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MASTER DOMESTIC GAS STUDY > GENERAL GAS QUESTIONS > Flashcards

GENERAL GAS QUESTIONS Flashcards

1
Q

what is the relative density of natural gas in air

A

0.6 (lighter than air)

Relative density is a comparison between 2 similar substances, in this case gas compared to air

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2
Q

what is the gross accepted average CV calorific Value of Natural Gas

A

38.76Mj/m3 metric

is the average accepted calorific value for Natural (Mains) or 1040Btu/ft3 imperial (gross

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3
Q

what are the lower flammability limits for gas in air

A

5-15%

Natural gas has a flammability range of approximately 5 to 15 %.

That means that any mixture containing less than 5 percent or greater than 15 percent natural gas to air would not support combustion.

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4
Q

what is the flame speed of Natural Gas in meters per second

A

0.36 Meters per second

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5
Q

what are the 3 family gases

A

Man Made Gas (coal)

Natural Gas (methane)

LPG (Liquefied petroleum gas - propane, butane, and propylene)

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6
Q

how do you work out the wobbe number

A

you divide the CV Calorific Value by the square route of the RD Relative Density of Natural Gas

RD:- 0.68kg/Sm3

CV:- Natural Gas 38.76 M1/m3 (gross) or 1040 btu/ft3

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7
Q

if you have 1m3 of Methane (Natural Gas)

how many meters cubed of oxygen will you require for complete combustion

A

2m3 of oxygen to make complete combustion

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8
Q

if you have 1m3 of Natural Gas (methane)

how any m3 of air will you require for complete combustion

A

10m3 of air

because 80% of air is Nitrogen an roughly 20% is oxygen

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9
Q

when flue gas analysing a fluless space heater what is your co/co2
ratio which you CANNOT exceed

A

0.001

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10
Q

when analysing a gas cooker, in the first 20minutes what is the maximum co levels the cooker can reach

A

90 parts per million of co

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11
Q

when was the gas safety installation and use regulations amended

A

2018

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12
Q

in what documents would you find the procedure for carrying out a tightness test in a domestic dwelling

A

IGE up 1b

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13
Q

what does BS 6891 cover

A

pipework up to 35mm copper or steel to inch and a quarter

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14
Q

in the gas safety and use regs what is regulation 36

A

landlord responsibilities

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15
Q

in the gas safety and use regs, what does regulation 26 paragraph 9 cover

A

that is what we have to do to examine appliances after we have worked on them

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16
Q

when you are taking working pressure at the meter, what is the range of figures that you are looking for to say it is the correct working pressure at the meter

A

21mbr + or - 2 mbs

so 19-23mbrs

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17
Q

what can be the maximum pressure loss across a working system

A

1mbr between meter and appliance

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18
Q

what is the maximum clipping spacing for a 35mm pipe running horizontily

A

2.5m between clips

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19
Q

what are the 3 main purposes of sleeving a gas pipe going through a wall

A

protect against

movement
gas leaking into cavity
corrosion due to chemical reaction

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20
Q

when drilling joist what is the minimum distance between the holes you can have

A

3 x the diameter of the hole you made

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21
Q

what is the maximum pipe volume where a domestic gas engineer can work on it

A

0.035m3

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22
Q

what is the maximum through port a meter can do for a domestic gas engineer to be able to work on it

(what is the largest meter a domestic gas engineer can work on)

A

60m3 hr

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23
Q

over what volume must the gas be continually ignited

A

0.02m3

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24
Q

1kw of input on an appliance requires how many m3 of gas

A

0.095m3

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25
Q

when pipe sizing what is the equivalent in straight length of pipe for a

35mm 90degree copper elbow

A

1m

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26
Q

what size (amp) fuse should be protecting a boiler

A

3amp

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27
Q

What is a wobbe number

A

Wobbe is used to compare the combustion energy output of different composition fuel gases in an appliance (fire, cooker etc.).

If two fuels have identical Wobbe Indices then for given pressure and valve settings the energy output will also be identical.

Typically variations of up to 5% are allowed as these would not be noticeable to the consumer.

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28
Q

If medium pressure pipe work enters the building through the back of a meter box, how would this be classed

A

AR

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29
Q

Where a gas pipe runs under the foundations of a building this can only be done if

A

Adequate steps have been taken to protect the pipe from movement & corrosion

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30
Q

All ventilation grills require a warning notice when

A

Installed in a compartment

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31
Q

The permissible movement on a digital manometor to 2 decimal places is

A

0.25

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32
Q

The industry standards for testing pipe work over 35mm & exceeding 0.035m3 is found in what documentation

A

IGE/UP 1 or IGE/UP 1A

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33
Q

A flue outlet of a combination boiler when facing a boundary shall be at least how far away

A

600mm

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34
Q

A plume management kit on a flue must terminate in what location to the air inlet of the same flue

A

Must terminate in the same pressure zone

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35
Q

what is the maximum spacing of supports on a horizontal 22mm copper pipe

A

2.0m

36
Q

When a gas pipe is run inside a duct, the duct must be what

A

Vented at the top & bottom

37
Q

When can a gas cooker grill on initial ignition exceed 10ppm co for a short period of time

A

If it conforms to BS 7967 part 2 & manufacturers instructions

38
Q

At which levels of co/co2 ratio must you take action on a flueless water heater

A

When co/co2 ratio exceeds 0.02

39
Q

If no manufacturer’s instructions are available, what is the minimum distance a non-condensing boiler can be installed to combustible material in a cupboard

A

75mm

40
Q

If no manufacturers instructions are available what is the minimum clearance between a fluless instantaneous water heater & a ceiling

