Carrier 48MA User Manual
Number One
AirConditbning
Maker
Carrier Parkway • Syracuse, N Y 13201
Packaged Rooftop Multizone Units
DX Cooling/Natural or LP Gas, Electric or Hot Water/Glycol Heat
CONTENTS
INTRODUCTION I
PHYSICAL DATA 2
CONSTRUCTION 3
General 3
Electrical - 3
Refrigeration System 3
Heating 5
i-x
....
mm
Page
INTRODUCTION
The Carrier 48MA/50ME modular multizone
differs markedly from the traditional hot deck/
cold deck reheat multizone. Carrier’s packaged
rooftop units do not employ the hot deck/cold
deck principle or the zoning dampers associated
with conventional units.
Carrier’s distinctive design — individual modules
for heating and/or cooling with constant module
airflow, is a true innovation to the multizone
market. The modular units heat, cool or dehumidify in each module simultaneously and
independently of all other modules. Modules can
serve individual zones or be grouped together to
serve larger zones.
The modular multizones are available in 6 sizes
based on cooling capacity.
SYSTEM SELECTION AND OPERATION 7
APPLICATION 10
Diversity 10
Limitations 10
Reheat Applications 11
Economizer 11
Economizer and Exhaust Performance 14
Economizer Economics 15
Night Setback 16
MISCELLANEOUS 19
Sound and Vibration 19 ■;
Thermostat Usage and Control 20
Return Air Systems 20
RATING TABLES 30-41
FAN PERFORMANCE 42
Pulley Selection 42
Balancing Dampers 42
Performance Table 43
HEATING PERFORMANCE 46
Electric 46
Gas 46
Hot Water/Glycol 47
ELECTRICAL DATA 48-52
Power Wiring 52
Capacity
(tons) Modules
15
20
25
28 5
30
37
No. of Unit
8
8 48MA/50ME024
10 48MA/50ME028
10 48MA/50ME030
12 48MA/50ME034
12 48MA/50ME040
Designation
48MA/50ME016
LP or natural gas, electric resistance or hot
water/glycol heating options are available to maxi
mize efficient use of local energy resources. Economizers, power exhaust, roll filters and
high-efficiency filters are also available as factory
installed options - all providing a greater
flexibility in applying the modular multizone to
specific job requirements.
A recent multizone energy study compared the
energy usage of the Carrier modular units with 3
competitive designs. The study simulated (by
computer) the operation of the units for one year
in a typical building in each of 14 major U.S. cities.
The cities represented complete coverage of the
climatic conditions experienced throughout the
country. Study results showed the Carrier multi
zone consumed less energy than the others in each
case considered under all climatic conditions.
Details of the energy study are contained in the
Carrier brochure, The Modular Multizone Versus
the Others.
© Carrier Corporation 1976
Form 50ME-1XA
Table 1 — Physical Data
UNIT 48MA OR SOME
Zone Modules
OPERATING WT (lb)
Bose Unit 48MA
Bose Unit SOME (with heat)
Roof Curb
REFRIG CHARGE (lb, R-22)
COMPRESSOR
No. 1 Type
Cylinders ... Unloaders
No. 2 Type
Cylinders (has no unloaders)
System Oil Charge (pts)
Unlaader Settings (psig)
Left Bank
Right Bank
Loads
Unloads
Loads
Unloads
Capacity Steps (%)
OUTDOOR AIR FANS
Mtr Hp ... Rpm ... Frame (NEMA)
No. 1
No. 2
No. 3
INDOOR AIR FANS
No. ... Size (in.)
Cfm (Norn)
Motor Hp ... Rpm Std
Opt
Fan Pulley
Outside Diameter (in.)
Bore (in..)
Fan Belt No. ... Size w/Std Mtr
w/Opt Mtr
Motor Pulley A
Outside Diam (in.) w/Std Mtr
w/Opt Mtr
Bore (in.)
Resulting Fan Rpm w/Std Mtr
w/Opt Mtr - - - -
Motor Pulley B
Outside Diam (in.) w/Std Mtr 6.0
w/Opt Mtr
Resulting Fan Rpm w/Std Mtr 995
w/Opt Mtr
HEATING SECTION (48MA)
Rise Range
Input (1000 Btuh) Min-Max Total
Each Module
Bonnet Cap. (1000 Btuh) Total
Stage 1/Stoge 1 ± 2
HEATING SECTION (SOME ELEC)
HEATING SECTION (SOME, GLY.)
Max allowable inlet temperature
Max allowable flow, each coil
Solution mixture
Max allowable working pressure
Total internol volume (gals)
PRESSURE SWITCHES
, _ Cutout
Low-Pressure r. ^ .
Cut-in
High-Pressure ^ul^n
Indoor Air Flow Switch (AFS 1)
Factory Setting (cfm)
Adjustment Range (cfm)
INDOOR AIR FILTERS
Std No. ... Size (in.)
High Efficiency (optional)
No. ... Size (in.)
