Straw Factory P340-2220 Commercial Programmable Thermostat Report

Introduction

Complaints have been received recently from our employees working in the Straw

Factory at Tetra Pak Jeddah, stating the comfort cooling of the factory as

insufficient and the room temperature to be uncomfortable. However, a probe

into the Straw Factory later found out that everything from the Air Handling Units

to the chillers installed at the factory seemed to be working in order, instead two

of the thermostats installed in the room were not properly programed according

to needs.

Description of Equipment

There are a total of five P340-2220 Commercial Programmable Thermostats

installed inside the factory of which two were programed incorrectly. They

possess the following features:

A large, clear display with backlighting displays the following on its home

screen:

1. Current Temperature

2. Set Temperature

3. Time

4. Date

5. Period of use (Occupied/Unoccupied)

6. Fan Status

7. Cool Load / Heat Load

Menu Driven Programming

Ability to select multiple days

Precise temperature control

Multiple Override options

Outdoor Temperature Indications

Heating and Cooling Schedule

The thermostat installed in the Straw Factory is capable of controlling up to four

different schedules per day. Between each schedule there is a 15-minute interval

before the next schedule can be started. The four schedules are divided as

follows:

1. Occupied 1 – Denotes the time when workers arrive.

2. Unoccupied 1 – Denotes the time when workers leave.

3. Occupied 2 – Second occupied time.

4. Unoccupied 2 – Second unoccupied time.

Temperature Overrides

1. Hold Temperature

2. Override

3. Holiday

Status of our Equipment

After investigation we found two out of the total five thermostats to be faulty.

Their set temperatures were set at high values and schedule set as unoccupied.

Even the time, day of the week and the year had to be reconfigured, due to which

the system, which was operating on auto settings, had turned off the fan of that

area.

To rectify the issue new schedule periods and temperature set points were

devised such that the system would run continuously 24/7, except for the 15-

minute intervals between each schedule, and provides comfortable working

temperatures for the workers as well as the processes.

The following illustrations displays data from all the thermostats installed in the

factory:

The above illustration displays the data of thermostat 1 and 2

before and after it was reconfigured. The data confirms that

both of the thermostats were configured incorrectly.

The illustrations shows the data from thermostat 3,4 and 5

before and after it was reconfigured.

Note: The settings were edited for the days Saturday to Thursday.

Friday was selected as a holiday.

Settings Explained

Thermostat 1 and 2

Set Temperature: The set temperature of these thermostats was set as 85 F

previously, but the room temperature was already lower, due to which the

system had turned off.

Current Day: We conducted our investigation on Monday, but the current day on

these thermostats was set as Sunday.

System Status:

Heat – Thermostat controls the heating system

Off – Both heating and cooling systems are off

Cool – Thermostat controls the cooling system

Auto – Thermostat controls both the heating and cooling systems based on

temperature

Em Heat – Thermostat controls the auxiliary heat.

Fan Status:

ON – Fan runs continuously. Use this setting for improved air circulation or

for more efficiency central air cleaning.

AUTO – Fan is controlled by the system.

Note: When the thermostat is running the fan, the fan blade symbol appears next

to FAN to indicate the thermostat has the fan on.

Heating and Cooling Schedules:

1. Occupied 1 – Work arrival time.

This is set to start from 5:45am in the morning.

Cool Set Temperature: 72 F (Beyond this the system starts cooling)

Heat Set Temperature: 40 F (Below this the system starts heating)

2. Unoccupied 1 – Work exit time.

This is set to start from 6:45pm in the evening and last for only 15 minutes

before the next schedule initiates.

Cool Temperature: 77F

Heat Temperature: 40 F

3. Occupied 2 – Second occupied time.

This is set to start just after 15 minutes of occupied 1 period to

make sure to maintain a comfortable room temperature throughout the day.

Cool Temperature: 75F

Heat Temperature: 40F

4. Unoccupied 2 – Second unoccupied time.

This, like the first unoccupied time is set just for 15 minutes before next

schedule, occupied 1, starts again.

Cool Temperature: 77F

Heat Temperature: 40F

Temperature Overrides

Hold Temperature Until: Holds the temperature until the time set by the user, or

the next scheduled period time.

Override: Changes temperature setting until the next period starts.

Holiday: Changes the temperature setting for a designated number of days.

In this case Friday was selected to be a holiday.

The illustration shows the settings and data that is reconfigured for

the day Friday.

Fan Coil Units (FCUs)

Operation

The Fan Coil Units are used for cooling or heating the air in the room, depending

upon the operator’s requirement. They can be found in Offices, Hotel Rooms or

Shopping Centers, and their operation involves much similarity to the Air Handling

Units or AHUs which are installed in the cooling systems of large industries or

factories, however, unlike the AHUs that require extensive ductwork to deliver

cool air to the air condition space, chilled water is piped directly to the cooling

coils of the FCUs, eliminating the need for ductwork. Room air is drawn into the

FCU, where it is first passed through filters located at the out stream of the fan.

The filters are responsible for providing clean air and they do this by removing any

airborne contaminants that may have been present in the room’s air. The filtered

air is then transferred through the fan to the cooling coil, which basically cools the

air by transferring its heat to the chilled water, piped directly to the coil.

