As a Manufacturer of Solid State Relays, (SSR's) Crydom has a wide variety of AC and DC switching relays.  If your objective is to switch the DC from your panels to storage or to inverters, or switch the AC power from inverters to various loads, then I can assist you with the selection of the appropriate SSR's. I will need to ask for a few more details to accurately suggest the correct ASR's.

If you require a complete system to gather and store the DC power from the panels, then convert to AC for distribution to your loads, then that is outside the scope of the Crydom SSR product line.

As for the details needed to select solid state relays...

1.  What is the current / voltage (DC or AC), that you need to switch?

2.  What is your preferred input voltage, (control voltage), to operate the SSR's?

3.  Do you have a preference on mounting style of the SSR's?  (Panel mount, PCB, din-rail mount?)

4.  What is your expected maximum ambient termpareture surrounding the mounting location of the SSR's?

Hi Rachel. 

Unlike mechanical contacts in relays, the MOSFET's used in our DC output Solid State relay are polarity sensitive, AND also include a reverse biased body diode integral to the FET topology.   Simple sketch a diode across the output with the cathode to the + terminal.      Therefore, the "+" output terminal of the DC SSR needs to be connected to the "+" of your 40 vdc source.  

So when you connected 40 Vdc (I'll assume that is +40 vdc), to pin 14 on the CN048D05, and your load connections were completed, the load current flowed through the body diode of the output FET keeping your load constantly on.     Another way to keep your wiring thinking correct, is to always understand that the "+" terminal of the DC SSR output needs to be connected to the "more positive" side of the circuit and the "-" output terminal has to go to the "more negative" side of the circuit.   I'm sure you've got the question of "has the SSR been damaged by doing this?"   Well, as long as your load was in the circuit (and it doesn't draw any more than the 100ma that the CN048D05 is rated), all should be fine.  The forward current rating of the FET's body diode carries the same rating as the FET does.

Your input wiring should be connected similarly.  The A1+ terminal needs to be connected to the + of your function generator.   As long as your function generator can supply the 10ma the CN048D05 input circuit needs, that should be fine.  

Here's a link to a "Tech Tip" on the Crydom website that goes through a thorough explanation of using DC output SSR's....

http://www.crydom.com/en/Tech/Tips/DC%20relays-technical%20guidelines.pdf

There are a couple of other items to comment on regarding your application.   First, be sure that the SSR is protected from "Back EMF" pulses from your load as the SSR output switches off at the end of every input pulse.   This is typicall done by placing a diode (in reverse bias), across the LOAD to "re-circulate" the inductive pulses produced as the load current switchies off.     The details of this and how to do this without adversely affecting the reaction speed of your load is explained in the Tech Tip Paper.   The second item to note is that although the turn-on and turn-off time of the CN048D05 is very fast, (total of 150 usec), the maximum PWM speed recommended is 500 hz. due to internal dissipation and heating of the FET.

Regards,

Pete B.