Monday, April 15, 2024

Some of the key Passive Fire Protection extract from NBC 2016

Some of the key Passive Fire Protection extract from NBC 2016 

Passive fire protection systems are integrated into the structure of a building, restricting the spread of smoke and fire to a compartment that is comprised of fire-rated walls, floors and ceilings. To the extent possible, all penetrations through these fire-rated walls, floors and ceilings should be fire stopped in accordance to a tested and approved system. Additionally, all bottom-of-wall, top-of-wall, and wall-to-wall joints in this fire-rated compartment should be fire stopped in accordance to a tested and approved system.

The use of and need for Passive Fire Protection Products in buildings/structures are highlighted in the National Building Code of India (NBC) (2016). It is the job of consultants to design the space, structure of any type of building whether residential, commercial or industrial.  They design buildings keeping in mind the guidelines outlined in the NBC. Furthermore, consultants are the ones who determine the types of fire stopping products to be used in each compartment and their fire rating.

1.   Scope:

This Code (Part 4) specifies occupancy-wise classification, constructional aspects, egress requirements and protection feature that are necessary to minimize danger to life and property from fire.

1.2 The provisions of this part are applicable to,

(a) all high rise buildings; and

(b) special buildings, those are,

(1) Hotel, educational, institutional, business, mercantile, industrial, storage, hazardous and mixed occupancies, where any of these buildings have floor area more than 500 m2 on any one or more floors;

(2) educational buildings having height 9 m and above;

(3) institutional buildings having height 9m and above;

(4) all assembly buildings;

(5) buildings, having area more than 300 m2 of incidental assembly occupancy on any floor; and

(6) buildings with two basements or more, or with one basement of area more than 500 m2; unless otherwise mentioned specifically in the provisions.

NOTE - The owner of the building and parties to agreement, may however decide to apply the provisions of this part to buildings other than those given above.

2.   Fire Resistance

2.28 Fire Resistance — Fire resistance is a property of an element of building construction and is the measure of its ability to satisfy for a stated period, some or all of the following criteria:

a) Load bearing capacity (Stability) (R) – The ability of a load bearing element to withstand fire exposure without any loss of structural stability.

b) Integrity (E) – resistance to penetration of flame and hot gases.

c) Insulation (I) – resistance to temperature rise on the unexposed face up to a maximum of 180°C and/or average temperature of 140°C.

3.   Fire Resistance Rating

Fire Resistance Rating — The time that a material or construction will withstand the standard fire exposure as determined by fire test done in accordance with the standard methods of fire tests of materials/structures as per the accepted standard.

[4(2)] - NOTES - (1.) The requirement of rating of various building elements as given in this part shall be applicable in accordance with the provisions given in the accepted standard [4(2)].

(2.) The fire resistance rating shall be specified in minutes. (3.) Fire resistance rating for non-structural material / assembly shall bear a label of compliance to such ratings as per the approval of competent authority based on testing and evaluation. The label shall be permanently affixed to the material / assembly and may carry other relevant details such as name and type of the product, and manufacturer's details.

4.   Fire Resistance Wall

Fire Resistant Wall (2.30) — Fire resistant rated wall, having opening(s) with specified fire resistant rating, which restricts the spread of fire from one part of a building to another part of the same building.

5.   Fire Stop

Fire Stop (2.32 ) — A fire resistant material, or construction, having a fire resistance rating of not less than the fire separating elements, installed in concealed spaces or between structural elements of a building to prevent the spread/ propagation of fire and smoke through walls, ceilings and like as per the laid down criteria.

NOTES - (1) Fire stop assembly for through penetrations is a combination of firestop compatible for use with the penetrant, penetration items such as cables, cable trays, conduits, ducts, pipes etc., and their means of support through the wall or opening that together restores the fire resistance rating of the fire separating elements in terms of its integrity and/or insulation properties.

(2) Fire stop assembly for joints is the one where fire stop with movement capability is used to seal the linear joints between adjacent fire separating elements, which should be installed within its tested design limits with regard to size of joint, type of assembly, and anticipated compression and extension of the joint.

6.   Fire Wall or Fire Separating Wall

Fire Wall or Fire Separating Wall (2.34) — A fire resistance rated wall having fire protected openings, which restricts the spread of fire and extends continuously from the foundation to the roof (and through the roof at least 1m above the roof in case of combustible roof), with sufficient structural stability under fire conditions to allow collapse of construction on one side or either side without collapse of the wall.