Roll Media (optionol)
0T6
8
3385
2985
_506
28 "
024
8
3805
3405
506
~~32
028
10
4075
3665
506
43
030
10
4080
3670
506
43
Reciprocating Hermetic, 1725 Rpm
06DE537
6 2
06 DE 824
6 .. 2
06DA824
6
22
06DE537
6 . 2
06DA824
6
22
06DE537
6 . . 2
06DA537
6
22
Compressor No. 1 Only
71.0 ± 1 5
57.5 ±25
76 0 + 1 5
62 5 ± 2.5
100,67,33
100,83,67
50,33,17
100,80,60
40,20
100,80,60
40,20
Propeller, Direct Drive
1 . 1075
1 ... 1140
2 ... 15x15
2 . 15x15 2 . 15x15 2 . 15x15
6000 8000 10,000
5 . . 1725
- - - -
10.6
Р/!б
1 3V630 1 ... 3V630 2 ... 3VS60 2 . 3V560
7/2 ... 1725
10.6
10 ... 1725
8 0 8 0
56 (1-phase)
56 (3-phase)
10,000
10 ... 1725
P/16
- - - -
Instai led
Factory
5.3
_ - - -
iVe
880
6.0
1%
995
6 9
— -
1145
- -
5 0
1%
1095
Shippec
5.6
1230
'5 0
1%
1095
With Unit
5 6
1230
2-Stage Furnace Assembly in Each Zone Module
25 F to 55 F at 0 75 in. v^g ESP
240-480
60
360
22.5/45.0
240-480
60
360
22.5/45.0
300-600 I 300-600 I 360-720
60 60 60
450 450 540
22.5/45.0 I 22.5/45.0 j 22.5/45.0
See Electrical Data Table for Electric Heat Data
1 Heating Coil in each Zone Module
ZOO F
6 gpm
20% glycol
30 psig
2.61
2.61
3.15 ] 3.15 1
29 ± 5 psig
39 ± 5 psig
400 ± 5 psig
300 ± 5 psig
6000
4000-6000
12 ... 20x25x2
Same but with 36.5% efficiency (NBS Dust Spot Test)
65 ft of 2-in. media
034
040
12
4800
4400
5700
5250
630
57
06DE537
6 ... 2
06DA537
"65 “■
06EE250
4 . . 1
06EA250
6
21
31
75.5 ± 1 5
58.0 ±25
100,83,67
50,33,17
100,75,
50,25
I 1 1140 . 56 (3-ph)
3 ... 15x9 3 . 15x9
12,000
15 ... 1725
20 ... 1725
12,000
15 ... 1725
20 ... 1725
8 0
1“/б 1‘Мб
2 3V630
3 . 3V670
2 ... 3V630
3 . . 3V670
5 0 5.0
6.0
1% 1%
1095
1320
1095
1320
5 6 5.6
6.5 6.5
1230 1230
1425 1 1425
360-720
22.5/45.0
3 76
3.76
9000
6000-9000
12
630
4
8.0
6.0
60
540
О
CONSTRUCTION
General — Carrier Modular multizones are sturdy
and lightweight. The units are ideal for rooftop
applications where low silhouettes are required.
^|p Maximum height of any 48MA/50ME unit
mounted on a matching roof curb is less than 5
feet. Each unit is of one-piece design with extruded
aluminum frame and 26 ga steel top and side panel
construction. Panels are easily removed for access
to unit interior. Assembled, the insulated unit will
not sweat at 77 E wet-bulb on cooling days. The
unit insulation conserves heat energy in the winter,
keeping energy costs to a minimum.
The unit roof curb, constructed of 14 ga
galvanized steel, is National Roofing Con
tractors Association (NRCA) approved. A
condenser run-off sheet is built into the curb and is
insulated to prevent heat transfer. The curb is
designed to be flashed to the roof and includes
wood nailers to aid installation. All duct and utility
connections are inside the curb perimeter.
Service access on side panels is accomplished by
removing latches on each side of panel. The side
panel gaskets provide complete perimeter sealing
when compressed against the base unit frame. Each
48MA/50ME unit has large, waterproof condensate
pans to prevent moisture leakage into the con
ditioned space. Galvanneal steel panel surfaces are
bonderized and finished with Carrier Weather
Armor, a baked enamel finish.
Enters are 2-in. throwaway fiberglass with an
NBS efficiency of 10%. High efficiency (36.5%
NBS) throwaway filters are available as a factoryinstalled option. With 41.5 square feet of zone
filter area standard, both the low- and high-
efficiency filters are extremely effective. With this
large area, filter velocity is low — 335 fpm in the
48MA/50ME040 and 145 fpm in the 48MA/
50ME016. A roll filter package is available as a
factory-installed option.
The package consists of 65 ft of 2-in. filter
media, automatic media advance switch, advance
motor and a runout switch. Outside air is drawn
into the unit thru louvered side panels and pre
filtered by cleanable outdoor air filters in the
panels.
Electrical — The Carrier Modular multizones
include factory-installed power and control circuit
breakers which are suitable for use as disconnect
switches where local codes permit. A 350-va,
115-volt convenience outlet on the main control
panel allows use of a trouble light or small power
tools.
Etched solid copper circuit panels with inter
changeable plug-in relays and marked terminal
boards are used in all units to improve reliability
and simplify the modular design. Conventional
commercial 24-volt, 2-stage heat/2-stage cool
thermostats are readily wired to marked terminals
on the zone control board. Modules combined to
make a single, large zone are controlled by a single
thermostat by wiring the zone module control
terminals as illustrated in thermostat usage section
using factory-supplied jumpers.
Refrigeration System — The modular multizone
units incorporate individual zone evaporator coils
plus an outdoor air (Humidry®) evaporator coil
(see Eig. 1). The zone coils are controlled by room
thermostats thru a liquid line solenoid valve. The
metering device for the zone evaporators is a
capillary tube.
The outdoor air evaporator coil cools and
dehumidifies the outside air drawn into the unit.
This coil is a “free floating” coil; that is, after the
first zone cooling coil is activated by cooling
demand, the outdoor air coil is controlled by
suction pressure only. Since the outdoor air evap
orator coil handles a varying load, a thermal
expansion valve is used to meter the correct
amount of liquid refrigerant to this coil.
The load on unit compressors varies depending
on outdoor air coil load and the number of zone
coils in operation simultaneously. Compressor
unloaders and hot gas bypass valves are employed
to compensate for the variation. The 15-ton unit
unloads to 1/3 or 5 tons, the 20-ton unit to 1/6 or
3.3 tons, the 25-ton unit to 1/5 or 5 tons, the
28-ton unit to 1/6 or 4.7 tons, the 30-ton unit to
1/6 or 5 tons, and the 37-ton unit to 1/4 or 9.3
tons. The unloaders operate from suction pressure
to maintain system suction temperature between
32 and 45 E. If the load is less than the minimum
step indicated above, a hot gas bypass valve meters
hot gas into the outdoor air coil to provide an
additional load to the system. This keeps the
compressor on the line and prevents the coils from
icing up due to low suction temperature.
Since the outdoor air coil would become a
condenser when the ambient temperature is below
the suction temperature, a thermostat closes the
outdoor air damper if the ambient drops below
32 E and compressors are operating. If there is no
airflow across the outdoor coil, there is no heat
transfer and the coil becomes an extension of the
refrigerant piping.
Head pressure is maintained by cycling one or 2
condenser fans with a condensing pressure switch
and modulating the remaining fan with a Motormaster® solid state speed controller, permitting
operation of the refrigerant system to -20
ambient. The Carrier modular design is not de
pendent on an economizer cycle for cooling at low
outdoor temperatures. (A factory-installed econo
mizer option is available.)
