Heating Flashcards
(T/F) Heating system required for almost every home?
True.
Homes need to maintain a temperature of _______ in every habitable space.
68 degrees F
Heat is the transfer of ___________________.
transfer between molecules.
Temperature is the measure of how FAST heat is transferred.
conduction
Heat that moves through solid matter
convection
heat that moves by circulation of gas/liquid
radiation
when heat is gained by absorbing electromagnetic energy
Hot liquid gasses are ___________________________ compared to surrounding materials allowing liquid/gas to rise relative to surrounding material (stack effect)
more lighter, more buoyant
(T/F) All combustion produces byproducts.
true
when gasses lose enough heat and become heavy to reach chimney/fall back into the home
backdrafting
What is creosote?
dangerous combustion byproduct that’s flammable and an ignite and cause fires
What are the stages of creosote?
Stage 1 - flaky ash
Stage 2 - heavy tar like ash
Stage 3 - hard, shiny coat. This is highly flammable and difficult to remove. Flue liner replacement necessary!
What does the presence of soot in or around the combustion area indicate?
significant combustion problems
How is incomplete combustion different from complete combustion?
Produces more water vapor and may produce carbon monoxide
Combustion air SHOULD be drawn from
outside the house, including vented attics/crawlspaces
Dilution air is mixed with ______
is mixed with vent gasses in the 1
Whats the purpose of combustion air?
To ensure complete and safe fuel burning and to ensure all combustion byproducts are safely expelled out of the house.
the term net free area refers to…
combustion air openings
What is the minimum opening dimension for a net free area?
minimum opening dimension is 3 1/2” inches
The standard method requires at least _________ cubic feet of volume in every room for 1000 btu/h input of appliances in the room
standard method for gas and oil appliances = at least 50 cubic feet of vol. for every 1000 btu/h
Combustion air may be draw from adjacent rooms inside the house on same story. What’s the requirements for this?
be drawn from other adjacent rooms, 2 openings commencing 12” from floor and 12” from ceiling and should have at least 1 sq. inch net opening space for every 1000 btu/h appliances.
Combustion air may be drawn from different stories inside the house. What’s the requirements for this?
1 or more opening total net free opening of at least 2 sq. inches for every 1000 btu/h of input of appliances.
Combustion air for a gas appliance drawn from outside the home may be provided by….
2 openings in wall/2 ducts 12” from floor, 12” from ceiling and the openings/ducts must commence directly outdoors (incl/ vented crawlspaces/attics)
1 opening in wall or ceiling w/in 12” of ceiling. This net free opening area is 1 sq. inch for every 3000 btu/h
What net free area requirements for gas appliances drawn from outside the house?
net free area wall openings and vertical ducts is 1 sq. inch for every 4000 btu/h
net free area for horizontal ducts is 1 sq. inch for every 2000 btu/h
Combustion air for solid fuel burning appliances should be taken from where?
outside.
H.I. should report lack of combustion air as defect or recommend for upgrade.
The duct to a masonry fireplace should have a combustion air duct that:
-terminates outside or in a vented crawlspace.
-terminate at or below firebox
-should be within 24” of firebox opening
-have an area of 6 sq. inches and no more than 55 sq. inches.
Combustion air ducts should terminate at least:
12” above grade (or above slow accum. level)
The minimum combustion air duct dimension is
3” inches.
Combustion air ducts should be constructed using:
28 gauge galvanized steel. 1 opening.
shouldn’t serve upper and lower duct.
Flexible duct and duct board not allowed.
Screen should be covering if terminates outside.
Makeup air is
the air that replaces the air removed by house appliances.
makeup air IS NOT combustion air.
Gas and oil burning appliances should not be located in or open up into…
bedrooms, bathrooms, closets
(these have no vents for combustion air ^)
(T/F) Home inspectors are required to determine if the capacity of heating system is appropriate.
False.
The heat source needs to maintain what temperature? Where do you take the temperature measurement from?
68 degrees F.
Measurement taken 3 ft above floor and 2 ft from exterior wall.
The heating and air conditioning loads for the house are determined by protocols set forth in…
ACCA, Manual J
Air Conditioning Contractors of America Manual J
((Manual J calculates estimated sensible loads for a house)
Manuel S would determine _____
system capacity (as based on Manual J).
(T/F) Manual S and Manual J protocols apply to steam heat and hot water heat.
False.
They don’t - sizing for these systems is according to manufacturer rec or engineer practices.
