The spray foam is virtually identical to the expanded poly urethane of which the insulated walls are made of.
So the additional fire risk is nil.
Further the topside is corked by the 4-square.
As for an internal ignition source...
You'd be talking sabotage.
In which case, nothing we build is immune from that.
The purpose of the seal is to stop heat entry into the chiller. Expanded foam has to beat Chico for such a purpose.
In all my days, I can never recall anyone needing to add additional conductors to a chiller penetration.