All multizone units function satisfactorily in
the full cooling or full heating mode. However, at
Fig. 1 — Refrigerant Piping Schematic (10-Zone Units Shown, 8- and 12-Zone Units Similar)
partial load operation, difficulties arise in conven
tional hot deck/cold deck units. When some zones
are at full heat, some at partial heat, some at
partial cooling, conventional multizones must
operate the hot and cold decks simultaneously at
high energy cost. The Carrier Modular design
satisfies each zone’s demand by a discrete
module(s). There are no hot decks, cold decks or
zone air mixing dampers to waste energy. The only
energy expended is that required to heat or cool
the individual zone. Since there is no mixing,
energy is saved and operating costs are significantly
lowered. In addition, the control system provides
excellent humidity and temperature control. Multi
stage cooling is available on larger zones where 2 or
more modules are used for efficient control of
zone space requirements.
The following features and safety devices are
provided on the refrigerant cycle:
1. Suction line accumulator
2. Crankcase heaters
3. High- and low-pressure switches
4. Discharge line thermostat
5. Time Guard® circuit
6. Airflow switch for indoor fan motor
7. Internal motor protection thermostats em
bedded in compressor motor windings
8. Hot gas bypass capability
9. Compressor unloading capability
10. Filter-driers
PSYCHROMETRICS ^ The 48MA/50ME units
differ psychrometrically from the conventional
multizones due to the operation of the outdoor air
coil. The coil in the Carrier units cools and
dehumidifies the outdoor air entering the unit thus
assuring that raw outdoor air is not passed along to
the zones. This air treatment by the outdoor air
coil (and also by the zone module evaporator coils)
provides excellent low load performance and
precise temperature control to the conditioned
space. The only large load variation occurs on the
outdoor air coil where a thermal expansion valve is
used. This allows the use of simple capillary tube
expansion devices on the zone coils. The zone coils
cool and dehumidify a mixture of return air and
outdoor air — outdoor air at the approximate dew
point temperature of the return air.
The psychrometric chart (Figure 2) illustrates
this air treatment for a typical set of conditions. As
an example: 1000 cfm of outdoor air at 95 F/75 F
having 99 grains moisture content enters the
outdoor air coil and is cooled and treated so that
the air leaving the coil has 68 grains of moisture
content. The outdoor air coil under these con
ditions has a capacity of 60,000 Btuh of which
39,000 Btuh is sensible. This is a coil sensible heat
factor of 0.65. By examining the room conditions,
it is evident that the outdoor air coil is very
effective in removing the latent load. At 75 F/50%,
the room content is 64 grains of moisture. The
percent moisture removed with respect to room
conditions is:
GRAINS OF MOISTURE/
LBS OF DRY AIR
% removed
99 - 68
99 - 64
100 =
88.5%
The 1000 cfm of outdoor air at 68 grains is mixed
with 8000 cfm of return air at 75 F/50% room
conditions (64 grains). This mixture then enters
the zone modules and is cooled and dehumidified
by the zone coil.
Heating (General) — The 48MA/50ME modular
multizone units offer a wide range of factoryinstalled heating options.
In all cases, the modular design provides a
number of small heating steps to maintain very
close discharge temperature control without wide
variation. Conventional multizones cycle a few
large increments to maintain the necessary hot
deck temperatures and, thus, cannot control dis
charge temperature as well as the modular units.
Another feature of the modular design is the
reduced impact of heater malfunction. Any unit
can have a malfunction — such as an open coil in a
relay or contactor or gas valve failure in a gas-fired
unit. The Carrier 48MA/50ME units, with 8, 10 or
12 independent heating sections, would experience
heat failure in one module only and all others
would operate normally. Conventional multizones
could lose a large percentage of heating capacity or
the entire heat source in the hot deck could
become inactive.
The Carrier modular multizone units are de
signed to provide reliability, serviceability, oper
ating economy and comfort control — features
difficult to match with conventional hot deck/cold
deck reheat multizone units.
GAS HEATING SYSTEM (48MA) Each module
has a 2-stage burner, with one pilot per pair of
modules. The first-stage gas valve (115-v) controls
gas flow to the main orifice and to the second-stage
valve. A 24-v solenoid valve provides gas to the
second stage when open (see Eig. 3). Both heating
stages are contained in one valve body.
The gas heating section has standing pilots and
continuous forced draft combustion. The pilots
have automatic spark relight for dependable
ignition.
The 48MA modular multizone has individual 18
ga Chromized steel heat exchangers and stainless
steel main burners in each module.
Safety features on the heating system include:
1. A.G.A. certification of the entire unit design as '
well as the furnace section.
2. Airflow switch for indoor fan motor.
3. Airflow switch for forced draft fan motors.
4. Door switch for combustion compartment.
5. Pilot switch to ensure a pilot flame
GV - Gas Vaive (Zone Module)
MOTSS:
t
MS ~ Main Burner
Pirst stage of gas valve is a 115-vott sok-noid; second stage is a
24-voit soienoid with .60% gas bvpess.
Gnits 48MA034 ano 040 fi ave one pilot shotoff valve feeding all
pilot burners.
Unit is eouipped with a forced-draft blower and: the foiiowing
Fig. 3 — Gas Piping Schematic (10-Zone 48MA Unit Shown, 8- and 12-Zone Units Similar)
MGV PS -
Main Gas Vaive
Pilot Sorrier
safety devices: forced-draft airfiow switcfi, tiame rcll-oot pro
tection switch, combustion dtarnbet access door switch, heating
lirrtt switches, and soark-ignitecl automatic pilots. Al! of these
switches are iccateci in the heating section and rrtust. be in safe
condition before tfie inain burners can ignite.
PV ~ Pilot Valve (shutoff;
6. Heating limit switches.
7. Flame rollout protection switch.
In special applications where natural gas supply
is limited, units must be modified to operate under
derated input/output conditions. The 48MA modu
lar multizones can be derated by changing the zone
module burner spuds and gas valve orifices as
follows:
NATURAL GAS FIRED UNITS
TOTAL MODULE
DERATED INPUT (%)
High F ire/Low Fire
90/45
80/40
70/35
SPUD SIZE
No 36
No 38
No 41
No 43
GAS VALVE
ORIFICE SIZE
No 36
No. 38
No. 41
No 43
Under these conditions, the units still have 2 stages
of derated heat input. Derating below these limits
is not approved. If single-stage heat is acceptable,
disconnect high fire stage to permit each module
low fire input only (% as shown under low fire).
Contact Carrier Service Department before de
rating to the above limits.
ELECTRIC HEATING SYSTEM (SOME) - The
SOME electric heating system contains single-phase
Nichrome wire coils (see Fig. 4), wired and phase
balanced to provide 2 or 3 steps of heat control.