When there is a change in the room temperature, the room’s thermostat sends a

signal to the Automatic Control Valve attached to the pipe carrying chilled water,

the valve then regulates the amount of chilled water entering by opening or

closing according to the settings on the thermostat, to provide an adequate

amount of cooling to the circulating air of the room. Traditionally FCU contain

their own internal thermostat or can be wired to an external thermostat which

provides flexibility to the occupant to alter the Fan Speed, Set temperature,

Cooling mode to either cool or heat the room depending upon the season and it

even allows the occupant to feed in it different schedules according to his/her

routine.

Design

A fan coil unit may be concealed or exposed within the room or area that it

serves.

An exposed FCU may be wall-mounted or ceiling-mounted and includes a proper

enclosure to conceal the fan itself. It consists of a return air grille and a supply air

diffuser that is also set into that enclosure to distribute air.

Grille

Grille is an opening of several

slits side by side in a wall, usually

to allow the air to enter.

A concealed FCU may be installed within a ceiling void. The return air grille and

supply air diffuser, will be ducted to and from the fan coil unit and thus allows a

great degree of flexibility for locating the grilles to suit the ceiling layout.

Incorporation of a Building Management System to control FCUs

In most common modern buildings the control of the Fan Coil Unit is done

through a Building Management System (BMS). A BMS is a computer-based

system that is installed in the building for controlling, monitoring and optimizing

the building’s mechanical as well as electrical equipment such as HVAC systems,

lighting, security system, etc. Building Management Systems are critical

components to managing energy demand. Improperly installed BMS can cost up

to 20% of energy usage.

Diffuser

Diffusers are very common in

HVAC systems and they are used

in both all-air or air-water HVAC

systems. They are able to

distribute conditioning and

ventilation air evenly in all

directions while maintaining

minimum amount of noise.

At Tetra Pak Jeddah Building Management System is currently installed in and

controlling the Printer Zone, Laminator Zone, Slitter and Palletizing Zone, Straw

Chillers and Factory and Chiller Systems from 3 to 7 as depicted in the illustration

above.

This illustration shows how the Building Management System is monitoring the

Straw Factory area.

AHU1-DA1: Sensor controlling the damper that draws in fresh outside air.

AHU1-CV1: Sensor controlling the automatic valve that regulates the flow

of chilled water to enter the AHU.

AHU1: Sensor that controls the AHU’s fan speed.

AHU1-ST2: Sensor that shows the temperature of air that is being supplied.

AHU1-ST1: Sensor that shows the room temperature of the factory.

AHU1-SH1: Sensor that shows the humidity that is being drawn out from

the room.

AHU1-ST3: Sensor that shows the temperature of the air that is being

drawn out of the room.

AHU1-DA2: Sensor controlling the 2nd damper that allows the exhaust air to

circulate by mixing with the supply air.

Out-ST10: Sensor that shows outside temperature.

Out-SH10: Sensor that shows outside humidity.

This illustration shows how the Building Management System is installed in and

controlling the chiller system from 3 to 7.

Chiller Tank: Acts as a reservoir of water for the chiller to draw and release water.

CT-ST2: Sensor that shows the temperature of the hot water from where the chiller

draws in water.

CT-ST1: Sensor that shows the temperature of the cold water where the chiller

releases its chilled water.

CH7-P1A / CH7-P1B / CH-20(A – D): These sensors are installed on the pumps that

pump water from the tank towards the chiller.

CH (3 – 7)-ST1: Sensor that shows entering water temperature to the chiller.

CH-ST2 / CH7-ST2: Sensor that shows the leaving water temperature, once it has

been chilled, towards the tank.

AHU-SP1: Sensor that shows the pressure of water that is being pumped towards the

AHUs from the chiller tank.

AHU-ST1: Sensor that shows the temperature of water being pumped towards the

AHUs from the chiller tank.

AHU-ST2: Sensor that shows the temperature of water returned back to the chiller

tank’s hot area from the AHUs.

The incorporation of a Building Management System with the Fan Coil Units

could benefit the factory in a number of ways:

The Fan Coil Unit can become a local digital controller that will be

controlled and adjusted from a central point.

The BMS will eliminate the need for an external wired thermostat to be

installed which could get prone to unwanted alterations from occupants in

the room and take control of the internal thermostats in the FCUs.

Only the person in charge of the BMS will be able to control it as it would

require the user to log in before making any alterations to the system.

The BMS will display temperature readings of all the fan coil units:

a. Temperature reading of the supply from chiller

b. Temperature reading of the room

c. Temperature set point

d. Temperature reading of the return to the chiller

With all the temperature readings being displayed on a single central

location, anomalies in the system can easily be detected, unlike with

thermostats where each one needs to be configured separately by visiting

and observing them one by one.

The BMS will display the percentage of humidity:

a. Percentage of humidity in the air being supplied from the FCUs

b. Percentage of humidity in the air being drawn back to the FCUs from

the room.

With all the humidity readings being displayed on a single central location,

anomalies in the system can easily be detected.

Scheduling of all the thermostats will be done from central location

controlled by the Building Management System, instead of visiting each and

every thermostat in the factory to do the scheduling.

The BMS will be able to shut down and turn back the entire system on

again from a central location.