之前講過入中電攞牛要入COP 215份Loading Estimation, 但其實入之前係顧問角度已經應該有份再Detail d既Electrical Loading Estimation. 因爲通常積師開積既時候, 已經要同佢講大約要幾多隻牛, 原因係唔同數量既牛間Transformer Room個Size都唔同, 佢要知道個數量先可以大概預個牛房位比你. 呢份Loading, 其實亦係一單Project派電既命脈, 做得到呢份Loading而又可以based on 呢份Loading畫到一份Schematic, 其實已經佔左成個Electrical design既一半.
其實呢份表要解釋就好簡單, 就係集合曬成單Project所有要用電既Equipment既Electrical Loading, 再Based on 大制房位置/座數等等去分牛派電. 擧個例子, 一個公屋Development有6棟公屋, 我就會計每一棟公屋既用電量, 然之後再睇個每一棟既總用電量, 再去睇要用幾多隻牛. For example, Block A 要2300 kVA, 我就會比2隻1500kVA牛比Block A (Housing好似最大剩係比用1500kVA牛, 有錯請更正), 如此類推.
咁要點計個總用電量?就係睇翻個棟Building有咩用電既Equipment, 以下係例子:
1. Lift/Escalator
2. Sump Pump/Wastewater pump/Submersible Pump/Sewage Sump Pump…等等有關Drainage既Pump
3. Potable Water Upfeed/Booster Pump…等等食水鹹水Pump
4. Street Fire Hydrant Pump/Sprinkler Pump…等等消防街龍頭/消防水Pump
5. Lighting & Power/External Lighting
6. IT Equipment
7. AHU/PAU/VAV/Chiller/CRAC unit/Carpark Jet Fan…等等冷氣Equipment
8. Gondola(吊船)/EV Charging..等等
通常會有份Excel表, List曬呢D Equipment既Loading, Power Factor, Diversity Factor, 等等既Information. 之後就加曬d loading, 就係咁簡單咋,下面比個Example比大家睇睇:
呢份係我其中一單Project入面既冷氣Equipment, 比大家睇睇Loading表既Format…
Diversity Factor
通常你就咁加曬d loading係會發現一定爆牛, 姐係人地平時一棟Building用1.5隻牛, 你呢家可能用緊3隻牛. 原因係D Load 要take一個Diversity factor (d.f.). 咩係d.f?試諗下, 如果一個Residential building有400伙, 你Design既時候會唔會預400伙同時間開曬全屋冷氣仲要較到最大?理論上就唔會, 所以我地做Design既時候, Consultant就會比一個合理既Diversity比個Load, 去預實際既用電量. 如果做開ArchSD project, 佢會容許你本身係load take完diversity factor, 再係牛既overall再take diversity factor.
因爲無Guideline/Standard去話你聽唔同既Loading應該要Take幾多Diversity(EMSD有個Reference, 不過係for <400A既裝置), 所以我地都係Based on project reference同平時用開既數去take. 至於Power factor, 通常就係睇Catalogue, 入面通常有寫個Equipment既Power factor係幾大.
Take曬diversity後, 份Loading基本上就已經完成, 之後你就可以諗d電點派: 例如大制房係邊, 跟住有幾多條Riser係要走上去上面, d Riser行咩Cable type (Busduct, Armoured Cable, Prefabricated Cable), d制要幾大, Cable行幾遠. 呢D information好重要, 因爲之後個一部就係做Cable Sizing, 去Size翻你條Cable要幾大.
有曬上面呢d information, 你就可以正正式式畫一份Electrical Schematic, 呢份野就係成單Project派電既命脈.
講住咁多先~有時間先再講下Cable Sizing/Schematic Design
bs student
多謝你分享，有兩個問題想請教下…
（1）上面計loading個excel list係根據equipment quantity去計。但前排我學校教design嗰陣比咗份consultant data都係計loading，但係佢係根據KW/m^2嚟計。係咪即係唔同firm有唔同做法？定係有其他specific原因？
（2）睇咗COP215-4.3：To compare the assessed load with applicant’s declared load in 4.1 and 4.2 and check the variance between the two parties’ load estimates. The load estimates are considered acceptable if （1）The load estimates from the applicant is greater than those from the planning engineer, or （2）The variance does not affect the overall distribution transformer room requirements. 呢度係咪就係compare緊你講嘅consultant份list 同 cop215 ADMD list？即係話如果consultant份list個數大過ADMD list個數 或者 ADMD list個數唔係大consultant list個數太多令到要裝多隻牛，咁就acceptable？
AC
(1) – 可能你計個個係講緊based on一個area既Loading, 咁你就會用kW/m2去計. 舉個例子, 如果一個Office area係500m2, 你點去計Office既Lighting & Power Load?呢d情況就用kW/m2去estimate. 其實我個單Project都要計到Office area, 係張圖無show到咁解. 所以可能你個Example係全部Loading都係要用Area去Estimate, 所以咪全部kW/m2…但如果你係做Loading Estimation既時候已經知道某D Equipment Load, 咁你一定係攞個Equipment Load去計.
(2) – 據我所知, Consultant係唔會入自己份Loading比CLP, 只會入CLP自己出個份215. 而CLP係收到你份215之前, 或多或少都已經做左個基本既Estimation, 估算左你棟野大概會用幾大Load. 所以你quote個句CLP應該係想講, 你入既215應該係要大過佢地自己内部估既Load, 同埋你要既牛數量唔可以影響到佢地個Planning, 同Consultant自己本身份Loading應該無關係. Consultant主要係要Make sure佢地攞夠牛就得.