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98 Cards in this Set
- Front
- Back
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standard/mid efficiency gas furnaces are known as |
condensing furnaces |
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high efficiency gas furnaces are known as |
condensing furnaces |
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condensing gas furnaces have a annual fuel utilization efficiency of |
90 97% |
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exhuast gases are depleted of heat which causes... |
condensation |
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flue of high efficiency furnace is |
a pvc pipe vs metal pipe |
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memorize ratings pg 3 |
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components of a mid efficient |
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4 catagories of a high efficiency furnace |
combustion air components burner assembly fan blower assembly electronic printed circuit control board (ECB) |
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4 main air combustion components of a high efficiency furnace |
combustion air blower combustion air prove switch heat exchanger primary high limit safety switch |
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secondary heat exchanger uses heat from the? |
exhaust gases |
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how are mid efficiency furnaces improved? |
by increasing heat exchanger surface area with thinner metals that transfers heat more efficiently |
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what three things continue to heat a high efficiency furnace after the combustion gases have cooled? |
primary heat exchanger secondary heat exchanger condensate drain line |
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primary heat exchange in high efficiency furnace is made from |
coded steel tube system |
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secondary heat exchanger is also known as |
condenser coil |
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without condensation pipe the heat exchanger would |
corrode ( potential for rust) |
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combustion air blower is also known as |
forced draft fan or induced draft fan |
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observe the difference between forced and combustion |
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a halfed voltage |
its still 0 but there but some volts are still induced |
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the blower may be used to |
purge the combustion chamber |
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why should the combustion be purged |
it removes explosive gases |
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2 comon mid efficient control boards |
the RAM electronic control board the ECG sure light control board |
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what control board pre purges and post purge times for ram |
45s pre purge 5 post |
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the ECG post pre purges |
15s pre purge 5 post |
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there is no industry standard for how long combustion air blower must blow before ignition t or f |
t |
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in mid efficient furmaces combination of control device and combustion air blower operation you encounter |
a combustion air blower runs before burner ignition the pre purge times can be different between models and brands combustion air blower may run after burner shuts down if there is a post purge cycle it can change between models |
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cps is |
air proving switch |
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the cps confirms |
the operation of the combustion air blower |
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the cps is nc? |
no is NO |
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when combustion air proving controller fails or has insufficient combustion |
the safety circuit is opened and prevents the burner from operating |
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high limit prevents what from operating |
burners |
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do mid efficient furnaces have 2 high limits? |
no they can have up to 3 |
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how does the H.L. work? |
with a bimetal disk or strip in a normally closed sw |
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H.L safety controls are set at |
82°C to 94°C |
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secondary H.L. is located in the _________ compartment |
blower compartment |
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what is a DSI |
direct spark igniter |
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another igniter other than a direct spark igniter |
hot surface igniter |
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a DSI can have a high voltage potential of |
5000v |
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DSI can be sensitive to |
dirt moisture and grounding issues |
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a DSI has a |
flame rod aswell |
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name 2 hot surface igniters |
intermittent pilot IP and HSI hot surface ignition system |
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IP is made of |
a material called silicon carbide |
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the hot surface igniter is 120v t or f |
t |
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how hot dose a hot surface conductor get |
980°C |
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when is a hot surface igniter energized |
a few seconds before mgv opens and a few seconds after flame sensor proves a flame |
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HSI are expensive? t or f |
F |
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HSI requires a flame sensor to |
detect successful ignition |
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HSI is made from |
ceramic |
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HSI silicone ceramic can withstand heat up to |
1370°C |
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flame rectification is |
running current through a flame to prove a flame this is detected by the control board |
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roll out limit control is a |
high temperature limit that prevents the furnace from firing while flame roll out condition exists |
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flame roll out is when |
gas and flames go somewhere other than the flue |
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how can flame roll out happen |
1inadequate building static pressure 2plugged or obstructed heat exchanger 3misaligned burners 4cracked burner tube 5 gas leak in manifold piping or value dirty or faulty combustion air fan 6cracked heat exchanger |
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how many roll out limits are in a furnace |
usually 2 on each side of the burner |
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flame rollout happens in initail ignition what happens |
ignition ceases gas valve closes |
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read pg 14 |
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mid efficiency blowers are driven by |
multyspeed permanent split capacitor |
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PSC |
permanent split capacitor |
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PSC are good for |
being efficient smooth and quite |
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PSC have how many operating speeds |
3 |
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multiple blower speed are fir heating cooling and ventilation t or f |
t |
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ECB is |
electronic control board |
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ECB dose |
most functions of the 24v low voltage side of a basic furnace including HRV hook ups |
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installing the wrong ECB can result in |
violent gas explosions |
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screw type terminals on the ECB are labeled |
RWGYC |
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R on a ECB is for |
power feeding tstat |
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C on a ECB is for |
common on tstat |
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G on ECB is for |
the fan |
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review pg |
17 |
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pvc can be used for what and why |
for the flue because exhaust is cool enough |
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roll out switches are automatically reset or manual |
manual |
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call for heats starts with what and ends with what |
starts with tstat and ends with tstat satisfied |
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rinse and repeat objective 2 |
its the sequence of a furnace |
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blower turns on how long after mgv opens |
45 seconds |
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purging will trigger the |
air prove sw and close it |
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blower time is detected by heat sensing t or f |
false it is a preset time |
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tstat opens what happens |
mgv closes combustion air blower runs for a few seconds and shuts down the blower fan runs for a few and shuts down as well |
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blower off delay is adjustable true or false? |
true |
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auxiliary equipment is everything other than the |
furnace |
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most domestic air filters remove |
partucles larger than 3 to 10 microns |
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air filters are usually in the |
return air plenum |
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filter cartridges are |
1 standard fiberglass 2mid efficient 3high efficient(traps to 1 micron) 4micro biocide treated filters( inhibits growth of micro organizisms) 5 electronic filters (can remove smoke particles but require power) 6 electrostatic filters (remove microscopic particles as they pass through not needing power)
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2 ways to activate electronic air filter |
ECB and air pressure sw |
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humidifiers are attached to the |
cold air return |
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standing water absorbent pad humidifier is |
wet pads in the plenum |
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rotating drum humidifier |
a sponge cycles thru water and supply air blows thru it |
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the sponge in rotating drums is bad when |
becomes breeding ground for mold and viruses and **** |
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rotating disc humidifier |
same as others but uses plastic disc so less mold and **** |
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flow through humidifier |
a water fall over a screen |
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humidifier circuit consists of what parts |
120/24v transfomer class 2 2 wire 22g a hunidistat |
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terminals for humidifer are labeled |
HUM or HTG ACC htg means heat mode auxiliary terminal |
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HTG ACC feed the |
transformer |
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a home needs --- airchanges per hour |
0.35 to maintain good air quality |
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HRV means |
heat recovery ventilator |
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HRV is used to |
warm outside air interlocked with the common air exhaustfan and the furnace |
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HRV dose with with warmed outside air |
returns it to furnace |
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why is proper ventalation needed |
negative air pressure will cause carbonmonooxide because it will suck outside air in! including the chimneys air |
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ACH |
air change per hour |
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ACH of 1 means |
air is changed in a home once per hour and home only needs 0.35 ACH |