7.   High Rise Building

High Rise Building (2.38) — A buildings 15 m or above in height (irrespective of its occupancy).

8.   Smoke Barrier

Smoke Barrier (2.56) — A continuous membrane, or a membrane with discontinuities created by protected openings, where such membrane is designed and constructed to restrict the movement of smoke.

9.   Smoke Compartment

Smoke Compartment (2.57) — A space within a building enclosed by smoke barriers on all sides.

10.Restriction on Existing Building

Restrictions on Existing Buildings (3.2.7) – The existing buildings in any fire zone shall not be required to comply with the requirement of the Code unless these are altered, or in the opinion of the Authority, such building constitutes a hazard to the safety of the adjacent property or the occupants of the building itself or is an unsafe building. In the event of alteration, it shall be necessary to obtain permission of the Authority for such alteration consistent with fire hazard (see Part 2 ‘Administration’ of the code). Alterations/modifications/renovations shall be accomplished so as to ensure conformity with all the safety requirements of the new buildings. Such alterations shall not in any way bring down level of fire and life safety below that which existed earlier. Any addition or alterations or construction of cubicles or partitioning, for floor area exceeding 500 m2 for all high rise buildings shall be with approval of local fire authority.

11. Str. & Non Stru Fire Resistance Rating (3.3.2)

It is required that a structural and/or non-structural element/component shall have the requisite fire resistance rating as per Table 1. The fire resistance rating for the structural and non-structural elements shall be based on guidelines as per approved and acceptable standards. The fire rating shall be validated and certified with a view to meeting the requirements of Table 1. In the absence of any validated/certified rating, guidance may be obtained from the information available in Annex C.

12. False Ceiling (3.3.4)

The false ceiling, including all fixtures used for its suspension, shall be of non-combustible material and shall provide adequate fire resistance to the ceiling in order to prevent spread of fire across ceiling.

13. Wording Change

(3.4.5.2) For Types 1 to 3 constructions, a doorway or opening in a fire resistant wall on any floor shall be limited to 5.6 m2 in area with a maximum height/width of 2.75 m. Every wall opening shall be protected with fire-resisting doors, having the fire rating of not less than 120 min. The openings in the floors shall be protected by vertical enclosures extending above and below such openings, having a fire resistance of not less than 120 min and all openings therein being protected with a fire-resisting assembly as specified in 3.4.5.6.

(3.4.5.3) For Type 4 Construction, openings in the fire separating walls or floors shall be fitted with 120 min fire-resistance rated assemblies.

14. Service Ducts & Shafts

Service ducts and shafts (3.4.5.4): Openings in walls or floors which are necessary to be provided to allow passages of all building services like cables, electrical wirings, telephone cables, plumbing pipes, etc., shall be protected by enclosure in the form of ducts/shafts having a fire resistance not less than 120 min. The inspection door for electrical shafts/ducts shall be not less than 120 min. Further, medium and low voltage wiring running in shafts, shall either be armored type or run through metal conduits. Further, the space between the cables/conduits and the walls/slabs shall be filled in by a fire stop material having fire resistance rating of not less than 120 min. This shall exclude requirement of fire stop sealing for low voltage services shafts. For plumbing shafts in the core of the building, with shaft door opening inside the building, the shafts shall have inspection doors having fire resistance rating not less than 30 min. For plumbing shafts doors which open in wet areas or in naturally ventilated areas or on external wall of the building, the shafts may not require doors having any specified fire rating.

15. Electrical Installations

Electrical Installation (3.4.7) For requirements regarding electrical installations from the point of view of fire safety, reference may be made to good practice [4(8)]. (see also Part 8 ‘Building Services, Section 2 Electrical and Allied Installations’ of the Code).

The electric distribution cables/wiring shall be laid in a separate shaft. The shaft shall be sealed at every floor with fire stop materials having the same fire resistance as that of the floor. High, medium and low voltage wiring running in shaft and in false ceiling shall run in separate shafts/conduits.

16.Air Handling Unit

(3.4.8.2.2) Shafts or ducts, if penetrating multiple floors, shall be of masonry construction with fire damper in connecting duct work or shall have fire rated ductwork with fire dampers at floor crossing. Alternatively, the duct and equipment may be installed in room having walls, doors and fire damper in duct exiting/entering the room of 120 min fire resistance rating. Such shafts and ducts shall have all passive control meeting 120 min fire resistance rating requirement to meet the objective of isolation of the floor from spread of fire to upper and lower floors through shaft / duct work.

