2005 Building Services Higher Finalised Marking Instructions
These Marking Instructions have been prepared by Examination Teams for use by SQA Appointed Markers when marking External Course Assessments.
2005 Building Services Higher Section A 1. (a) Less pipework Reduced labour costs Drinking water available at all outlets Space saving due to omission of HWSC Any three from the above will be acceptable (b) Locating service pipe 760mm min below ground level Locating rising main away from the external wall Lagging cisterns and pipework They are lightweight Less joints Ease of jointing To remove odours To remove dust To remove moisture To reduce the ambient temperature Any three from the above will be suitable (b) Volume Extraction rate (m3/hr) = = = = = = = 8.2 x 5.4 x 3.1 137.27 m3 Vol x ACH 137.268 x 5 686.35 m3/hr 686.35 x 1000 3600 190.6 l/sec 3 3
3
(c)
2
2.
(a)
Extraction rate (l/sec)
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(c)
Stack effect ventilation is a natural ventilation system that works on the principle of natural convection caused by temperature and pressure differentials within a column (or stack) of air. When air is heated it expands, becomes less dense and therefore rises. This effect can be created using a stack (e.g. pipe, duct, etc) that can entrain air in at low level and expel it at higher levels. This method is widely used in 2 storey domestic buildings. Environment in which luminaire is located Frequency of maintenance Lamp life expectancy Frequency of cleaning Re-lamping intervals Ib is the system design current which must be less than In In is the circuit protective device which must be less than Iz Iz is the current carrying capacity of the circuit conductor
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3.
(a)
5
(b)
3
4.
(a)
(i) (ii)
local heating:- space heating with the heat source at the point of use. central heating:- space heating with the heat source remote from most rooms. Heat is distributed from the source to emitters via pipes or ducts. warm air:fast response time for heat delivery space saving in rooms (no radiators) ease of decoration no risk of water leakage or burst pipes even distribution of heat to all parts of the room space saving ease of decoration choice of electric element or water pipes
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2
(b)
(i)
2
(ii)
underfloor:-
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5.
(a)
Thermal comfort is subjective because there is no definitive value that ‘guarantees’ that each person in a room will feel comfortable simultaneously. The feeling of comfort depends upon personal variables such as clothing, activity, age and perhaps gender. Each person has their own threshold of comfort due to individual metabolisms. Thermal comfort is also dependent upon, air movement, radiant temperature, dry bulb temperature and humidity level in rooms. tc tr = = 1/ 2tr + 1/2tai
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(b)
Awtw + Actc + Aftf ------------------------------Aw + Ac + Af (60 x 18) + (24 x 19) + (24 x 17) ---------------------------------------( 60 + 24 + 24) 18oC & tai = 20oC
tr tr so, tc tc tc
= =
= = =
(1/2 x 18) + 9 19oC +
(1/2 x 20) 10 4
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Section B 6. (a) (b) see worksheet Q6(a) Water is heated instantaneously via some form of heat exchanger ie cold water enters the heater and is subjected usually to electric elements or gas burners. This provides a high level of heat exchange with the water due to the small quantity passing through the heater at any given moment in time. Hot water at normal domestic hot water temperature leaves the heater for outlets, etc. Examples are electric shower units and ‘combi’ boiler systems. (c) Room thermostats TRV’s Programmers Timers Boiler thermostats Motorised valves Any 4 from the above will be acceptable 7. (a) Ib In Iz = = = 31A 32A (from table 41B2) In ----------------Cg x Ca 32A ---------------0.73 x 0.71 61.7A 2 6 12
Iz
=
Iz
=
From Table 4D1A (column 6) @ 65A select a 10mm2 cable Check voltage drop is within limits Maximum permitted voltage drop Actual voltage drop = = 4% of 230V = 9.2V
mV/A/m x Ib x L -----------------------1000 4.4 x 31 x 21 ------------------1000 2.86V is ok as this is less than 9.2V. 10
Vc
=
Vc
=
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(b) N =
E x A ------------------F x MF x UF
E = 500 lux A = 1000m2 F = 7600 lumens MF= 0.85 LxB RI = ---------(L+B)He 40 x 25 RI = --------------(40+25)3.1 RI = 4.96
Therefore: UF = 0.7 N N = = 500 x 1000 --------------------7600 x 0.85 x 0.7 110.6 luminaires
Try 5 rows of 22 luminaires Max. spacing permitted = Room width ----------------No. of rows Room length ----------------No. of luminaries SHR x He = 1.75 x 3.1 =5.425m 25 = 5 40 = 22 5m < 5.425m so, ok.
