Kees MUA TEMPERED MAKE-UP AIR UNITS - Heating & Cooling Coil I & M Manual - Manual (Page 6)

Traps (continued):
3. Bucket traps are recommended for use with on-off control only.
4. Locate traps at least 12 inches below the coil return connection.
Controls:
1. On high pressure installations, a two-position steam valve with a face and bypass
arrangement is preferred where modulating control is required.
2. Modulating valves must be size properly. DO NOT UNDERSIZE.
Freezing Conditions (Entering air below 35°F):
1. 5 PSI steam must be supplied to the coil at all times.
2. Modulating valves are not recommended. Control should be by means of face and bypass
dampers.
3. Provision should always be made to thoroughly mix fresh air and return air before it enters
the coil on return air units. Also, temperature control elements must be properly located to
obtain true air mixture temperatures.
4. As additional protection against freeze-up, the trap should be installed sufficiently far below
the coil to provide an adequate hydrostatic head to ensure removal of condensate during
an interruption in the steam pressure. Estimate 3 feet for each 1 PSI of trap differential
required.
5. On start up, admit steam to coil ten minutes before admitting outdoor air.
6. Provision must be made to close fresh air dampers if steam supply pressure falls below
minimum specified.
Coil Maintenance
Filters:
Filters upstream of the coil should be checked regularly for dirtiness and clogging. If the filters
are dirty, they should be cleaned or replaced. It is important that the coils stay clean to
maintain maximum heat transfer capability.
Cleaning:
Coils must be clean to obtain maximum performance. Soiled fins reduce the capacity of the
coil, demand more energy from the fan, and create a medium for order and bacteria to grow
and spread through the conditioned zone. High pressure water (700 Psi or less) may be used
to clean coils with fin thickness over .0095 inches thick. TEST THE SPRAY PRESSURE over a
small corner of the coil to determine if the fins will withstand the spray pressure. For coils with
fragile fins or high fin density, foaming chemical sprays and washes air available. Many coil
cleaners contain harsh chemicals, so they must be used with caution by qualified personnel
only. Care must be taken not to damage the coils. FINS ARE SHARP! Use caution when
working with coils.