17.Duct Work

(3.4.8.3.3) Wherever the ducts pass through fire walls or floors, the opening around the ducts shall be sealed with materials having fire resistance rating of the compartment. …….

3.4.8.3.5 The material used for insulating the duct system (inside or outside) shall be of non-combustible type. Any such insulating material shall not be wrapped or secured by any material of combustible nature.

18. Glazing

(3.4.10.1) The glazing shall be in accordance with Part 6 'Structural Design, Section 8 Glass and Glazing' of the Code. The entire glazing assembly shall be rated to that type of construction as given in Table 1. This shall be applicable along with other provisions of this part related to respective users as specified therein. The use of glass shall not be permitted for enclosures of exits and exit passageway.

19. Glass Façade Requirements

(3.4.10.2) Glass facade shall be in accordance with the following: -

a) For fully sprinklered buildings having fire separation of 9 m or more, tempered glass in a non-combustible assembly, with ability to hold the glass in place, shall be provided. It shall be ensured that sprinklers are located within 600 mm of the facade glass providing full coverage to the glass. NOTE – In case of all other buildings, fire resistance rating of glass facade shall be in accordance with Table 1. b) All gaps between floor-slabs and facade assembly shall be sealed at all levels by approved fire resistant sealant material of equal fire rating as that of floor slab to prevent fire and smoke propagation from one floor to another. c) Openable panels.....,

20.Fire Command Center

(3.4.12) Fire Command Center (FCC) (d) The fire staff in charge of fire command center shall be responsible for the maintenance of the various services and firefighting installations in coordination with security, electrical and civil staff of the building.

21. Exit Requirements

(4.2) General Exit Requirements

(4.2.17) Penetrations into and openings through an exit are prohibited except those necessary like for the fire protection piping, ducts for pressurization and similar life safety services. Such openings as well as vertical passage of shaft through floors shall be protected by passive systems.

22. Protected Escape Routes

(4.4.2.5) Smoke control of exits

(a) In building design, compartmentation plays a vital part in limiting the spread of fire and smoke. The design should ensure avoidance of spread of smoke to adjacent spaces through the various leakage openings in the compartment enclosure, such as cracks, openings around pipes ducts, airflow grills and doors. In absence of proper sealing, smoke and toxic gases will obstruct the free movement of occupants of the building through theexits. Pressurization of staircases is of great importance for the excusion of smoke and toxic gases from the protected exit.

23. Compartmentation Area

(4.5.2) All floors shall be compartmented/zoned with area of each compartment being not more than 750 m2. The maximum size of the compartment shall be as follows, in case of sprinklered basement/ building:

In addition, there shall be requirement of a minimum of two compartments if the floor plate size is equal or less than the areas mentioned above. However, such requirement of minimum two compartments shall not be required, if the floor plate is less than 750 m2.

Compartmentation shall be achieved by means of fire barrier having fire resistance rating of 120 min.

1.    Additional requirements for high rise buildings

Annex E - Additional requirements for high rise buildings

For high rise buildings, seismic bracings shall be considered for fire-fighting installations depending on seismic vulnerability of the region and type of occupancy.

2.    E-7 Fire and Life Safety Audit

Annexure E: Clause E-7

a) Fire and life safety audit shall be carried out for all buildings having a height of more than 15 m.

b) Such audits shall preferably be conducted by a third-party auditor having requisite experience in life safety inspections.

c) Frequency of such audits shall be once in two years.

3.    Annex J - Fire and life safety requirements for metro stations.

J-6 Fire separation and compartmentation -

J-6.1 Fire compartments shall be provided in transit stations in accordance with the provisions of this section. Fire ratings of various occupancies within open stations and enclosed stations shall be as indicated in Table 27.

J-6.2 Further transit station shall be divided into fire compartments by means of compartment walls and compartment floors by a fire separation of at least 120 min between following occupancies:

a) Public area and non-public area,

(b) transit and non-transit area, and

(C) Ancillary areas located beneath and within 3m of the train way in open stations.

J-6.3 No fire separation shall be required for occupancies like ticketing offices, toilets, other offices and the like.

J-6.4 Incidental kiosks inside stations for other purposes like commercial use, etc. shall be fire separated (120 min rating) from the station building, if areas occupied by such occupancies exceed 6 m2.

