MyStat 2 Pipe Fan Coil Unit

| Overview

The Carrier ClimaVision MyStat 2 Pipe Fan Coil Unit (2PFCU) is a unique profile that provides both heating and cooling conditioning.

Based on the system's conditioning and fan modes, and the temperature of the supply water from the chiller, the heating and cooling operations are triggered and the corresponding actions and conditioning are achieved.

The reheat capability is enabled with the auxiliary heating stage, which is only triggered during Auto and Heat Only mode (where additional heat is required).

The MyStat 2 Pipe Fan Coil Unit (2PFCU) provides the flexibility to choose between fully modulating and staged equipment control. Possible equipment configurations include:

2-stage fan speed control
Single-stage auxiliary heating control
Single-stage water valve control
Single-stage DCV damper control
Humidifier and dehumidifier controls
Fan enable and occupied enable
Modulating fan, water valve, and DCV damper control
Universal input for supply water temperature measurement (10k type 2 thermistor required)

| Wiring

| Configuring the Profile

Before configuring the profile, you must first pair the MyStat to the CCU. See "Pairing to CCU" in MyStat Start-up.

Once paired, configure the profile parameters. See the table below. Then click Save.

Parameter	Purpose	Default Value	Values in the drop-down list
Temperature Offset	To set the temperature offset value for the profile.	0 (°F)	Range from -10 to + 10 in .1 increments
Auto Force Occupied	To enable Auto force occupied Note: Auto Forced occupied/forced occupied and Auto-Awayc cannot work together.	Disabled	Enable
Auto-Away	To enable auto-away Note: Auto Forced occupied/forced occupied and Auto-Away cannot work together.	Disabled	NA
Relay 1	To enable staged conditioning controls	Water Valve	Fan Low Speed Fan High Speed Aux Heating Water Valve Fan Enable Occupied Enable Humidifier Dehumidifier Externally Mapped DCV Damper
Relay 2	To enable staged conditioning controls	Fan Low Speed
Relay 3	To enable staged conditioning controls	Auxillary Heating
Relay 4	To enable staged conditioning controls	Fan High Speed
Analog Out	To enable modulating conditioning controls	Water Modulating Valve	WaterModulating Valve Fan Speed Externally Mapped DCV Modulating Damper
Universal In	To enable the supply water temperature measurement	Supply Water Temperature	NA

| Control System Object List

Object Name	Type	Input/Output Type/Default Value
Heating Desired Temp	User Intent	NA
Cooling Desired Temp	User Intent	NA
Current Temp	Input	MyStat Onboard
Humidity	Input	MyStat Onboard
User Cooling Max Limit	User Intent	NA
User Cooling Min Limit	User Intent	NA
User Heating Max Limit	User Intent	NA
User Heating Max Limit	User Intent	NA
Conditioning Mode	User Intent	NA
Operation Mode	Input	NA
Fan Mode	User Intent	NA
Occupancy Mode	Input	MyStat Onboard
Auxiliary Heating	Output	MyStat Relay
Water Valve	Output	MyStat Relay
Fan Low Speed	Output	MyStat Relay
Fan High Speed	Output	MyStat Relay
Humidifier	Output	MyStat Relay
Dehumidifier	Output	MyStat Relay
Modulating Water Valve	Output	MyStat Analog Out
Modulating Fan Speed	Output	MyStat Analog Out
Modulating DCV Damper	Output	MyStat Analog Out
Supply Water Temperature	Input	MyStat Universal In
waterValveSampleingWaitTime	Tuner	58 Mins
waterValveSamplingOnTime	Tuner	2 Mins
waterValveSampling DuringLoopDeadband WaitTime	Tuner	5 Mins
waterValveSamplingDuring LoopDeadband OnTime	Tuner	2 Mins
auxHeatingActivate	Tuner	3F

| Sequence of operation

The sequence of operation is driven based on Occupancy mode, Space Current Temperature, set Cooling and Heating Desired Temperatures, Supply Water temperature, and Space CO2 levels.

The sections below describe the sequence of operations based on the occupancy modes, and how the other factors contribute to the sequence of operations during different types of occupancy modes.

| Occupancy modes

The occupancy mode (occupied or unoccupied) is determined through a user-adjustable, graphical, seven-day schedule with a holiday schedule, alongside the configurable auto-away and forced occupied options (external schedule influencers) for optimized controls and enhanced energy savings.

Based on the above aspects factoring into the occupancy the following can be the possible applicable occupancy modes:

Pre-conditioning
Occupied
Unoccupied
Auto-away
Forced occupied

| Sequence of Operation During Pre-Conditioning

Warm-up:

If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning initiates the morning warm-up via HeatingLoopOutput / Auxiliary Heating Stages, as shown below.

Then

Supply water temperature is above the 2-pipe Fancoil Heating Threshold (85F) (Tuner)

The HeatingLoopOutput is mapped to the Water valve loop output

The FanLoopOutput is enabled based on HeatingLoopOutput (FanLoopOutput= HeatingLoopOuptut* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.

Supply water temperature is below the 2-pipe Fancoil Heating Threshold (85F) (Tuner)

The Auxiliary heating is enabled.

Fan speeds are enabled based on the Auxiliary Heating.

Supply water temperature is greater than 2-pipe Fancoil Heating Threshold (85F) (Tuner) & less than 2-pipe Fancoil Cooling Threshold (65F) (Tuner)

During this condition, to ensure that the water is flowing and the water temperature is not measured for stagnant water, the Water Sampling Process is enabled. See below.

