***Cont../ Useful Information for Electricians & Apprentices***

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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


2392-10/ Domestic Installation Oven(s)

Ovenhas 4 Rings ( 2 x 1kW ) & ( 2 x 1.5kW ) & Grill ( 2kW ) & Oven (3kW )

-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

UsingDiversity allowance stated ↑↑ ( 43.48A sub 10A = 33.48A )

I= 33.48 x 30 ÷ 100 = 10.04A

Youradding the ( 5A ) for Socket outlet . I = 10A + 10.04 + 5A = 25.04A )- Asa Designer this is your Expected Current Demand .

Remember )- Supply Cables Rated to suit DesignCurrent ( Iz )

 

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□ Safe Working Procedure .

Regulation 12 . of the Electricity at Work Regulations1989 . deals with means of cutting off the supply & for isolation .

- cutting off the supply of electrical energy to anyelectrical equipment . &
- the isolation of electrical equipment .

Regulation - 611.1.1. . Reminds us. “ States “ that inspection shall precede testing &shall normally be done with that part of the installation under inspectiondisconnected from the supply .

 

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Reading the latest examiners report of the 2391-10 exam. States that candidates lost marks for not putting down that Insulationrésistance ohmmeters need leads to GS-38 .

Before you lose an all important mark for using yourcommon sense .
GN-3 . p/81. 4.1. Instrument Standard .

GN-3 : By it’s Own Admission . it is Notcompulsory or statutory .

Reference was made to the use of test leads whichconform to HSE Guidance Note GS-38 . should be observed for ALL instruments .leads . probes & accessories . it should be NOTED that some test instrumentmanufacturers advise that their instruments be used in conjunction with ( Fused Test Leads &Probes )

Other manufactures advise the use of Non-fused leads . & probes when the instrument has ( in-built electrical protection )

2391-10 . Forthe Sake of -&-s.
GN-3 / GS-38 : BUT “ itshould be NOTED that such electrical protection does NOT extend to the PROBES & LEADS . Why looseMarks . GS-38Leads .


Am waiting for my GN-3 / 2012 . it does not get published until 2April .

 

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“ Initial Verification “

( R[SUP]1[/SUP] + R[SUP]2 [/SUP] ) isrequired on a NEW INSTALLATION because you should NOTenergise without ascertaining that the installation is safe to do so .

NEW WORK “Initial Verification “ 2392-10 : to comply with BS-7671:2012 .

“ Initial Verification “ is to be completed for any NEW WORK &Alterations & Additions .
The purpose being to ensure that the equipment &accessories are to a relevant standard . the installation complies withBS-7671:2011 & that it safe .

The responsibility for comparing Inspection & Testing results with relevant criteria / lieswith the Inspector .

 

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The purpose of this “ Condition Report “ is toconfirm .

Section E . summary of the condition of the Installation . p/396

C1 : ( Danger present ) the safety of thoseusing the installation is at risk . p/399 ( 7 )
The Report should identifyany damage . deterioration . defects & / or conditions which may give riseto danger .

C2 : ( Potentially dangerous ) the safety of thoseusing the installation may be at risk .
It is recommended that acompetent person undertakes the necessary remedial work as a matter of urgency.

Section F . Recommendations . p/399 . ( 10 )

For safety reasons . the electrical installation shouldbe re-inspected at appropriate intervals by a competent person . therecommended date by which the nextinspection is due is stated in Section F . ofthe Report under “ Recommendations “ & on a label near to the Consumer Unit / Distribution board .

Section F p/396 . Subject to the necessary remedial action being taken . I / we recommendthat the installation is further inspected & tested by ……….. date ….

 

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State :
Apart from loose connections. Three . circumstances that would result in an increase in conductorrésistance .
i) Increase in ambient temperature .
ii) Increase circuit length /additions .
iii) Decrease conductor cross-section / modifications .

“ Insulation Résistance “

• for the Insulation Résistance Test on a 230Vinstallation
State the :
a) test voltage to be applied .
b) minimum value of résistance acceptable .
c) Value below which further investigation isrequired .

for the Insulation RésistanceTest on a 230V installation .
a) 500V .
b) 1.0MΩ
c) 2MΩ

State : the effects onInsulation Résistance of an installation if .

i) Additional circuits are added )- Decreases .
ii) Circuits weredisconnected / removed )- Increases
iii) The length of a 10A lighting circuit wasextended )- Decreases.

 

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2011: BS-4444: 1989 ( 1995 ) p/278.

This may come up on the 2012. -&-s . Hospitals’ / Earthing. Yeah .

Guide to Electrical Earth Monitoring.

□ Q)- Explains the principles involved in thedesign & construction of earth monitoring devices . & the prerequisitesfor their successful application .
Which of the following has an impact upon earthing . ?? [ BS-4444 ] :mad2:

543.3.4.
543.7.1. 102 (iii)
543.7.1. 103 (iv)

 

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Apprentices .

