Can I use an aftermarket heat exchanger instead

but never use a lower voltage rating

Fast Response Time: Pilot-operated diaphragm design allows for rapid opening and closing cycles in critical HVACR processes

Universal Application: Rated for both residential and light commercial 24-volt control circuits

ABB OT25F3 Disconnect 322838-754 Can I use an aftermarketThe ABB OT25F3 Disconnect is a premier 3 pole non fusible disconnect switch designed for superior performance in demanding industrial and commercial environments. This 30 Amp front operated disconnect features a compact, modular design that is ideal for use as a motor disconnect, in service entrance equipment, or within industrial control panels. Built with finger proof construction and IP20 rated terminal shrouds, it significantly enhances workplace