Specifications

JOHNSON CONTROLS
24
FORM ET102.19-NOM1 (809)
14. Freezing conditions (entering air temperature be-
low 35ºF)
a. 5-psi steam must be supplied to coils at all
times.
b. Modulating valves are not recommended. Control
should be by means of face and bypass damp-
ers.
c. Consideration should be given to the use of two
or three coils in series with two position steam
control valves on that coil or coils which will be
handling 35ºF, or colder, air. The desired degree
of control can be obtained with a modulating
valve on the downstream coil.
d. Provision should always be made to thoroughly
mix fresh air and return air before it enters the
coil. In addition, temperature control elements
must be properly located to obtain true air mix-
ture temperatures.
e. As additional protection against freeze-up, the
trap should be installed sufciently below 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.
f. On startup, admit steam to coil ten minutes before
admitting outdoor air.
g. Provision must be made to close fresh air dampers
if steam supply pressure falls below minimum
specied.
Water Heating Coils
1. Water supply and water return connections extend
through the end panel of the coil section. All con-
nections are labeled on the end panel.
2. Water supply and water return connections are male
N.P.T copper pipe.
3. When installing couplings, do not apply undue
stress to the connection extending through unit
panel. Use a backup pipe wrench to avoid breaking
the weld between coil connection and header.
4. Follow recommendations of the control manu-
facturer regarding types, sizes and installation of
control valves.
5. Hot water coils are not recommended for use with
entering air below 40ºF.
6. If fresh air and return air are to be heated by a hot
water coil, care should be used in the design of the
system to assure thorough mixing before air enters
the coil