Heating systems are classified by _____ source and ______ method.
energy source: solid fuel, liquid fuel, electricity
distribution method: forced air, gravity, hydronic, radiant
Forced air distribution systems use which type of heat transfer?
forced air uses convection to distribute heat.
can have uneven distribution and movement of air over skin evaporates moisture leading to cooling effect.
Gravity distribution uses which heat transfer type?
Convection and stack effect to move heat up through the furnace.
very inefficient and uneven air distribution.
Hydronic distribution distribute heat in which heat transfer type?
Convection (or radiant depending on system like in floors)
How is the heat from radiant systems distributed?
move heat by heating a material and allowing heat to flow over by radiation, conduction and convection..
(ex. fireplace and wood stoves.)
Category I appliance characteristics
-hot vent gas (300 degrees) that vents through stack effect.
-appliance vents incl/ Type B vent, masonry chimney, and single wall vents.
Category II appliance characteristics
-vent gas cool (around 140 degrees)
but still vent through stack effect.
no cat II appliances but if so, backdrafting could be an issue.
Category III appliance characteristics
-vent gas cool (around 140 degrees)
under positive pressure
not condensing appliances but condensation can be a problem.
Category IV appliance characteristics
- vent gas is cool and is vented under positive pressure.
-condensing appliances!! b/c water vapor produced by combustion process.
-appliances use plastic pipe, PVC as vent. Recommended to insulate if in uninsulated cold climates.
Name the gas furnace components and what they do
return air enters the cabinet and is moved using a squirrel cage fan (blower).
The __________ is the heart of the gas furnace.
heat exchanger.
(Gas fire heats the interior of the heat exchanger making walls very hot. Fan pushes air across heat exchanger hot walls. Air absorbs heat and blows across (evap coils if any) into the ducts. Combustion gasses remain in heat exchanger expelled out thru vent.
(T/F) Heat exchanger cracks are not a reportable defect.
FALSE!!
Heat exchanger cracks are a MAJOR safety issue b/c this allows gasses to air circulating back to the house.
-cracks caused by metal fatigue from yrs of use or by a faulty high limit switch that allows heat exchanger to get too hot.
Serpentine
heat exchanger with curves that increase the surface area (which make higher efficiency b/c air flowing over increased surface area means more heat absorbed.
Works with a DRAFT INDUCER to pull combustion gasses thru the curves
(T/F) Flexible gas connectors are permitted to enter cabinets.
False. NOT PERMITTED to enter cabinets. Gas should be supplied thru solid pipe.
flame-rollout sensor
high limit (fan limit) sensor
safety sensors that shuts off the furnace if they senses excess heat.
flame rollout is silver colored buttons near burners.
high limit in small box or small round button on burner compart. wall
draft sensor
stops the ignition sequence if the draft inducer is malfunctioning and creating an inadequate draft in heat exchanger.
connected by a tube to the draft inducer fan.
Draft hood furnaces have _______ burners, while induced draft furnaces have _______ burners. Bother are Category I furnaces.
draft hood has ribbon burners (low efficiency; ~65%)
induced draft furnaces have inshot burners (medium efficiency; ~80%)
When inspecting a Category I furnace, there should be:
-no scorching or staining that indicates flame rollout.
-pilot light should be stead and lit.
-automatic safety controls should not be bypassed and should be in factory installed condition.
-electrical cables should enter cabinet thru bushing/grommet
-vent sys should be in tact and complete from appliance to visible termination point
(T/F) Heat exchangers are rarely visible on induced draft furnaces, otherwise, the home inspector should inspect it for cracks.
True..
Ignition success followed by shut down and repeat ignition should be reported as what?
reportable defect if does not ignite properly
What color is the gas flame for gas furnaces
properly burning gas flame is blue w/ slight yellow tip.
yellow/orange flame is a reportable defect!
flame should be strong and steady and not flicker or distort after fan has activated
The condensate collection sys in a cat. IV furnace should:
should not be crimped and should be sloped to drain to the collection tank
Thermostats for the floor furnace should be located ____
in the same room or an adjacent room (w/ no doors betwn rooms)
floor furnaces are cat. I furnaces
Floor furnace grills should be:
(clearances to materials, combustibles, wall, door, etc.)
at least 6” from the wall
-at least 12” away from swinging doors, curtains
-at least 18” walkway on 1 side (if in corner)
-at least 5’ feet below projecting combustibles (wood shelves)
There should be at least ________ between the draft hood and combustible materials such as wood floor joists.
at least 6” between draft hood and combustible materials (wood flr joists, supports, etc.)