If the Heating Water Valve has not been turned on for the last waterValveSampleingWaitTime (Minutes) (Tuner)

Then the Heating Water Valve is turned on for the last waterValveSamplingOnTime (Minutes) (Tuner)

Supply water temperature is between 2-pipe Fancoil Cooling Threshold (65F) & 2-pipe Fancoil Heating Threshold (85F) (Tuner)

During this condition, to ensure that the water is flowing and the water temperature is not measured for stagnant water, the Water Sampling Process is enabled. See below.

If the Heating Water Valve has not been turned on for the last waterValveSampling

DuringLoopDeadband

WaitTime (Minutes) (Tuner)

Then the Heating Water Valve is turned on for the last waterValveSamplingDuring

LoopDeadband

OnTime (Minutes) (Tuner)

The dcvLoopOutput is disabled.

Pre-cooling:

If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning initiates the morning pre-cooling via CoolingLoopOutput. See below.

Then

Supply water temperature is below the 2-pipe Fancoil Cooling Threshold (65F) (Tuner)

The CoolingLoopOutput is mapped to the Water valve loop output
The FanLoopOutput is enabled based on CoolingLoopOutput (FanLoopOutput= CoolingLoopOuptut* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.

Supply water temperature is above the 2-pipe Fancoil Heating Threshold (65F) (Tuner)

The FanLoopOutput and WaterValveLoopOuptut, Auxiliary heating stages are disabled.

Supply water temperature is greater than 2-pipe Fancoil Heating Threshold (85F) (Tuner) & less than 2-pipe Fancoil Cooling Threshold (65F) (Tuner)

During this condition, to ensure that the water is flowing and the water temperature is not measured for stagnant water, the Water Sampling Process is enabled. See below.

If the Cooling Water Valve has not been turned on for the last waterValveSampleingWaitTime (Minutes) (Tuner)

Then the Cooling Water Valve is turned on for the last waterValveSamplingOnTime (Minutes) (Tuner)

Supply water temperature is between 2-pipe Fancoil Cooling Threshold (65F) & 2-pipe Fancoil Heating Threshold (85F) (Tuner)

During this condition, to ensure that the water is flowing and the water temperature is not measured for stagnant water, the Water Sampling Process is enabled. See below.

If the Cooling Water Valve has not been turned on for the last waterValveSampling

DuringLoopDeadband

WaitTime (Minutes) (Tuner)

Then the Cooling Water Valve is turned on for the last waterValveSamplingDuring

LoopDeadband

OnTime (Minutes) (Tuner)

The dcvLoopOutput is disabled.

| Sequence of Operation During Occupied

At all occupied times: (based on a set schedule)

The device maintains a space temperature within the Heating Desired Temperature and Cooling Desired Temperature Range.

During Deadband:

A minimum fan speed is maintained, and the minimum fan analog voltages are set to 2V (customizable) for linear fans, and a recirculation fan speed voltage for staged fans.

During Heating:

When the space current temperature falls below the HeatingDesiredTemperature the HeatingLoopOutput is enabled as shown below.

Then

Supply water temperature is above the 2-pipe Fancoil Heating Threshold (85F) (Tuner)

The HeatingLoopOutput is mapped to the Water valve loop output
The FanLoopOutput is enabled based on HeatingLoopOutput (FanLoopOutput= HeatingLoopOuptut* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.

Supply water temperature is below the 2-pipe Fancoil Heating Threshold (85F) (Tuner)

The Auxiliary heating is enabled.
Fan speeds are enabled based on the Auxiliary Heating.

Supply water temperature is greater than 2-pipe Fancoil Heating Threshold (85F) (Tuner) & less than 2-pipe Fancoil Cooling Threshold (65F) (Tuner)

During this condition, to ensure that the water is flowing and the water temperature is not measured for stagnant water, the Water Sampling Process is enabled. See below.

If the Heating Water Valve has not been turned on for the last waterValveSampleingWaitTime (Minutes) (Tuner)

Then the Heating Water Valve is turned on for the last waterValveSamplingOnTime (Minutes) (Tuner)

Supply water temperature is between 2-pipe Fancoil Cooling Threshold (65F) & 2-pipe Fancoil Heating Threshold (85F) (Tuner)

During this condition, to ensure that the water is flowing and the water temperature is not measured for stagnant water, the Water Sampling Process is enabled. See below.

If the Heating Water Valve has not been turned on for the last waterValveSampling

DuringLoopDeadband

WaitTime (Minutes) (Tuner)

Then the Heating Water Valve is turned on for the last waterValveSamplingDuring

LoopDeadband

OnTime (Minutes) (Tuner)

When the space CO2 level is above the CO2 threshold set, the dcvLoopOutput is enabled with the dcvCalculatedDamperPos = (sensorHyperStatCo2 - zoneCO2Threshold )/zoneCO2DamperOpeningRate, modulating between the analogOutxAtMinDCVDamperPos and analogOutxAtMaxDCVDamperPos

During Cooling:

When the space current temperature is above the Cooling Desired Temperature the CoolingLoopOutput is enabled as shown below.

Then

Supply water temperature is below the 2-pipe Fancoil Cooling Threshold (65F) (Tuner)

The CoolingLoopOutput is mapped to the Water valve loop output
The FanLoopOutput is enabled based on CoolingLoopOutput (FanLoopOutput= CoolingLoopOuptut* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.