Monday, April 1, 2024

Relays used for in Fire Alarm Systems

Relays used for in Fire Alarm Systems 

In an emergency you may wish your fire alarm system to perform a number of automated tasks – this could include grounding a lift or closing doors. To do this you will require fire alarm relays, devices which allow the automation of certain functions.

A relay is a simple electromechanical switch. While we use normal switches to close or open a circuit manually, a relay is also a switch that connects or disconnects two circuits. But instead of a manual operation, a relay uses an electrical signal to control an electromagnet, which in turn connects or disconnects another circuit.

The function of relay module in fire system control is to provide a way for a high-voltage device to be controlled by a low-voltage signal. This is done by closing a switch that activates the device when the fire alarm sends a small current to it. In practice, a relay in a fire alarm system may be used to perform the following functions:

·        Close Doors: A fire alarm relay can be used to automatically shut fire doors in a building when the fire alarm is triggered. This helps to contain the fire and prevent it from spreading.

·        Activate Sprinklers: The fire relay module can be used to activate the sprinkler system in a building when the fire alarm is triggered.

·        Sound Alarms: A fire alarm relay module is often used to activate a sound alarm in an emergency. This warns people in the vicinity of the fire and helps them to evacuate the area.

·        Switch OFF AC Systems: The stream of air coming out of an air conditioner can spread the fire in a building or even smoke and fumes. A fire alarm relay can be used to switch off the AC system and prevent the fire from spreading.

·        Switch On Smoke Exhaust Systems: The smoke exhaust system in a building helps to clear out smoke and fumes. A fire alarm relay can be used to switch it on.

·        Switch Off Loud Music: During a fire, it is important to be able to hear fire alarms and other warnings. a fire alarm relay module is often used to switch off loud music when the fire alarm is triggered so that people can hear the warnings.

 

Relays can be used to control voltage feeding a particular supply and either apply or drop voltage in the event of a fire activation.

Relays can be used to signal to monitored inputs, these inputs would monitor a nominal EOL resistance and in the event of a fire alarm activation would switch to pick up the trigger value resistance.

Relays can also be used to signal a simple NO/NC contact.

The relay’s load may be AC or DC, but must be within amperage rating of the relay contacts. The relays must be fire alarm listed and supplied by the FACP manufacturer, or be a Listed Fire Relay from a manufacturer.

Off-the-shelf electrical supply relays are not permitted to be directly wired to a fire alarm system. Additionally, polarity must be observed because of the integrated diode used in the relay.

Testing of the fire alarm system includes only verifying the relay changed state, and not necessarily the operational performance of the fire-safety function itself. Proper fire alarm relay operation will be verified by using a meter or by observing an activation LED on the relay.

Question 1: Will your relay be used to supply electrical power or turn it off? You are not responsible for the connection and operation of any other trade’s equipment or function, but you cannot allow the relay to be used improperly. If your relay states it has contacts rated at 10 amps and the owner wishes to turn on 20 amps of outdoor lighting, then they will have to use your relay to switch another device having the proper load rating (i.e. 20 amps or less).

While it is true that the relay, wiring, contactor or equipment could fail without causing a trouble signal on the fire alarm system, you are only responsible for the relay and circuit that you provide up to the switched contacts of the relay. All equipment after your relay contacts is the responsibility of another trade or another contractor.

 

Question 2: Will your relay be used to switch a small current and low voltage signal used by another electrical system, rather than the safety equipment load? Sometimes the load you need to switch amounts to an electrical control signal of just 5V – which another system’s data input needs in order to perform a function. Since you must supply a relay that is used to perform a certain function, you are not responsible for performing everything the owner wants to do. For example, your relay cannot pulse an illuminated street address sign.

 

Question 3: Is the safety function to be performed a code-required fire alarm feature such as controlling elevators, or is it a customer nicety such as opening a driveway gate or turning on outdoor lighting? For a code compliant relay, its wiring must be either fail-safe or cause a Trouble Signal when power to the relay fails.

For Illustrated Relay A

Power to certain emergency safety functions may need to be turned off during an alarm. Examples of these functions commonly include power to electro-magnetic door holders or electro-magnetic door locks. These two examples are normally well within the electrical rating of a fire relay, but a contactor may also be needed if you intend to cut power to a club’s DJ booth, for example, that is providing amplified sound, light and stage effects. If a contactor/relay is also needed, the electrician will supply it.

