What relay for high power circuit, low power controller?
Switching can be done on high or low side, AC or DC.  Safety in the off state is a consideration and if isolated or not.  

Low side DC switching makes it easy to perform with optoisolation and a very low swing between open circuit voltage and ground.  Opto MOSFETS exist or one can use Optotransistors and MOSFET if soldering or  wiring in sockets is feasible for you.
Relays with high voltage >=400V start with 24V  For safety you should consider a relaiable switch that will not turn on from a power line transient contact arc when being serviced. but more info is needed for me choose what is best, since the "best" criteria is not given and ther are no datasheets on anything nor installation environment.

Relays perform worse on power supplies due to the inrush current of the storage caps unless it has soft start.  Zero crossing photo triac switches exist but are typically more expensive due to packaging.

I would say a DPDT relay on both DC outputs +/- is safe , effective but may cause issues with the supply without any specs.

Any scenario can have problem when the power supply is an unknown.