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PLUMBING CONNECTION
WINTER 2015
One can only assume that this refers to using mesh over a
ventilation opening, and that by doubling the size of the vent
area it should be suitable.
‘Should be’ says it all. Has the AS/NZS 5601 committee
just made assumptions that this will work as efficiently as an
opening of the right size, as determined in Clause 7.3.1, with
no mesh fitted?
Has this being tested in practice or is it theory?
The build-up of dust and dirt on a vent fitted with fly wire is
even, and there is no minimum mesh size in the Standard.
Who will be responsible should an incident occur with
mesh over a ventilation opening? This is not a requirement
of Clause 7.3.1 in Part 2, rather a few throw-away lines in
an example calculation. Will the committee accept any
responsibility or will it all fall on the plumber/gasfitter who
fits the mesh?
Fitting mesh over a vent is not a new concept. When I worked
for the Victorian Gas & Fuel Corporation the idea was looked
at, but it was soon realised that linting takes place at the same
rate over the whole mesh – regardless of mesh area.
Wall vents with fly wire over them were common in
dwellings years ago. They became blocked with dust and dirt
and in many cases were painted over.
This recent idea of having mesh over a vent has
come about only since AS\NZS 5601-2010 was written.
Coincidently, that was when the Standard became a
combined Australian and New Zealand document and New
Zealand regulators became involved in writing it.
Australia is a much drier land, so why are Australian
authorities prepared to roll the dice when it comes to
protecting the public.
CLARIFICATION
Clause 7.3 of Part 2, Ventilation Openings – Caravans
and Boats, is a general description of what is required and
the example calculation allows for mesh to be placed over
ventilation openings as detailed in Clause 7.3.1.
So, is mesh to be placed over ventilation openings that may
serve a refrigerator, space heater or ducted heater when all of
these are to be installed in sealed compartments?
The proposal to fix a label next to vents, warning that they
must be kept open and clean to provide air flow when gas
appliances are in use, is no more than cosmetic.
Given the minimum type height of 4mm, one would have to
kneel on a caravan floor or stretch up to read labels next to vents
that are to be no more than 150mm from the floor or ceiling.
GAS MATTERS
ROGER LAMBIE
In all three examples above both vents are to atmosphere and the top vent was always higher than the condenser/
absorption fins of the refrigerator for maximum efficiency of operation as it is now shown and required in AS/NZS 5601.
STORAGE,
COUNTER OR
RANGE TOP
SECTION
REFRIG.
CARAVAN ROOF
EXTERNAL
WALL
ROOF VENT
VENT DOOR
STORAGE,
COUNTER OR
RANGE TOP
SECTION
CARAVAN ROOF
EXTERNAL
WALL
LOUVRE
PANEL
ROOF VENT
VENT DOOR
REFRIG.
STORAGE,
COUNTER OR
RANGE TOP
SECTION
CARAVAN ROOF
METAL
DEFLECTOR
EXTERNAL
WALL
VENT DOOR
REFRIG.
CARAVAN VENT ORIENTATIONS