TYPICAL SPECIFICATION

Chilled Water Plant Control (Section 15900)

0.1 GENERAL

The chilled water plant shall be a water cooled all variable speed plant with centrifugal variable flow and variable speed chillers, variable speed cooling towers (variable fans and pumps) and variable speed distribution pumps. The system design shall be either variable flow primary system or variable flow primary/variable flow secondary system.

  1. Chilled Water Plant control system Description

The chilled water plant control system shall be an all variable speed plant control system that executes the following control sequences:

•Sequencing of the centrifugal chillers

•Variable speed control instruction to the cooling tower pumps and fans

•Control of the variable primary [and/or secondary] chilled water distribution pumps in response to process variable from the load (DP signal sensors, flow meters, valve positions and or kW meters)

•Control of pump stations for parallel or duty/standby operation

•Provide instruction to the isolation valves and modulate the bypass valve

•Provide system alarms and warnings

•Communication of plant room operation and alarm data to the building automation system and optional control through IP.

The proposal of the control system shall be capable of operating the chilled water plant for this comfort cooling application at less than or equal to 0.48 kW/ton on an average annual basis and the submittal package shall indicate calculations to confirm this based on the selected chiller, cooling tower and pumping system.

The chilled water plant control system shall utilize demand based control for the tower fan and pump speed and shall provide the chiller with a chilled water supply temperature set-point for the chiller to govern its operation to. The chillers shall be sequenced/staged, both on and off in a manner to maintain their operation as close as possible to the Natural Curve. The cooling tower fan speed and pump speed settings shall vary in accordance with the Equal Marginal Performance principle. The “natural curve”, “demand based control” and “equal marginal performance principle” methodologies described above are to be in accordance with the Hartman LOOP™ operating principles of an all variable speed chiller plant. Alternate plant control sequences that can be proven to provide a net plant efficiency level of 0.5kW/ton or better will be considered with a written proposal submitted at the time of quotation. Net plant efficiency level is calculated as the average annual kW/ton for the annual energy input to the chiller, cooling tower, condenser pumps and distribution pumps, divided by the annual tons delivered to the system.

The chiller plant control system (IPC 11550) shall be specifically designed for the control of a chiller plant that involves up to five chillers, up to five cooling towers, up to six constant and/or variable chilled water primary pumps, [up to six constant and/or variable chilled water secondary pumps] and up to six constant and/or variable condenser pumps. Chilled water primary pumps, [secondary pumps] and condenser pumps could be in parallel or duty/standby operation.

This section shall conform to the “General Provisions, Basic Materials and Methods” Section. The equipment installed in this section shall conform to all other relevant sections of the mechanical and electrical sections of this specification. The following specification details the minimum requirement for equipment for a complete factory assembled plant control system

The IPC 11550 system shall allow field adjustments of control parameters as described below.

The IPC 11550 system shall be capable of accepting and processing appropriate signals for the following serial data points from associated panels:

•Analog inputs for zone differential pressure (DP) transmitter signals 4-20 mA

•Digital inputs for pump DP switches for primary [and secondary] pump fault signals

•Digital inputs for remote connection for pump start/stop

•Digital inputs for primary [and secondary] pump remote start/stop signals from up to 5 chillers

•Digital inputs for alarm horn (buzzer)

•Digital inputs for alarm silencer

•Digital outputs for primary [and secondary] pumps run signals

•Digital outputs for alarms of pump/motor/VFD alarm, DP transmitter alarm, primary [and secondary] pump fatal alarm and general system alarm

•Analogue inputs for primary [and secondary] pump motor temperatures selectable between NTC or PT1000

•Digital inputs for primary [and secondary] pump motor run feedback signals

•Analogue outputs for primary flow, kW, supply and return temperature sensors

•Serial port for communication with the BAS

•Serial port for communication with the VFD’s

The IPC 11550 system shall perform online self diagnostic testing of the CPU(s), RAM and flash memory. No data shall be lost during power supply interruptions.

  1. Related Sections

•Chiller specifications (Section 15620)

•Cooling tower specifications (Section 15645)

•HVAC packaged pumping system (Section 15540)

•Plant design specifications (Section ...…)

•Building automation system (Section ...…)

3.Standards and References

•ANSI – American National Standards Institute

•NEMA – National Electrical Manufacturers Association

•UL – Underwriters Laboratories

•CSA – Canadian Standards Association

4.Installation and Control Contractor Responsibilities

The controls contractor is responsible for the following:

•Inspect interior and exterior and report any obvious damage or equipment shifting that may have taken place between the time the unit arrived on site and when in its final resting position

•Re-align and level controller

•Install all life safety equipment as needed

•All field electrical connections to the unit

•Hook up electrical utilities needed for the controller

•Field connect equipment including pressure/temperature sensors, flow meters and their associated wiring to the unit (a list of field installed equipment will be supplied, along with installation instructions)

•Touch up and paint scratches and minor dents occurred during hoisting and rigging

•Permits and inspections needed to start up the system

•Start up of system with the supervision of manufacturer personnel

5.Submittals and Operation Manuals

Submittals shall include the following as a minimum:

•Description of system operation

•Electrical power and control wiring diagram

•Control layout drawing with sequence of operation

Operation and maintenance manuals shall include the following as a minimum:

•System summary sheet

•Description of system operation, with equipment and control sequence of operation

•Electrical power and control wiring diagrams

•Installation and maintenance manuals from equipment manufacturers

•Submittals and operation and maintenance manuals shall be assembled in a neat and orderly manner and bound in booklet form. Include a front page that identifies the job particulars followed by a table of contents.

