Selection, Installation and Maintenance of Control and Indicating Equipment for Fire Detection and Alarm System Code of Practice

IS 15908: Scope - Key Points & References

Scope Overview:
IS 15908 primarily covers specifications related to fire alarm systems and associated components.

Key Specifications:

• Spares (Clause 10.9):

  • Essential spares include covers for manual call points and fuses.
  • Quantity depends on installation specifics.

• Battery Capacity Calculation (Annex B, Clause 5.2(k)):

  • For Valve Regulated Lead Acid Batteries, use the formula:
    [ \text{Capacity (Ah)} = \frac{\text{Load Current (A)} \times \text{Backup Time (h)}}{\text{Discharge Efficiency}} ]
  • Ensure rounding as per IS 2:1960.

• Environmental Noise Levels (Annex D, Clause 8.10(a)):
  Typical occupational noise levels (dB) for various locations:

Referenced Indian Standards (Annex A):

• IS 5:2004 – Colours for paints and enamels
• IS 513:1994 – Cold-rolled steel sheets
• IS 694:1990 – PVC insulated cables (up to 1100 V)
• IS 1255:1983 – Power cables installation (up to 33 kV)
• IS 9779:1981 – Heat sensitive fire detectors
• IS 11360:1985 – Smoke detectors for fire alarms
• IS 1554 (Part 1):1988 – Heavy duty PVC insulated cables

Summary Diagram: Fire Alarm System Scope

graph LR
A[Fire Alarm System Scope] --> B[Spares & Maintenance]
A --> C[Battery Capacity Calculation]
A --> D[Environmental Noise Levels]
A --> E[Referenced IS Codes]

B --> B1[Manual Call Point Covers]
B --> B2[Fuses]

C --> C1[Valve Regulated Lead

IS 15908 Key References, Formulas & Tables

1. Referenced Indian Standards (Annex A, Clause 2.1)

2. Standby Battery Capacity Calculation (Annex B)

For Valve Regulated Lead Acid Batteries:

[ C = I \times t \times D ]

• C = Battery capacity (Ah)
• I = Load current (A)
• t = Backup time (hours)
• D = Correction factor (1 or 1.75 as per Clause 1.75)

Use next available capacity if exact C not available.

3. Occupational Noise Levels (Annex D, Clause 8.10)

4. Spares (Clause 10.9)

• Essential spares: manual call points, fuses.
• Quantity based on installation size and criticality.

Summary:
IS 15908 references multiple IS codes for materials and devices, provides a formula for battery sizing, lists typical occupational noise levels, and advises on essential spares. Use the battery capacity formula with correction factors and consult manufacturers for other battery types.

IS 15908: General Requirements - Key Points

1. Spares (Clause 10.9)

   • Essential spares: Manual call point covers, fuses.
   • Quantity based on installation specifics; no fixed table.

2. Battery Capacity Calculation (Annex B)

   • For Valve Regulated Lead Acid Batteries:
     [ D = \begin{cases} 1 & \text{if } \frac{C_{min}}{20} \geq I_2 \ 1.75 \text{ or manufacturer's value} & \text{if } \frac{C_{min}}{20} < I_2 \end{cases} ]
   • Use next available battery capacity if exact not available.
   • For other batteries, consult manufacturer considering standby load, alarm load, derating for alarm current and aging.

3. Environmental & Noise Levels (Annex C & D)

   • Environmental stresses per Table C-3.3 (Clause 8.10).
   • Typical occupational noise levels range from 30 dB (storage) to 90 dB (AC plants).

4. Rounding Off (Clause None)

   • Follow IS 2:1960 rules for rounding numerical results.

Summary Table: Typical Occupational Noise Levels (dB)

For detailed design and installation, refer to IS 15908 clauses and related referenced IS standards listed in Annex A.

IS 15908: Control and Indicating Equipment – Key Points

1. Installation & Wiring (Clause 3)

• Flexible conduits max length: 1.2 m for vibrating equipment.
• Saddles: galvanized steel, 6 mm thick, spaced ≤ 500 mm.
• Fixing screws: cadmium plated brass, round/cheese head.
• Conduits: run parallel/right angles, no cross-overs unless necessary.
• Embedded conduits: fixed with staples ≤ 500 mm intervals.
• Conduits in concrete: fastened to reinforcement before pouring.
• Fish wires: galvanized steel, ≥ 0.63 mm diameter.
• Inspection boxes: flush, spaced ≤ 12 m or two 90° bends.

