Combustion Chambers

Question 1

The combustion chamber on a wood-burning furnace is typically made of ________________ or ________________.

Answer 1

Heavy steel plate or brick

Question 2

All combustion chambers have a grate.

Answer 2

False

Question 3

What is the maximum depth of ash usually recommended in a combustion chamber before cleaning?

Answer 3

Three inches

Question 4

List six common problems with combustion chambers.

Answer 4

1. Poor door seal
2. Dirty combustion chamber
3. Warped grate
4. Warped door
5. Deteriorated brick
6. Warped or cracked firebox

Question 5

Wood furnace heat exchangers tend to be more complex and have more sharp bends and recesses than gas or oil heat exchangers.

Answer 5

False

Question 6

Heat exchangers rarely fail at welded corners.

Answer 6

False

Question 7

List three common heat exchanger problems.

Answer 7

1. Cracks or holes
2. Rust
3. Soot or creosote deposits

Question 8

List six common barometric damper problems.

Answer 8

1. Rusting
2. Inoperative
3. Missing
4. Poorly adjusted
5. Inadequate draft air
6. Spillage

Question 9

List three significant differences between vent connectors on wood furnaces and vent connectors on gas furnaces.

Answer 9

1. 18 inches clearance from combustibles is normally required.
2. Galvanized steel should not be used because the zinc coating can melt and/or vaporize at high temperatures, giving off dangerous gases.
3. Vent connectors for wood furnaces are typically black or stainless steel.

Question 10

The high-temperature limit switch on a wood furnace is typically set at:

Answer 10

250 to 280°F (121 to 138°C)

Question 11

List two duct issues that are unique to wood furnaces relative to gas or oil.

Answer 11

1. Combustible clearances – higher than gas/oil
2. Combustible return ducts – cannot use empty joist spaces, sheet metal ducts are typically used

Question 12

Add-on furnaces are similar to stand alone wood furnaces, except they are missing:

Answer 12

A fan and filter

Question 13

Add-on wood furnaces should be installed:

Answer 13

Downstream of an oil furnace

Question 14

What are the implications of a duct arrangement that allows reverse flow through the ductwork in an add-on furnace situation?

Answer 14

Overheating the primary furnace, and possible electrical wire or
equipment damage.

Question 15

How would you determine whether a furnace is suitable for use as a dual fuel system?

Answer 15

Check if the system is a listed or certified dual fuel furnace. Otherwise,
recommend further investigation by a specialist.

Question 16

Dual fuel furnaces usually have how many heat exchangers?

Answer 16

They typically have one heat exchanger.