Each zone has 2 or 3 steps of strip heat available,
controlled simultaneously by the zone thermostat
and the outdoor air thermostat. When heat is
required, the first stage of zone thermostat ener
gizes the first step of zone heating. The second step
(on 3-step units) of heating is controlled by the
second stage of the zone thermostat. The second
(on 2-stage units) and third step of heating is
controlled by the outside air thermostat (OAT.)
and operates simultaneously with the second stage
of the thermostat (on 3-stage units) when the
outside air temperatures are below OAT. setpoint.
The setpoint on the outside air thermostat is
adjustable from 0 to 55 F.
Safety features include:
1. UL certification on entire unit, as well as
electric heat section
2. Manual reset circuit breakers
3. Klixon high-temperature protection
4. Airflow safety for indoor fan motor
5. Fusible links in each heater phase
6. Two-pole contactors on each element
Fig. 4 — Electric Heating Unit (50ME)
нот WATER/GLYCOL HEATING SYSTEM -
Hot water is a frequent selection for heating due to
simplicity of the piping system, the ease in
maintaining uniform temperature control and
quieter operation. In addition, when renovating an
existing building, a hot water heating plant is
usually available.
Carrier’s hot water/glycol heating option
(Fig. 5) is ideally suited for these renovations. Each
zone module has its own high capacity heating coil.
All controls, solenoid operated shutoff valve and
balancing valves are included in the option. There
is no internal piping or wiring; only one connection
is required for supply and return hot water/glycol.
The option does not include internal pressure relief
for partial load operation. External piping to the
unit must be in accordance with existing codes. It
must include proper relief for water flow (the
maximum allowable hot water/glycol system work
ing pressure is 30 psi.) or a modulating control to
compensate for decrease in water flow rate to zone
coils under partial load conditions when some coils
are cycled closed. System heater coils are designed
for operation with a water/glycol solution of 20%
minimum glycol for proper freeze-up protection.
Figure 35 located in the Heating Capacity Section,
page 47 portrays an example of selecting and rating
hot water/glycol heating coils for use with SOME
multizone units.
The hot water/glycol option is not intended for
use on a steam system. Where steam is the only
heating medium available, a steam-to-water con
verter or a steam-to-water interchanger should be
used.
typical multizone design considerations. Using the
Engineering Guide, calculate cooling and heating
load estimates for the areas to be served by the
multizone unit. Divide each area into zones based
on the peak load and control requirements within
the area.
The resulting loads in a typical building have
been calculated as follows:
Cooling
Grand Total Load (GTE) .................... 275,000 Btuh
Sensible Load (SL)
..............................
215,000 Btuh
Room Design....................................75 F db/50% Rh
Outdoor Air (OA) Cfm
.......................................
1000
OA Ambient Temperature .... 95 F db/75 F wb
Electric Power Source
у XT Room Total Load* Room Sensible Load
zone JNo. (RTL)/Zone (RSL)/Zone
1 19,000 Btuh 16,935 Btuh
2 25,000 Btuh 22,505 Btuh
3 25,000 Btuh 22,505 Btuh
4 70,000 Btuh 59,160 Btuh
5 22,000 Btuh 19,720 Btuh
6 25,000 Btuh 22,505 Btuh
7 40,000 Btuh 33,870 Btuh
Total 226,000 Btuh 197,200 Btuh
*Loads are peak loads.
.................................
460/3/60
Heating (Electric Resistance Heat required)
Zone No
1 34,000 Btuh 10.0 kw
2
3
4 111,000 Btuh 32.5 kw
5
6
7
Total*
*Zone Peak Capacities.
Heating Load/Zone
44,000 Btuh 12.9 kw
44,000 Btuh
42,000 Btuh 12.3 kw
44,000 Btuh
81,000 Btuh
400,000 Btuh
Electric Resistance/Zone
12 9kw
12 9kw
23 7 kw
117 2 kw
Fig. 5 — Hot Water/Glycol Heating (50ME)
SYSTEM SELECTION AND OPERATION
To better understand the actual operation of
the modular multizone, a typical design example is
provided.
Refer to Carrier’s Engineering Guide for Multi
zone Unit Systems and contents of this booklet for
Selection:
Due to the many heating options and ranges on
each 48MA/50ME unit, multizone unit selection is
normally based on cooling load requirements.
Enter the 48MA/50ME rating tables in the Per
formance Data Section and select the unit that
meets or exceeds the grand total load at the
specified conditions. (Interpolation may be neces
sary to obtain unit rating at certain conditions;
extrapolations are not advised. Contact Carrier
Engineering for performance data at points beyond
the range of published tables.) The 024 size unit
does not have sufficient capacity to meet load
requirements at any cfm. The 028 size exceeds
load requirements; however, it is the smallest unit
that meets specifications. Thus, the 48MA/“'
50ME028 at: 9000 cfm; 1000 cfm OA; 95 F/75
OA temperature; and 75 F/50% Rh room design
has a TC of 282,000 Btuh, SHC of 219,000 Btuh,
compressor kw of 27.5 and a RSHF of .835.
Calculate the RTC and the RSHC by deducting the
outdoor air load from the unit capacity.
The outdoor air load with respect to room condi-
as follows:
outdoor ail
total heat (OATH) = 4 5 (hgg:,- Ьго,ошХ (OA cfm)
= 4.5 (38.61 - 28.29) (1000)
= 46,440 Btuh
Or, a graph, shown 'in Fig. 6, can be used to find
the OA load factor, 4.5 (hoa “ hfoom). for all
conditions illustrated in the 48MA/50ME rating
tables (Performance Rating Section). Thus,
OATH = (OA load factor) (OA cfm)
= (46.5) (1000)
= 46,500 Btuh
which agrees with the above calculation.
Outdoor air
sensible heat (OASH) = 1.09 (toa ■" boom) (OA cfm)
= 1.09(95 - 75) (1000)
= 21,800 Btuh
<
О
2
u.
0
\
1
z>
H
Ш
Q
<
о
<
I-
o
h-
Ш
a
CO
I-
Э
о
OA WET BULB
Fig. 6 — Outdoor Air Load Selection Chart
8
The unit capacity available to offset room loads is.