2. Control Centre (Clause 7)

• Area: 15–20 m², preferably ground floor.
• Facilities: WC, drinking water, emergency lighting, intercom, direct phone to fire brigade.
• Mimic panel showing fire system details and fire orders.
• Fire walls and independent AC for air-conditioned control rooms.

3. Equipment Features (Clause 8.11)

• Manual controls: clearly labeled, secured from outsiders.
• Indicators:
  • Red LED for fire origin.
  • Amber LED for faults.
  • Sounders with distinct fire/fault alarms.
  • Acknowledge/silence button with LED.
• Meters: voltmeter & ammeter on main DC circuit.
• Isolation & test facilities for zones/sectors.
• Failure of indicator circuits does not disable alarms.
• Earthing mandatory for all panels.

4. Documentation (Clause 9)

• Record drawings showing equipment, cables, junctions.
• Circuit diagrams if requested.
• Log book for alarms, faults, tests, maintenance.

Summary Table: Conduit & Control Centre Specs

IS 15908 Key Points on Power Supply and Batteries for Fire Alarm Systems

Power Supply Requirements (Clause 5.2)

• Normal supply: Single-phase mains with dedicated switch-fuse/MCCB labeled "FIRE ALARM - DO NOT SWITCH OFF".
• Standby supply: Automatic switch-over to exclusive secondary batteries or captive power (generator) if available.
• Capacity:
  • Normal supply must handle total quiescent load + all sounders + 25% zones in alarm.
  • Standby batteries must maintain normal operation for ≥48 hours after mains failure, then support full load for ≥30 minutes.
• Charging: Automatic charging with appropriate rate to restore battery capacity within 24 hours.
• Monitoring: Battery voltage and low voltage must be indicated on control panel.

Battery Capacity Calculation (Annex B)

• For Valve Regulated Lead Acid batteries:

[ D = \begin{cases} 1 & \text{if } \frac{C_{min}}{20} \geq I_2 \text{ or } \frac{C_{min}}{20} < 12 \ 1.75 \text{ or manufacturer's value} & \text{otherwise} \end{cases} ]

Where:

• (C_{min}) = minimum battery capacity (Ah)

• (I_2) = current drawn in alarm condition (A)

• Select next available battery capacity if exact (C_{min}) not available.

• For other battery types: Consult manufacturer considering standby/alarm loads, derating for alarm current and aging.

Installation & Safety (Clause 5.2 & 6)

• Batteries must be mounted on metal stands in ventilated areas.
• Power supplies must be isolated from other loads and protected against unauthorized switching.
• Visual indicators for mains presence and battery status are mandatory.
• Distributed power supplies must be powered and monitored from control panel backup.

Summary Table: Power Supply Requirements

Key Specifications & Formulas for Cabling and Wiring (IS 15908)

1. Cable Characteristics (Clause 6.2.1)

• Voltage drop, current carrying capacity, impedance must suit the system.
• Data transmission capability considered where applicable.

2. Conduit Wiring (Clause 6.3)

• Minimum conduit size: 25 mm diameter.
• Flexible conduits: max length 1.2 m for short extensions (hung ceilings, vibrating equipment).
• Support: Saddles/clamps of galvanized steel, 6 mm thick, spaced ≤ 500 mm.
• Fixings: Cadmium plated brass screws with round/cheese heads.
• Conduit runs: Parallel or at right angles to walls; neat bends using junction/pull boxes.
• Inspection boxes: ≤ 12 m apart or after two 90° bends.
• Fish wires: Galvanized steel, ≥ 0.63 mm diameter, drawn before embedding.
• Conduit termination: Junction boxes ≥ 32 mm deep with smooth bushings and check nuts.
• No joints allowed between two points; sleeves tapered like pencils.

3. Installation Practices

• Avoid choked conduits.
• Conduits embedded in concrete must be secured before pouring.
• Avoid sharp edges and grease on conduits.
• Skilled labor required; avoid cable kinks; bend radius per manufacturer.

4. Control Centre (Clause 7)

• Area: 15–20 m², preferably ground floor.
• Facilities: WC, drinking water, emergency lighting, intercom, fire brigade hotline.
• Fire walls and independent AC with dampers and mimic panel status display.

5. Material Use (Clause 6.2.3)

• Metallic/rigid PVC conduits.
• PVC conduits only in concealed spaces.

