Robyn wrote: "How is the vented cat actually vented?"

To visualize how the plat cat is vented:
Imagine a cooking stove with a vented range hood
directly attached to the top.
There is a small collector on top of the plat. cat,
not unlike a range hood, with a small electric blower.
Fumes or unburnt gas are sucked up into the
range or catalytic converter hood and blown to
the outside through a flex plastic hose.
Just by looking at the vented and unvented cat heaters,
you couldn't tell the difference, except for the
1.5 inch flex plastic hose that exits the Platinum cat.
The plat. cat is very fuel efficient, because it
constantly cycles on and off, with a thermostat
maintaining the desired temperature.
The vent makes it possible for the heater to
cycle, since at each start-up, the
catalytic combustion is not as complete and
unburnt gas and fumes could escape,
if the heater was not vented.
The unvented cat heaters do not come with
a thermostat, and do not cycle on and off,
to maintain a temperature.
Harald
90 westy