FEM 101 Past papers Q&A PDF

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July Semester 2015Question 1 A building has a centralised air-conditioning system comprising 2 chillers, A and B. Each chiller has a 300 RT cooling capacity and uses the same type of refrigerant.The chillers’ operating sequence is as follows: i. One chiller operates in the morning and one in the aft...

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July Semester 2015 Question 1 A building has a centralised air-conditioning system comprising 2 chillers, A and B. Each chiller has a 300 RT cooling capacity and uses the same type of refrigerant. The chillers’ operating sequence is as follows: i. One chiller operates in the morning and one in the afternoon to meet the cooling demand of the building. ii. From 0800hr to 1200hr (noon) - Chiller A operates and Chiller B switched off. From 1200hr to 1600hr - Chiller B operates and Chiller A switched off. From 1600hr to 0800hr – no chillers operating. An ideal refrigeration cycle is shown in Figure Q1.

Given that: Chiller A has the following parameters throughout the operation hours: P1= 0.58 P2= 0.9 H4= 97 H1= 248 H2= 266 Flow rate of the chiller refrigerant = 4.92 kg/s Chiller B has the following parameters throughout the operation hours: P1= 0.58 P2= 1 H4= 105 H1= 248 H2= 270 Flow rate of chiller refrigerant = 4.92 kg/s (1 RT is equivalent to 3.517 KW of cooling load) (a) Determine the coefficients of performance and the efficiencies of Chiller A and B in KW/RT. (6 marks)

Chiller A: coefficients of performance (COP) = (h1-h4) / (h2-h1) or Cooling Capacity (kW) / Power Input (kW) = (248-97)/ (266-248) = 8.389

Efficiency = 3.517/COP = 3.517/8.6 =0.41kW/RT Chiller B: coefficients of performance (COP) = (h1-h4) / (h2-h1) = (248-105)/ (270-248) = 6.5

Efficiency = 3.517/COP = 3.517/6.5 =0.54kW/RT (b) Determine the heat load of the building during operation hours in KW. Suppose Chiller B is now out of service and only Chiller A operates throughout from 0800hr till 1600hr. What is the increase or decrease in energy consumption in KWh per day? (13 marks) 1 RT is equivalent to 3.517 KW of cooling load Energy Consumption from 1200 to 1600hr 3.517 x 300 = 1,055.1kW Current heat load = (300RT x 0.41kW/RT x 4hrs) + (300RT x 0.54kW/RT x 4hrs) = 502.8kwh + 649.2kwh = 649.2kwh Given chiller B is down = (300RT x 0.41kw/RT x 8hr) = 1005.6kwh Increase energy consumption per day = 1005.6kwh – 649.2kwh = 356.4 kwh (c) From the list of parameters above, determine FIVE (5) operating parameters of Chiller A from 1200hr to 1600hr. Calculate the chiller refrigerant flow rate in kg/s, assuming the operational needs and heat load of the building remain unchanged when Chiller B is out of service. (6 marks) 5 Parameters as follows; 1. Sensible Cooling or Sensible Heat Gain (QS) 2. Flow Rate (Vma) 3. Specific Heat of Moist Air (Cair) 4. Density of moist air (Pair) 5. Change of Temperature (ΔT) Under standard operating condition for moist air: Density, ρair= 1.2 kg/m3 Specific heat, cair=1.025 kJ/(kg K) Qs= Vma x 1.2 x 1.025 x (TB-TA) Qs= 1.23 x Vmax (TB-TA) Vma= Volume Flow Rate [m3/s] Qs= Flow Rate x Specific Heat of moist air x Density of air x ΔT = Vma x cair x ρair x ΔT Vma= Qs / [1.2x(25-13)] =10kW/[1.2x12] = m3/s

Question 2 (a) In the fire protection system, there are two types of main riser system – dry and wet. (i) Identify the height of the building in which each of the riser system is more suited for use. (2 marks) Dry Riser – 1) any floor of has a height of more than 24 m and not more than 60m above the ground level 2) Building under “category II, III, IV, V, VI, VII and VIII purposes" of the Fire Code, having a height of more than 10m but not more than 60 m

Wet Riser - any floor more than height of 60m above ground level The following criteria are also valid in high-rise buildings: The overall height must not exceed 120m The pressure regulator is designed to control the pressure at the outlet of the hose valve to a running pressure of not more than 5.5 bar. The pressure on the inlet side of the pressure control unit does not surpass the device's opera ting pressure rating. All other system pipe fittings and equipment are assessed as not less than the maximum syst em pressure (ii) Name the key components of each type using a schematic diagram. Review the main functions and working principles of the key components. (11 marks)

Dry Riser

Wet Riser

It is required for the provision of water tank at the ground level or roof level with a minimum storage capacity of 45m 2. Water pump will continue to pump water to the specific levels so that the fire brigade can continue to fight the fire. While for dry riser, the fire brigade are able to pump water to the upper floors.