Room TC = Unit TC — outdoor air TC
= 282,000 -46,500
= 235,500 Btuh
Room SHC = Unit SHC — outdoor air sensible heat
= 219,000 -21,800
= 197,200 Btuh
For comparison:
GTL
SL
RTL
RSL
Load
275.000 Btuh
215.000 Btuh
226.000 Btuh
197,200 Btuh
Unit Capacity
TC = 282,000 Btuh
SHC = 219,000 Btuh
RTC = 235,500 Btuh
RSHC = 197,200 Btuh
The 48MA/50ME size meets or exceeds the
total and zone load requirements at the specified
conditions. The excess RTC decreases space
average relative humidity slightly below the room
design of 50%. By increasing air quantity above
9000 cfm, this excess latent capacity can be
converted to additional sensible capacity if desired.
Since the modular multizone is a constant
volume machine, the selected supply cfm per zone
must be proportioned to satisfy each zone’s peak
load condition.
Room sensible capacities (RSC) are divided
equally among the modules if an equal cfm is going
to each. In this example, the 48MA/50ME028 has
10 modules and the nominal cfm is 900 cfm per
module.
The cfm to each zone can be varied (with
field-supplied manual dampers in zone ducts) to
match different zone requirements, but since the
original rating was based on 9000 cfm supply air,
all variations must total 9000 cfm. The effects of
changing cfm quantities on room TC and room
SHC in each module are shown in Fig. 7. When the
cfm is changed (by some percent) from the
nominal in a specific module, then the room
capacity multipliers in Fig. 7 are used to correct
room TC and room SHC. Capacity versus cfm
changes for the example is given in Table 2.
By analyzing each zone’s ratio of deviation
from equal sensible heat allocation, the proper cfm
change is determined. In the example, if building
room SHC is 197,200 Btuh and 10 zones are used,
each zone’s normal room SHC is 19,720 Btuh. But
if zone 3 has 22.505 Btuh room SHC, then by ratio
of 22,505 : 19,720 or 1.14, the cfm change is
+20% (see Fig. 7). Correspondingly, if zone 1 had
16,935 Btuh room SHC, the cfm change is -20%.
In applications where the zone selection is not
an increment of the number of unit modules (i.e.
one zone requiring 500 cfm in a 48MA/50ME028
with 10,000 cfm), refer to Module Cfm Limits,
page 10, for details on using cfm’s below
600 cfm/module.
Formulas required to use ratings are:
Outdoor Air Total Heat (OATH)
OATH = 4.5 (OA cfm) (hoa-hioom)
Outdoor Air Sensible Heat (OASH)
OASH = 1.09 (OA cfm) (toa ~ troom)
Room Total Capacity (RTC)
RTC = Unit TC-OATH
Room Sensible Heat Capacity (RSHC)
RSHC = Unit SHC - OASH
Room Sensible Heat Factor (RSHF)
portp _ RSHC
Leaving Air Temperature (LAT)
LAT = room temperature
RSHC
1.09 cfm
Determine Heating Capacity:
The specified requirement for electric heat
dictates the selection of a 50ME028 unit with a kw
option that meets or exceeds the heating load.
Table 9, page 50 indicates that the 028 unit has
heating capacity options of 66, 88 and 132 kw.
The 132 kw option is selected as it provides
adequate heat for this application. The kw/zone
and number of heat stages available are:
Zone No.
1
2
3
4
5
6
7
Total
Load
10.0 kw
kw 13.2 kw
12.9
12.9 kw
kw
32.5
kw 13 2
12.3
kw 31.2 kw
12.9
23.7 kw 26 4 kw
117.2 kw 132.0 kw 30
Zone Heating
Capacity
13.2
kw
13.2 kw
kw
39.6
kw
Stages
of Heat
3
3
3
9
3
3
6
Stages of heat are controlled individually in the
small zones or collectively in large zones to provide
flexible and continuous control for each zone.
Table 2 — Capacity vs Cfm Changes
ZONE
*Unit total capacity multiplier is obtained from Fig. 7. Use % change from nominal and read multiplier from graph.
RSHC — Room Sensible Heat Capacity RSL — Room Sensible Load RTC — Room Total Capacity
NO. OF
NO.
MODULES
1 1 16,935 16,935/19,720 = 86
2
3 1 22,505
4 3 59,160 59,160/3 X 19,720 = 1.00 0 2700 1 0
5 1
6
7
1 22,505
1 22,505 22,505/19,720 =1.14 +20 1080 1.1
10 197,200 9000
2
RSL/ZONE
PEAK LOAD
19,720 19,720/19,720 =1.00 0
33,870
% DEVIATION
(RSL/NOM UNIT RSHC)
22,505/19,720 =1.14
22,505/19,720 =1.14
33,870/2 x19,720 = .86
% CFM CHANGE
FROM NOMINAL
-20
+20 1080 1 1
+20 1080 1 1
-20 1440 .9
UNIT TOTAL
CFM
CAPACITY
MULTIPLIER*
720
900 1.0
X
9
X
X
X
X
X
X
X
UNIT
NOMINAL
RTC/ZONE
23,550
23,550
23,550
3 X 23,550
23,550
23,550
2 X 23,550
ADJUSTED
UNIT RTC
21,195
25,905
25,905
70,650
23,550
25,905
42,390
235,500
LJ
a
z>
2
a:
II
2
O
O
•% CFM CHANGE ■
FROM NOMINAL
I 0
95
90
85
<
a.
<
80
75
Fig. 7 — 48MA/50ME Room Capacity Multipliers
Power Wiring Data — The 50ME028, 460-3-60 unit
with 132 kw of electric resistance heat, has a 75.8
cooling circuit minimum wire ampere and a heating
circuit minimum wire ampere of 207.0. If any
module is operating on mechanical cooling (com
pressor operating), one heating stage in each
module is locked out and cannot be energized.
This, a common feeder can be sized for minimum
wire ampere of 221 (see Fig. 37).
APPLICATION
Diversity — The size, shape and orientation of the
building — as well as the application and location
of zones, influence the degree of diversity that may
be applied to a multizone system.
Since the normal application of multizone units
involves zones where loads are shifting due to solar
energy, people, equipment and lights, diversity will
exist.
The Carrier modular multizones will be affected
by building diversity only on the refrigeration
system. When a particular zone (or zones) thermo
stats are satisfied, a solenoid shuts off the zone
evaporator coil. This enables more refrigerant to
flow to other operating zone coils, creating a larger
capacity for that zone. However, the diversity will
lower the selected unit total capacities.
The 48MA/50ME ratings do not reflect diver
sity but can be converted to diversity ratings by
using the capacity correction factors and formulas
in Table 3.