ST
=
SL
=
1.818m < 5.425m so, ok.
NB the following arrangements will also be acceptable, however the number of luminaries needs to be increased slightly: 6 rows of 19 7 rows of 16 8 rows of 14 = = = 114 luminaires 112 luminaires 112 luminaires 5
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SL / 2 = 0.909
SL = 1.818m
ST /2 =2. 5m
ST = 5m
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8.
(a) (b)
see Worksheet Q8(a) Pipe materials Gradient (invert levels) Bedding Access provision Testing arrangements Jointing Backfill Ventilation of system NB any six from the above will be acceptable
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6 IL 98.82 Rise ---------Run 1 --------0.0246 Il 98.46 98.82 – 98.46 = ----------------- = 0.0246 14.64 = 1:40.7 4
Gradient
=
=
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9.
(a) layer Ris Rplaster Rblock Rcavity Rbrick Ros Thickness (t) 0.02 0.1 0.1 k-value (k) 0.16 0.22 0.84 t/k 0.02/0.16 0.1/0.22 0.1/0.84 Sum of resistances Target U-value = 0.35 w/m2 = 1 -----------------Target U-value 1 -----------------0.35 2.857m2oC/w 2.857 – 1.056 = Thickness of polyurethane required = = = 1.8m2oC Rshortfall x K-value 1.8 x 0.03 0.054m or 54mm 8 Resistance 0.123 0.125 0.454 0.18 0.119 0.055 1.056
Target Sum of resistances
= = Shortfall of resistances =
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(b)
(i) Qt Qf = = Qf + Qv
Σ U A ∆T =U A ∆T =U A ∆T =UA T =U A ∆T =U A ∆T =U A ∆T =U A ∆T =0.35 x 16.335 x 20 =2.2 x 8.46 x -3 =2.2 x 1.055 x 1 =0.25 x 14.76 x 20 =0.6 x 14.76 x 20 =2.8 x 1.76 x 20 =3.0 x 2.0 x 1 = = = = = = = 114.345 55.836 2.321 73.8 177.12 98.56 6 --------416.31 ---------
Qext.walls Qint.walls1 Qint.walls2 Qroof Qfloor Qwindpw Qdoor
Qf
=
416.31 watts V x Cv x N x ∆T -------------------------------3600 34.686 x (1.2 x 1000) x 1.5 x 20 -------------------------------------------3600 346.86 watts Qf 416.31 + + Qv 346.86 10
Qv
=
Qv
=
Qv Qt Qt Qt (ii)
= = = =
763.17 Watts
There are many radiators that would be suitable as the windowsill height is 0.9m from floor level and the room is large, there are few restrictions. Radiators should have an output rating of not much greater than 763.17 Watts. Suggested suitable radiators are: 960 640 1120 x x x 300mm high 450mm high 817mm high
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10
(a)
Purpose and type: - this outlines the priority of design related to detector type eg Category M – Manual system designed for no automatic control Category L – Automatic system designed to protect life Category P – Automatic system designed to protect property Zoning: - This is essential for large buildings to inform those responding to the fire alarm signal, particularly the fire service in order to locate the fire quickly. Type & Spacing: - The type of detector selected will be related to the environment in which it is located. Heat, smoke, flame and combustion gas types will be selected based upon speed of response, the nature of the hazard and to minimise false alarms. Spacing to be in accordance with BS5839-1. Testing & Maintenance: - The system should be tested every week. Regular maintenance is required; the frequency of maintenance will depend upon the type and scale of the system. Communication with emergency services: - To provide maximum benefit from the system the fire service should respond each time the alarm system operates.
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(b)
Active and passive fire control measures are required in most buildings to protect occupiers and property. Active measures are required to control fires by actively fighting fire once it has started. Active fire control equipment may be manually or automatically activated. Examples of manual equipment include manual call points, portable extinguishers, fire hoses, etc. Automatic equipment may include detectors, sounders, sprinklers, drenchers and sprays. Pressurisation and venting are also used to contain and release smoke respectively by automatic means. Passive fire control measures rely upon the design and construction to reduce the risk of fire spread and to ensure occupants of buildings are able to evacuate buildings within a short timescale. Passive design principles may be to contain fire or to provide adequate periods of fire protection to structural elements. Other examples include, the use of non-combustible materials, keeping buildings with openings a safe distance from the boundary, the use of fire doors etc. Similar descriptions of 5 measures of fire control will be acceptable.
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[END OF MARKING INSTRUCTIONS]
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