Rising Mains

1) Floor not exceeding 24m above the ground level and is within 38m from a landing valve 2)For one or a series of floors greater than 24m above ground level, 1 rising main is provided Size of Rising Mains 1) If the rising main does not exceed 45 m in habitable height and there is only one landing valve on-level, 100 mm 2) 150mm where the rising main:  more than 45m in habitable height, or  two landing valves are allow on any floor Breeching Inlets to Rising Mains 1) Inlets with instantaneous male couplings for connection to the standard hose diameter of 63.5mm of SCDF shall be connected to each rising main as follows:  2-way breeching inlet for a 100 mm bore rising main  4-way breeching inlet for a 150 mm bore rising main (b) A building is served by 2 traction lifts located side by side and the lift motor room is at the roof. (i) Determine TWO (2) major sources of heat generated by this lift system when it is in operation. (2 marks) The 2 major heat source is the equipment from the lift motor room such as: 1) Friction of the brakes

In these lifts, a gearbox is used to reduce the shaft speed and produce the required torque to start the lift car moving. Gearing allows the use of smaller, less expensive motors. However, energy is dissipated as heat caused by friction between the gear’s teeth, and churning losses in the lubricant. 2) Heat generated from Motor; (ii) To keep the temperature of the lift motor below the designated value, an extraction fan and exhaust fan are turned on to provide ventilation. If this lift system generates 3400 kcal/hr of heat, calculate the minimum design flow rate of the extraction and exhaust fan in m 3/s, to maintain the room temperature below 38°C. Assume both fans has the same capacity. According to the past 5 years’ records, the average temperature of outdoor air was 32°C during day. For the hottest months of the year, the highest outdoor temperature recorded was 36°C. (10 marks) Given that: Specific heat of air, C p,air = 1.005 kJ/kg K; Density of air, = 1.2 kg/m3 1 kcal/hr = 1.1621 W

Total number of lift = 2 Total heat of 2 lifts = 3400kcal/hr = 3400 x 1.1621w = 3951.14 Qs = Vair x Pair x Cp,air x (Tmotor room – Toutdoor) 3951.14 = Vair x 1.2 x 1.005 x (38-36) Vair = 3951.14/ 1.2 x 1.005 x 2 = 1638.12m3/s

Question 3 (a) A 6-storey residential building in Singapore is constructed on a ground level at 105.00 mRL. The building has a uniform floor to floor height of 4.0m. (i) Determine the mode of water supply to this building and review if water storage tank(s) is/ are necessary and determine the location, if required. (4 marks) Given the follow: Each Floor = 4m Building height = 4m x 6 = 24m Highest Water fitting = 105m RL + 24 = 129m RL

In accordance to CP636:2018, COP for Water Services, for height more than 125m RL but less than 137m RL, the building may use Indirect supply through high level storage tank. (ii) Illustrate with a schematic diagram, and describe the main function of THREE (3) major equipment/ components in supplying water from the PUB main to the water appliances/ fittings of the building. (8 marks) Pum p

Tank L6 L5 L4 L3 L2 L1

PUB Incoming

Booster Pump - The booster pump connected to the Tank at the roof is to provide sufficient pressure to serve the top 3 floors (i.e. 4 th, 5th & 6th). Hence, should the booster pump fails, there will be no water to the top 3 floors Water tank - The tank capacity should be size equivalent to 1 day water requirement. The bottom 3 floors are served via gravity feed from the tank at the roof and is therefore shall not be affected. Main Bulk Meter – The main bulk meter is normally installed near at the water compartment near the main incoming where it shall takes reading of the total incoming consumption to the building

(b) (i) In accordance with the code of practice on Sanitary Plumbing and Drainage System, state with reasons, the type of sanitary plumbing system for this building. With the aid of a schematic diagram, describe THREE (3) key features of the sanitary plumbing system of this residential building. (6 marks)

Fully-ventilated system. 3 features: use of ventilating pipe, appliances can be far apart hence there is no number restriction of appliances, and the use of ventilating stack. Only one main pipe is provided in this system that collects from the buildings both foul soil waste as well as unfoul waste. Directly connected to the drainage system is the main conduit. The lavatory blocks of different floors are positioned one above the other if this system is pro vided in multistorey buildings, so that the waste water discharged from the different units can be carried into short branch drains.

