[AC] 問﹕Heat Pump 係乜嚟？

答﹕

簡單嚟講就係同冷氣原理相同既嘢，但一頭攞熱之餘另一頭都攞凍嚟用

攞嚟既熱相對低能，每Loop一次升5-10℃, 要Loop多幾次先做到高能既熱。

COP不俗原因係凍同熱都同時用到﹕

EMSD文件寫，COPheating有3, COPCooling有2, 即係加埋COP有5

BEEO 2018 要求 heat pump min. COP Air to Water 大概3; Water to Water 大概4.5;

Air to Water 係Evaporator嗰loop用空氣嚟降低溫度，即係空氣入完Evaporator後，以更低溫度出返嚟，從而令Condenser嗰loop加熱；

由於要Loop幾轉嚟提高水溫，所以要個儲水箱，同埋留意溫度要去到60℃以避免退伍軍人症

有啲新型啲既Heat Pump係可做到即熱效果，因為用咗唔同Refrigerant

應用例子﹕

餐廳+廚房，一頭要冷氣一頭要暖氣

Heat Pump 同 Heat Recovery Chiller 分別見 https://elvissharing.blogspot.com/2020/04/ac-innovative-environmental-friendly.html

--------------------------------------------------------------------------------------------------------------------------------

For reference only, why Why COP can be greater than 1 and smaller than 1:

QH=QC+W 

According to the first law of thermodynamics, in a reversible system we can show that Qhot=Qcold+W and W=Qhot-Qcold where Qhot is the heat transferred
to the hot reservoir and Qcold is the heat collected from the cold heat reservoir.

COP=Qc/W , 係描述緊 Output/loss 既關係

(Source: EMSD)

[EL] [FS] 問﹕Genset 設計有啲乜要留意？

答﹕

香港基本上只有FSI 要Genset, 如
Fixed fire pump intermediate booster pump Sprinkler pump Fireman’s lift Fire detection system Smoke extraction system Staircase pressurization Exit sign/ emergency lighting 斷電時1秒鐘要著發電機，15秒內全數起動消防裝置，要行到六個鐘

---------------------------------------------------------------------------------------------------------

如果油缸過500L就要入dangerous good
-人手加油 -會放近GENSET房，方便管道連接 - Sizing 係查catalogue, 會講乜嘢loading 用幾多L per hour Dangerous Goods 房有個Louver要放低位，因為嗰啲油釋放既氣體係重過空氣；裡面裝FM200 (FM200係removal of heat), Fusible links 57-63°C融斷Damper密封咗間房後先噴。Earthing / Bonding 都要做好晒因為有電荷會好易起火。

如果機底缸行唔到六個鐘就要加個Daily Services Tank 或地底有缸, 有個return pump將啲用唔晒既油返缸，由面有level senson, 如果non FSI load 掛上去後，裡面既level sensor就係用嚟檢查仲有幾多油，確保淨返落嚟既油夠FSI Load用。同埋呢啲額外油缸都會有個把手，如果發電機起火就可以一嘢拉停cut油。

詳情見﹕https://elvissharing.blogspot.com/2020/04/fs-gaseous-extinguishing-system.html

---------------------------------------------------------------------------------------------------------

發電機條煙通個牌煙位係要做submission比EPD，證明5m範圍內冇louver (Air Pollution Control (Furnaces, Ovens and Chimneys) (Installation and Alteration) Regulations)

---------------------------------------------------------------------------------------------------------

Non FSI Load 掛上 FSI Load Genset 有啲乜要留意

留意當中只係包消防Lift, 但唔包Lift Homing; 仲有好多Load那怕你係覺得好重要，冇電就會水浸既Underground潛水泵，LV Switch / Genset Room Ventilation. 如果想用FSI 隻Genset 備份，就要寫信比FSD批準。
如果要掛，呢樣嘢一定要留意，就係個ATS位置，單單JOB都癩嘢﹕ Location of ATS - if no non-FSI load was connected to the emergency generator, the ATS should be located at the main switch room. If non-FSI loads were connected to the emergency generator and the proposal has been agreed by FSD, the ATS should be located at the generator room. 用ATS切換電源個過程大概要5s

至於乜嘢係Auto Transfer Switch ATS, 詳見﹕https://lifelectrical.blogspot.com/search?q=ATS

---------------------------------------------------------------------------------------------------------

