48V relay question [RE-wrenches]

[Todd Cory, Mt. Shasta Energy Services]

Allan,

This sounds nearly identical to a system I am doing, but my way of handling it
was much different. The customer had an array direct ETA pump already set up. He
called me about doing the rest of the system. I said it would make more sense to
use the existing array to feed batteries and run the ETA battery direct. I
called Dankof and they said it would be no problem to disable the MPPT circuit
in the ETA controller (jumpering  terminals 6 & & I believe) and it would not
void the warranty. In the winter they will not be using much water, and the PV
array can feed the home. In the summer they will be using more water, but the PV
system will be putting out more power because of the longer and sunnier days. I
am putting in a PS2AC/DC and the VFX 3648 inverter.

Todd

Allan Sindelar wrote:

> Fellow Wrenches,
> Here's a fun one that I could use advice on, please:
>
> We are installing a 48V full Outback PS2DC system for a new offgrid
> residence. The client already had an ETApump 48V PV-direct deep well
> installation, with an array of 7.9A @48V nom. The well pump is feeding a
> storage cistern, with a separate 48V Booster Pump on a DC line from the home
> power system for its power.
>
> I would like to use the float switch to actuate a relay that directs the
> well pump array through an additional pair of conductors to boost the home
> array input. This way, in winter when water use is low, this array adds to
> battery charging capability once the cistern is full. I would like this to
> be automatic, hence the relay. Switching to battery-based ETApump operation
> is not an option.
>
> 48V relays are hard to find, because standard coil/contact units have arcing
> problems at higher DC voltages. I can use an MDI 48V-coil mercury contactor
> (as used in the old APT Powercenters) but it's a single action relay
> (normally open is standard), and I need both NO and NC to easily direct
> power between two loads.
>
> Is there a way I could use the ETA reverse-action float switch circuit to
> control this? Can the float switch also power a relay coil, so that
> close-on-rise also activates a 48V relay? Could I bypass the float switch
> control in the ETApump controller, and simply let the float switch divert PV
> input power away from the pump when the tank is full? Could I use a
> dual-action float switch (3 wires, both NC and NO action in the same switch)
> to control a NO relay?
>
> Any good ideas would be appreciated. Must be simple, reliable, and
> foolproof.
>
> Thank you,
> Allan @+E

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