Typical 2 stage gas or straight electric
furnace with 2 stage cooling. Choose
“Timer” or “Outside Air Sensor” to delay
2nd stage, or use 2 stage T-stats on all
zones.
Typical A/C
Split System
2 stage heat
2 stage cool
Figure 18. Single transformer 2 Stage Heat / AC system
SYSTEM WIRING CONTINUED
2 STAGE GAS
FURNACE
2 STAGE
OUTDOOR
CONDENSING
UNIT
Some HVAC manufacturers are designing HVAC Systems
with 5 - 18 vdc control circuits. Standard 24 vac thermostats
will not work on these systems. These systems can only be
controlled with their own thermostat. But the
SYSTEM
connections on a UZC4 are all dry contacts! Virtually any
HVAC low voltage control circuit can be connected and
controlled. All you have to do is ask the manufacturer which
numbered terminals correspond to the standard terminals.
Theoretical diagram only shown below.
HVAC system with OEM Voltage Control Circuitry
W2
W1
Y1
G
C
R
W2
W1
Y1
G
C
R
Y2
Y2
Figure 20. OEM system with 5 - 18 vdc control circuit.
1
2
3
4
5
OEM Geothermal or Ground Source
Packaged Heat Pump. 3 stage heat &
1 stage cool with “O” type reversing valve.
EWC Controls Inc. 385 Highway 33 Englishtown, NJ 07726 800-446-3110 FAX 732-446-5362 E-Mail- [email protected]
13
Note that you can route a Common wire back to the
“System” terminal block, but it should
never
be
connected! Use it as a TEST point while
troubleshooting. It should be marked as such and remain
capped off when not in use!
UZC4
W2
W1
RH
RC
Y2
O
Y1
G
RC/RH
LINK
RC/RH
LINK
B
E
H
V
A
C
-
S
Y
S
T
E
M
Y1
C
Y2
R
*
*
“R” wire may
not be required
on your Outdoor
Condensing Unit
6
UZC4
W2
W1
RH
RC
Y2
O
Y1
G
RC/RH
LINK
RC/RH
LINK
B
E
H
V
A
C
-
S
Y
S
T
E
M
LUXAIRE High Efficiency “Acclimate” Heat
Pump System. Refer to Mfr’s data for
specific equipment dip switch settings and
logical program settings. Set up the UZC4 to
control the staging based on “Time” with
single stage Conventional Thermostats. Or
you can install 3 stage Heat Pump
Thermostats on all zones.
High Efficiency
Heat Pump.
3 or 4 Stage Heat
and 2 Stage Cool
Warning:
All of the wiring diagrams provided are general in
nature and may not perfectly match your particular
application. This is due to differences in the HVAC
Mfr’s terminal designations and functions!
Variations on these diagrams and other System or
Thermostat applications are available by
contacting the EWC Technical Support Hotline, or
visit our web site at
www.ewccontrols.com
HEAT PUMP EMERGENCY OPERATIONS:
Any Thermostat can demand Emergency Mode!
When emergency mode is activated, the UZC4 will
energize the “E” output terminal and the “W1” terminal.
The “W2” terminal will also energize after a 3 minute
delay.
There is no need to jumper the “E” terminal to the
“W” terminals.
The UZC4 does this to ensure that the
Emergency backup system energizes, regardless of
which terminal it is connected to. In fact, the design of
the UZC4 encourages you to separate up to three (3)
electric strip banks, preventing large in-rush currents
when all banks are tied together. This will also reserve at
least one bank dedicated for Emergency mode and De-
humidify/Reheat operations .
Make sure that you have correctly selected either “Dual
Fuel” or “Conventional” Heat Pump to obtain the proper
staging operations for your particular system.
IMPORTANT NOTES:
Figure 19. 3 or 4 Stage High Efficiency Heat Pump System
Variable Speed
FURNACE OR AIR HANDLER
WITH 1 0R 2 STAGE
BACKUP HEAT
High Efficiency
HEAT PUMP
2 STAGE
W
O
Y1
C
R
UZC4
W2
W1
RH
RC
Y2
O
Y1
G
RC/RH
LINK
RC/RH
LINK
B
E
H
V
A
C
-
S
Y
S
T
E
M
W/W1
Y1
G
C
R
O
W2
Y2
Y2 Out
HUM
W2 Out
W1 Out
Y2/Y
X/L
X/L
Optional Humidistat
See Mfr’s Data
