Connecting a 6 Unit Internal System Controller Setup a Commercial System Controller for Tankless Updated on April 10, 2021 Tagged: tips Was this article helpful? Yes No Related Articles Clean or Change the Fan for a Pre-Mix Unit Clean or Change the NRC663 (EZTR40) Fan Replacing a Circuit Board for Pre-Mix Units SS-HBC-3 Scale Shield SS-HBC-2 Replacement Cartridge SS-HBC-1 Replacement Cartridge