Quality Mechanical Ventilation Systems

Quality Mechanical Ventilation Systems = Quality Air for All 

Breathing comes so naturally to us that we are sometimes barely conscious of it. But, bad air quality can affect us in many ways—from mere discomfort to loss of life. Since a lot of us spend time indoors nowadays, how do we ensure that the air we breathe is safe?

This is where the Mechanical Ventilation System comes in; it plays a major part in our daily lives by

• circulating the air in buildings so that all occupants are able to enjoy good air quality
• continuously replacing the air from the space with fresh, outdoor air
• removing heat from the space and also possible contaminants, such as products of respiration, bacteria, odours, products of combustion, building materials and furnishings, etc.

The role of the Mechanical Ventilation System in Fire Protection

The Mechanical Ventilation System is also a key component of fire safety. In the event of a fire, smoke and polluted air can spread rapidly throughout the building and in most incidents, death and injuries usually result from smoke inhalation rather than the heat from the flames.

This system reduces the risk factors by ensuring that the evacuation routes are safe and secure for people to leave the building.

Who is responsible for the Mechanical Ventilation System?

Thus, according to the requirements from 1) the Code of Practice for Fire Precautions in Building 2018 (Fire Code 2018) - Chapter 7 and 2) the Code of Practice for air-conditioning and mechanical ventilation in building (SS 553: 2016+A1: 2017), Building Owners and Council Members are responsible for installing the Mechanical Ventilation System to

• Provide air ventilation in the building where natural ventilation is not a suitable or effective smoke control measure
• To purge or prevent smoke build-up in certain key aspects of the building, especially where means of escape are critical in the event of fire i.e. staircases

Additional Requirements:

• The common frequency of inspection, testing and maintenance of the Mechanical Ventilation System in buildings, as per regulations, is monthly
• In any building of which habitable height exceeds 24m, any internal exit staircases without provision for natural ventilation shall be pressurized to comply with the requirements
• In a building comprising more than 4 basement storeys, any exit staircase connected to fire fighting lobby in basement storeys shall be pressurized to comply with the requirements

Basic features of the Mechanical Ventilation System

The system is made up primarily of 4 types of mechanical ventilation system that you will usually hear or see in use:

Jet Fan (High and Low speed)

• Also known as impulse or induction fans
• Usually used at underground carparks and multi-storey carparks where due to exhaust gases, the air is severely contaminated with carbon monoxide, nitrogen oxide and LPG. The Jet Fan is use to quickly extract the polluted air from the area.
• Supports the natural flow between the supply air and extract air zones, without ducts

Fresh Air Fan

• Supports the inflow of fresh air from the external environment into the building

Exhaust Fan

• Supports the extraction of polluted air or smoke out of the area and/ or building, usually installed with ducts

Pressurization Fan

• Supports the pressurization of staircases that does not allow for natural ventilation of purging smoke out of the stairway that is the emergency escape route for the building

Where is the Mechanical Ventilation System found?

• Car parks
• Kitchens
• Bathrooms, toilets and locker rooms
• Exit facilities
• Fire Command Centre
• Engine driven pump room
• Generator room
• Spaces involving the use of flammable and explosive substances

How BSE Can Help?

Fire Protection Specialists like BSE, MCST Managing agencies, and/ or technicians are engaged to assist Building Owners and Council Members. We provide the

• Inspection of the Mechanical Ventilation System and equipment
• Testing of Mechanical Ventilation System and equipment under fire and fault conditions
• Identification of defects for recommendation and rectification in a timely manner

Ventilation is important, and many factors can influence how well it works or if the building has the proper balance of air flow throughout especially in the event of a fire incident. Contact us today to find out how we can value-add to your existing Fire Protection Maintenance Services.

Tips On an Optimum Mechanical Ventilation System

• Ensure that TESTS are conducted based on Pressurization Systems (Code of Practice for Fire Precautions in Buildings)
• Ensure that SIGNALS from the Fire Alarm Panel can AUTOMATICALLY ACTIVATE the Fan Controller Panel to trigger the system in the event of fire
• Ensure there are NO OBSTRUCTIONS or blockages at the start and end of the duct-work or fan grille to ensure that the proper airflow path is being observed

 For consulting regarding subject matter, please contuct with us.

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 

১. এসি রিলে 

২.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

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

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

৩ রিলে নিজে নষ্ট হয়ে সার্কিট রক্ষা করে।

৪.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 ৪ পিনের হয়ে থাকে 

       *SPDT রিলে মূলত ৫পিনের হয়ে থাকে 

       *DPDT রিলে মূলত ৮ 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।