GENERAL GAS QUESTIONS Flashcards
what is the relative density of natural gas in air
0.6 (lighter than air)
Relative density is a comparison between 2 similar substances, in this case gas compared to air
what is the gross accepted average CV calorific Value of Natural Gas
38.76Mj/m3 metric
is the average accepted calorific value for Natural (Mains) or 1040Btu/ft3 imperial (gross
what are the lower flammability limits for gas in air
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.
what is the flame speed of Natural Gas in meters per second
0.36 Meters per second
what are the 3 family gases
Man Made Gas (coal)
Natural Gas (methane)
LPG (Liquefied petroleum gas - propane, butane, and propylene)
how do you work out the wobbe number
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
if you have 1m3 of Methane (Natural Gas)
how many meters cubed of oxygen will you require for complete combustion
2m3 of oxygen to make complete combustion
if you have 1m3 of Natural Gas (methane)
how any m3 of air will you require for complete combustion
10m3 of air
because 80% of air is Nitrogen an roughly 20% is oxygen
when flue gas analysing a fluless space heater what is your co/co2
ratio which you CANNOT exceed
0.001
when analysing a gas cooker, in the first 20minutes what is the maximum co levels the cooker can reach
90 parts per million of co
when was the gas safety installation and use regulations amended
2018
in what documents would you find the procedure for carrying out a tightness test in a domestic dwelling
IGE up 1b
what does BS 6891 cover
pipework up to 35mm copper or steel to inch and a quarter
in the gas safety and use regs what is regulation 36
landlord responsibilities
in the gas safety and use regs, what does regulation 26 paragraph 9 cover
that is what we have to do to examine appliances after we have worked on them
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
21mbr + or - 2 mbs
so 19-23mbrs
what can be the maximum pressure loss across a working system
1mbr between meter and appliance
what is the maximum clipping spacing for a 35mm pipe running horizontily
2.5m between clips
what are the 3 main purposes of sleeving a gas pipe going through a wall
protect against
movement
gas leaking into cavity
corrosion due to chemical reaction
when drilling joist what is the minimum distance between the holes you can have
3 x the diameter of the hole you made
what is the maximum pipe volume where a domestic gas engineer can work on it
0.035m3
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)
60m3 hr
over what volume must the gas be continually ignited
0.02m3
1kw of input on an appliance requires how many m3 of gas
0.095m3
when pipe sizing what is the equivalent in straight length of pipe for a
35mm 90degree copper elbow
1m
what size (amp) fuse should be protecting a boiler
3amp
What is a wobbe number
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.
If medium pressure pipe work enters the building through the back of a meter box, how would this be classed
AR
Where a gas pipe runs under the foundations of a building this can only be done if
Adequate steps have been taken to protect the pipe from movement & corrosion
All ventilation grills require a warning notice when
Installed in a compartment
The permissible movement on a digital manometor to 2 decimal places is
0.25
The industry standards for testing pipe work over 35mm & exceeding 0.035m3 is found in what documentation
IGE/UP 1 or IGE/UP 1A
A flue outlet of a combination boiler when facing a boundary shall be at least how far away
600mm
A plume management kit on a flue must terminate in what location to the air inlet of the same flue
Must terminate in the same pressure zone
what is the maximum spacing of supports on a horizontal 22mm copper pipe
2.0m
When a gas pipe is run inside a duct, the duct must be what
Vented at the top & bottom
When can a gas cooker grill on initial ignition exceed 10ppm co for a short period of time
If it conforms to BS 7967 part 2 & manufacturers instructions
At which levels of co/co2 ratio must you take action on a flueless water heater
When co/co2 ratio exceeds 0.02
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
75mm
If no manufacturers instructions are available what is the minimum clearance between a fluless instantaneous water heater & a ceiling
300mm
A natural gas cooker is installed in a kitchen with a volume of 7m3 how much ventilation is required for the room
50cm2
Chimneys used for an inset live fuel effect fire normally requires a minimum size across its axis of