測試方面，一開始係行No Load Test, 即係冇負載下運行；之後會比個Dummy Load Test; 可參考人地個Blog: https://lifelectrical.blogspot.com/2018/03/blog-post_20.html , 睇人寫好過睇我寫。

---------------------------------------------------------------------------------------------------------

Genset Size:

- 要留意一開始個Step Load, 隻Genset起嗰下大概只有50% efficiency;

- 考慮Motor相關equipment 個Starting要乘好幾倍；

- 考慮15% Safety factor;

- 第一個Step比FSI Load 起動後由於冇咗Starting, 個Load會細返一截，再考慮埋Step 2 Non FSI Load, 就得出實際Size

Genset Size Example, 得個知字

Example 1

Lighting (FSI): 100kVA

Pump (FSI): 150kVA

如果Starting x4

Total= 100+150x4=700kVA

Genset 要逐步上，一開始只係行50% step load, 即係起動嗰下得50% efficiency

700/0.5=1400kVA

留15%safety factor, 即係1400kVA x 1.15 = 1610kVA

Example 2

乘上題

Lighting (FSI): 100kVA

Pump (FSI): 150kVA

Other pumps (non fsi): 400kVA

Step 1: 起晒FSI Load 起碼要用1610kVA (FSI)

Step 2: 但係考慮埋起Non FSI Load, 100+150+400x4=1850kVA (FSI Normal, Non FSI with Starting)

1850kVA > 1610kVA

so genset = 1850kVA x 1.15 = 2127.5kVA

---------------------------------------------------------------------------------------------------------

萬一隻舊Genset唔夠大有乜計？

- 換隻大啲既 (廢話);

- 搵多隻可以同舊嗰隻run in parallel;

---------------------------------------------------------------------------------------------------------

Genset 用4 Pole Auto Change Switch 而唔用3 pole原因

主要係萬一有返市電，兩條中性線駁通之餘個電壓有少少唔平衡的話就會引起好大電流燒咗條線，詳見 https://lifelectrical.blogspot.com/2018/03/blog-post.html

Autochange Principle: https://lifelectrical.blogspot.com/2018/03/automatic-change-over-contactor-with.html

(鳴謝﹕鼎喵, 肥喵)

[AC] 問﹕新冠肺炎啲 isolation room 隔離病房 MVAC 上有啲乜設計要留意？

答﹕

- 要啲既乾又暖既空氣比病人，惟有用冷氣櫈乾空氣啲水再加返熱
- No re-circulation of air
- 續級負壓，Corridor 零壓，到Anteroom (比醫護人員換衫嗰間)負啲，入到病房再負啲，再廁所再負啲
- Supply / Exhaust 都用High Efficiency Particulate Air (HEPA) Filter
- Flow pattern 先吹向醫生，再吹向病人，先至exhaust出街

(Source: HKIE CPD, Francis Yik)

[EL] [Renew./Inno.] 問﹕Lift / Elevator 响設計上有啲乜要留意？

答﹕

首先係揀 lift, 主要有三種

有機房Lift (Traction, 拖帶，平時最常見)

無機房Lift (Traction, 慳返間Lift機房，則師最鐘意，但要留意唔係完全冇晒，個頂一樣有啲嘢；而且慳電)

油壓Lift (Hydraulic, 特點係慢，真係好慢，高度有限制，極限幾層樓； 同時可負好重既重量，地鐵站經常見到有用到，或停車場載車)

----------------------------------------------------------------------------------------------

之後就根據Rule of thumb 大概預四、五層樓就要一部Lift

再之後就要根據CIBSE Guide D 入機進行精確啲既估算

有兩個重要概念一定要知﹕

5 mins handling capacity 五分鐘裡面，可以載走整棟大樓幾多人。如成棟樓800人, 5 mins handling capacity is 15%, 即係可載走120人。大概預 11-15%
Interval
Travelling Time=Round Trip Time/電梯數量，大概預30s

*Round Trip Time: 一部lift 由地下行完棟樓一圈再返落樓下開門既時間

仲有啲林審嘢要留意，如Car fill factor: 一部16 人Lift未必裝得滿16人，可能得14人；Builder related e.g. lift core requirements, overhead / lift pit size, travel distance etc.

----------------------------------------------------------------------------------------------

Innovative 啲既設計﹕

Hall Call Allocation - 即係電腦系統會自動派部LIFT比你

Double Deck - 一個lift car 裡面有兩層

Energy reclaim (EMSD) - Regenerate 返啲電比其他Lift, 重load向下及輕Load Counter Weight 向下個效果會明顯啲

Variable Voltage Variable Frequency VVVF - 通過同時調整Voltage & Frequency, 可以响加速及減速期間降低個Current從而達至Energy Saving.