Table 3 — Capacity Correction Factor (CCF)
LOAD
TC (Unit)
SHC (Unit)
RTC (with diversity)
RSHC (with diversity)
DIVERSITY FACTOR
1.0
1 0
1 0
90 .80
97
94
[TC (CCF) - OATH]
(Diversity Factor)
[SHC (CCF) - OASH]
Diversity Factor
94
89
This is accomplished by rating the unit assum
ing that no more than 9 of 10 zones would be on
at one time, 90% diversity. The same logic applies
to other diversity factors on an average basis, such
as 85 or 95%.
A rating with a diversity factor results in a
lower room SHF; therefore, a reselection at a
higher total unit cfm is advisable to take full
advantage of the building diversity.
Limitations
MODULE CFM LIMITS AND FAN PER
FORMANCE — The cfm limits per zone are
1200 cfm maximum and 600 cfm minimum. The
10
outboard zones in the 8-, 10- and 12-module units
are limited to a maximum of 1000 cfm. The
maximum limit is necessary to prevent blow-off to
the heat exchangers and into the ductwork. The
minimum limit prevents burner cycling on limit
switches and prevents electric heater cycling. At
reduced cfm’s, zone evaporator coils overfeed
refrigerant, but there is no liquid flood-back to the
compressor as it is protected by a suction line
accumulator.
For applications below 600 cfm, it is recom
mended that the heating controls be modified as
follows:
Gas fired (300 to 599 cfm) — Use first-stage
heat only, deactivate second stage.
Electric Resistance (450 to 599 cfm) — Use
first- and second-stage heat on 3-stage units.
Electric Resistance (300 to 449 cfm) — Use
first-stage heat on 2- or 3-stage heat units.
Optimum performance is delivered in the 800 to
1000 cfm range. Extremely low cfm requirements
reduce unit cooling capacity. Low zone cfm
applications may also be handled by sizing the
zone for a higher cfm (to increase unit efficiency)
and diverting the extra air into the return air
system or a larger interior space. Extra air should
not be diverted into spaces with different
perimeter wall orientations.
Fan performance data. Table 4 and Fig. 32, 33
and 34, (Fan Curves) are located in the Fan
Performance Section and are based on 15% out
door air. When the outdoor air dampers are closed
and there is no outdoor ventilation air into the
unit, unit cfm is reduced by 2 to 6%. This
reduction is due to the static pressure drops
existing in the separate airflows thru the unit. This
reduction should be considered in special applica
tions where little or no ventilation is required and
cfm requirements are critically designed.
MAXIMUM VENTILATION LIMITS Under
normal mechanical cooling, the amount of ventila
tion air that can be introduced is a function of the
outdoor air damper setting and negative static
pressure at the return air intake of the unit. Figures
8 thru 11 show ventilation air versus negative static
pressure at various settings of the outdoor air
damper. A 5.5 setting of the ventilation control
dial is the maximum opening of the dampers. The
ventilation dial can be set in any position from 0 to
5.5 to obtain the desired cfm of outdoor air. The
ventilation dial is located on the control panel
adjacent to the heating section.
Reheat Applications — A space with a high latent
load and a very low sensible load may require
reheat capability for dehumidification. Typical
spaces of this type are conference rooms or visual
aids rooms where people congregate with the lights
out.
Reheat control is achieved on the 48MA/50ME
unit by wiring a humidistat (Fig. 12) in parallel
with the cooling thermostat on any zone requiring
reheat capability. This may be done on one module
or all modules. When using reheat control on
electric resistance heat units, extreme care must be
exercised with power wiring as heating and cooling
can operate simultaneously in each module.
When the zone’s humidity level reaches the
setpoint of the humidistat, mechanical refrigera
tion is activated for that zone module and the air is
dehumidified and then reheated on thermostat
demand before being discharged to the zoned
space.
The 48MA/50ME Economizer — The 48MA/50ME
units can be equipped with an economizer control.
The control functions as follows: with ambient
temperatures above the economizer changeover
point, the outdoor air damper is set at the
ventilation position, cooling is accomplished by the
compressors when the room thermostat calls for
cooling. If the zone is not calling for cooling, the
mixed air is circulated thru the space. When the
ambient temperature drops below the economizer
changeover point, the compressors are locked out
and the damper motor is under control of a mixed
air thermostat to maintain a mixed air temperature
low enough to provide cooling when the room
thermostat demands it. (See Fig. 13.)
11
3,000
100
I 15 2 25 3 .4 5 .6 7 8 9 10
NEGATIVE STATIC PRESSURE AT UNIT RETURN
Fig. 8 — Ventilation Air Chart,
48MA/50ME016
Fig. 9 — Ventilation Air Chart,
48MA/50ME024
Fig. 10 — Ventilation Air Chart,
48MA/50ME028,030
Fig. 11 — Ventilation Air Chart,
48MA/50ME034,040
12
If a zone thermostat calls for cooling while in
economizer mode, a set of cooling relay (CR)
contacts close, energizing the economizer relay
(ECR). See Fig. 14. The ECR is a DPDT plug-in
relay. For economizer damper control, the ECR
locks out the outside air damper adjustable poten
tiometer and shifts the damper control to a Mixed
Air Thermostat (MAT.). The MAT. sensor, located
in the fan section, adjusts the outside air damper to
maintain a preset mixed air temperature (see
Fig. 15).
The 48MA/50ME economizer operation pro
vides economic use of outdoor air for low-cost
cooling. When all zone cooling thermostats are
satisfied, economizer controls are bypassed and the
outdoor dampers are modulated to the minimum
ventilation position. The mixed air temperature
increases, minimizing the amount of reheat re
quired in other zones that require heating.
Refer to Economizer Economics, page 15 to
determine if the addition of an economizer is
justified.
