Chapter 11 Environmental Considerations

Question 1

which environmental conditions affect the operation of gas appliances

Answer 1

altitude
barometric pressure
airborne contaminates
air temperature extremes

Question 2

how does the barometric pressure affect gas burners

Answer 2

less air to aspirate into the gas burner (richer mixture)

orifices flow more gas at high pressures b/c of the pressure drop

Question 3

what is the 2/4 rule

Answer 3

starting at 2000 ft altitude, reduce gas flow rate by 4%

for every 1000 ft extra continue to reduce by 4%

Question 4

what are examples of airborne contaminates

Answer 4

lint, grease, halogens, dust, dirt, steam

Question 5

what is “in Situ” and why is it important

Answer 5

it means “burned in place”
This refers to the contaminates that are deposited on the inside and outside surfaces of the appliance and are eventually burned up

Question 6

what can happen if airborne contaminates are not cleared out

Answer 6

creates a blockage which interferes with the gas and/or air flow
if not resolved it can cause such bad F/A that combustion turns bad

Question 7

what is lint and explain its affect on a furnace

Answer 7

tiny particles that come off of clothes, cloth, rugs, paper, etc.
becomes airborne, eventually can ger aspirated into the inlet of the gas burners
sometimes can get burned off
typically, it slowly builds up until problems arise with the F/A ratios
This is a serious problem

Question 8

how is grease a problem

Answer 8

builds up in gas burner air shutters restricting airflow

the build up can cause combustion to become dirty

Question 9

how are dust and dirt a problem

Answer 9

not as serious a problem as lint

dust/dirt are heavy and tend to deposit upstream of the gas burner

Question 10

how is steam a problem

Answer 10

not a serious problem
steam is created when water falls on the hot surfaces and it is drawn into the burners with combustion air and replaces some of the primary air
this causes the mixture to become temporarily rich and the flames to have yellow tipping

Question 11

how are airborne halogens a problem

Answer 11

halogens are highly reactive chemical family (Chlorine, fluorine, iodine, and bromine)
These will cause corrosion of metal surfaces destroying gas burners, flue surfaces and other appliance surfaces

Question 12

how is recirculated air a problem

Answer 12

causes gas flames to be soft and float looking for secondary air. may or may not become a big problem depending on the magnitude of the combustion air re-circulation

Question 13

what can the ingestion of very hot air cause

Answer 13

flashback

temperatures will affect flame speed