TM 5-852-9/AFR 88-19, Vol. IX
(b) Hot water systems. The same types of hot water systems are used in arctic areas as in temperate
climates, however, positive control and system reliability must be provided. As mentioned above, the primary
advantages of hot water over steam are uniform temperature control, relatively quiet operation, and much
less maintenance because there is no condensate return system. To prevent freezing, antifreeze solutions
should be utilized. Hot water or antifreeze systems are very effective in panel heating, which provides even
heat distribution over large radiating surfaces. Radiant floor temperatures should not exceed 70EF. However,
when outside temperatures are below -65EF, radiant floor panels may not give off sufficient radiation to heat
the building unless the floor temperature is raised above the comfort limits recommended by American
Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) Handbook of Fundamentals.
Additional insulation or dual systems may be required to maintain proper floor temperatures in this case.
Where insulation is used under the floor heating system, designers need to consider its effect on the thaw
bulb. Consideration also needs to be given to: the heat's effect on the floor slabs; effect of shrinking on the
designers selection of contraction joint spacing; designing heating loops to contraction joint spacing to
minimize crossing of control joints. High density polybutylene tubing is recommended rather than copper or
steel because of its greater flexibility and lower corrosiveness. If leaks develop, radiant floor systems are hard
to repair because such leaks are difficult to locate. Hot water or antifreeze systems are most widely used in
building perimeter heating systems (fin-tube radiators), which are very effective in providing even heat
distribution. The hot water or antifreeze system can be set up with temperature reset controls which reset the
hot water or antifreeze operating temperature based on the outside air temperature, thus saving energy.
(3) Electric heating systems. Electric heating systems can be utilized in areas where electric power
is economically available. The advantages of electrical systems-ease of installation, distribution, control, small
space requirements, and low initial cost-make electric heating appealing. The operating costs for electric
heating systems are generally higher than for other systems. Where major changes such as increasing the size
of wall studs to accommodate the extra insulation are required to make operational costs competitive, the
total cost of installing an electrical system may exceed that of other systems. Electric heating may also be
limited by the size of the base power plant. Favorably, however, electric heaters can also be used for
tempering outside air for ventilation.
(4) Gas heating Systems. Both propane and natural gas heating systems can be utilized effectively
in arctic climates. When using propane, precautions should be taken to heat and maintain the propane cylinder
and regulator at the proper temperature to vaporize the gas. At atmospheric pressure, propane liquefies at
a temperature of 44EF, therefore, tanks must be protected from such cold, non-vaporizing temperatures.
Where these tanks are enclosed, a ventilation system is necessary to prevent any hazardous gas
accumulations. Natural gas can be piped long distances even in arctic climates. Orifices and controls can
freeze and become inoperative when gas containing water vapor expands or is subjected to freezing
temperatures. In these cases, heaters and water separators must be used. An alcohol can also be entrained
into the dried gas to prevent freezing of condensed moisture in the system. The water-alcohol mixture is
collected at low drain points in the piping systems, where it is expelled using a blow down connection.
Natural gas can also be used effectively for heating outside air for ventilation.
b. Heating problems in cold areas. Problems outlined below may be encountered in mechanical systems
because of the arctic environment. The systems must be modified to operate properly.
(1) Freezing of water and steam systems. A temperature alarm system should be installed in each
remote unoccupied building to alert maintenance personnel when the building's inside temperature
approaches freezing.
(a) Heating lines and equipment Running hot water lines in exterior walls is not recommended.
If lines must be placed in exterior walls, however, they must be properly protected. When the boiler, furnace,
or heat exchanger ceases to function, localized freezing of water in the system can be delayed if constant
circulation is utilized. Other problems can occur. Where automatic room temperature control is not provided,
personnel may open windows to provide necessary control and lines may freeze when the room is left
unattended. For this reason, individual room thermostat controls should be provided. In garages or hangars,
unit heaters installed within 20 feet of doors should be interlocked with those doors, so that the fans on the
unit heaters shut off when the doors open. When fans are left running, cold outside air is blown over the coil,
and it frequently freezes.
(b) Antifreeze system design problem. The most common antifreeze solutions are made up of
approximately 50 percent by volume of ethylene glycol and 50 percent by volume of water. Pumps in ethylene
4-2
Previous Page
