SPX Cooling Technologies MARLEY CLASS F400 - Manual (Page 6)

6
Caution
FREEZING WEATHER OPERATION –During periods of low temperature
operation, 35°F to 40°F or below, ice will form on the relatively dry parts of the
cooling tower that are in contact with the incoming air. Primarily, this includes
the air inlet and adjacent structural framing. Your understanding of cold weather
operation will be enhanced if you read “Operating Cooling Towers in
Freezing Weather”
Technical Report #H-003 available at spxcooling.com.
Ice forming characteristics on any given cooling tower will vary, depending on
velocity and direction of wind, circulating water rate, and heat load. Excessive
ice formation may be controlled by regulating air and water flow through the
tower by one or more of the following procedures:
1–Shut the fan down. This reduces the cooling air rate to a minimum and in-
creases the quantity of warm water at the air inlet to a maximum. However,
normal “fan off” operation causes reverse air flow by aspiration and may
cause water blowout and therefore must be done with caution and moni-
toring. For automatic operation, a timer switch can be provided to shut the
fan down for a few minutes each hour.
2–When a cooling tower has two-speed motors, operate the fans at half speed
forward. This reduces the cooling air rate (heat transfer) and increases the
quantity of warm water at the air inlet.
3–With no heat load on the circulating water, icing cannot be controlled. Towers
must not be operated with reduced water rate and/or no heat load during
freezing weather. If a bypass directly into the cold water basin is used, all
water must be bypassed.
Reverse operation of fans is not recommended . See “Fan Drive”
for fan speed change precautions.
INTERMITTENT OPERATION –When the unit is operated intermittently dur-
ing freezing weather, it is necessary that the water be drained from the tower
piping to insure protection against freezing and possible rupture.
operation