----------------------------------------------------------------------------------------------

Lift T&C and Inspection

Safety Related:
- Over speed governors test; - Safety Break;
- Overload Test;
- Lift door mechnical interlock;

Electrical Related:
- Apparent Power, Total Harmonic Distortion 量度; - Reverse phase, Phase loss (反相，缺相) Test;

Builder Related: - 部LIFT停响最頂嗰層既時候，度 over run 距離； 記咗堆safety components, 因為實要Inspection呢堆嘢

做好晒，行完慢車(比正常慢既速度)嚟試行部LIFT，一切準備就緒，就可以入Form 5 叫EMSD班人嚟驗LIFT
成功驗LIFT後，EMSD 會出一張叫"Use Permit", 你部LIFT就可以正式使用

Fireman Lift係用FSI Genset backup; Non-fireman lift sequential homing用Non FSI Genset backup. 當然一樣可以用FSI Genset嚟backup, 咁就要比FSD批，詳見 https://elvissharing.blogspot.com/2020/03/el-fs-genset.html
Lift Supervisory System都有機會用UPS嚟頂一陣， Say 15mins.

----------------------------------------------------------------------------------------------

無機房Lift嘅Lift Shaft 風扇計算﹕

把扇有四個條件係要滿足﹕

1. 足夠MRL 個摩打嘅散熱量；

2. 把扇有兩段控速或以上；

3. 把扇可維持五度至四十度；

4. 把扇做到10ACH for machine room or machinery space at the top of the well and its associated working space for machine room-less lift;

要求1.係要滿足Lift佬；而要求2., 3., 4.係要滿足EMSD嘅Code of Practice on the Design and Construction of Lifts and Escalators, 要留意，呢本嘢係冇得免費下載，以下係部份內容嘅截圖﹕

假設Lift佬嘅摩打散熱要求係1580kcal/h, 我地首先要搵返究竟係幾多個kW, 其實只要用一啲簡單嘅字眼响google search, e.g."kcal to kW online convertor", 就可以搵到點轉，如呢個 huansuan-danwei.info , 即時知道1580kcal/h=1.84kW:

之後我地就用中學會考物理嘅E=mc△T嚟計，為咗易計啲，將條公式兩邊同時除second, 咁就變成 Q = airflow rate * specific heat of air * △T;

而density of air = mass flow rate / volume flow rate, 我地最終目的係要搵個volume flow rate出嚟，成條式reform完就變成﹕

V = Q/ (cp)(△T)(d)

V = airflow rate; (m3/s)

Q = Total heat emitted; (kW)

cp = Specific heat of Air; (1.01 kJ/kg/oK)

△T = Genset room temperature rise; (oK), 跟據EMSD CoP, 最高溫度係40, 假設吹入lift shaft散熱嘅風係由室外吹入去，跟據BEEO 2018, outdoor design temperature 係35度，即係(40-35)=5

d = Density of air (1.20 kg/m3)

V = 1.84/(1.01*1.2*5) = 0.304m^3/s

之後就要先搵個static出嚟，搵風扇也好，泵也好，Static+Flow Rate係必備。假設Lift shaft 係2.9m x 5.2m x 53.2m(H), 頂同底有兩個0.3 meter square嘅louver, 咁個static應該點計？

首先假設咗成條lift shaft係一條石屎風喉；由於條shaft太大以致唔可能由CIBSE Guide C搵到送風嘅有效面積，所以一般會以橫切面嘅方形畫到最大嘅圓形直徑嚟估算，即係2.9m. 之後我地再用google大神search "concrete duct friction loss calculator"類似字眼，就會搵到大量嘅online calculator, 就以 Good Calculators 為例子，輸入晒數據就可以發現，原來呢個風量嘅情況下，個pressure drop (or say friction loss) 係可以ignore:

再之後估算一個louver個pressure drop有幾多，一般顧問會say落去如10-50Pa; 又或者可以大概計下，都係可以用google大神search "louver pressure drop calculator" or "louver pressure catalogue": 

Air volume flow rate, louvre area等數都有(留意係入個有效面積，即係如果係一個0.3m x 1m = 0.3meter square嘅builder窿，一般係會take返0.5 efficiency, 即係0.15 meter square); 而個discharge loss coefficient 可以搵啲類似嘅catalogue攞返個數。計完之後，見到個pressure大概係17Pa, 一上一下兩個louvre即係34Pa.

