NorAire NC-FE series, Installation & Operating Instructions Manual

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05/16/2014 23 NI216
Control Sequence Information
Basic – first, there are six factors or “variable” which need to be reviewed before beginning your analysis of the
control sequence.
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Field setup or programming – see previous section
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Outdoor temperature sensor (OT reported value) – defines which operating line within the next page
sequence charts
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Mode selection – determines backup or auxiliary relationship to the heat pump system
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Stat – the external W and Y inputs which begin the sequence process, set up internal safety monitors,
starts various built-in diagnostics, and the basic operation flow
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Front panel lights – see Operation Indicators section, it is important to observe and determine any
abnormal conditions
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Optional Buffer Tank Controller – its operating manual will need to be evaluated because most of the
operating conditions now reside within this controller
Turn-on or go – this controller is in wait or idle condition until there is either a W or Y input. This W or Y
input can come from an external room thermostat, water temperature sensing aquastat, zone controller (W-OUT),
another temperature sensing and process controller, Buffer Tank Controller, etc.
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W call – configures the internal process for the heat pump and internal electric boiler to produce heating
water out.
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Y call – configures the internal process for the heat pump to product chilled water out.
From the above the controller follows the appropriate Figure 1, 2, 3, or 4 sequence chart.
Sequence chart definitions – these comments should assist in communicating the microprocessor operation.
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OT – the specific line selection is controlled by above or below the outdoor temperature value. For
illustration purposes, the OT value is the factory default from the PC setup.
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MU1 – a timer which begins with the W input. The setup default value is 60 minutes.
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MU2 – a timer which begins with Y or W input. The setup default value is 120 minutes.
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Heat pump – controller output action at the Heat Pump terminal block.
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INT – the result of utility interrupt remote device. However, depends upon setup utility interrupt
selection illustrated in Figure 5.
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SW OVER – the above or below OT temperature as selected by the SW OVER dial switch. Probably
do not use positions 7 or 0, the front panel switch is more convenient. If the OT temperature changes to
affect a specific line item, the sequence finishes out the W call.
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Boiler – internal electric boiler action.
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K2 close – isolated contact for starting and stopping external water heating boiler.
Note: All backup or boiler finish out stat W call before resetting back to heat pump.
Chart modes B and C are very similar. Mode B activates the internal Electro-Boiler with stage 1 modulation
(line 4) and lines 5 and 7 the boiler operates at the setup boiler target temperature. Mode C simply closes
and opens the backup relay contact continuous until stat-W call is satisfied. The external boiler connected
to the backup contact must have its own limits or temperature sensing.
Internal housekeeping or overrides – these can effect an expected observation and need to be considered.
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Anti-cycle delay ( ACD ) – at power-up, and each time there is a compressor interrupt or a change in
compressor mode, there is a 5-minute (setup) wait or delay. During ACD there is no stat input checking,
no outputs, no 3-way valve motor, etc. At the end of ACD all appropriate monitors, logic sequence, and
outputs take place. If the connected ODU has its own ACD timer, the PC setup time for this IDU
function must be the same or slightly longer.
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Internal pump – follows W or Y call, is active 30 seconds before compressor turn-on, and continues 60
seconds after the completion of W or Y call. There is also a jumper tab turn-on override provided and
the pump is held on through any defrost cycle.
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Backup – this mode is activated from the front panel switch, below SW OVER setting, or alarm Hard
Hold. If mode B, the electric boiler will be controlled by its built-in temperature sensor and the stages
are modulated at its target temperature (factory default is 130° F (54° C)). If mode C, the “backup”