THE SMART SOLUTION FOR ENERGY EFFICIENCY
MPC MultiProtoCol DDC Controls
November 19, 2018
49
Q. Why does the set point go to 45°F in heating
mode 5 minutes after unit startup?
A. This is the default condition if there is not a valid
resistance between the GND and SW terminals on
the MPC. IF this occurs, check the MPC for loose
strands of copper or a missed wire.
Q. Why is my compressor, fan or RV not energizing?
A. First wait 5 minutes after startup, if the unit has not
yet started, check the out LEDs on the MPC. If they
are OFF, make sure that the unit is not in unoccupied
mode, if any of them are ON and you still have to
activity, verify that you have 'R' wired to the 'R' on
the unit controller. If not, jump 24Vac to 'Y', 'O', or
'G' and see if they are energized. If not, contact tech
support.
Q. I replaced a CXM/DXM control board and when
I applied power the MPC board was destroyed,
Why?
A. By default the AL1 and AL2 terminals are powered by
R (24Vac) on the CXM/DXM. If the JW1(CXM/DXM2)
or JW4 (DXM) jumper is not cut BEFORE APPLYING
POWER then the 24Vac is going from AL2 (CXM) to
Gnd (MPC) and that will destroy the board. Cutting
the alarm jumper makes the contact dry thus no
voltage will be present when powered. The jumper is
pre-cut and this only applies on replaced CXM/DXM/
DXM2.
Q. Why does the alarm relay indicate the unit is in an
alarm state on the BMS but not at the CXM?
A. The jumper IN1 on the MPC is set to 0-5Vdc instead
of dry. Jump back to dry contact to resolve this issue.
Q. Can I use another sensor besides the ASW?
A. A 10k type 2 tempeature thermister can be
connected to the RNet terminals. Connect to temp
and ground. Plus connect a 2.4k 1% resistor between
SW and ground. Thermostats will not work with
the MPC.
Q. My unit is not communicating on the network?
Why?
A. Verify that all baud rates, protocol and
communication selections are correct. Then verify
that the Tx and/or Rx leds are ickering. Make sure
that the addressing is correct, unique and not sharing
a same address as another controller.
Q. Why is my temperature reading incorrectly than
the actual temperature?
A. Make sure that the gain jumper is set in the OFF
position. The jumper puts the temperature on a
sharper curve meant for water to water applications.
Also, make sure that the sensor is in a reasonable
location and not right in front of the airway of
the unit.
Q. Why is my RNET sensor all buggy?
A. Make sure that you move the jumper from LSTAT
to RNet.
Q. Can a thermostat be used with MPC?
A. No, ASW… sensors must be used.
Q. What type/size of wire do the ASW… sensors
require?
A. Typical thermostat cable is suitable 22 to 18 gauge.
ASW08 sensor requires 5-conductor all others require
4-conductor.
Q. Is temperature averaging available?
A. Yes using the RNet sensors. Up to ve sensors may
be daisy chained. One ASW15 and up to 4 ASW13
can be connected. Wire to ASW15 rst and then to
the ASW13’s. Address each ASW13 with a unique
address.
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