NorAire NC-FE series, Installation & Operating Instructions Manual

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05/16/2014 24 NI216
contact is closed and further controlled by W call. There is no controller temperature sensing relating to
mode C backup contact.
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Electric boiler stage OT disable temperatures – there is a PC setup outdoor temperature assigned to
each of the four boiler element stages. If the OT reported value is greater than this disable, the
appropriate stage will not be active.
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Low water flow – 6 minutes after W call and heat pump active, the return water (RT) temperature is
subtracted from the heat exchanger supply water (STc) temperature. If this differential is greater than
the PC setup value (factory default 11° F (6° C)), the service LED and sequence are activated.
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Pressure/temperature limit – there are safety and diagnostic temperature and pressure sensors which can
interrupt the “Y1” control wire to the ODU. These are observed by the SERVICE light, see Operational
Indicators section. The heat and cool temperatures have factory default values (120° F (49° C) and 41°
F (5° C)) but the pressure is fixed at 500 psig.
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No water flow – internally at the “IN” water pipe is a flow switch. This is checked 20 seconds after a
stat W or Y call (before compressor turns on). The controller bottom OPT tab must be switched to
board common by the flow switch.
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Return < 42° F – this test makes sure the hydronic water is not too cold for proper heat
pump/refrigerant cycle operation. See Troubleshooting section.
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ODU 2
nd
stage (HP-Y2) – this is an available output for ODU’s having PL and FL capability (see
sequence chart, next page). Also, the connection or hookup (back panel relay) for this function is
detailed relating to the specific ODU which has 2
nd
stage capability.
ALARM/Hard Hold – these limit conditions cycle off similar to the SERVICE limits with two retries separated
by two ACD delay times. At the third retry the controller declares Hard Hold. If mode B or C, the W call will
begin controlling the backup heat. When Hard Hold is declared HP-Y1 or ODU is off, pump is on, power-on
LED is slow pulsing, and the W input now controls the internal electric boiler and “backup” K2 contact. The
backup boiler will continue until the stat W call is completed. At this point the next stat W or Y call cancels the
Hard Hold condition and the NorAire controller sequence again evaluates these inputs. If it processes through to
the next Hard Hold, the stat W call will use the backup boiler to provide heating energy and prevent building
freeze-up.
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Freeze protect, count 1 – with a Y input or during the full chilled water mode, the temperature at the
heat exchanger output is equal to or below 38° F (3° C), alarm is initiated.
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Compressor no response, count 2 – this is an important diagnostic and safety feature. It allows certain
indicators to the user but more importantly it automatically switches to backup to prevent building
freeze-up or major discomfort. There are two internal sequence logic methods to detect “dead” ODU –
ODU fault wire connected to E-tab OR an internal temperature comparison sequence. See
Troubleshooting section. This Alarm indicator LED (or Service LED) provides no diagnostic
information about the ODU. ODU diagnostic information must be determined from the control board
within the ODU.
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Return < 42° F, count 3 – 20 seconds after HP-Y1 or heat pump on, the return water sensor is checked.
If at any time after the initial 20 seconds the return water is < 42° F, shut down and this alarm is
declared.
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No water flow, count 4 – 20 seconds after stat-W or Y, the flow switch input, OPT tab, is checked. If it
indicates an open, no flow is declared.
Note: The Hard Hold visual status or internal logic condition actually is not reset until there is a new stat-W
(or Y) call. This allows further opportunity to evaluate the alarm condition.
Note: As soon as the user recognizes an ALARM condition, copy down the pulse count and the alarm cause.
At this point the continual sequencing of alarm conditions can be terminated by the user setting the front
panel switch to “boiler” for continuous heating with the internal Electro-Boiler or mode C backup relay
contact.