(ii) There is a 6-storey shopping centre nearby with the same ground level at 105.00m RL. Determine the sanitary plumbing system for this 6-storey shopping centre. Provide justification for the chosen system. With the aid of a schematic diagram, describe THREE (3) key features of the sanitary plumbing system of this building. (7 marks)

Fully Ventilated System (with Secondary Discharge Stack) - large numbers of sanitary appliances in range or where they have to be widely dispersed separate discharge & ventilating stacks

Two pipes are given in this scheme. The foul soil and lavatory waste are collected by one pip e, while the second pipe collects unfoul water from the kitchen, toilets, house washings, rain water, etc. The soil pipes (surface waste pipes) are directly connected to the drain, while the waste pipes (surface water pipes) are connected to the drain via the trapped gully. In this meth od, all the traps used are completely ventilated.

Question 4 (a) Explain the functions of a standby generator. Describe the FOUR (4) main components in the alternator. (13 marks) -SS535:2007(FormerlyCP31) Code of Practice for installation, operation, maintenance, performance and construction requirement of main failure standby generating System

The standby generator is to provide backup power supply for the essential and critical equipment within the building in the event of main power failure. E.g of critical equipment are fireman lift, data server and fire fighting system. Rotor - The rotor is a component that spins and rotates the pulley within the alternator and drives along the belt system. It functions like an electromagnet that spins. Stator - An iron ring containing multiple coils of wire wrapped around it is a stator. The portion of the stator acts as the body of the alternator, generating an electrical current when a magnetic fi eld is created. Diode - have the potential to allow current to flow readily in one direction only, stopping the flow if the direction reverses. In alternators, several diodes are positioned such that current flows from the alternator to the battery (creating DC in one direction only), but not from the battery to t he alternator. Voltage Regulator -The voltage regulator is a feature that regulates the amount of power that is supplied to the battery from the alternator. This governs the process of charging because, dependi ng on their implementations, it is constructed with different functions and work.; is an surge protector and adjust the current when necessary (b) Draw a schematic diagram of an uninterruptible power supply (UPS) and briefly explain its operation when failure occurs in the normal AC power supply. (12 marks)

The UPS is for critical load in some critical equipment (e.g. server) which cannot allow any moment of power failure. It provides continues power supply at all times. The UPS takes over immediately from the rectifier / charger to supply the inverter before the main supply returns or a stand-by generator takes over the power supply to the device. Depending on the capacity of the battery installed, the back-up time typically varies from 5 to to 30 minutes for a rated load. In the case of a short circuit or very high inrush current on the load or an internal circuit or very high inrush current on the load or an internal fault in the static power supply, the load is transfer instantaneously to the stand-by supply by means of a static switch without disrupting the load. Similarly, as soon as normal operating conditions return, the load will be switched back to static control.

Question 5 (a) You are a Facility Manager responsible for the electrical upgrading works and overseeing the electrical maintenance in a building. Demonstrate your understanding by stating the fundamental requirements for safety in the design of electrical installations for buildings as stipulated by the code of practice for electrical installations. (15 marks) In accordance to SS 638 : 2018, Code of practice for electrical installations, as a FM, integrating maintenance requirements into the design of an electrical system is an important first step to provide workplace safety. During Installation, the person responsible for such electrical installation (i.e. LEW) shall comply with requirement and authorised submission to necessary authorities. Use of a high-sensitivity residual current circuit breaker or the adoption of other safety measures/ equipment (e.g. Earthing Equipment, RCCB, ELR, etc) for such electrical installations or class of electrical installations as it may determine Ensure only authorised personnel are allow to access the premises during installation and maintenance. It is also necessary to submit the Permit to Work (PTW) and Risk Assessment (RA) before work commencement. Ensure fire fighting and Safety equipment are available in the room. Ensure all personnel are aware of the Safety Rules. Upon the completion of the upgrading work, Testing & commission for the Equipment is required.