Relay A rules: Common and Normally Open relay contacts are used to supply a CLOSED circuit to keep safety equipment operational.

This relay’s wiring is “Fail-Safe,” since loss of power to the relay coil will cause the fire-safety function to be performed. No EOL resistor or power supervision relay is required if the emergency function is performed when loss of power to the relay causes the safety function to be performed.

For Relay B

Power to safety functions may need to be turned on during an alarm. This may include smoke exhaust fans and indoor/outdoor lighting. Typically, a 10 amp relay will be used to switch an additional contactor/relay that would be needed for a large rooftop fan, for example.

 

Relay B rules: Common and Normally Open relay contacts are used to supply a CLOSED circuit to deactivate safety equipment upon a polarity reversal signal from the FACP upon alarm conditions.

This relay wiring is NOT “Fail-Safe,” since loss of power to the relay will not cause the fire-safety function to be performed. Instead, this wiring method will cause a FACP trouble signal should there be a fault on the wiring supplying power to the relay.

A circuit fault or any other loss of power to operate the life safety function may need to be supervised. For example, supervision of the electrical power to operate the elevator’s shunt controller is required to ensure the 110vac power to perform the emergency shunt trip is constantly present. The modern self-contained elevator shunt-trip panels contain a set of relay contacts that will close should the shunt-trip lose its operational power for any reason. Wire a dedicated IDC with an EOL resistor across these provided open terminals. Any loss of that 110vac operating power will cause their relay contacts to close and initiate a Supervisory signal. This signal must be specifically and descriptively annunciated (ie “elevator shunt-trip power loss”).

For Relay C

Use only for non-life safety applications or as allowed by the exception (see below).

 

Relay C rules: Common and Normally Closed and/or Normally Open Relay contacts may be used to activate or to deactivate customer’s equipment. This Relay is NOT “Fail-Safe,” since loss of power to the relay will not cause the fire-safety function to be performed. Also, power wiring to the relay coil can experience a fault without causing a FACP Trouble signal.

An exception allows this relay’s wiring configuration to be used to perform code-required safety functions. This is when a relay output within a control unit is used to activate a function performed by another control unit. This happens when an FACP on-board relay is used to close a set of input contacts of another control panel. For example, you can trip a NAC power booster using the alarm output relay of the main control panel. This exception allows a relay circuit to connect two control units even though the relay wiring is neither monitored for integrity nor provides fail-safe operation.

This wiring exception is only permitted if both control units are located in the same room, the control units are within 20 feet of each other, and the relay wiring connecting both panels is protected against mechanical injury by running it either inside the wall or on the surface using conduit

An elevator company provides a shunt-trip panel whenever the machine room or hoist way includes sprinklers. This panel ensures the elevators will be shut down before sprinkler water can reach sensitive electrical and mechanical components. Your job will be to provide a fail-safe relay (example A) or power-supervised relay (example B), and contacts that will close upon an alarm signal from the hoist way or elevator equipment room detectors.

রিলে কি? 

রিলে একটি সুইচিং ডিভাইস। রিলে এমন একটি সুইচিং ডিভাইস যা সার্কিটে কোন ধরনোর শর্ট সার্কিট সৃষ্টি হলে নিজে ধংস হয়ে সার্কিট কে রক্ষা করে। এই জন্য রিলেকে অতন্দ্রী পহরি বলা হয়ে থাকে।  রিলের মধ্য দিয়ে যদি কারেন্ট প্রবাহিত হয় তাহলে কয়েল মেগনেটাইজ হয়ে কন্টাকের মাধ্যমে সার্কিট কে অন অফ কন্ট্রোল করে থাকে। জরুরি অবস্হায় সার্কিট পুড়ে যাওয়া বা ধংস হয়ে হাত থেকে রক্ষা করে থাকে রিলে। 

