-22-
creates its draft pressure like a chimney in a wood stove. The rising, heated air in the
stack pulls fresh air into the heater/stove as it rises up the stack and exits the flue cap. The
greater the draft pressure the more able the heater/stove will be to resist strong winds,
overcome flue elbows (that inhibit draft) and the hotter you will be able to get your
heater/stove without sooting. A CO alarm should be installed in the boat along with the
Sig Marine (appropriate diameter) high heat shut-off , if you are unable to fully attend
the heater/stove and still be on board the boat.
If when lighting the heater/stove, the smoke from the burning tissue is sucked up the
chimney then the boat has a positive pressure (good draft), but if the smoke comes out of
the heater/stove before closing the door or replacing the lid then the boat has a negative
pressure. Air is drawn in by way of the chimney instead of a vent and will have to be
corrected in order for the heater/stove to have a good draft and operate correctly. For this
reason you may decide to install the heater using balanced draft. This is taking the vent
and attaching it directly to the heater and connecting the other end of the vent to a deck
fitting air intake so the heater is not effected by the air in the boat. This will require
special attention to the install and the purchase of the deck air intake fitting and a rain cap
along with stainless steel piping, or solid plastic pipe, or even flex tubing, depending on
how cosmetic the install will look.
Draft Assist Fan
During start up, at higher settings or during windy conditions, you may want to use the
combustion assist fan on your heater/stove to artificially boost the draft. Your heater/stove
should operate without the use of the fan but it is convenient during start up and some
heater/stove installations are accomplished with only the minimum flue heights or with flue
elbows that can inhibit the draft. Due to these possibilities, the combustion assist fan will
balance the fuel to air mixture.
1 To speed start-up and pre-heating.
2 To ensure complete combustion and avoid flooding the burner when the fuel supply is
turned up too quickly.
3 To limit the effects of back draft should this occur during windy conditions.
4 To operate the heater/stove at high fire settings without carboning or smoking.
NOTE: Operating the fan can deliver too much air and cause the burner to run too lean
(too much air in the fuel to air mixture). When using the fan try to give as much air as
possible until some of the flames drop down and burn below the top burner ring, then
back it off slowly until all the flames are again burning above the burner ring.