User Guide

7
Flow Rate
Atomizing nozzles are available in a wide range of flow rates, all
but eliminating the need for specially calibrated nozzles. Between
1.00 GPH and 2.00 GPH, for example, seven different flow rates
are available. Generally, with hot water and warm air heat, the
smallest firing rate that will adequately heat the house on the
coldest day is the proper size to use and the most economical.
Short on-cycles result in low efficiency. Another guideline is to
select the flow rate that provides a reasonable stack temperature
regardless of the connected load. (According to the New England
Fuel Institute, aim for a stack temperature of 400°F or lower on
matched packaged units or 500°F or lower on conversion burners.)
If the boiler or furnace is undersized for the load, it may be
necessary to fire for the load and ignore the efficiency.
Proper Flow Rates
The proper size nozzle for a given burner unit is sometimes
stamped on the nameplate of the unit.
The following guidelines may be used for determining the proper
flow rates:
If the unit rating is given in BTU per hour input, the nozzle size
may be determined by…
If the unit rating is given in BTU output…
On a steam job, if the total square feet of steam radiation,
including piping, is known…
If the system is hot water operating at 180° and the total square
feet of radiation, including piping, is known…
GPH =
BTU Input
140,000
GPH =
BTU Output
(Efficiency %) x 140,000
GPH =
Total Sq. Ft. of Steam x 240
(Efficiency %) x 140,000
GPH =
Total Sq. Ft. of Hot Water x 165
(Efficiency %) x 140,000