(should be 6” above crawl space flr)
the vent and vent connector from a OIL floor furnace should be…
Type L or appropriate chimney
The ignition sequence for a gas appliance is:
gas valve opens, burner ignition…
Wall and floor furnaces distribute heat by…
radiation and convection.
Wall furnaces are vented using..
Type B or Type BW vent (gas) and some are direct vented.
(T/F) wall furnaces may not use a chimney for the vent.
True
The shut off valve for vented room heaters:
may be located in another room if valve is permanently labeled
(T/F)Vented gas fireplaces include vented oil fireplaces, inserts for installation into masonry fireplaces, and logs intended for installation into factory built/masonry wood burning fireplaces
true
(decorative gas appliances)
Vented gas fireplaces or decorative gas appliances should be vented using…
Type B vent and some are direct vented
Gas fireplaces should keep what clearances to combustible materials:
side/trim sidewalls at least 3-6”
top clearances/mantels 8-16”; hearth extension in front 0-10”
The shut off valve for gas fireplaces…
may be located in another room if permanently labeled.
(T/F) Appliances listed for Type B venting may not use the chimney as the vent
TRUE!!
they should vent using a type b vent.. they’re gas appliances under cat I.
(Chimney can be used as a chase for type b vent.
Vented gas logs may use existing chimney.)
The chimney damper should be _________ when vented gas logs are installed in factory built/masonry chimney
permanently closed. May be accomplished w/ damper stop (clamp installed on damper that props it open)
Category I vent system consists of:
-vent pipe (Type B or single wall occasionally) or a chimney
-vent cap (if chimney, then rain cap recommended)
-vent connector
Where are single wall pipes mostly used?
as vent connectors in warm climates.
Single wall pipes are limited b/c they lose heat more rapidly and don’t conduct combustion gasses out of sys as effectively.
Restrictions on using a masonry chimney as Category I gas appliance include:
-chimney must be enclosed w/in the house until it penetrates the roof
-chimney may not serve as a vent for 1 induced draft furnace!!!
-chimney area should be at least large as the vent connector area and smaller than 7x the vent connector area when the chimney serves as the vent for one draft hood-equipped appliance
*Chimney may serve as a common vent for multiple induced draft or draft hooded gas appliances.
Most Category IV appliances use what material for venting and combustion air intake?
PVC
can also be schedule 40 pvc, abs, cpvc
Vents and combustion air pipes should terminate at least _______ above grade.
12” above grade
The heart of an oil burner is an ___________ which is activated when the thermostat calls for heat.
electric motor
Where does combustion occur in an oil burner?
refractory chamber, also called fire pot
The flame in a modern oil burner should be _______ in color.
white with a little yellow.
flame shouldnt be impinging (touching) the surface of the refractory chamber.
What does a refractory chamber do in an oil burner?
purpose of refractory chamber is to contain the flame and the heat and to direct heat toward heat exchanger (combustion happens in the refractory chamber)
Ignition sequence for a modern oil burner includes which cycle?
pre-purge cycle which activates air flow and the ignition arc before the oil valve opens to allow oil to flow to nozzle
(helps clean stable flame at moment of oil ignition)
puffback
ignition of unburned oil in the refractory chamber (dangerous!)
An oil burner safety controls are:
[modern; post 80s] cad cell (fire eye sensor) detects light from flame and shuts the burner off if flame is not detected
[older] stack relay detects heat from flame, shuts off if flame not detected
Oil burners have a red reset switch which can be used…
only once.
red reset switch allow occupant to restart if sensor shuts down the burner.
H.I report if tripped but shouldn’t reset the switch.
(T/F) A manual shut off is a substitute for a oil line safety valve.
False. manual shut off valve IS NOT a substitute for an oil line safety valve..
but oil line safety valve may serve as required manual shut off.
the required electrical shut off switch for an oil burner should be located….
within sight of the appliance or at top of basemen stairs if in basement, etc.
vent system for oil fired appliance include:
-vent
-vent cap
-barometric damper (draft regulator)
-vent connector
Whats the purpose of the barometric damper?
to control draft conditions in vent system
oil vent connectors that use chimney as vent should be equipped w/ barometric damper.
Type L vents should terminate at least __________
at least 2’ ft above obstructions within 10’ ft.