Г
HA — Heat Anticipator S)
Hu - H umidistat
TC — Thermostat, Cooling
TH — Thermostat, Heating
-------------------
----------------------
~l LI
LEGEND
-------
Fig. 12 — Humidistat Connections
Screw Terminal
Printed Circuit
Factory Control Wires
Field Wiring
SEQUENCE;
1 — Ambient temperature decreases
2 — Compressor is locked out by economizer control thermostat
3 — Outside air damper is regulated by mixed air thermostat
to maintain fixed mixed air temperature
Fig. 13 — Economizer Operation
C — Compressor Contactor
CCP — Capacity Control Pressurestat
CHR — Crankcase Heater Relay
CR — Cooling Relay
DLT — Discharge Line Thermostat
ECR — Economizer Relay
ECT — Economizer Thermostat
EXC — Exhaust Motor Contactor
EXR — Exhaust Relay
FCPS — Ean Cycling Pressurestat
HPS — High Pressure Switch
HR — Holding Relay
IT — Internal Thermostat
LPS — Low-Pressure Switch
MCR — Master Cooling Relay
MHR — Master Heating Relay
OFC — Outdoor Fan Contactor
TM - Ti mer Motor
LEGEND
Fig. 14 — Economizer Condensing Schematic
13
OA damper adjust
MOTOR POT
CHR — Crankcase Heater Relay
ECR — Economizer Relay
LAT — Low Ambient Thermostat
OA — Outside Air
Fig. 15 — Economizer Damper Control Schematic
Economizer And Exhaust Performance — An
MIXED AIR THERMOSTAT
LEGEND
economizer can be readily factory installed on the
48MA/50ME since the damper motor and outdoor
air damper are standard equipment. The econo
mizer package consists of a return air damper,
linkage, plug-in relays, MAT. wiring, and mixed air
thermostat.
When the 48MA/50ME unit is on full econo
mizer control, the supply cfm to the space drops
off slightly since the resistance of the outdoor air
intake is generally greater than that of the return
air ductwork. To partially offset this, the return air
dampers have a built-in bypass.
With the outdoor air dampers fully open and
the return air dampers fully closed, the total cfm
drops 15%. The total cfm consists of 70% outdoor
air and 30% return air thru the built-in bypass. If,
for example, the unit normally operates at
10,000 cfm supply air, the minimum supply cfm
when the economizer is operational is 8500. This
8500 cfm consists of 6000 cfm outdoor air and
2500 cfm return air. As the ambient temperature
drops from 48 F (recommended economizer setpoint), the proportion of outdoor air to the supply
air required to maintain mixed air temperature is
less, the outdoor air damper begins to close, and
return air damper begins to open (see Fig. 13). As
this happens, total supply cfm progressively
increases from 8500 cfm to 10,000 cfm (design).
An exhaust damper option is also available for
use with the economizer. It is located between the
return air plenum and the condenser fans. The
option consists of a TPDT plug-in relay (EXR), an
exhaust damper, and a plug-in jumper. The damper
provides a forced exhaust of indoor air during the
economizer operation. The exhaust damper opens
when the return air damper is 25% closed. With the
damper installed, ECR and EXR are energized
simultaneously. The EXR locks out outdoor fan
motor (OFM) controls (32LT on OFMl and FCPS
on OFM2 and OFM3) and outdoor (condensing)
fan motors operate at full speed, discharging excess
return air to the atmosphere thru the open exhaust
damper (see Fig. 16).
The 48MA/50ME exhaust operation is similar
in performance to a relief damper except that the
exhaust dampers are mechanically linked to the
return air dampers and the condenser fans operate
to produce a pressure differential which aids the
exhaust cycle. At approximately 0 in. wg at the
return air opening, the 48MA/50ME units exhaust
between 150 to 200 cfm/ton. With positive return
static, more air is exhausted. At -0.40 in. wg
(.25 in. wg on the 016 unit) return air static,
exhaust capabilities of the units drop to zero.
In the example, the 4000 cfm exhausted at
0 in. return static accounts for all but 1100 cfm
outdoor air introduced by the economizer outside
air section. In practice, this excess cfm is con
sidered a nominal ventilation rate, slightly pres
surizing a building to eliminate drafts and
unwanted air seepage. This excess air filters out of
the building thru doors and window spaces. The
^slight positive pressurization of the building aids
the exhaust fans in removing air. If, however, the
balance between the building static and exhaust
system leaves the building with unacceptably high
positive static pressures, a relief ventilator or roof
power exhauster may be used. For extensive or
SEQUENCE:
1 — Return damper closes 25%.
2 — The exhaust damper opens
3 — The OFM (condensing fans) speed controls are bypassed and
fans run full speed, exhausting return air to atmosphere
Fig. 16 — Exhaust Damper Operation
14
m
complicated return air duct systems with static
pressure greater than -0.2 in. wg at the return air
plenum, duct mounted return air exhaust fans can
be installed for proper airflow. However, return air
exhaust fans add to the operating cost and increase
noise level. More efficient duct design methods
should be investigated to eliminate the need for
special return air exhaust fans.
Economizer Economics — Economizer control on a
multizone unit does not necessarily reduce
operating cost as it would on a single zone unit. A
single zone unit either heats or cools; a multizone
unit can do both simultaneously. Therefore, in a
multizone, the economizer operates to maintain a
mixed air temperature low enough to cool a zone
with a high internal load. The remaining zones
requiring less cooling or heating must have heat
added to offset cooling capacity available but not
needed. This is true of any multizone with any
type of control system.
The amount of heat required to neutralize the
overcooling capacity is dependent on:
1. The percent cooling capacity required from the
unit, and
2. The mixed air temperature required to satisfy
the zone with the highest internal load.
As the ambient temperature drops, the percent
of outdoor air needed to maintain a mixed air
temperature is less. Since the reheat or wasted heat
added is a function of the difference between
outdoor air introduced and ventilation rate,
operating cost is reduced at lower ambients. A high
ventilation rate also reduces the reheat requirement
and associated cost. The following example illus
trates the need for a careful analysis of job
requirements before arbitrarily selecting on econo
mizer control.
Example:
A 48MA/50ME unit is operating with econo
mizer control and supplying 10,000 cfm of 55 F
mixed air. The normal ventilation rate is 2000 cfm.
Assuming a realistic cooling load of 50%, 5000 cfm
of the 55 F air is used for cooling. Since the
ventilation rate is 2000 cfm, half is sent to the
cooling zones leaving 4000 cfm of low-cost cool
ing. The remaining 5000 cfm of 55 F air, including
1000 cfm of ventilation air, is going to zones with
either no load or a heating load and must be
neutralized.
Although 4000 cfm or low-cost cooling is ob
tained, an extra 4000 cfm of air must be heated to
some degree above and beyond that in a unit
without economizer controls.
For an identical unit without economizer con
trol, only 4000 cfm of the 5000 cfm needed for
cooling requires mechanical cooling, since the
1000 cfm of ventilation air is already cooled. Of
the other 5000 cfm, 4000 cfm is return air and is
neutral, and 1000 cfm is ventilation air to be
heated. In the final analysis, it must be determined
if it is more economical to heat 4000 cfm from
55 F to 75 F, or to cool it from 75 F to 55 F. The
answer depends on the efficiency of the cooling
and heating source.
