Hello,

I am trying to model a tankless hot water heater. IN the boiler properties on the waterside, i have specified the burner capacity as 150 000Btu, is this correct? The input on the boiler is 150 000 Btu, is it the same as the burner capacity? Also, I have a reply from Jeff Hirsch himself about this quest:

"the eQUEST capacity is the burner useful output; when multiplier by the HIR is the gas input
rate. You can calculate the HIR buy using their specification on max temp rise for a given GPM.
For many products that get more like a 80-85% efficiency ... but you need to use real specifications." -JJH

The only things I am able to get from the manufacturers and is the heat input (150 000 Btu), their energy factor (around 0.9), their efficiency (98%), and a 2.9 GPM rate for a 75 degrees F temperature rise.

I still do not know how to actually calculate HIR and what numbers to use. Do i divide the gpm by the heat rise or vice verca?

Any help would be greatly appreciated.

Arslan