最後要check埋把扇達唔達到"10ACH for machine room or machinery space at the top of the well and its associated working space for machine room-less lift"要求，一般係lift shaft overrun嘅volume除一個鐘頭嘅秒數3600, 設overrun為5m

2.9m x 5.2m x 5m x 10 / 3600 = 0.209m^3/s

0.304m^3/s > 0.209m^3/s，所以係滿足得埋條件4.所要求嘅10ACH.

之後就可以去catalogue揀風扇﹕

為咗滿足條件2.嘅要求，當然係要搵啲有兩段速以上嘅風扇。

(Source: 香港電梯資料網 hkelev.com)

[AC] 問﹕Chilled Water Distribution Loop 有幾多種類？各有乜特點？

答﹕
Type 1: Single loop, constant flow,
Pressure sensor (installed in critical part) control bypass modulating valve, temperature sensor detect changing zone load and control 2 way valve.

For old or small building, 最舊式。

隨住時代既進步，VSD 同 Chiller技術都進步咗，以前舊樓冇用VSD, 個Chiller Evaporator 又唔可以Handle variable flow, 但上述問題都隨住時代進步而解決咗。而家一loop過搞掂，用嚟改裝Type 1, 即係Type 2 係 Type 1既升級版。
Type 2: Single loop with VSD,
Variable flow, pressure sensor (installed in critical part) control VSD, temperature sensor detect changing zone load and control 2 way valve. 條bypass 同埋個modulating valve唔洗再用。

For small building

Type 3, EMSD當年出過書仔叫大家用

Type 3: Primary & Secondary Loop, primary loop constant 可以令部chiller行得更穩定，secondary loop 行VSD. Keep primary loop constant flow, only need to consider primiary loop resistance (呢個講法可能有啲舊，我見Primary Loop都有VSD, 盡量令條by-pass flow rate 同Secondary 同步，但primary side 個flow點都大過secondary, 如果唔係return chilled water就會响條by-pass度同supply chilled water mix埋。Chiller evaporator 有個最低Limit, 大機50% 細機70%); Secondary loop use VSD to achieve variable flow with 2 way modulating valve, Primary loop 唔會受Secondary loop 既 arrangement 影响。
Primary Loop Size 大過或等於Secondary Loop, 原因為如果大唔過的話有機會條decoupler反流，到時相對高溫既水又流返入個coil度個2 way valve又會開盡，做成out of control (https://www.youtube.com/watch?v=9WeRclR1X_c)

而家可以再响Secondary Loop 度加一樣叫 "Predictive System Curve Controller" 既嘢，配合VSD使用。
原理 - Air terminal 駁住個2 way valve, 如果冇用呢舊嘢，當Air terminal 冷水需求降低時，個Valve就會收緊，同時多咗水經 by-pass. 用呢舊嘢目的係要同VSD配合，儘量開大個2 way valve從而降低系統既壓力，以達到節能效果。要做pricise commisioning.

For large building and variable load


仲有種叫做Variable Primary Flow, Primary loop 有個Flow meter control bypass valve (其實同Type 2有啲乜本質上分別？除咗一個係Pressure Sensor control primary pump; 另一個係Flow Meter control bypass)

相對於Primary - Secondary, 好處包括裝少set Secondary Pump, lower initial cost; all pumps are VSD installed (P - S 組 Primary pump 係constant, 如果用量低的話就直接開泵又關泵， low load嗰陣optimize唔到pump energy). 壞處最主要係個Control複雜咗，同埋Chiller前要加isolation valve




Also reference: https://www.youtube.com/watch?v=-ahb6g3mrnE ; https://www.youtube.com/watch?v=41jRD61MW1o

----------------------------------------------------------------------------------------------------------------------

此外仲可以配合埋响個Return Water 度加個Differential Pressure Control Valve做Total Hydronic Balancing.

