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60 Cards in this Set
- Front
- Back
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Can you use a direct fired make up air in a building serving spaces with sleeping areas? |
No |
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For the test, read seek and destroy A, B, and MUA. Read answers in the back of each ILM. Read the presentation on Eng A |
Yes |
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The safeties are in series with the flame rod, T or F? |
True |
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Identify 3 different applications for make up airs? |
Commercial kitchens Fitness centers Hallway pressurization |
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What are the 2 types of MUA? |
Direct fired Indirect fired |
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What are the 2 types of MUA? |
Direct fired Indirect fired |
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What type of MUA (of the 2 major types) must be interlocked with an exhaust fan? |
Direct fired |
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What is the required airflow for a direct fired MUA? |
2500-3200 fpm |
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What are the problems associated with poor airflow across the burner? |
Inefficient operation Odors Incomplete products of combustion entering space |
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Name 4 different typical safeties on MUAs? |
Flame proving High velocity air switch Low velocity air switch High limit switch |
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What are the 2 main applications for MUAs? (Generally!) |
Make up air heating and cooling Space pressure control |
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What are 7 problems that happen to MUAs if the building has a negative pressure? |
Exhaust fans lose performance Exit doors difficult to open Drafts through doors and windows Backdraft from hood vents Infiltration of unwanted outdoor air Poor air quality |
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name 3 different types of applications of MUA? |
Direct compensation ventilation (MUA serves area where exhaust fan is located) -kitchen General area venting (MUA serves a larger area and has several exhaust fans) -An apartment hallway has 1 MUA and 1 exhaust fan on each floor Door Heater Serves warm air directly to door entrance. Think Grocery store entrance being warm in the winter |
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2 methods MUAs use to achieve space pressure control? |
Constant air MUA with variable exhaust
Variable air MUA with variable exhaust |
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Why is shielded wire recommended a the conductors for sensors? |
Removes the possibility of induced voltages. Note: 1 end of the shielding should be grounded. |
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What are 4 design features common to all burners? |
Fuel delivery Air delivery Fuel/air mixing Safe ignition/complete combustion |
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Why are natural draft burners often called atmospheric burners? |
Air for combustion is at atmospheric pressure |
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3 categories of air being delivered for combustion? |
Primary (air mixed with fuel prior to combustion) Secondary (air mixed with flame immediately after ignition) Excess (air added to combustion zone that is not needed in theory but is in practice. Its called “Trim” ;) |
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2 types of equipment with power burners? |
Large boilers Some indirect MUAs (Power burner pressurizes the inlet air to the burner) |
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Common name for fan assisted burner? |
Mid efficient burner |
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Radient tube heaters use which type of burner? |
In shot |
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Which type of burner is used on domestic hot water tanks? |
Ring burner |
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Turn down ratio? Define it! Name some equipment! |
Ability to have variable firing rates of fuel and combustion air
20:1 turn down ratio means the unit can have 1/20 of the fuel used and maintain complete combustion.
MUA Modulating Furnace |
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What are the main Categories of power burners? |
Fan mix Closed Open |
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What is a method for modulating gas flow? |
-modulating gas valve with variable speed inducer Or -modulating gas valve with modulating damper |
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Category 1, 2, 3, and 4 venting? |
Category 1 (non-positive, non-condensing) Category 2 (non-positive, condensing) Category 3 (positive, non-condensing) Category 4 (positive, condensing)
Category 2 doesn’t really exist. |
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What are the 2 standard for gas fired appliance efficiency? |
Annual Fuel Utilization Efficiency AFUE takes into account losses in the venting system Steady State Efficiency Only efficiency of the appliance alone |
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What is the main purpose of dilution air? |
To cool exhaust gasses and dehydrate the flue gases |
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55% to 80% efficient furnace changes? Name 3? |
(1) motorizes damper prevents losses through draft hood (2) electronic ignition (not pilot) (3) heat exchanger improved so that no dilution air required because exhaust is so cool. |
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80% to 91% efficient furnace changes? Name 1 |
(1)Secondary heat exchanger 970 btu/lb (2) Counter flow heat exchanger |
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80% to 91% efficient furnace changes? Name 1 |
(1)Secondary heat exchanger 970 btu/lb (2) Counter flow heat exchanger |
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4 ways to control draft |
(1) natural draft (hot air rises) (2) forced draft (push the air) (3) induced draft (pulls the air) (4) Balanced draft (pushes and pulls the air through) |