Typical Cable Voltage Drop Formula

[ V_d = \frac{2 \times L \times I \times R}{1000} ]

Where:

• (V_d) = Voltage drop (Volts)
• (L) = Length of cable (meters)
• (I) = Current (Amps)
• (R) = Resistance per km of cable (Ohms)

Conduit Fill Guidelines (Typical)

| Conduit Size (mm) | Max Cable Diameter (mm)

IS 15908: Installation Practices - Key Points & Formulas

1. Installation Practices (Clause 1.2 & 10.2)

• Flexible conduits for short extensions (≤1.2 m) to outlets or vibrating equipment.
• Surface-mounted cables/conduits supported on galvanized steel saddles (6 mm thick) at max 500 mm intervals.
• Conduits embedded in walls fixed by staples at max 500 mm spacing; chases refilled neatly.
• Conduits in concrete fixed securely to reinforcement before pouring.
• Fish wires (≥0.63 mm dia galvanized steel) drawn in conduits before embedding.
• Inspection boxes flush with wall/ceiling, spaced max 12 m or two 90° bends apart.
• Junction boxes covered with 6 mm clear plates fixed with cadmium plated brass screws.
• No wire exposure; conduits terminate rigidly with bushings and check nuts.
• Cable bends smooth, radius per manufacturer recommendations.

2. Standby Battery Capacity Calculation (Annex B, Clause 5.2(k))

For Valve Regulated Lead Acid Batteries:

[ \text{Capacity (Ah)} = \frac{\text{Load Current (A)} \times \text{Backup Time (h)}}{\text{Depth of Discharge (decimal)}} ]

• Load Current: Total current drawn by panel and devices.
• Backup Time: Required hours of operation during power failure.
• Depth of Discharge: Typically 0.8 for VRLA batteries.

3. Spares (Table 10.9)

• Essential spares to be kept: manual call point covers, fuses.
• Other spares based on installation complexity and criticality.

4. Control Centre Specifications (Clause 7)

• Area: 15–20 m², preferably ground floor.
• Facilities: WC, drinking water, emergency lighting, intercom, direct fire brigade communication.
• Firewalls and independent AC for air-conditioned control rooms.
• Mimic panel displaying system status prominently.

5. Conduit Installation Summary

flowchart LR
A[Start Installation] --> B[Fix conduits with staples (≤500mm spacing)]
B -->

IS 15908: Fire Alarm Signals and Indications - Key Points

Fire Alarm Intimation (Clause 8.7)

• Activation of detector/manual call point triggers:
  • Audible signal on control & indicating (C&I) equipment.
  • Visual signal on C&I equipment.
  • At least one external alarm sounder.
  • Visible indication per zone/sector where alarm triggered.
  • Audible alert on sector/zonal panel (if provided).
• Two-stage alarm system:
  If first alarm not acknowledged within 60 seconds, a general evacuation alarm sounds on all floors.

Indicating Equipment Layout (Clause 3.7)

• Must display a diagrammatic building plan showing:
  • Building entrance.
  • Main circulation areas.
  • Division into zones or a correctly oriented plan if zones absent.

Networked Fire Alarm Systems (Clause 4)

• Distributed C&I equipment via networked sub-panels.
• Network types:
  • Ring/loop (highly resilient).
  • Radial (less resilient).
  • Peer-to-peer with central processor.
• Sub-panels can operate standalone; network failure should not affect primary alarms.

Summary Table of Signals

Diagram: Fire Alarm Signal Flow

graph LR
  Detector/ManualCallPoint -->|Signal| C&I_Equipment
  C&I_Equipment -->|Audible & Visual| Internal_Alarm
  C&I_Equipment --> External_Alarm_Sounder
  C&I_Equipment --> Zone_Indicator
  Zone_Indicator --> Sector_Panel
  Sector_Panel -->|Audible Alert| Sector_Alarm
  C&I_Equipment -->|If no Ack in 60s|

IS 15908: Testing and Commissioning Key Points

1. Initial Installation Inspection Tests (Clause 10.2)

• Verify installation completeness and compliance.
• Check wiring, connections, and physical conditions.
• Ensure correct positioning of detectors, MCPs, and panels.

2. Functional Test Sequence (Clause 2.2)

Perform these steps in order:

• a) Trigger a device (detector/MCP) to confirm alarm operation.
• b) Operate alarm silencing switch.
• c) Trigger another device from a different zone (for large systems).
• d) Operate reset control.
• e) Check audible/visible warnings on mains power failure.
• f) Restore system to quiescent state.

3. Standby Battery Capacity Calculation (Annex B - Clause 5.2(k))

For Valve Regulated Lead Acid Batteries:

[ \text{Battery Capacity (Ah)} = \frac{\text{Load Current (A)} \times \text{Backup Time (h)}}{\text{Depth of Discharge (decimal)}} ]

• Load Current: Total current drawn by panel and devices.
• Backup Time: Required autonomy (e.g., 24 hours standby + 30 minutes alarm).
• Depth of Discharge: Typically 0.8 for VRLA batteries.

