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PLUMBING CONNECTION
SUMMER 2015
Service or maintenance personnel have control over some
of these points – gas operating pressure, volume, position of
injector and area of aeration opening. The manufacturer is
responsible for other requirements.
This makes it obvious that when the correct settings are
not applied before testing for CO, incomplete combustion is
possible.
A visual inspection will not determine correct operating
gas pressure or volume. If these are not checked before a CO
test, it will be a waste of time and money for the customer.
Any Tom, Dick or Harry may conduct CO testing, without
any professional understanding of how to recognise signs of
CO. Having charged a fee, they will recommend engaging a
plumber/gasfitter to rectify faults that show up.
The problem is compounded by potential danger for users
of the appliance.
Authorities generally recommend servicing gas appliances
every two years. Several manufacturers now stipulate that
their appliances be inspected at least annually by authorised
personnel.
CONCERNS
These matters arise from one page in one of the
amendments put out for public comment on AS/NZS 5601-
2013.
I’m worried about the industry’s direction. What depth of
practical working knowledge does the committee have at its
disposal when basic practices are overlooked?
ESV, in co-operation with Consumer Affairs Victoria, has
issued what is called a comprehensive check list outlining
responsibilities for plumbers/gasfitters when conducting
rooming house safety checks.
However, plumbers/gasfitters are not legally permitted
to adjust gas meters. Whether Consumer Affairs is aware of
this is another thing.
Knowing and having the correct operating pressure and
volume from a gas meter is critical to this Rooming House
safety check list let alone when servicing an appliance.
In one case, an expert witness told a Coroner that a
variation in gas pressure is irrelevant in the operation of a
gas burner. This goes against our understanding of the safe
operation and efficiency of a gas burner – in particular an
atmospheric gas burner.
The AS 601 committee is mainly made up of personnel
from gas authorities and manufacturers. In one situation a
gasfitter was ridiculed for not setting the correct operating
pressure on an appliance for which the setting was 140Pa
too high.
In the Coronial case above it was 150Pa too low and was
passed off as irrelevant.
Now we have an amendment to the Standard that requires
only a visual inspection before testing an appliance for CO.
Another expert witness indicated to the same Coroner
that when combustion products flow into a room from a
conventional flue on an appliance with an atmospheric burner
it is safe until there is incomplete combustion at the burner.
The term for this is ‘vitiation’. The air becomes
contaminated by having its oxygen content lowered through
combustion or pollution. (AS/NZS 5601-2013 Clause 6.4.2)
VITIATION
Vitiation of combustion air in appliances burning natural
gas lowers the burning velocity and further reduces the
range of its flammability limits.
Lifting or streaming of burner flames will result – the
degree of lifting depending on the amount of vitiation.
In layman’s terms a wall furnace that takes its air for
combustion purposes from the room to safely and efficiently
operate a gas burner is compromised where any negative
pressure created by dissimilar pressures within a premise
will see combustion air reversing down the flue get gradually
worse.
The negative flow of combustion products down the flue,
caused by dissimilar pressures in a building, may continue
to increase in percentage until the flame on the burner lifts
off ‘looking’ for oxygen to burn. In turn, the potential for CO
is greater.
So, the production of vitiated air constitutes a serious
hazard.
Much of the above is based on readily available
information on the characteristics of gas and long-term
safe practices.
In the case of Victoria, there has been no gas appliance
service training for about 10 years. Practical experience and
knowledge have dropped away, to the point where those who
should know have little of either – and no one to challenge
their decisions.
GAS MATTERS
ROGER LAMBIE
IN THE CASE OF VICTORIA, THERE HAS BEEN NO GAS APPLIANCE
SERVICE TRAINING FOR ABOUT 10 YEARS.