1.1 PRODUCT

1.Acceptable Manufacturers

The chilled water plant control shall be by the IPC 11550 System, by Armstrong Pumps Incorporated.

2.Hardware

a.Front End Main Panel and Associated Equipment

The front end main panel of the chilled water plant control system (IPC 11550) shall be a combo PC-based and PLC controller.

The chilled water plant control system (IPC 11550) shall have an internal circuit breaker and run on 115/1/60 Vac power supply. As an option, the IPC 11550 system shall run on 230/1/50 power. The IPC 11550 system shall have a key lockable NEMA 1 rated cabinet. NEMA 12, 3R and 4 are available as an option.

  • 15.1” 1024x768 TFT 200nit high brightness LCD panel
  • Resistive type touch screen
  • NEMA 4/12 certified front bezel
  • Operation temperature range: 0°C - 40°C (32°F-104°F)
  • Operation humidity range: 5% - 95%, non-condensing
  • Power supply: AC 100-230 V, 100 W
  • CE mark, FCC compliant

The IPC 11000 controller shall have a key lockable NEMA 1 rated cabinet. NEMA 12, 3R and 4 are available as an option. A wall-mounted, factory-assembled steel enclosure shall be provided. All operator interface control switches, indicators and displays shall be physically separated from any field terminations. Manual backup control switches and indicators must be protected from unauthorized operation by a key lockable door.

The IPC 11550 system shall have a battery or capacitor that keeps the memory in the panel alive long enough to get the system through temporary power failures. Also, the IPC 11550 system shall provide some means of backing up the entire database to disk, either in parts or all at once.

The IPC 11550 system shall be listed by and bear the label of Underwriter’s Laboratory, Inc. (UL) and of Canadian Standards Association (CSA).

b.Screen

The chilled water plant control system shall have a large touch screen color display operator interface of at least 15" with on-screen menu-driven operator interface and active element schematic displays that generate sub-menus for status reports, data and setup menu options. Keypad based interfaces, LCD readouts and LED displays shall not be accepted.

c.Temperature and Pressure Sensors/switches

Temperature sensors, pressure sensors and flow meter shall be installed by the contractor as indicated in the drawings to modulate the chilled water system. Temperature sensors shall be self contained RTD type temperature transmitter with a temperature range of 32°F-122°F for chilled water systems. The temperature probe shall use a platinum, wire wound, sensing element in a 316SS sheath, spring loaded and inserted into a ¾” NPT stainless steel thermo well. The thermo well shall penetrate one-half the pipe diameter. For applications measuring the supply and return temperatures for a loop type water system, the two probes shall be matched pair. Sensors shall not be locally adjustable. The accuracy of the temperature sensor shall be 0.25% of span and shall be calibrated and traceable to NIST. The temperature transmitter shall receive its power input and sends its current output, 4-20 mA, over the same pair of low voltage wires. Each transmitter head shall be explosion proof. Sensors shall be mounted such that effects of radiation from heating elements are minimized and rapid response to changing temperature is achieved. The stability of the transmitter/probe assembly shall be +/0.001% of span/100 Ohms of lead resistance. Wiring installed by the contractor between the control system and the transmitters shall be equal to Belden 9320, 2-wire, shielded, twisted cable and shall not be included in conduit containing wiring for alternating current. All temperature transmitters shall be packaged mounted and wired where possible. All remaining transmitters not package mounted shall be field installed and wired by the contractor.

Pressure sensors shall be complete, self-contained, variable capacitance type, stainless steel construction differential pressure transmitters rated to withstand 10,000 psi. Provide 4-20 mA signal. The accuracy of the pressure sensor shall be 0.25% of span. Provide a certified test on each sensor verifying its accuracy to NIST. Wiring terminals and electronics shall be in separate compartments, so the electronics remain sealed during installation. Reverse polarity protection shall be included to keep wiring mishaps from damaging the transmitter. Wiring between the control system and the transmitters, provided by the installing contractor, shall be Belden 9320, two wire, shielded twisted cable and shall not be included in conduit containing AC electrical wiring. External zero and span adjustment, over-pressure to 2,000 psi and no humidity effects. Pressure switches shall have adjustable ranges and adjustable differentials to suit the application. Pressure switches shall be sensitive enough to ensure correct monitoring.