4. Spares (Clause 10.9)

• Keep essential spares like manual call point covers and fuses.
• Other spares based on installation specifics.

Summary Table: Functional Test Steps

flowchart TD
    A[Start Functional Test] --> B[Trigger device (detector/MCP)]
    B --> C[Operate alarm silencing switch]
    C --> D[Trigger device in another zone]
    D --> E[Operate reset control]
   

IS 15908: Maintenance and Servicing Key Points

Clause 10.3 & 10.4: Servicing & Maintenance Schedule

• Periodic servicing is mandatory to ensure system reliability.
• Maintenance intervals and tasks should be clearly defined in a maintenance schedule.
• Tasks include: testing detectors, control panels, power supplies, and communication devices.

Clause 10.9: Spares (Table 10.9)

• Essential spares to be kept onsite:
  • Covers for manual call points
  • Fuses
  • Other critical spares based on installation specifics
• Avoid unnecessary stockpiling; keep only what is essential for quick repairs.

Battery Capacity Calculation (Annex B)

• For Valve Regulated Lead Acid Batteries:

  [ \text{Battery Capacity (Ah)} = \frac{\text{Load Current (A)} \times \text{Backup Time (h)}}{\text{Depth of Discharge (decimal)}} ]

Accessories & Controls (Clause 8.11)

• Control panels must have:
  • Clear labeling
  • LED indicators for fire (red) and fault (amber)
  • Audible alarms with distinct sounds
  • Test and isolation facilities
  • Proper earthing for all control equipment

Documentation (Clause 9)

• Provide:
  • Record drawings with equipment locations and cable routes
  • Circuit diagrams if requested
  • Log book for alarms, faults, tests, maintenance, and downtime

flowchart TD
    A[Maintenance Schedule] --> B[Periodic Testing]
    B --> C[Detectors]
    B --> D[Control Panels]
    B --> E[Power Supplies]
    B --> F[Communication Devices]
    G[Spares Inventory] --> H[Manual Call Point Covers]
    G --> I[Fuses]
    G --> J[Other Critical Spares]
    K[Documentation] --> L[Record Drawings]
    K --> M[Log Book]

Summary: Maintain a clear schedule, keep essential spares, ensure control panel functionality, calculate standby battery capacity properly, and maintain thorough documentation for effective servicing and maintenance as per IS 15908.

IS 15908: Environmental and Performance Tests Summary

Key Specifications & Procedures

• Pre-conditioning & Recovery (Clause 2.1.1)

  • Stabilize equipment temperature for ≥ 3 hours at 15℃ to 37℃
  • Relative humidity: 45% to 85%
  • Maintain stable ambient conditions during preconditioning, recovery, and functional tests.

• Test Environments (Clause 2.3)

  • Equipment subjected to:
    • Dust test per IS 11360
    • Corrosion test in SO₂ atmosphere per IS 2175
    • Vibration test on vibrating table per IS 2175

• Environmental Stresses (Clause 3.3)

  • Housing must protect against dust and environmental damage.
  • One device for each test type (dust, corrosion, vibration).

Functional Testing Flow

flowchart TD
    A[Pre-conditioning: Stabilize Temp & RH] --> B[Functional Test (Pre)]
    B --> C[Environmental Test (Dust/Corrosion/Vibration)]
    C --> D[Recovery: Stabilize Temp & RH]
    D --> E[Functional Test (Post)]

References for Tests

Note: Always refer to the respective IS codes for detailed test setups, durations, and acceptance criteria.

IS 15908: Special Systems - Key Formulas, Tables & Specifications

1. Power Supply Requirements (Clause 5.2)

• Normal Supply: Single phase mains with dedicated switch-fuse/MCCB labeled "FIRE ALARM - DO NOT SWITCH OFF".
• Standby Supply: Automatic switch-over to batteries or captive generation.
• Capacity:
  • Normal mains must support quiescent load + all sounders + 25% zones in alarm.
  • Standby must operate system for 48 hours normal + 30 minutes full load (all sounders + 25% zones + fault indicator).

2. Battery Capacity Calculation (Annex B)

• For Valve Regulated Lead Acid Batteries:

  [ C = \frac{I \times t}{D} ]

  Where:

  • ( C ) = Battery capacity (Ah)
  • ( I ) = Load current (A)
  • ( t ) = Backup time (h)
  • ( D ) = Depth of discharge (decimal)

• Battery charging must restore capacity within 24 hours.

