1 February 1999
3-1. SYSTEM SELECTION. Chapter 3 provides guidance regarding the eligibility of a facility
for air conditioning, dehumidification, evaporative cooling, mechanical ventilation, or heating.
3-2. HEATING SYSTEMS. Use steam or high-temperature water for large distribution systems.
a. Steam. Do not use single-pipe systems. For safety purposes, use low-pressure steam
[100 kPa gage (15 psig] and below) where terminal equipment is installed in occupied areas.
High-pressure steam [above 100 kPa gage (15 psig)] unit heaters may be used for space
heating in areas such as garages, warehouses, and hangars where the discharge outlets are a
minimum of 4 meters (13 feet) above floor level.
b. Hydronic Systems.
(1) Do not use gravity flow hot-water systems.
(2) For safety purposes, use low-temperature hot water [120 degrees C (250 degrees
F) and below] where terminal equipment is installed in occupied areas. Medium-temperature
hot water [120 to 175 degrees C (350 to 420 degrees F)] or high-temperature hot water [175 to
200 degrees C (350 to 400 degrees F)] unit heaters may be used for space heating in areas
such as garages, warehouses, and hangars where the discharge outlets are a minimum of 4
meters (13 feet) above floor level.
(3) Freeze protection will be automatically provided by operating circulating pumps
when outside temperature drops below 2 degrees C (35 degrees F) or will be provided by the
addition of an appropriate antifreeze solution.
c. Warm Air. Do not use gravity flow warm air furnaces. Direct-fired heaters are
prohibited in areas subject to hazardous concentrations of flammable gas, vapors, or dust.
d. Infrared Radiant Heating. Consider infrared radiant heating for high-bay areas or
where spot heating is required. Gas, oil, and electricity may be considered as fuel sources.
Use night setback where it is both appropriate and cost effective.
e. Electric Resistance Heating. Do not use electric resistance heating except under the
conditions outlined herein:
(1) Family Housing. Electric resistance heating may be used where a bathroom has
been added and the existing heating system is inadequate to heat the addition, or where a
bathroom has been added and it is unreasonable from an engineering or economic position to
extend the existing heating system to the new area. Provide an occupant-activated time switch
with a maximum time setting of 30 minutes for electric resistance or infrared heaters in family
housing bathrooms. Family housing served exclusively by the Bonneville Power Authority
(BPA) may use resistance heating in all rooms, provided a detailed engineering study has
shown electric heating to be the most economical method on a life cycle cost basis, with