MBVC Installation Manual

6
AUXILIARY ALARM SWITCH
The control is equipped with two Auxiliary Alarm terminals la-
beled CAS which can be utilized with communicating mode
setups (typically used for condensate switch wiring but could
be used with compatible C0
2
sensors or fire alarms).
Legacy mode use
In a legacy system (Non-communicating), this feature is not
operational. Any auxiliary alarm switch must be used to inter-
rupt the Y1 signal either to the indoor or outdoor unit.
CAS
SWITCH
Communication mode use
This feature can be activated or deactivated through the ther-
mostat user menus. An auxiliary alarm switch must be nor-
mally closed and open when the base pan’s water level in the
evaporator coil reaches a particular level. The control will re-
spond by turning off the outdoor compressor and display the
proper fault codes. If the switch is detected closed for 30 sec-
onds, normal operation resumes and the error message will
be removed.
CIRCULATOR BLOWER
This modular blower is equipped with a variable speed circu-
lator blower. This blower provides ease in adjusting blower
speeds. The Specification Sheet applicable to your model
provides an airflow table, showing the relationship between
airflow (CFM) and external static pressure (E.S.P.), for the
proper selection of heating and cooling speeds. The heating
blower speed is shipped set at “21 kW”, and the cooling blower
speed is set at “D”. These blower speeds should be adjusted
by the installer to match the installation requirements so as to
provide the correct electric heating CFM and correct cooling
CFM.
Use the CFM LED (green) to obtain an approximate airflow
quantity. The green CFM LED blinks once for each 100 CFM
of airflow.
1. Determine the tonnage of the cooling system installed
with the modular blower. If the cooling capacity is in
BTU/hr divide it by 12,000 to convert capacity to TONs.
Example: Cooling Capacity of 30,000 BTU/hr.
30,000/12,000 = 2.5 Tons
2. Determine the proper air flow for the cooling system.
Most cooling systems are designed to work with air flows
between 350 and 450 CFM per ton. Most manufacturers
recommend an air flow of about 400 CFM per ton.
Example: 2.5 tons X 400 CFM per ton = 1000 CFM
The cooling system manufacturer’s instructions must be
checked for required air flow. Any electronic air cleaners or
other devices may require a specific airflow; consult installa-
tion instructions of those devices for requirements.
3. Knowing the modular blower model, locate the high
stage cooling air flow charts in the Specification Sheet
applicable to your model. Look up the cooling air flow
determined in step 2 and find the required cooling
speed and adjustment setting.
Example: A MBVC1200 modular blower installed with
a 2.5 ton air conditioning system. The air flow needed
is 1000 CFM. Looking at the cooling speed chart for
MBVC1200, find the air flow closest to 1000 CFM. A
cooling airflow of 1000 CFM can be attained by setting
the cooling speed to “C” and the adjustment to
“Normal” (no adjustment).
4. Locate the blower speed selection DIP switches on
the integrated control module. Select the desired
“cooling” speed tap by positioning switches 1 and 2
appropriately. If airflow adjustment is required, set
dip switch S8 (trim enable) to ON (trim enable default
is off). Then select the desired “adjust” tap by
positioning switches S3 and S4 appropriately. Refer
to the following figure for switch positions and their
corresponding taps. Verify CFM by counting the
number of times the green CFM LED blinks.
5. Continuous fan speeds that provide 25, 50, 75, and
100% of the furnace’s maximum airflow capability are
selectable via dip switches S12 and S13.
If the furnace’s maximum airflow capability is 2000
CFM and 25% continuous fan spped is selected, the
continuous fan speed will be 0.25 x 2000 CFM = 500
CFM.
1
2
1
2
1
2
1
2
OFF OFF OFF OFFON ON ON ON
Tap A Tap B
Cooling Air flow Speed Tap (*indicates factory setting)
Tap C Tap D*
3
4
+5%* -5%
A
ir flow Adjust Taps (*indicates factory setting)
+10% -10%
OFF OFF OFF OFFON ON ON ON
3
4
3
4
3
4
3
4
-5%
A
ir flow Adjust Taps (*indicates factory setting)
+10%
OFF OFF OFF OFFON ON ON ON
3
4
3
4
3
4