To make you use the Regulations . BS-7671:2011 . [ -&-s Open Book ]

Q) -&-s . A radial circuit . wired in 2.5mm[SUP]2[/SUP] T&E insulated & sheathed cable protected by20A overcurrent protective device . may feed any number of sockets . provided the totalfloor area does not exceed . [ 50m[SUP]2[/SUP] ] p/426

Q) -&-s . A ring final circuit . wiredin 2.5mm[SUP]2[/SUP] T&E insulated & sheathed cable protected by 30AOr 32A overcurrent protective device . may feed any number of sockets . provided the totalfloor area does not exceed . [ 100m[SUP]2[/SUP] ] p/425

p/425 : (iv) Takingaccount of the floor area being served ( Historically ) a limit of 100m[SUP]2[/SUP] has been adopted .

□ A visual inspection of a new installation mustbe carried out . When !. During erection . beforetesting & upon completion.

□ The testrequired by the regulations to ascertain that circuit protective conductors arereliably & correctly connected is . Continuity of CPCs . 612.2.1.

□ Equipment which displays the BSI kite mark .
A) Has beenproduced under a system of supervision & control by a manufactures holding a license .

□ Electrical equipment must always .
A) Conform toa BS – Or BS-EN standard .

□ The CE mark .
Is an indication that the product meets the legalsafety requirements of the European commission .

 

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Insulation Résistance Testing to Earth .

p/38 : For the sake off GN-3 : Althoughan insulation résistance value of not less than 1.0MΩ complies with the Regulations . ◄◄
GN-3 : Where an insulation résistanceof less than 2MΩ is recorded the possibility of a latentdefect exists . ◄◄ . Exams 2391-10

Regulations Note 2 table 61 : insulation résistance values are usually much higher thatthose of Table 61 .

□ When testing a 230V installation . an insulation résistance tester must supply a voltage of ! . 500V D.C.
□ The value of a satisfactory insulation résistance test oneach final circuit of a 230V installation must be ! . Notless than 1.0MΩ .
□ The value of a satisfactory insulation résistance test ona SELV circuit must be ! . Not less than 0.5MΩ .

□ The maximum recommended periodic inspection &test interval for a Domestic Installation is !
P/63 - GN-3: Domestic . Maximum period betweenInspections & Testing as necessary . : A)- Changeof occupancy / 10 years

 

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□ The IET WiringRegulations ( BS-7671:2008:2011 ) are recognized as . [ being in compliancewith statutory regulations ]
□ The legislationwhich prohibits live working exceptional circumstances is . [ Electricity at Work Regulation 1989 ]
□ When calculationsshow that the voltage drop between the supply terminals & a heating loadwill exceed 5% of the supply voltage . the action to be taken is to .
[ increase the size of the cable supplying the load ]
□ To comply withIET Wiring Regulations the voltage drop on a three-phase 400V powercircuit should not exceed . [ 20V ]
□ A componentdesigned to disconnect a supply under full load conditionsis . [ A switch]

 

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TT- system . The CPC still needs to carry the [ PFC ] current for a fraction of a secondrequired for the RCD to operate .
TT- system . in order to comply with the 17[SUP]th[/SUP] Editionwhere Addition Protection is required this needs to be provided by a 30mA RCDor RCBO .

TT- system .

Discrimination . Ability of aprotective device to operate in preference to another protective device inSERIES . “ Example “

Time delayed 100A / 100mA . RCD .
Opposed to the Normal 100A / 100mA RCD .

if you used the Non-time delayed RCD & your [ 30mA – RCD ] tripped you could loseboth RCDs protected circuits due to there being NO discrimination between the RCDs.

Time-delayed RCD only the [ 30mA– RCD ] wouldtrip . “ Wehave Discrimination BS-7671:2011 “ :juggle2:

 

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TT- system . 30mA / RCD(s) O.S.G. – P/16

If ALL finalcircuits have RCD protection within a Dwelling that has a TT-system . Then NO additional RCDdevice would be required at the Main Intake .

OR ON A Dual board containing two 30mA / RCDs

 

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Regulation& it’s Implications’ .

Table55.1 . p/174. Low voltage circuits .

Q). Plugs & socket – outlets ( Industrialtype ) 16 . 32 . 63 . 125 . BS-EN-60309-2 .
ExtensionCable . should be evaluated to make sure it is suitable for use in theEnvironment where it is intended for Use .

Example – Portable / Mobile Equipment [ On wheels] will be disconnected form the supplywhen not in Use . BS-EN-60309-2 .

725.55.2.6. “ Example “
Themeans of connection to the caravan pitch socket-outlet shall be supplied withthe caravan & shall comprise the following .
(i) A plug complying with BS-EN-60309-2 .