রিলে কতো প্রকার কি কি 

ভোল্টেজ অনুযায়ী রিলে দুই প্রকার 

. এসি রিলে 

.ডিসি রিলে 

*এসি রিলে আবার ভোল্টেজ উপর ভিত্তি করে অনেক ধরনের হয়ে থাকে

1. 5VAC,6VC,12VAC,24VAC,36VAC, 110VAC,220VAC,440VAC

 কয়েলের ভোল্টেজের উপর ভিত্তি করে এসি রিলে এতো ধরনের হয়ে থাকে।

*ভোল্টেজ উপর ভিত্তি করে ডিসি রিলে বিভিন্ন ধরনের হয়ে থাকে 

1. 5VDC,6VDC,12VDC,24VDC,36VDC, 110VDC,220VDC 440VDC

কয়েলের ভোল্টেজের উপর ভিত্তি করে ডিসি রিলে এতো ধরনের হয়ে থাকে।

রিলে কেন ব্যাবহার করা হয়

.এসি ভোল্টেজ কে ডিসি রিলে দিয়ে কন্ট্রোল করার জন্য রিলে ব্যাবহার হয়। 

.সার্কিটে কোন ধরনের ক্রটি বা ক্ষতির সম্মুখীন হলে রিলে হতে জানা যায়। 

রিলে নিজে নষ্ট হয়ে সার্কিট রক্ষা করে।

.সার্কিটে কোন ফল্ট হলে রিলে থেকে জানা যায়।

রিলে ব্যাবহারের নিয়ম

প্রতিটি রিলেের গায়ে ডায়াগ্রাম দেওয়া থাকে,  কতো ভোল্টেজ কতো এম্পিয়ার,  কোনটা কোন কন্টাক।

যদি রিলের বডিতে কিছু লিখা না থাকে তাহলে ভিতরে কয়েলের মধ্যে ভোল্টেজ এম্পিয়ার লিখা থাকবে।সেই ভোল্টেজ এবং এম্পিয়ার দেখে কোন জায়গায় ব্যাবহার করা যাবে তা নির্ধারণ করতে হবে। 

রিলে প্রকারভেদ 

সাধারনত তিন প্রকার রিলে হয়ে থাকে 

1.SPST  (Single Pole Single Throw)

2.SPDT (Single Pole Double Throw)

3.DPDT (Double Pole Double Throw

       *SPST রিলে মূলত পিনের হয়ে থাকে 

       *SPDT রিলে মূলত ৫পিনের হয়ে থাকে 

       *DPDT রিলে মূলত পিনের হয়ে থাকে

রিলে পিন পরিচিতি 

রিলেতে মূলত তিনটি পিন থাকে 

1.Common 

2.NO 

3.Nc 

1.Common: কমন কয়েলে সার্কিটের সুইচিংয়ের মান অনুযায়ী ভোল্টেজ প্রবাহিত করা হয়। রিলে কয়েলে কোন পজিটিভ নেগেটিভ প্রান্ত নেই তাই এটি পজিটিভ নেগেটিভ যে কোন প্রান্তে সংযোগ করা যায়। রিলের পরিচিত প্রকাশ পায় মূলত তার কয়েল ভোল্টেজ উপর ভিত্তি করে। যে ভোল্টেজে রিলে চালু হয় সেটি রিলের ভোল্টেজ ধরা হয়। 

2.NO: NO এর ফুল মিনিং Normally Open,  অর্থাৎ রিলে যখন নরমাল অথবা কয়েল না ধরা অবস্হায় থাকবে তখন Common এবং NO প্রান্ত বিছিন্ন অবস্হায় থাকবে।  যখন রিলে কয়েল ধরবে তখন অথবা রিলে কয়েল এবনরমাল হবে তখন Common এবং NO প্রান্তটি নিরবিচ্ছিন্ন অবস্হায় কাজ করবে। 

 3.NC: NC এর ফুল মিনিং Normally Close, অর্থাৎ রিলে নরমাল অবস্থা বা কয়েল না ধরা অবস্হায় Common এবং NC প্রান্ত নিরবচ্ছিন্ন অবস্থায় থাকবে বা সংযোগ থাকবে। যখন রিলে কয়েল ধরবে বা রিলে এবনরমাল অবস্হায় থাকবে এখন Common এবং NC বিচ্ছিন্ন অবস্হায় থাকবে। 

রিলে কয়েল পরিচিতি:

রিলে কয়েল ভোল্টেজ অনুযায়ী অনেক ধরনের হয়।  আমরা যে রিলে ব্যাবহার করবো তার কয়েল ভোল্টেজ অনুযায়ী ভোল্টেজ সাপ্লাই দিলে কয়েলটি ধরবে এবং রিলের উপরে থাকা ইন্ডিকেটর লাইটি জ্বলে উঠবে। আবার যখন ভোল্টেজ সাপ্লাই বন্ধ হয়ে যাবে ইন্ডিকেটর টি বন্ধ হয়ে যাবে এবং কয়েলটি বন্ধে হয়ে আগের অবস্হানে চলে আসবে।