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Remotely turn on/off solar
#1
Hi,

I'd like to be able to remotely turn on/off my solar array as if I were standing in the room and flipped the circuit breaker manually.  I've already got the ability to flip back and forth from my grid and (off grid) inverter power using these

https://www.amazon.com/Contactor-LC1D12-...076Y1TW2C/

And a contactor tutorial I saw on Daniel Romers YT channel a while back.

But i need something that does, DC (90ish) Volts   AND   around 25 Amps max

What is the best way to do this?  Can I use this AC contactor and just split the current 3 ways (I only need a single pole anyway of this 3-pole contactor), so each channel handles 1/3 of the current?  I assume the max current in the specs is for each individual channel.  Or do I need something special that might cost more?
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#2
Find yourself a DC rated contactor to suit ...... 

Theres plenty to pick from, some AC rated ones might also be rated at a DC voltage that suits your application.

https://new.abb.com/low-voltage/products...-switching

Don't forget you'll need to remove the load first, unless you want to spend a fair bit more.
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#3
You shouldn't use an AC rated switch of any kind for DC loads, unless it specifically states it can handle DC loads. The reason is because the disconnect arc from DC is sustained for a much longer period of time, and will wear out the contact pads of the switch. Even low voltage DC will damage AC switches given time.
Get a DC rated contactor, as Sean mentions.
The reason he also says to remove the load (turn off the loads) is because the more loads there are, the higher the current draw, the larger the arc can travel and the duration. Arcs can lead to failure, or fire
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#4
Yeah I found this page helpful a few mins ago at explaining it.

https://temcoindustrial.com/product-guid...-contactor

But I still think I'm failing to understand something here. How exactly do I remove the load if it's connected to the PIP inverter? That's the load right? Isn't the point of the contactor ITSELF to remove the load (by disconnection)? This would need to be done remotely so I might not be physically present to do such a thing.

What then would be the best way to handle that?
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#5
The load is the inverter, plus whateveris connected to its output - you can reduce the load by turning off everything on the AC output of the inverter, or just turn off the AC isolator.

Most breakers have a load carrying, and a load switching rating - the more expensive breakers will have a load switching rating at, or very close to, its load carrying rating.
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#6
Are you really only using 12A from the grid and inverter? That is hard to believe...
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#7
(01-07-2019, 08:23 AM)whoinow Wrote: Are you really only using 12A from the grid and inverter? That is hard to believe...

Because ?
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#8
If you are talking to me... I'm using slightly more than 12A, I max at around 30A. It's because I'm not putting my whole house on solar. Just a small part of it (1 wall AC, 1 fridge, and some computers). I can probably add a bunch more resistive loads but I don't wanna add anymore inductive loads as I would need to upgrade my inverter.
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#9
(01-07-2019, 03:53 PM)nrm21 Wrote: If you are talking to me... I'm using slightly more than 12A, I max at around 30A. 

Just for clarity, is that 30A AC or DC ?
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#10
If you are switching the DC from the solar before the charge controller / inverter then you can just use some FET's or a pre-built SSR.

SSR (Solid State Relay) that is DC rated for 150V like this one at 40 A only containt one or more MOSFET's in an array
https://uk.rs-online.com/web/p/solid-sta...s/9045778/
There are variations on Aliexpress (60V) that are 10% of the price... I seem to remember some 150V versions and trying to find some links.

With DC at 100V if there is no inductive load the issue on disconnecting under load will just be handling the terminal voltage without any issues of back EMF from coil discharge. The charge controllers / inverters all tend to have input capacitors to smooth out the FET switching current so these would counter any small inductive element of the inverter.

Some use 3 phase rated AC rated contactors/equipment and put the contacts in series to create a large enough air gap to cope with breaking the DC arc.

Use FET / solid state approach as you will then not have any issue with contact wear, coil drain power user while energised and noise if it is located somewhere it could be annoying :-)

Use one of these :
https://www.aliexpress.com/item/SSR-40a-solid-state-switching-relays-3-32V-DC-to-5-220V-DC-relay-module-KS1/32659755841.html
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