Expansion tank sizing for tankless heater?
I am slowly getting my act together for a tankless install, looking at the Rinnai RC98HPi.
The Seattle area plumbing code appears to require an expansion tank be installed with all water heater. Looking at online calculators for expansion tank sizing, they don't seem to take tankless heaters into consideration.
While I wait for the inspector to call me back to confirm it is indeed required with a tankless heater, can anyone offer any sizing guidance?