The most common cause of poor draft is an improperly sized flue liner. We recommend that the chim- ney liner’s inside dimensions be at least as large as the appliance’s col- lar size and no larger than 125% of the collar for a round flue. For instance, an 8" furnace collar is 50 square inches; increased by 25"% would be 63 square inches, or approximately a 9" round flue. In general for round liners we recom- mend that they not be increased more than 1" from that of the Harman’s collar size. The reason for the above is that Harman appli- ances are designed to produce the maximum amount of heat per amount of fuel burned. A a result, the flue gas temperature is lower than for some similar equipment.
TO SUMMARIZE, A HEATING UNIT CAN PERFORM ONLY AS WELL AS ITS VENTING SYSTEM WILL ALLOW IT.
5.Creosote and Soot
5.1General and Specific C reosote Maintenance Wa rn i n g s
One of the most critical aspects of operating a woodburning stove is the control of creosote and soot. This is especially important when there is a low demand for heat, such as in the fall or spring. A good understanding of the causes and cures for excess creosote or soot formation is essential to the opera- tion of the stove.
Your stove and for that matter, all types and makes of woodburning equipment will give trouble with cre- osote deposits under certain condi- tions. You should be aware of these conditions and avoid them.
When wood is burned slowly, it pro- duces acetic and other pyroligneous acids that combine with expelled moisture to form creosote. Highly combustible in its solid and
Creosote condenses from the flue gases more quickly when the tem- perature of those gases is low. The actual amount of creosote deposited depends on (1) the amount of mois- ture in the flue gases, (2) the tem- perature of the stack, (3) the rate at which the wood is burned, (4) the amount of draft in the stack, and (5) how completely the combustible ele- ments in the flue gases have been burned in the combustion chamber. Most problems with creosote are due to insufficiently dry wood, poor chimneys with low draft and cold
walls, and/or a low rate of burning when little heat is required during the spring and fall months.
Moisture in the Flue Gases May Be Controlled by:
A. Using properly seasoned fire- wood.
B.Mixing small pieces with every full load.
C.Never using only large (usually less dry) wood during mild weather when combustion is relatively slow.
The Temperature in the Stack May be Controlled by:
A. Using as short a length of stovepipe as possible between the stove and the chimney.
B.Using an insulated flue pipe to connect the stove to the chimney.
The Amount of Draft in the Stack May be controlled by:
A . Having as few bends as possible.
B. Insuring adequate chimney height and preventing air leaks.
C. Eliminating external obstruc- tions in the chimney outlet.
D.Having only one appliance per flue.
C A U T I O N ! O W N E R ’ S R E S P O N S I B I L I T Y
YOU MUST CHECK YOUR CHIMNEY FLUE PIPE CONNEC- TOR FREQUENTLY WHEN FIRST STARTING TO BURN WOOD TO DETERMINE THE AMOUNT OF CHIMNEY MAINTENANCE (CLEAN- ING) THAT WILL BE REQUIRED. THIS OF COURSE, IS ALSO DEPENDENT ON WOOD TYPE, MOISTURE, AND IN GENERAL, HOW THE STOVE IS USED.
The chimney connector and chim- ney should be inspected at least twice monthly during the heating season to determine if a creosote
