[RE-wrenches] SMA Load Shedding Contactor 100A, 2P

Thu Jan 21 14:37:02 EST 2021

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 <
jason at floridasolardesigngroup.com> 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 <maclewis1 at gmail.com> 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/507c3cd242097f112c86a155d1e20d50857a422b?url=https%3A%2F%2Fwww.mdius.com%2Fmercury-relays%2Ftwo-pole-relays-contactors%2Ftwo-pole-100-amp&userId=1613865&signature=1f785f791758ce12>
>>
>> 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 <
>> jason at floridasolardesigngroup.com> 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
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>>
>> --
>>
>>
>>
>> Mac Lewis
>>
>> *"Yo solo sé que no sé nada." -Sócrates*
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-- 

Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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