IF this system has yet to be built I would STRONGLY suggest that AC coupling is NOT considered. IF it is them i would consider HV CC DC coupling. T > On Jan 21, 2021, at 3:15 PM, Jason Szumlanski > <[email protected]> wrote: > > Hi Mac, > > Yes, I considered using a pilot relay - it makes sense to run it on 120V > because relays are readily available. I had the exact same concern - more to > fail. > > In this scenario, the inverter/battery room is remote from the house so there > is only one load I can switch easily with a contactor, and that's the whole > house load. Otherwise, I would definitely consider switching non-critical > loads in a low battery situation. > > It just seems prudent enough to use the integrated Battery Preservation Mode > (BPM), even in this AC coupled system. I considered a small DC array to > charge the batteries in a heavily depleted situation, but it's a 60kWh > battery so I would need a pretty substantial "backup" array I think. It does > not seem like a reasonable solution. I would expect BPM to do it's job and > keep the batteries from reaching a state that they are not recovered quite > easily. > > Jason > > > > On Thu, Jan 21, 2021 at 2:37 PM Mac Lewis <[email protected] > <mailto:[email protected]>> wrote: > Hi Jason, > > The only reason to load shed, without using the internal preservation mode is > if you have certain loads you'd like to keep on longer than other loads that > you shed. The various preservation modes can be complex, especially if you > are AC coupled, so you really have to think through your strategy. > > You can always use a pilot relay, with a coil rating that suits your needs, > and then feed the 100A contactor with that. Unfortunately, its just one more > piece to fail... > > On Thu, Jan 21, 2021 at 12:13 PM Jason Szumlanski > <[email protected] > <mailto:[email protected]>> wrote: > I just learned from the manufacturer that the mercury displacement relay's > coil is rated for 43.2 to 52.80V. Obviously, the battery voltage can exceed > 52.8 pretty significantly. Does the Sunny Island regulate the output voltage > on this relay to 48V or is the actual battery voltage passed through on this > terminal? > > The more I read about this load shedding strategy, the more it seems overly > complicated. It's also another thing to fail. If the N.O. contactor coil > fails, the loads to the house are going to lose power. That's not good for a > remote installation. I guess you have to weigh battery protection with how > critical the loads are. > > I'm wondering why the internal Battery Preservation Mode isn't sufficient > enough. What's the purpose of load shedding if the BPM does effectively the > same thing. I can see perhaps shedding some parts of the load and that is a > nice feature, but to protect the batteries, why isn't BPM enough? > > Jason > > > > > On Tue, Jan 19, 2021 at 8:48 PM Mac Lewis <[email protected] > <mailto:[email protected]>> wrote: > Hi Jason, > > I have done this with mercury displacement relays: > https://www.mdius.com/mercury-relays/two-pole-relays-contactors/two-pole-100-amp > > <https://mailtrack.io/trace/link/ff30c111d75d78887f17a5ed3e3b04bfe2cd428a?url=https%3A%2F%2Fwww.mdius.com%2Fmercury-relays%2Ftwo-pole-relays-contactors%2Ftwo-pole-100-amp&userId=1613865&signature=0abdef13355136e0> > > They do have a 100A 2P 48V coil relay. They seem to work perfectly. > > Good luck > > On Tue, Jan 19, 2021 at 2:51 PM Jason Szumlanski > <[email protected] > <mailto:[email protected]>> wrote: > Does anyone know where I can get a load shedding contactor described in SMA > documentation for use with a multi-function relay in a Sunny Island? > > Thanks, > > Jason Szumlanski > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > <mailto:[email protected]> > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > <https://mailtrack.io/trace/link/dc696cbe05b3c1c168fc9a22231ca0ead130049f?url=http%3A%2F%2Flists.re-wrenches.org%2Foptions.cgi%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=faa967f05b00e2a4> > > There are two list archives for searching. 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