 

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BS-7671:2008:2011 . Requirements for Electrical Installations .
Definesthe [ WiringStandards for the UK ] Installationsto this standard are regarded [ AS ] giving conformitywith the relevant parts of Electricityat Work Regulations 1989 . Whilst theiruse is not [ Mandatory ] Electricity supply Authorities may refuse toconnect an installation [ NOT ] conforming to this standard .

Thisstandard requires the use of { RCDs ] inassociation with main extensions leads as follows .
Theuse of RCDs under Normaluse & Outdoors .

Regulation. 411.3.3. .
States)- In a.c. systems . additionalprotection by means of an [ RCD ] in accordancewith Regulation 415.2. shall provide for :
i) Socket – outlets with a rated current notexceeding 20A that are for use by Ordinary Persons . & are intended forgeneral use . &
ii) Mobile equipment with a current ratingNot exceeding 32A for use Outdoors .

RCDs. are required as Additional Protection . ( ADS)
Regulation. 415.1.1. . States

Theuse of [ RCDs ] with a rated residual operating current [IΔn ] not exceeding 30mA & an operating time not exceeding 40mS at the rated residual operating currentof 5 x IΔn . is recognised in a.c. system s

Asadditional protection in the event of failure of the provision for basic .protection &/or the provision for fault protection or carelessness by User.

Theuse of an [ RCD ] does not prevent the need forother means of protection . such as suitable earthing .

Regulation. 415.1.2. . States .
Theuse of [ RCDs ] is not recognised as a solemeans of protection & does not obviate the need to apply one of theprotective measures specified in Section – 411to 414 .

Overcurrentdevice MCB . & RCD must be used .

Thisis to ensure that the automatic disconnection of the supply will occur within aspecified time [ 0.4 – 230V . Open Circuit ] supply for socket-outlets which supply [ Mobile Equipment ] intended for manual movement whilst in use or handheld Class 1 equipment .

Regulation. 411.3.2.2. – Table 41.1.requires maximum disconnection time for a TT- system earth system . 0.2s

Toensue that these conditions are Met any purchased equipment should be of such constructionto meet all the conditions in which it May Be Used.

 

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Q)Which of the following determines whether the selected protective devices willoperate within the required time frame : A) value of earth faultloop impedance [Zs]
takeyour pick . 41.3. MCB / BS-EN-60898 . RCBO / BS-EN-61009-1

The current ratingsof cables given in the tables of the IET Wiring Regulations are based on an Ambient temperature of : [ Unless stated Otherwiseon Exams ]
50 deg C.
40 deg C.
30 degC.
20 deg C.

 

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It’shere to Stay [ SPD ] 2012

Section 443 – Simple Risk Assessment ]

Thefollowing are different consequential levels of protection:

(i) . Consequences relatedto human life, e.g. safety services, medicalequipment in hospitals
(ii). Consequences relatedto public services, e.g. loss of public services, IT centres, museums
(iii). Consequences to commercial or industry activity,e.g. hotels, banks, industries, commercial markets,farms
(iv) . Consequences togroups of individuals, e.g. large residential buildings, churches, offices,schools
(v) . Consequences to individuals, e.g. small ormedium residential buildings, small offices.

For levels of consequences(i) to (iii) protectionagainst overvoltage shall be provided.

IsProtection Required – Section 443 / BS- EN -62305

( Yes ) - Risk of direct lighting to or near structure .BS-EN-62305 : or Lighting protection system installed . ? 443.1.1.
□ Lightning current [ Type 1 SPD ] or combined [ Type 1 + 2 SPD ] on main switch board to prevent dangerous flashover ( 534.2.1 )

Overheadline supplying the building at risk of direct strike – see BS EN-62305 (443.1.1)

( Yes ) - Overheadline supplying the building at risk of direct strike : BS-EN-62305 . 443.1.1.
[ Alternativesimplified risk assessment: 443.2.4. ]

Installation presents higher risk (e.g. fire) or requires higherreliability (443.2.2 Note) - see BS EN-62305
[ Alternativesimplified risk assessment: 443.2.4. ]

□ Protection against overvoltages not required ( 443.2.1, : 443.2.2 ) if equipment impulse withstand voltage toTable 44.3
Installationpresents higher risk (e.g. fire) or requires higher reliability ( 443.2.2Note ) - see BS EN-62305

Consequences related to human life? For example safety/medical equipment (443.2.4)
[ simplifiedrisk assessment : 443.2.4. ]

Coordinatedset of overvoltage SPDs for equipment protection e.g. Type 2 or Type 2+ 3 for distribution boards feeding sensitiveelectronic equipment (534.2.6)

□ Protection against overvoltages not required if equipment withstandvoltage to Table 44.3

Consequencesrelating to groups of individuals or individuals - for example residential buildings (443.2.4)

Consequencesrelated to loss of public service ? For example IT centres, museums (443.2.4)

Consequences related to loss of commercial/industry activity? For example hotels, banks, farms (443.2.4)

□ Check if data, signal and telecom lines require protection (443.1.1, 534.2.1)