A

300mm

41
Q

A natural gas cooker is installed in a kitchen with a volume of 7m3 how much ventilation is required for the room

A

50cm2

42
Q

Chimneys used for an inset live fuel effect fire normally requires a minimum size across its axis of

A

125mm

43
Q

When installing a gas free standing heating stove into a builders opening the flue must project how far through the register plate

A

150mm

44
Q

What is the minimum void volume of an unlined masonry chimney with a gas fire fitted with a flue kit

A

12 dm3

45
Q

From November 2006 co detectors must conform to

A

BS EN 50291

46
Q

Currently standards categories an SE duct with which letters & numbers

A

C21

47
Q

how far from electrics should a gas pipe be

A

25mm

48
Q

what is the maximum KW gross an open flued gas fire can be when installed in a bedroom with an ASD fitted

A

14KW gross

49
Q

what does the acronym RIDDOR stand for

A

Report of Injuries & Diseases Dangerous Occurrences Regulations

50
Q

under IGEM G11 how would you categorise an ECV that is letting by with obviously no smell of gas

A

AR

51
Q

what is the maximum in days that a landlord must give their tenant the gas safety certificate

A

28 days

52
Q

what building regulation covers ventilation

A

F (for ventilation)

53
Q

a boilers electrical supply can only be fed by a fused spur,

TRUE or FALSE

A

FALSE it can be plugger but socket must be in an unswitched socket

(would be not to current standards if plugged into switched socket)

54
Q

no perceptible movement when using a U gage is

A

0.25mbrs

55
Q

what is the minimum flow rate through a gas meter when checking the regulator is working correctly

A

0.5m3 an hr

56
Q

what is the maximum absorption rate of a gas meter in mbrs

A

4mbrs

57
Q

how many BTU’s British thermal units are there in 1 KW

A

3412

58
Q

when flue gas analysing a flueless fire or flued water heater what’s the maximum ratio

A

0.02

59
Q

after November 2006 what must the EN number be on a CO detector

A

EN 50291

60
Q

with the concentration levels of 300 PPM of CO,

what is the maximum time the alarm must activate

A

3 minutes

61
Q

what BS number must copper pressfit fittings comply with

A

BS 8537

62
Q

what does PTFE stand for

A

Polytetrafluoroethylene (PTFE)

63
Q

what is the maximum clipping distance of a 15mm gas pipe run vertically

A

2m

64
Q

TRUE or FALSE

a wooden joist must not be notched if the joist is less than 100mm deep & the notch in the joist is no more than 250mm

A

TRUE

65
Q

if a pipe duct or shaft is between 0.01 & 0.05 m2 what must be the cross sectional area of the vents High & Low

A

they must be at least the cross sectional area of the duct

66
Q

what is the average o2 reading in outside air

A

20.9% oxygen

67
Q 
the current standards categorise flue systems with letters and number,
what letters are used for:-
flueless:-              type ?
open flued:-         type ?
room sealed:-      type ?
A

flueless:- type A
open flued:- type B
room sealed:- type C

68
Q

what are the standard ventilation requirements for a DFE fire under 20KW

A

100cm2

69
Q

when installing a vent for a flueless space heater how far away should the vent be from the flueless space heater AND why

A

1m because if they are too close then they can allow the ASD to stay on by feeding it air even when the room has become vitiated

70
Q

what is the minimum cross sectional area of the equipotential bonding at a gas meter

A

10mm2

71
Q

a flue duct outlet when facing a boundary has to be how far away

A

600mm

72
Q

when using a plume management kit, how far away does the air inlet need to be from an opening in a building

A

150mm

73
Q

according to IGEM unsafe situations how would you categorise a room sealed appliance failing its flue gas analyser reading

A

AR

74
Q

what is the minimum void volume for a unlined masonry chimney with a gas fire connected ? dm3

A

12 dm3

75
Q

when purging a G4 gas meter with pipework less than 28mm, your 1st reading on you gas meter is 1.111.

what will the reading be when the purge is completed and why

A

1.121dm3 because you must pass 10dm3 of gas to purge

76
Q

purge volume is how many times the installation volume

A

1.5 times the size of installation volume

77
Q

OF floor standing boiler of 10kw net installed in a room

what ventilation requirements are needed

A

15cm2 because 10 - 7 (adventitious air) = 3 * 5 = 15cm2

78
Q

flueless space heater 2.5kw net in a room of 45w per meter3

what size ventilation is required

A

100cm2 as the standard ventilation because its less than 2.6kw net

79
Q

10kw net DFE installed in a living room

what size ventilation is required

A

100cm2 because this is the standard up to 20kw net

80
Q

RS condensing boiler 24kw net in a bedroom

what ventilation is required

A

no ventilation required because it is RS

81
Q

10kw net cooker in a kitchen of 9m3 with an openable window

what if any ventilation is required

A

50cm2

82
Q

flueless space heater 6.4kw net installed in an internal space of 90w per meters 3

what if any ventilation is required

A

127.5cm2 is required

83
Q

6.9kw net OF radiant space heater in a room of 30m3

what if any ventilation is required

A

no vent required

because it is under 7kw net & covered by adventitious ventilation

84
Q

10kw net flueless water heater in a room of 15m3

what if any ventilation is required

A

50cm2

85
Q

12kw gross ckr & 14kw gross OF boiler in a kitchen of 9m3

what if any ventilation is required

A

50cm2

because the CKR requires 50cm2
the BLR is 14 / 1.11 (gross to net) = 12.6 -7 (adventitious) =28cm2

but you only install the largest vent size which is the CKR in this case

50cm2

MASTER DOMESTIC GAS STUDY (6 decks)

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