Flow meter shall be a high precision flow meter. Field mount and wire flow transmitter in accordance with manufacturer’s instruction. The meter shall have two counter-rotating axial turbines, each with its own rotational sensing system and an averaging circuit to reduce measurement errors due to swirl in undeveloped flow locations caused by short straight pipe runs. Rotational sensing of each turbine shall be accomplished electronically by sensing impedance change and not with magnetic or photo-electric means. Paddle type rotors will not be acceptable. The sensor shall have a maximum operating pressure of 400 psi, maximum operating temperature of 180F. Accuracy shall be within +0.5% of actual reading at the calibrated typical velocity and within +2% of reading over 50:1 turndown (from 0.4 to 20 fps). Provide certificate of calibration with each flow transmitter. The sensor shall have integral analog outputs of 0-10 VDC linear to within +0.1% of calibrated span for connection to the control system. The flow sensor shall be constructed of plated brass with an aluminum electronics enclosure and gasketed cover. Contractor shall supply hot tap installation, in order to be both insertable and removable through a ball valve when the pipe is under pressure.

3.Software

a.Capabilities

The chilled water plant control system software shall perform, but will not be limited to, the following:

  • Manual or automatic system control
  • Schedule start/stop
  • Optimum start/stop
  • Duty cycling
  • Automatic temperature control
  • Maximum demand control
  • Calculation point
  • Scanning and alarm processing
  • Load shedding
  • Graphic screen reporting
  • Trend logging
  • Totalization
  • Global communication

b.User Friendliness

The chilled water plant control system software shall be easy to operate and to program. Operators shall be able to perform the following operations after one day of training:

  • View systems parameters
  • Select relevant screens, systems and points
  • Turn on and off controlled points manually
  • Acknowledge alarms
  • Log trend data

c.Input/Output

A complete point schedule shall be provided detailing analogue and digital input and output point description, functions, types and any special requirements.

d.Trending and Reporting Capabilities

The chilled water plant control system shall have alarm and event logging capability and shall store logged data, in the memory and the data must be easily retrievable. The chilled water plant control system shall display live and trend data on demand. The controller shall allow the operator to select points, group of points and mechanical systems through a menu. The controller shall provide graphic screens of system schematics.

e.Communication Protocol

The chilled water plant control system shall communicate with one or more of the following protocols: Lonworks, Modbus or BACnet.

f.BAS/BMS Access and Internet

The chilled water plant control system shall provide BAS/BMS access and internet access through either or both the BMS/BAS serial network and an internet TCP/IP internet address with read/write functionality. This access shall allow the relevant staff to:

  • Program remote controllers from the BAS/BMS room
  • Receive alarm messages, automatically process and convey them to the maintenance personnel via the network
  • View live and trend data from the remote stations

g.Alarms

Whenever abnormal conditions arise, alarms shall be generated and the alarm messages shall be displayed in clear textual form on the screen, until it is acknowledged.

h.Totalization

The IPC 11550 shall have “Totalization” capability, i.e. to calculate, store and show the accumulated equipment run time.

i.Graphics

Graphics shall be included for ease of system operation. Graphic screens shall include, but will not be limited to, the following:

  • System schematic
  • Chiller system schematic
  • Cooling tower loop schematic
  • Building loop schematic

j.Access Security

The IPC 11550 system shall have three levels of password security: one level for field adjustable parameters, a second for factory/commissioning setup parameters and a third for BAS communication commissioning.

k.Sequence of Operation

The chilled water plant control system shall utilize demand based control for the tower fan and pump speed and shall provide the chiller with a chilled water supply temperature set-point for the chiller to govern its operation to. The chillers shall be sequenced/staged, both on and off in a manner to maintain their operation as close as possible to the Natural Curve. The cooling tower fan speed and pump speed settings shall vary in accordance to the Equal Marginal Performance principle. The “natural curve”, “demand based control” and “equal marginal performance principle” methodologies described above are to be in accordance with the Hartman LOOP™ operating principles of an all variable speed chiller plant. Alternate plant control sequences that can be proven to provide a net plant efficiency level of 0.5kW/ton or better will be considered with a written proposal submitted at the time of quotation. Net plant efficiency level is calculated as the average annual kW/ton for the annual energy input to the chiller, cooling tower and distribution pumps, divided by the annual tons delivered to the system.

  • Automatic operation mode

When the chiller plant IPC 11550 system is in automatic operation mode, the chiller plant is automatically started and all equipment is sequenced and modulated entirely automatically to meet the current cooling load with optimum operating efficiency.

  • Manual operation mode

When the chiller plant IPC controller is switched to the manual operation mode by the operator, there is no automatic operation or sequencing of any equipment and operation of chillers, chilled water distribution pumps, condenser water pumps, cooling towers and cooling tower fans continue at the same status when operation mode was switched to manual mode, until further changes by the operator. When the manual operation mode is switched off, the automatic operation mode is restarted.

1.2 EXECUTION

1.Quality Assurance

The chilled water plant control system manufacturer must hold an ISO 9000 QA certification or approved equal. The Chilled water plant control system shall be manufactured and labeled in accordance with UL508A (CSA C22.2 #14 for use in Canada). Supplying UL recognized individual components is not sufficient. The assembled control enclosure, as a whole, must be inspected for proper wiring methods, fusing, etc. and must be labeled as conforming to UL508A. Inspection and labeling shall be supervised by UL or OSHA approved Nationally Recognized Test Lab (NRTL). Lack of an NRTL certified UL508A wiring methods inspection and labeling will be grounds for control enclosure rejection.