) that I cant bring myself to throw out, but I cant bring myself to commission the unit either. After taking the batteries out it took every ounce of strength I had to get it into my truck bed without hurting myself.

    Im running a Liebert Nfinity chassis. The prices on them have really come down so that they are affordable. My OCD got the best of me and somehow I got the 16kva chassis so I had to switch it out since they are externally identical and my boss wanted one too, so in total I have 2x 20kva and a 16kva, one of them being extra.


    But whats the use of having the generator off for a quiet night if all the neighbors are running gasoline screamers through the night?
    It's not that I have too many generators, it's that I don't have enough room.

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