先講一般既water balancing. 每條Branch前都有隻Manual Balancing Valve 較水，由於chilled water去得遠啲，pressure head就會細啲，即係越近pump既branch就要較得實啲。

之後講Total Hydronic Balancing. 如果响某啲Branch度忽然個load好細，就會引致其他Branch個flow好大，咁隻控制Zone load既Modulating Control Valve就要較到好好好細，但細極有個極限，有啲類似VAV個Damper, 太細就會non linear characteristic out of control. 隻Differential Pressure Control Valve 就响呢個時候發揮作用，幫補隻Modulating Control Valve 收細個Flow, 從而比信號隻VSD令Motor減流速節能。

(鳴謝﹕Kelvin Mak)

[PD] [FS] [AC] 問﹕一組Water Pump 前後都有好多部件，分別係啲乜嚟，有乜用？

答﹕

Globe Valve: 

- 因舊嘢個樣成個波咁而得名。可用嚟調較水量，同埋由於裡面成隻碟向下座，更低leakage; 但重，Pressure Drop大，

Check Valve:

- 阻止水倒流，同二極管原理類似；上面有個鏍絲開蓋換裡面塊Disc

Pressure Guage:

- 顧名思義，攞嚟度Pressure. 原理係少量水隊上去頂住裡面隻碟再調個指針

Y-Strainer

- 啲水流過隔垃圾

Gate Valve

- 因個閘成個Gate咁款而得名。只能用嚟做開關，難以較水量。好處係平、簡單設計、Low pressure drop；但如果關唔實會有Vibration, 同埋由於塊disc插入方向，冇Globe Valve關得咁實。

Gate Valve (駁住Pressure Guage嗰個)，又叫Plug Valve, 同Ball Valve好似，外形上唔易分

- 細件，可經常開關，Low Pressure Drop. 呢類轉九十度開關既Valve相對反應快；用於相對細flow

仲有啲係上面張圖冇但係又經常用既Valve:

Butterfly Valve

- 反應快，Low Pressure Drop, 用响High flow low pressure, 

Pressure Reducing Valve

- 顧名思義，降壓用

(鳴謝﹕K; Source: https://www.youtube.com/watch?v=DVd0TW7HffU)

[Renew./Inno.] 問﹕有邊啲Solar Related system? With explain

答﹕

1. Solar hot water system

Two Types: Flat-plate Collector, Evacuated Tube Collector

Flat-plate Collector - 成本低，但重，只能提供中等熱量；
Evacuated Tube Collector - 相對貴，但較輕盈，可以供相對高熱量(60℃-80℃)
安裝時要留意唔好比第二塊個影遮到，同埋反起22度

連埋熱水爐配合使用

Solar Cooling for Absorption Chiller - 得個知字UP下，不太實用，因為要用好大面積去收集熱力嚟餵個Chiller

2. Photovoltaic

Three types: Monocrystalline, Polycrystalline, Thin-film

Monocrystalline 個efficiency 比Polycrystalline 稍高啲，大概係15%；Thin-film 最低，得7%；
當然價錢同效率係成正比。

設計﹕
D.C.輸出，要配合Inverter轉返做A.C.嚟用；有舊後備電池，有找就充電，唔夠太陽能就放電；

用呢啲再生能源，太陽能也好，風能也好，最終都要接入自己棟樓個電網Grid
EMSD出過個指引，大致如下
- 1500kVA牛只可以揹200kW 再生電源；
- 再生能源都係發電，會同供電端(即CLP/HEC)連接；
- 見下圖，如果有人打咗個ACB，諗住同電力公司切斷後就冇電到，但個再生電源端會繼續供電過嚟，咁就會好危險；
- 所以就要有個叫"Anti Islanding" 既概念，即係不論任何情況電力公司嗰邊冇電到，再生能源端都要切斷停止供電；用指示牌提示電工要兩邊電都同時切斷先可以開始做嘢；
- 响Inverter方裝isolation transformer, 避免D.C. current進入供電端 (直流電過唔到個Transformer)；
- 同時可用Power Analyzer, 只要再生電源端電源質量ok(有機有Harmonic)先接入電網；

吹水嘢﹕
可掛facade/roof, 即BIPV；
塊嘢唔乾淨會降低效率；
單塊做下樣既可配合Tracking devices (single or two axis) 使用

(鳴謝﹕紅豆; Source: EMSD, BSRIA)

[FS] 問﹕幾時需要Intermediate Booster Pump? Jockey Pump又攞嚟做乜？

答﹕

Fire Hydrant & Drencher System會用到Intermediate Booster Pump, 要one duty one standby

由個 FS inlet 至最高嗰個Drencher head / Fire Hydrant 超過60m就要用。
消防車比8bar入嚟，個Outlet要比返3.1bar出去。

