UZC4 ADVANCED FIRMWARE AND HARDWARE FEATURES CONTINUEDUZC4 ADVANCED FIRMWARE AND HARDWARE FEATURES CONTINUED
RETURN AIR
MONITORING
FEATURE
Enhanced
HVAC System
Safety and
Energy
Savings
Solution
Note: If this
feature is
“Enabled”
but the “RAS” is
not connected or
is not detected;
The “RAS” LED
will blink rapidly
as a warning and
The UZC4 will
not allow RAS
operations to
occur.
Note: When the
Return Air sensor
detects a return
air temperature
between the
Stage Up Value
and
the Stage Down
Value, the “RAS”
LED will blink
slowly as a
warning. The UZC4
will also hold at the
current staging
until the system
status changes
sufficiently to
allow a stage up
or down.
The UZC4 includes a RETURN AIR TEMPERATURE SENSING feature.
Connect an OPTIONAL Return Air Sensor (#RAS) to the UZC4 and achieve the ability to
STAGE DOWN the HVAC system if the return air temperature exceeds the return air
temperature limit set points. Set the “RAS” Dipswitch #6 to the “ON” position, and
choose either (0) or (+10) at the “RA LIMIT” Dipswitch # 7. Both switches are located
on the Dipswitch Bank#2.
The UZC4 will now monitor the return air temperature and allow Stage up, or if necessary
Stage Down the cooling or heating operation to maintain a return air temperature within
the following values. As stated above, choose either (0) to accept the default return air
limit values for your particular HVAC system or choose (+10) to offset the default values
10 degrees higher. Note: The (+10) offset applies to heating operations only. The default
return air temperature limit set points for cooling operations cannot be offset.
RETURN AIR LIMITS DURING HEATING CYCLE FOR HEAT PUMPS ONLY:
Default (0) set points:
If the Return Air temperature is:
80 degree F. or below, Stage Up is allowed.
105 degree F. or above, Stage Down is forced.
Default (+10) set points:
If the Return Air temperature is:
90 degree F. or below, Stage Up is allowed.
115 degree F. or above, Stage Down is forced.
RETURN AIR LIMITS DURING HEATING CYCLES FOR GAS, OIL, STRAIGHT ELECTRIC:
Default (0) set points:
If the Return Air temperature is:
80 degree F. or below, Stage Up is allowed.
115 degree F. or above, Stage Down is forced.
Default (+10) set points:
If the Return Air temperature is:
90 degree F. or below, Stage Up is allowed.
125 degree F. or above, Stage Down is forced.
RETURN AIR LIMITS DURING COOLING CYCLES FOR ALL HVAC SYSTEM TYPES:
Default (0) set points:
If the Return Air temperature is:
65 degree F. or above, Stage Up is allowed.
55 degree F. or below, Stage Down is forced.
Default +10 applies to heating operations only.
The Return Air Sensing Feature cannot cycle the 1st stage equipment off-line. It can only force a
Stage Down when the equipment is in 2nd stage cool or 2nd, 3rd, or 4th stage heat, and the selected
return air set points above have been exceeded. The Supply Air Sensing feature is the only monitor
that can cycle the 1st stage equipment off-line.
A three minute delay will occur after a forced stage down. If a stage up demand is present, the UZC4
will allow the stage up to re-occur when the three minute delay has expired and the return air
temperature is back to normal.
The UZC4 will automatically adapt to the “GAS,OIL,ELECTRIC” set points when a Heat Pump
system stages up to Fuel or Auxiliary mode.
This powerful feature will enhance the efficiency of your Zoned HVAC system and protect the
equipment from excessive bypass temperatures during low load conditions.
4
EWC Controls Inc. 385 Highway 33 Englishtown, NJ 07726 800-446-3110 FAX 732-446-5362 E-Mail- info@ewccontrols.com
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