125mm
When installing a gas free standing heating stove into a builders opening the flue must project how far through the register plate
150mm
What is the minimum void volume of an unlined masonry chimney with a gas fire fitted with a flue kit
12 dm3
From November 2006 co detectors must conform to
BS EN 50291
Currently standards categories an SE duct with which letters & numbers
C21
how far from electrics should a gas pipe be
25mm
what is the maximum KW gross an open flued gas fire can be when installed in a bedroom with an ASD fitted
14KW gross
what does the acronym RIDDOR stand for
Report of Injuries & Diseases Dangerous Occurrences Regulations
under IGEM G11 how would you categorise an ECV that is letting by with obviously no smell of gas
AR
what is the maximum in days that a landlord must give their tenant the gas safety certificate
28 days
what building regulation covers ventilation
F (for ventilation)
a boilers electrical supply can only be fed by a fused spur,
TRUE or FALSE
FALSE it can be plugger but socket must be in an unswitched socket
(would be not to current standards if plugged into switched socket)
no perceptible movement when using a U gage is
0.25mbrs
what is the minimum flow rate through a gas meter when checking the regulator is working correctly
0.5m3 an hr
what is the maximum absorption rate of a gas meter in mbrs
4mbrs
how many BTU’s British thermal units are there in 1 KW
3412
when flue gas analysing a flueless fire or flued water heater what’s the maximum ratio
0.02
after November 2006 what must the EN number be on a CO detector
EN 50291
with the concentration levels of 300 PPM of CO,
what is the maximum time the alarm must activate
3 minutes
what BS number must copper pressfit fittings comply with
BS 8537
what does PTFE stand for
Polytetrafluoroethylene (PTFE)
what is the maximum clipping distance of a 15mm gas pipe run vertically
2m
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
TRUE
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
they must be at least the cross sectional area of the duct
what is the average o2 reading in outside air
20.9% oxygen
the current standards categorise flue systems with letters and number, what letters are used for:- flueless:- type ? open flued:- type ? room sealed:- type ?
flueless:- type A
open flued:- type B
room sealed:- type C
what are the standard ventilation requirements for a DFE fire under 20KW
100cm2
when installing a vent for a flueless space heater how far away should the vent be from the flueless space heater AND why
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
what is the minimum cross sectional area of the equipotential bonding at a gas meter
10mm2
a flue duct outlet when facing a boundary has to be how far away
600mm
when using a plume management kit, how far away does the air inlet need to be from an opening in a building
150mm
according to IGEM unsafe situations how would you categorise a room sealed appliance failing its flue gas analyser reading
AR
what is the minimum void volume for a unlined masonry chimney with a gas fire connected ? dm3
12 dm3
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
1.121dm3 because you must pass 10dm3 of gas to purge
purge volume is how many times the installation volume
1.5 times the size of installation volume
OF floor standing boiler of 10kw net installed in a room
what ventilation requirements are needed
15cm2 because 10 - 7 (adventitious air) = 3 * 5 = 15cm2
flueless space heater 2.5kw net in a room of 45w per meter3
what size ventilation is required
100cm2 as the standard ventilation because its less than 2.6kw net
10kw net DFE installed in a living room
what size ventilation is required
100cm2 because this is the standard up to 20kw net
RS condensing boiler 24kw net in a bedroom
what ventilation is required
no ventilation required because it is RS
10kw net cooker in a kitchen of 9m3 with an openable window
what if any ventilation is required
50cm2
flueless space heater 6.4kw net installed in an internal space of 90w per meters 3
what if any ventilation is required
127.5cm2 is required
6.9kw net OF radiant space heater in a room of 30m3
what if any ventilation is required
no vent required
because it is under 7kw net & covered by adventitious ventilation
10kw net flueless water heater in a room of 15m3
what if any ventilation is required
50cm2
12kw gross ckr & 14kw gross OF boiler in a kitchen of 9m3
what if any ventilation is required
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
