Draft &Venting

Question 1

What is draft?

Answer 1

A Current of air in an enclosed area that is created by a difference in pressure.

Question 2

How does draft work during the combustion process?

Answer 2

Hot gases rise through the heating appliance to the flue pipe and travel up the chimney creating a negative pressure or suction.(Negative draft)

Question 3

What are the two types of natural draft?

Answer 3

Thermal &currential

Question 4

How is thermal draft created?

Answer 4

When air in the chimney is hotter and lighter then the air outside. As lighter air moves up the chimney more air moves in from the surrounding room to replace it.

Question 5

What causes currential draft?

Answer 5

Suction created from wind rushes over a chimney top creating negative pressure in chimney.

Question 6

What affects draft?

Answer 6

• temp of outside air
• temp of glue gases
• barometric pressure
• humidity of air

Question 7

How high must a chimney extend above nearby objects?

Answer 7

2 FT

Question 8

What are the affects of low draft?

Answer 8

Will cause the burner fan to push against higher air pressure regulating in less air for combustion and smoky fire.

Question 9

What will high draft cause?

Answer 9

Cause to much air to rush into the combustion zone resulting in reduced effiency. Will cause air to leak into the unit increasing stack temp.
Higher draft give tempuyu

Question 10

Where should the draft regulator be installed?

Answer 10

In flue pipe between chimney and stack mounted primary if there is one.

Question 11

How do we measure chimney draft?

Answer 11

Inches of water column. Checked over the fire &land in the flue pipe. Unit should be close to -.05 inches.

Question 12

What is the normal range for draft over a fire?

Answer 12

-.01 to -.02”

Question 13

What draft should be tested first and is most important?

Answer 13

Draft over the fire

Question 14

What is a reason for significant draft drop?

Answer 14

Soot and scale deposits in the unit.

Question 15

What are some regulations when installing a flue pipe?

Answer 15

-18” from a combustible wall or ceiling.
-flue pipe must never be smaller the the breech
-should not exceed 10FT in horizontal run unless draft fan is used.
-1/4” or FT pitch from the appliance up to the chimney l.
-limits number of elbows
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Question 16

What is isolated combustion and what is it used for?

Answer 16

Do to buildings being so air tight the indoor air pressure drops below the outdoor pressure and the appliance becomes back vented.odors,spot and carbon monoxide may be drawn into building.
-duct outside air to burner

Question 17

How do Install a flue pipe to a chimney if you have an oil furnace & water heater?

Answer 17

• using a “y” connector. The exit should be one size bigger after the “y”.
• by making a second opening in the chimney. Water heater on top Furnace on bottom. Separate draft regulators for each.

Question 18

What is a draft inducer?

Answer 18

Electrically powered fans installed in the flew pipe.push air from unit up chimney. Also can boost draft with weak draft.

Question 19

What is power venting?

Answer 19

No chimney a fan is attached to flue pipe and pulls products of combustion outside.

Question 20

What is direct venting?

Answer 20

A positive pressure system that use static pressure created by burner fans and pushes combustion gases through the heat exchanger and out of building.

Question 21

What are some positives of direct venting?

Answer 21

-positive control of draft
-no chimney warm up problems.
-Lower construction cost
-lower burner noise
-elimainates back draft
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