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What do you need to do to convert a furnace from a nat. Gas to propane? |
(1) install low pressure cut off (2)replace spring in gas valve (3) replace orific (4)set manifold pressure |
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Clearances of gas fired equipment? |
Boiler top, sides, rear - 18” front - 48” Forced air furnace top 1” sides, rear - 6” front - 24” Gravity furnace top, sides, rear - 6” front - 24” |
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Maximum setpoint high limit on a furnace? |
250F |
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The heat exchanger of a mid-efficient furnace has restricted flow in order to… |
Increase heat extraction and therefore increase efficiency. |
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An inducer motor pulls or pushes? |
Pulls the products of combustion through the heat exchanger |
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What is the effect of doubling the flow rate through a heat exchanger? |
Quadruple resistance to flow |
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Inspirated vs aspirated burner |
Aspirated= air is pushed through a venturi effect and gas is mixed in as the air expands out of the venturi. Think car carburetor. Aka air then fuel added Like a turbo pushing air into the engine. Inspirated: The natural gas is pushed through and orific and as it expands air is pull inwards and mixed with the gas. Aka fuel then air added |
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What type of venting is used with category 1 appliances? |
B-vent |
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Which oil burning combustion chamber cannot be converted to propane? |
Revertible. |
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Combustion air proving switch is N/C or N/O? |
Normally open. On the shelf when you buy it. The switch is open |
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What is a common supply air temperature for a MUA? |
50F to 100F |
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What does it do? High pressure switch Isolation gas cock Main gas pressure reg Main gas shut off valve Pilot gas burner Pilot gas manual valve Pilot gas pressure reg Pilot gas needle valve Pilot solenoid valve Safety shutoff valve |
Card
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What damper blades are preferable on MUAs? |
Low leakage parallel blade isolation dampers |
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What is the maximum recyclable air for a MUA? |
80% return - 20 % fresh |
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Why is it usually either: Aspirated and closed Or, Inspirated and open? |
Open vs closed: this is in reference to how the air is allowed into the combustion chamber. If its open think a direct fired MUA where the combustion air passed over the burner. If it is closed think of a indirect fired MUA that is pressurized with an inducer motor.
If its closed then then they use the high velocity air to mix the gas into with the use of a venturi. Hence, why closed burners are usually aspirated. If it is open then you will have gas shooting through an orific and the oxygen around it will get pulled towards the flame. Hence why open burners are usually inspirated. |
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What is the main difference between open and closed burners? |
When talking about air… open burners will allow air into the burner section that was not directly added through the burner itself. Closed burners will only allow air into the burner section that is directly added through the burner itself. |
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Aspirated burner? |
A burner in which combustion air at high velocity is drawn over an orifice, creating a negative static pressure and thereby sucking fuel into the stream of air; the mixture of air and fuel is conducted into a combustion chamber, where the fuel is burned in suspension. Youre gonna need a fan! |
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Standing, interrupted, intermittent? |
Standing pilot: stays on all the time Intermittent: stays on for the entire call for heat Interrupted: turns off once the main burner is lit |
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4 types of power burners? |
Aspirated, mechanically premixed, nozzle, injection. |
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Mid-efficient cat 1 piping? Mid-efficient cat 3 piping? High-efficient cat 4 piping? |
Mid-efficient cat 1 piping? -Type B venting, anodized steel Mid-efficient cat 3 piping? -stainless plus drain connected to venting High-efficient cat 4 piping? -636 plastic, stainless heat exchanger |
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4.3 installers responsibilities? All 6!!! |
(1) install, setup, and test to code (2) instruct client (3) leave manuals (4) replaced components must meet specifications required (5) if converting you must render old fuel system safe (6)if converting you must inform client on how to dispose of old fuel supply system |
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Suitability of use? All 6? |
(1) must be able to use gas supplied to building (2) installation should not create a hazard (3) must follow manufactures instructions for conversion. (4) must modify nameplate after conversion (5) damaged unit cannot be used (6) use old appliances if safe |
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What temperature does flue gas condense? |
126F |
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A roll out switch opens when? |
Secondary air section gets too hot |
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Which safety responds to a dirty filter situation on a MUA |
N/O low velocity pressure switch |
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Recommend spark gap? |
1/8 inch |
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What is a glow coil on the 48 DD wiring diagram? |
It is the hot surface ignitor There is a resistor in series with it because the glow coil is a motorcycle part that works off a 12V battery. (Apparently). So the resistor drops the voltage to the glow plug. |
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Maximum temp for B vent? |
470F |
