The Rinnai 104000237 Heat Exchanger Kit transfers heat from the burner to the water, supporting efficient hot water production in compatible tankless water heaters. Designed for RL75iA and VC models with circulation logic, this assembly allows heat generated during combustion to pass through the exchanger surfaces and warm the flowing water. Its function is important for maintaining c... https://www.hnkparts.com/104000237-rennai-kit-hex-rl75ia-vc-w-circ/4-104000237.html