Jockey Pump用嚟做乜？

JockeY pump 係比Duty pump細一級既pump, 用嚟減少隻大pump既運行。如果有人開消防嘢用水/偷水，就會用jockey pump補壓，但如果兩分鐘都補唔到壓，就會開大pump。簡單嚟講就係用隻細泵嚟保護隻大泵，等隻大泵唔洗咁容易就開。

(鳴謝﹕Jakcy Chan; Source: FSD)

[EL] 問﹕燈有啲乜種類及特點？有啲乜節能方式？

答﹕

首先搞清楚以下幾點基本概念

LED:
如果問你Lighting方面有啲乜節能方式，可以答

Luminous Flux: (光通量)

單位(Lumen)  ，描述一個光源既發光能力

 [1 lux=1lm/m2, 概念同 Density=mass/volume 一樣]

Efficacy: (發光效率)

發光效率, 單位 (lm/W)

燈膽 8-18lm/W; 光管 37-100lm/W, 明顯地光管發光效率較高

Colour Temperature: (色溫)

顏色描述，低過3300K屬暖色，3300-5300K屬中間色，5300K屬冷色

Colour Rendering: (顯色性)

用Ra, 0-100, 數值越高，越能令物件體現出其真實顏色, 鎢絲燈及卥鎢燈可去到95

Design 上，Lighting Power Density 跟EMSD BEEO; 用幾多Lux就跟CIBSE Code
for Interior Lighting

Incandescent Lamp:

即係普通鎢絲燈膽，由25W-200W。

特徵﹕Low installation and replacement cost, Excellent colour rendering, Instantanouos
on/off, Short life, Low efficacy, high heat output

Tubular Fluorescent Lamp:

原理係加熱燈絲，電子撞擊Hg蒸氣，Hg蒸氣令其發紫外線，紫外線射到管內壁螢
光物質，從而發可見光。

分T12/T10/T8/T5

Good efficacy, Broad range of colour rendering & temperature, With control gear

Compact Fluorescent Lamp:

原理同 fluorescent lamp 一樣，只不過個型狀係燈膽型燈膽頭

特徵﹕Direct replacement for incandescent lamp, Control gear integral in the lamp,
relative high initial cost, less efficiency than tubular

Sodium Lamp:
External lighting, Highest efficacy, Long Lift, Poor colour rendering

High Pressure Mercury Lamp:
Replaced by high pressure sodium and metal halide lamp, 冇乜點用，得個知字

Metal Halide Lamp:
Good efficacy, Good colour rendering, Long life, floodlight, long start up and
restrike time, 由於colour rendering好，所以响啲精緻裝飾地方會用

LED:

High efficacy, instant light, fitted into existing lighting fittings, various colour temperature,
low voltage supply, long life, realiable, colour rendering都好
隨住LED起嚟越平，用電少散熱少效率高應用又廣泛，將會對比其他種類既燈有
絕對優勢，會取代幾乎所有燈﹕

Lighting Energy Saving Strategies有下列幾種
- Digital & Addressable Lighting Interface (DALI): 簡單嚟講即係CCMS;
- Occupancy Sensor: 冇人郁就算動熄燈；
- Photocell Sensor: 放近窗邊，夠光就自動關啲燈；

- Task Lighting, 即係大環境放少啲燈，但跟據辦公室佈置每位比啲localized啲既燈；

- T5管或Electronic Ballast, 相對Low既答法，因為都已面臨全面淘汰；
- Astronomical Time Switch - 自動決定某啲燈如Landscape Lighting幾時開，配合埋
Photocell Sensor用

-------------------------------------------------------------------------------------------------------------------

Emergency Lighting
當冇咗燈嗰陣，照住成條exit route.
紅皮書要求Escape Route 1 Lux, Staircase 1 lux;
一冧Normal電就要五秒之內起動到，發電機冇可能咁快起到，所以要自己揹舊
Central Battery, 呢舊電起碼要頂到30mins直到發電機著

Exit Sign
min. 2 hours

---------------------------------------------------------------------------------------------------------------

Lumen Method

N = number of lamps required.

E = illuminance level required (lux)

A = area at working plane height (m2)

F = average luminous flux from each lamp (lm)

UF = utilisation factor, an allowance for the light distribution of the luminaire

          and the room surfaces.

MF = maintenance factor, an allowance for reduced light output because of

deterioration and dirt.

---------------------------------------------------------------------------------------------------------------

Also reference: Football Field / Stadium Lighting Design

鳴謝﹕Ir.理查德