O.S.G.. The use of other methods’ of determining Maximum Demand is Not Precludedwhere Specified by the Installation Designer
FirstlyI make no Apologies for the Way am Writing on any Matters . it can be a first day Apprentice or some one Needing aJog of Memory . Sowe are all in the Same Boat . “ To Learn “
For the Apprentices . The Day we stop learning is the Day we hang Upour Tool-Bag
CookerDesign Current Calculations
Thefirst thing you have to do is get Your Head around the Calculations !!
(From a Design point of View ) 2392-10
DomesticInstallation Oven(s) & Hob(s) are to be Calculated upon their MAXIMUM LOADING Startwith a simple Calculation ( An Oven has a rating of 2kW ) 2000
(I = P/V ) Formula … I = 2000 ÷ 230V = 8.70A …. Weare Using the Unit Amps
-Controlled via a CookerSwitch with a Socket outlet .
Asa Designer . we’ll have to Apply Diversity ??
Important )- Diversity allowance to be Applied to the FULL LOAD CURRENT for CookingAppliances .
TheO.S.G. is telling us . Purpose of the Final Circuit fed from theConductors ) O.S.G.Table 1B p/97 – column (3) Cooking Appliances → At the Top of the Page Note : Type ofPremises ( 2392-10 → Household Installations ) Domestic Installation(s)
DomesticInstallation(s) Only O.S.G. - 10A + 30% f.l – Full Load ) of connected Cooking Appliances in the Excess of 10A+ 5A if a socket-outlet is incorporated in the Control Unit . ( C.C.U. ) – 45A + 13A Socket Switched with Neon .
Fromyour point of View ( The First 10A ofthe rated current plus 30% of the reminder ( Plus) 5A if the Control Unit incorporates s Socket.
Calculations)- You bank “ Hold OFF“ the first 10 Amps of the Maximum Load Current ) The10A will be used at the End of the Calculations’
-So your Work out the Total Power Rating & then calculate the Full Load Current
Calculations)- Power = ( 2 x 1 ) + ( 2 x 1.5 ) + ( 2+ 3 ) = 10kW
I= 10000 ÷ 230V = 43.48A … round it up to the first four numbers43.47826087 ( 48 ) 43.48A
Terequired Tests to be for “ Initial Verification“ New /Installation . Thetests should be carried out in a prescribed Sequence . Some prior to the Circuits being “ Energized “
Tests– Prior tothe installation being “ Energized “ Dead / Testing :6: 612.2.- Continuity of protective conductors . 612.2.2.- Continuity of rind final circuit conductors . 612.3.- Insulation résistance – ( IR ) 612.4.- Protection by SELV . PELV . or by electricalseparation 612.4.5.- Basic protection by a barrier or an enclosureprovided during erection . IP2X or IPXXB .or IP4X or IPXXD . 612.5.- Insulation résistance / impedance of floors & walls . 612.6.- Polarity . 612.7.- Earth electrode .
Testsfollowing the Installation being “ Energized “ :6: 612.9.- Protection by AutomaticDisconnection of the Supply- Earth Fault LoopImpedance . 612.10.- Additional protection ( RCDs ) 612.11.– Prospective faultcurrent . ( PFC ) 612.12.– Check of Phase sequence . 612.13.– Functional testing . – 2392-10 . LastTest to do . 612.14.– Verification of voltage drop . 2392-10- Verification of voltage drop is not normally required during Initial Verification . New / Installation .
526.1 – For every connectionbetween conductors . or between conductor & other equipment shall provide durableelectrical continuity & adequate mechanical strength & provide protection .
TheEarth Loop Impedance can be calculated before making the equipment live . by adding the ( R1 + R2 ) to the Earth Loop Impedance to the point of Supply . This would satisfy the First requirement of Regulation 14 –Electricity at Work Regulation 1989 .
“ Which Requires “ There must be good reason for thecircuits to be ( Live ) whilst work is carried out on them .
Working On or Near Live Conductors . Regulation 14 – Noperson shall be engaged in any work activity on or near any ( Live Conductor) other than one suitably covered with Insulating Material so as to preventDanger . That Danger may arise unless .
a)it is unreasonable in all the circumstances for it to be Dead . & b)it is reasonable in all the circumstances for him to be at work on or near itwhile it is Live . & c)suitable precautions ( including where necessary the provision of suitableprotective equipment ) are taken to prevent Injury.