3. Alarm System Features (Clause 8.6)

• Alarm signals at control centre with optional public address.
• Two-stage alarm requires zonal/sector panels; single stage may omit them.
• Audible & visual alarms maintained without continuous detector signal.
• Uniform alarm sound characteristics throughout premises.

4. Spares (Clause 10.9)

• Keep spares for manual call points, fuses, and essential parts based on installation size.

Summary Table: Power Supply Requirements

flowchart LR
    A[Mains Supply] -->|Normal Operation| B[Fire Alarm System]
    A -->|Failure| C[Automatic Switch-Over]
    C --> D[Standby Battery Supply]
    D --> B
    B --> E[

Silencing and Resetting Procedures (IS 15908)

Key Clauses:

• Clause 8.3 (Silencing Switch Operation):

  • Activating the silencing switch for fire alarm sounders or internal C&I equipment audio alarms must trigger a distinctive audible signal near the C&I equipment.
  • This signal acts as a reminder that silencing is active.
  • Not required if automatic reset is provided.

• Clause 8.8 (Silencing of Fire Alarm):

  • Audible alarms continue until manually silenced; no automatic silencing.
  • Silencing triggers an audible/visual signal at C&I equipment until reset.
  • If a new detector/MCP triggers in another zone after silencing, the alarm sounders must activate again.
  • Automatic reset systems are exempt.

• Clause 2.2 (Functional Test Sequence):

  1. Trigger a detector/MCP to verify alarm.
  2. Operate silencing switch.
  3. Trigger another detector/MCP in a different zone.
  4. Operate reset control.
  5. Check warnings on power disconnection.
  6. Restore to quiescent state.

Battery Capacity Calculation (Annex B)

For Valve Regulated Lead Acid Batteries:

[ C = \frac{I \times t}{D} ]

Where:

Summary Table: Silencing & Resetting

flowchart TD
  A[Fire Alarm Triggered] --> B[Alarm Sounders Activated]
  B --> C[Silencing Switch Operated]
  C --> D[Audible Reminder Signal ON]
  D --> E{New Detector Activated?}
  E --

IS 15908: Documentation and Log Books Key Points

1. Documentation (Clause 9)

• Record Drawings & Operating Instructions:
  • Supplied by installer after completion.
  • Must show equipment positions, junction boxes, cable sizes/routes.
  • Circuit diagrams may be supplied on user request.
  • Kept updated and available in the control room.

2. Log Book (Clause 9b)

• Provided by installer to user.
• Records details of:
  • All alarms (genuine, practice, test, false).
  • Faults, service tests, routine inspections.
  • Servicing/repairs.
  • Periods of disconnection/in-operation.

3. Quarterly Inspection & Testing (Clause 10.4.5)

• Check log book entries and take action.
• Test batteries and connections.
• Verify electrolyte specific gravity for secondary batteries.
• Test primary batteries for serviceability.
• Check alarm functions via trigger devices.
• Inspect control equipment for moisture/deterioration.
• Ensure detectors have 750 mm clear radius and manual call points are unobstructed.

Summary Table: Documentation & Log Book Requirements

flowchart TD
    A[Installation Complete] --> B[Record Drawings & Operating Instructions]
    B --> C[Log Book Provided to User]
    C --> D[Quarterly Inspection & Testing]
    D --> E{Issues Found?}
    E -- Yes --> F[Record & Correct Defects]
    E -- No --> G[Continue Operation]

Note: Maintain log books diligently for compliance and effective fire alarm system maintenance.

IS 15908: Key Annexes & Reference Standards Summary

Annex A: List of Referenced Indian Standards (Selected)

Annex B: Battery Capacity Calculation for Fire Alarm Panels

• Applicable for Valve Regulated Lead Acid Batteries

Formula:

[ C = I \times t \times K ]

Where:

• ( C ) = Battery capacity (Ah)
• ( I ) = Load current (A)
• ( t ) = Backup time (hours)
• ( K ) = Correction factor (usually >1 to account for battery efficiency and aging)

Annex D: Typical Occupational Noise Levels (dB)

Notes:

• Clause 10.9: Essential spares such as manual call points and fuses should be stocked based on installation specifics.
• Clause 1.2: This standard sets minimum protection levels; higher protection systems may be installed.
• Refer to latest editions of referenced IS standards for up-to-date provisions.

flowchart LR
    A[Load Current (I)] -->