Section 7

Propane wall-mounted tankless water heaters: input, flow and altitude

This table lists burner input, maximum flow, placement, UEF, altitude approval and flow at a 63 F rise for 7 propane wall-mounted tankless models from Rinnai and Eccotemp. Burner input ranges from 80,000 to 180,000 BTU/h.

Sources: Rinnai ratings come from the V65e^[1] and V75e^[2] spec sheets and the V53De table^[3]. Eccotemp ratings come from its product pages^[4][5][6][7]. Eccotemp's product pages list no altitude limit and no UEF.

Propane is the fuel where there is no electric service or no room in the panel. Burner input sets the upper limit on flow. The share of that heat that reaches the water sets the actual flow.

7.2 Altitude approval

Rinnai lists the V53De, V65e and V75e as approved up to 10,200 ft^[1][3]. Thinner air changes how a burner runs, and some units need their settings changed above a given altitude. Many mountain cabins sit between 6,000 and 9,000 ft. Eccotemp lists no altitude approval for the SmartHome models, so an approval for those models has to come from Eccotemp in writing.

7.3 Eccotemp SHLX-LP rating

Eccotemp rates the SHLX-LP at 4.5 GPM with a 35 F rise from an 80,000 BTU burner^[5]. Heating 4.5 GPM by 35 F takes about 78,800 BTU per hour, which is 98.5 percent of the burner's input. A non-condensing unit does not usually reach that. The SH12-A-LP also has an 80,000 BTU burner and is rated at 4.0 GPM at the same rise^[4], which is 88 percent. The SHLX-LP rating is marked not confirmed and is not used in the sizer until Eccotemp lists a rise chart. Section 9 has the details.

Gas supply pressure, pipe size, venting and clearances follow the manufacturer's installation manual and local code. A licensed gas installer or plumber does the work. Section 11 lists what each manufacturer publishes.