General - TM-38-2600088

TM 38-260

range from 150 cubic feet to 60,000 cubic feet. The requirements will depend upon the amount and nature of the

material stored in the area to be dehumidified and also the moisture vapor transmission through the storage structure.

(2) The dehumidification of any enclosed structure has two distinct phases:

(a) The initial pull-down period where water is gradually removed from the structure and the skidding of the

equipment.

(b) The subsequent period during which the humidity is maintained at the desired operating level. The time

to reduce the relative humidity in a storage enclosure can take up to 120 days.

(3) Dynamic dehumidification machines are manufactured by several different companies in the United States

and may be purchased by the using agency or by the contractor concerned. Dry, desiccant type dehumidification

machines for dynamic dehumidification will conform to military specification MIL-D-28594.

(4) Wiring. Care should be taken to ensure that the dehumidification unit, in combination with other items

drawing from the same power source, does not exceed the maximum load for that power source. For maintenance,

repair, and emergency shutdown, a remote fused disconnect switch should be installed.

(5) Location and ducts. A plan of the site should be prepared showing the arrangement of the dehumidification

units and, if applicable, the hutments, support panels, duct work, equipment entrance of the hutment, humidistat,

electrical line connections and the source of power for the dehumidification units. The dehumidification unit must be

installed in a flat, level surface with sufficient room to perform service and repair. The length of the duct work should be

kept to a minimum. For dehumidification of a building, machines should be installed on the inside of the dehumidified

building, preferably adjacent to an outer wall of the building with the machine and sensing element of the controller in the

region of the building which is normally the coolest. This will eliminate the effects of temperature variations due to

uneven heating by the sun and help ensure the operation of the dehumidification machine to correct localized relative

humidity conditions and reduce the amount of duct work for the reactivation air outlet and inlet. For dehumidification of

hutments, the preference is to install the dehumidification machine on the outside of the indoor hutments, although they

can also be installed on the inside. Here too, it is recommended that the dehumidifier be placed near the hutment in the

coolest region practical, if temperature variations exist. In addition, ducts shall be located so as not to short circuit

dehumidified air with return air or so as not to interfere with moving equipment inside the hutment. Duct connections

from the dehumidification unit to the hutment shall be of the size recommended by the manufacturer.

(6) Control equipment. The humidistat shall be installed in the vicinity of the absorption air return to the

dehumidifier. Care should be taken not to locate it in the general area of the dried air outlet.

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