1 February 1999
condenser in rejecting heat, so the refrigerant condenser can be reduced in capacity equal to
the amount of heat extracted by the oil cooler.
d. Electrical and Mechanical Drives. Base the choice of drives for refrigeration equipment
on the availability and price of fuel, cost of electricity, or the capability of using waste heat. The
operating characteristics of the refrigeration compressor are typically a major factor in
determining the compatibility of the drive and compressor.
(1) In areas of high electric demand rates, evaluate the impact of air conditioning of the
facilities' peak electric demand to determine economic feasibility of electric drive. Compare this
to the cost per kWh, installation peak load, and any demand charges or incentives provided by
the utility serving the installation. Deregulation in the electric utility industry may change the
cost structure paid by the installation, so take into account any known or potential changes that
may result from deregulation.
(2) Where steam turbine drives are used, evaluate using the exhaust steam of non-
condensing turbines as the input to low pressure steam absorption refrigeration in the life cycle
(3) Use only split-shaft gas turbines for air conditioning due to the poor starting
characteristics of single-shaft machines. Whenever gas turbines are used, evaluate using
exhaust gases to generate steam in a waste heat boiler to power absorption refrigeration in the
life cycle cost analysis.
e. Absorption Refrigeration.
(1) Consider absorption equipment only where waste steam from incineration of solid
wastes, heat recovery engine or gas turbine exhausts, or exhaust from steam turbine drives for
refrigeration compressors or electric generators are available.
(2) Absorption chillers must have the capability of operating at variable condenser
water temperature without crystallization.
(3) Use a throttling valve to modulate flow to the absorbent generator with chilled water
temperature, as well as an automatic steam valve which reduces steam pressure and
temperature, for energy efficient part load capacity control.
(4) Consider using two-stage absorption refrigeration whenever high-pressure steam
or high-temperature water is available. The life cycle cost analysis will address the economic
feasibility of using the higher first-cost, two-stage machine.
5-3. BOILERS. This paragraph provides criteria for gas- and oil-fired low-temperature hot
water boilers and low-pressure steam boilers that are used primarily for single building
applications. Central heating plants will be in accordance with TM 5-815-1.
a. Boiler Types.
(1) Cast iron boilers are available in sizes up to 3800 kW (13,000 MBtuh or 1.3 x 10 7
Btuh) gross output. Advantages include low maintenance and sectional construction.