(b) An energy audit of a building shows that electricity consumption can be reduced by having more efficient motors. The building has 3 sets of condensing water pumps and 2 sets of chilled water pumps operating continuously for 24 hours per day. The existing condensing water pumps are rated at 60 hp with an efficiency of 85% and the existing chilled water pumps are rated at 75 kW with an efficiency of 83%. If new motors with an efficiency of 90% are used, calculate the annual electricity savings, given that the electricity tariff is 20 cents per kWh. (10 marks) (Assume: 1HP = 0.7457Kw, 1 yr 365 days) 3 CWP = 60hp = 60x0.7457 = 45kw, 85% 2CHWP = 75kw, 83%75*2

Energy saving for new CWP= 45 kw x 3 pumps =135kw x 5% = 6.75kW Energy saving for new CHWP= 75 kw x 2 pumps = 150kw x 7% = 10.5kW

Annual savings= (6.75 x 24hrs x 365 x $0.20) + (10.5kW x 24hrs x 365 x $0.20) = $30,222 January Semester 2016

Question 1 As shown in Figure Q1, an eight-storey office building is to be constructed on a ground level at 101m RL (Reduced level). Every storey of the building has a uniform floor-to floor height of 4.5 metres and is designed for office/commercial use except for the roofs. The cold water supply system and the sanitary system of this building must meet the relevant Singapore code of practice and regulations. If any M&E services (e.g. water tank, etc.) are required, it can be located either on Roof A or Roof B. Some areas on any of the storey may also be used to house the M&E services. In addition, either Direct or Indirect water supply system should be used, but NOT a mixture of Direct and Indirect.

(a) With the aid of a labelled schematic diagram (entitled “Schematic 1A”), elaborate on the mode of water supply for this building. Support your answer with calculation of relevant parameters such as height etc. Describe the main functions and operations of the major equipments/components for the cold water supply system in supplying water from the PUB main to the water appliances/fittings of the building.(10 marks) (b) With the aid of a labelled schematic diagram (entitled “Schematic 1B”), elaborate on an alternative water supply system for this building. Discuss about the major differences between Schematic 1A and Schematic 1B. Describe how Schematic 1B meets the relevant codes/regulations, with calculation of relevant parameters such as height, etc. To reduce the construction cost of the cold water supply system, which design i.e. Schematic 1A or 1B should be adopted? Provide a justification for the selection. (8 marks) (c) Based on the Singapore code of practice and with the aid of a properly labelled schematic diagram, elaborate on the types of sanitary plumbing system for this building. Describe at least TWO (2) key design features of this type of sanitary plumbing system that are different from other types of sanitary plumbing system. Every storey of this building has a male and

female toilet. Each toilet has at least three water closets (WC), three wash basins and other appliances. Toilets on every storey are similar in design and location. The schematics should include the stacks, pipes, appliances and other details of at least one typical toilet (either male or female) for every storey. (7 marks) Question 2 A fire has just started on the eighth storey of a ten-storey office building in Singapore. The fire may spread to other areas if it cannot be put out in time. There are at least two fire protection systems (listed below) to protect the building from such an outbreak. For each of the system and with the aid of a labelled schematic diagram, describe the major components and sub-systems, their key system functions, main working principles, operational status during normal and fire condition (e.g. activated, ready, standby, etc.) and how they are being used to achieve the aim of fire protection. State the relationship between the related systems. (a) Automatic Fire Sprinkler System (13 marks)

In accordance to SS CP 52: 2004- COP for Automatic Sprinkler System, all buildings, other than residential buildings with habitable height of more than 24m are required to install a sprinkler system in the building. Assuming that the office building has a floor to floor height is 3m, then the habitable height = 24m/3m= 8 storey building. As most offices are more than 8 storeys high, the building will require a wet pipe sprinkler system. As seen in the diagram above, a sprinkler tank should be supplied by the main supply, in conjunction with SS 636:2018- Water services. Upon activation, water flow will be detected by the Flow Switch (FS) and send signal to the fire control panel. Duty pumps will start to pump up water from the sprinkler tank to allow the sprinkler system to continue fighting the fire. The fire brigade will also be alerted to the site to combat the fire or ensure it has been extinguished.

(b) Detectors and fire alarm system (12 marks)

Smoke detector, Heat detector, Flame detectors will send signal to the Fire alarm Panel which will trigger the alarm bell after received signal from the Call Point or fire panel. The security may check and make announcement via the PA Speaker to all occupant in the building, at the same time to the FSM and owner. The fire alarm will sound the necessary device, and will be triggered and the DECAM signal will be transmitted to the company monitoring the alarm. Upon confirmation of real fire, the fire department will be alerted and the firemen & fire engine will be activated to tackle the fire on site via Wet.Dry Riser and hydrant (if applicable). Prior to the arrival of the fire department, the building occupants or the security or CERT team or fire fighting team may assist to extinguish the fire (if possible) via the use of Fire Hosereel and/or Extinguisher.

Question 3 An equipment room operates with a constant sensible heat load daily, from 8 am to 6 pm. A unitary air-conditioning unit (Window Unit) operates from 8 am to 6 pm daily t...