Did you calculate head pressure? I have my sump in the basement nd have 14' head. I use a sicce syncra 9.0. I cleaned it after 1 year and it was clean.
To avoid a tank crashing, I always recommend 2 smaller heaters to handle total water volume. 1 in the display and 1 in the sump. If the pump dies you still have heat.
To avoid a tank crashing, I always recommend 2 smaller heaters to handle total water volume. 1 in the display and 1 in the sump. If the pump dies you still have heat.