Sanctionfor ( Live ) Functional Checking .
Thesatisfy regulation 14 – You have . Sound SafeSystem of Work Onlymake circuits ( Live ) wherenecessary . for the Testing . making sure which is Live & which isDead .
Workat a distance if possibly . Takenecessary precautions .
Sorry for nitpicking, but isn't copper is a better conductor than gold. Gold is better for using in contacts, as it is more resistant to oxidization. Silver has less resistance than copper.
Thanks for the posts, these are great for revision, and I couldn't resist but to comment, as I thought this myself before I lost the argument. lol
EarthFault Loop Impedance . will also need to be measured with the terminals’ disconnected .
To do this Live canbe a little bit awkward . To avoid the complication .The measurements of ( R1 + R2 ) are simply added to the Earth Loop Impedance ofthe Panel & NOTmeasured Live .
TheIlluminated Switched Probe accessory replacesthe RED 4mmtest lead . Itcan be used anywhere that the 4mm lead set is specified in this user guide . &it will add Extra Résistance to a Loop Test measurement . ◄◄
TheImpedance of the Earth Fault Current Loop starting & ending at the point ofEarth Fault . ThisImpedance is denoted by ( Zs ) TheEarth Fault Loop comprises the following . starting atthe point of Fault .
- Thecircuit protective conductor . - Theconsumer’s earthing terminal & earthing conductor - For. TN Systems . the metallic return path . - For. TT & IT Systems . the earth return path . -The path through the earthed neutral point of the transformer . - Thetransformer winding . - TheLine conductor from the transformer to the pointof fault .
RCCB:- Residual Current Breaker . RCBO:- Residual Current Breaker withOver-current protection .
An RCCB differs from an RCBO in thatthe RCBO will additionally respond to over-current conditions whereas the RCCBwill NOT respond to such conditions .
Apprentices : RCDs
The magnitude of thecurrent flowing to the Load will equal the magnitude ofthe current returning from the Load back to the supply . Any difference in the current flowing to the Load &returning from the Load is known as a ( Residual Current ) – Dual / Two / Line & Neutral :svengo:
RCDs– can be provided with any value of Residual Current Operating Current ( I∆n ) . 10mA: 30mA : 100mA : 300mA : 500mA : ↔ 704.4.1.1.3.2.1. :20:
30mA : isthe maximum value permissible for additional protection & 300mAis the maximum value permissible for fire protection. Non-standard values may be Used . BUT the Additional Protection & Fire must NOT beexceeded . :svengo:
General Type :- These RCDs have no specified minimum responsetime but have specified maximum response times as follows . I∆n ≤ 300mS ↔ Note:- BS-EN I∆n ≤ 40mS
S Type :- These RCDs have no specifiedminimum response times but have specified maximum response times . I∆n ≤ 130 – 500mS 5 . I∆n ≤ 50 – 150mS
Delayedresponse ( S – Type ) RCDs are commonly fitted Upstream of general type RCDsbut general type RCDs should never be fitted Upstream of Delayed Types . The “ Term “ Upstream. refers to proximity to the origin of the Installation & “ Downstream “ refersto proximity to the Load .
Maycomprise One or Two poles for use on Single-phase supplies . ( Two currentpaths ) . Three-poles for use on Three-phase supplies . ( Three-current paths ) or Four-polesfor use on Three-phase & Neutral supplies( Four-current paths )
Inspection& Testing of an installation should be completed by . A competent person
ByDefinition . RCDs :17:
A.C.current comprises of Positive & Negative half cycles with respect to a Zero reference point . & an A.C. fault current canstart to flow to Earth at any point during either half cycle . An A.C. type RCDwill only trip in response to either the Positive &Negative half cycles of the A.C. Earth faultcurrent . Whereasas ( A ) type RCDwill respond to both half cycles . As the A.C. type RCD is Blind to either the Positive & Negative halfcycles of the A.C. fault current . Thefault current could flow for up to 10mS before the RCD will see the faultcurrent .
This10mS will be added to the response time of the device . RCDtesters are usually provided with a button to enable the user to start the flowof the test current at ( 0 degrees / 180degrees ) starting on a Positive goingor a Negative going half cycle respectively .
Bystarting the testing of the RCD at both settings of the test current conductionangle . The user will be able to determine the maximum trip time of the RCD . Thiscan be done at different test current levels .
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