Selection Procedure; How To Select - Trane HUV Installation Operation & Maintenance

Trane classroom air conditioners
provide air delivery and capacities
necessary to meet the require-
ments of modern school class-
rooms. They are available with the
industry's widest selection of coils
to precisely satisfy heating, venti-
lating and air conditioning loads
with the best individual type of
system. Unit ventilator selection
involves three basic steps.
• Determine classroom unit
cooling and/or heating loads
• Determine unit size
• Select the coil
Capacity Required
The first step in unit ventilator se-
lection is to determine room heat-
ing and, in the case of air
conditioned schools, air condition-
ing loads. Accurate determination
of heating requirements and air
conditioning load is essential if the
equipment is to be economical in
first cost and operating cost.
Adequate ventilation is mandatory
in classroom air conditioning de-
sign. The amount is often specified
by local or state codes and, in air
conditioned schools, may be ei-
ther the same or less than that
specified for heating systems. The
usual requirement is for between
15 and 25 cfm of outside air per oc-
cupant, based on the intended use
of the room. For instance, a chem-
istry laboratory normally requires
more ventilation for odor control
than a low occupancy speech clin-
ic.
Ventilation is an important con-
cern and should be accurately de-
UV-PRC001-EN

Selection Procedure

Hydronic Coils
termined to assure good indoor air
quality. Purposely oversizing units
should be avoided, since it can
cause comfort and control prob-
lems.
Unit Size
Unit ventilator size is determined
by three factors:
• Total air circulation
• Ventilation cooling economizer
capacity required
• Total cooling or heating capac-
ity required
Total air circulation, if not speci-
fied by code, should be sufficient
to ensure comfort conditions
throughout the room. This is usu-
ally from six to nine air changes
per hour, but can vary with room
design and exposure. Often rooms
with large sun exposure require
additional circulation to avoid hot
spots.
Ventilation cooling capacity is de-
termined by the amount of outside
air delivered with the outside air
damper fully open, and the tem-
perature difference between the
outside air and the classroom. In
air conditioning applications, ven-
tilation cooling capacities should
maintain the comfort setting in the
classroom whenever the outside
air temperature is below the unit
or system changeover tempera-
ture.
Example:
Ventilation cooling capacity =
1.085 x cfm x (T
t 1
cfm = Total air capacity of unit with
t
outside air damper open 100%.
T = Room temperature.
1
T = Outside air temperature.
2
In classrooms with exceptionally
heavy air conditioning loads, unit
size may be determined by the to-
tal cooling requirement. Good
practice dictates 375 to 425 cfm
per ton of hydronic cooling capac-
ity. Normally, however, Trane
classroom air conditioner coils
have sufficient capacities.
Example:
Given: Air circulation specified = 8 air
changes per hour
Classroom size = 35 ft long x 25 ft
wide x 10 ft high
Inside design air temperature = 75
degrees F
Ventilation cooling required at 58
degrees F = 29,000 BTU
CFM required =
8 changes/hr x (35 x 25 x 10)ft
= 1170 cfm
Checking ventilation cooling capacity:
29,800 BTU = 1.085 x CFM x (80-58)
CFM = 1250
This indicates that a 1250 cfm (size
12 unit) would have satisfactory
ventilation cooling capacity at the
design changeover point of 58-de-
grees F. Coil capacity will become
confirmed when the coil is select-
ed.
- T )
2
3
60 Minutes/hr
45