An example of economizer economics is illus
trated in Fig. 17. The graph plots percent cooling
load versus relative energy cost (electricity to gas)
and is based on the following typical assumptions:
48MA028 — 10,000 cfm, 15% outdoor air
48 F outdoor changeover temperature
75 F room design
55 F supply air temperature
Compressor changeover point (COP.)
of 3.3 (100 F condensing temperature
and unloaded compressor were used
to obtain this value)
The relative cost figures are in $/Btu input for
gas and $/kwh electric cost converted to Btu.
Example:
$.10/100,000 Btu (input) - gas cost
$.015/kwh - electric cost
Convert electric cost-
$.015/kwh X kwh/3413 Btu x |q5qqq
= $.44/100,000 Btu
Cost Ratio:
$.44/100,000 Btu _ , ,
.10/100,000 Btu
Therefore, if cooling load is less than 45%
(from graph) at the changeover temperature, the
economizer is uneconomical for 48MA units.
For 50ME electric heat units, the cooling load
break-even point is 70%; the internal load must be
greater than 70% to justify economizer control.
Fig. 17 — 48MA/50ME Economizer
Break-Even Point
15
The cooling load for this comparison is the
internal load (lights and people) minus the negative
transmission at the changeover temperature (48 F).
To determine the percent cooling load, compare
this value to the unit design cooling capacity.
Night Setback — Niglit setback control can be
added to a 48MA/50ME unit using field-supplied
components. There are 3 sets of terminals on the
accessory section of the unit zone control board
(see Fig. 18). The terminals are used in combina
tion to achieve the system desired. Terminal sets
are: cooling lockout (CL), night setback (NS) and
“Short To Close Dampers.” Red jumpers are
factory wired across CL and NS; “Short To Close
Dampers” are bare (see Fig. 19). If the circuit
between CL terminals is broken, 115-v power to
the compressor control circuit liquid line solenoids
and economizer thermostat (if used) is shut off. If
the circuit between NS terminals is broken, 115-v
power to the zone control transformers is shut off.
By replacing both jumpers with appropriate
switches and connecting proper switch across
“Short To Close Dampers,” NS control is attained.
Although many versions of NS are possible, the 3
most common methods are detailed here.
METHOD NO. 1 - HEATING NIGHT SETBACK,
COOLING LOCKED OUT, AND CONTINUOUS
INDOOR EAN OPERATION
This automatic NS system requires a Honeywell
S659A seven-day timer, a Honeywell R8227B fan
center (night setback relay) and a Honeywell
T822D thermostat (heating type) 24-v service. In
this system (see Eig. 20), when the timer reaches
the “Night” position, the switches are as shown.
CL opens, dampers close and NS opens. The fan
continues to operate.
As the temperature falls, the NS thermostat
located in the average temperature space energizes
the NS relay (fan center) which in turn energizes
the zone control transformers. The individual
zones then heat until the NS thermostat is satis
fied. The dampers remain closed and cooling is still
locked out. If a day/niglrt switch is used, the NS
thermostat is overridden and heating is controlled
by the normal thermostats.
Accessory remote panel assembly and/or ac
cessory economizer may be used with this system
if desired. Cycling indoor fans with NS thermostat
is possible if the accessory remote panel is not
used. Connect the field wiring to the MU terminals
instead of the NS and the indoor fan contactor will
cycle with the heaters. Although this system does
not provide a time off delay for the fans after
heater shutdown, test experience indicates that this
is not a problem on these units.
METHOD NO. 2 - HEATING NIGHT SETBACK,
COOLING LOCKED OUT AND CYCLING IN
DOOR EANS
This system requires a Carrier remote control panel
assembly 48MA900041, Honeywell S659A sevenday timer, Honeywell R8227B fan center (night
setback relay) and a Honeywell T822C thermostat
(cooling type).
The number of candidate systems for NS
increases with the use of the remote accessory
panel. A typical system is shown in Eig. 21. The
use of the master unit relay (MUR) and the master
cooling relay (MCR) requires 24-v wiring only.
Installing the timer and the NS relay in proximity
to the remote control panel results in all wiring
being located inside the building in one area.
16
LEGEND
1
AB — Accessory Board
AFS - AirfI ow Switch
APS — Air Pressure Switch
C — Compressor Contactor
Cap. — Capacitor
CB — Circuit Breaker
CCB — Compressor Circuit Breaker
CCP — Capacity Control Pressurestat
CH — Crankcase Heater
CHR — Crankcase Heater Relay
CL — Switch, Cooling Lockout
CO — Convenience Outlet
Compr — Compressor
CR — Cooling Relay
DLT — Discharge Line Thermostat
ECR — Economizer Relay
ECT — Economizer Thermostat
EXR — Exhaust Relay
FCB — Fan Circuit Breaker
FCPS — Fan Cycling Pressurestat
FL — Fusible Link
FRS — Filter Media Runout Switch
Fu — Fuse
GV - Gas Valve
Gnd — Ground
HA — Heat Anticipator
HC — Heater Contactor
— High Pressure Switch
HPS
— Holding Relay
HR
— Heater
Htr
— Ignitor
I
— Indoor Fan Contactor
IFC
— Indoor Fan Circuit Breaker
I FCB
— Indoor Fan Motor
IFM
— Internal Protector
IP
— Low Ambient Thermostat
LAT
— Liquid Line Solenoid
LLS
— Low-Pressure Switch
LPS
— Limit Switch
LS
MCR
— Master Cooling Relay
(MC)
MHR
— Master Heating Relay
(MH)
MUR
— Master Unit Relay
(MU)
— Normally Closed
IM.C.
— Normally Open
N.O.
— Night Setback Switch
NS
— Outdoor Air Thermostat
OAT.
— Outdoor Fan Contactor
OFC
— Outdoor Fan Circuit Breaker
OFCB
— Outdoor Fan Motor
OFM
— Plug
Pig
— Resistor
R
RB
Sw
TB
TC
TH
TM
T ran
ZB
' o
□□ s
□
o
A
Relay Board
Switch
Terminal Block
Thermostat, Cooling
Thermostat, Heating
Timer Motor
Transformer
Zone Board
Receptacle
<
Plug
Terminal Block
Terminal (marked)
Terminal (unmarked)
Circuit Board Terminal
Splice
Terminal, Circuit Board,
Factory Connected
Terminal, Circuit Board,
Field or Accessory
Factory Wiring
Accessory or Field Wiring
Circuit Board Run
To indicate common potential only, not to
indicate wire.
Loading...