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18 Cards in this Set
- Front
- Back
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Shaded pole motors are cheap. |
Replace it |
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Check inducer motor for wear |
Wheel is free of debris |
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What are the 2 types of blower motors? |
Direct drive and belt drive |
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ECM |
Electrically commutated motor 120V is converted to three phase pulsed DC with 24Vac signal to motor Permanent magnet The motor is just a 3 phase motor. You can ohm out all three legs.
High static pressure kills them If you close of diffuser or the furnace is oversized, filter is bad |
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Pressure switches |
You cant jump them out because it knows… |
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On a 208Vac system what happens if you are trying to diagnose a system if you are checking the system to ground? |
120V shows up everywhere |
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Roll out switches are manual reset? T/F? |
True |
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How do you clean the a flame sensor? |
Scotchbrite pad or 000 steel wool. |
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On a carbide HSI what can happen? |
Hot spot shows up as a white spot. check with amp clamp |
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Nitrite HSI are smooth? |
Yes Carbide one is rough |
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What are the 2 types of gas valves? |
Solenoid and diaphragm On a TQ they say you con ohm out the gas valve |
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How do you test a sparker transformer? |
Pull wire out 1/8 of an inch and look for spark. Dont hold wire with your hands |
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What does a dirty burner do? |
Delayed ignition. Loud noises. |
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Heat exchanger tests? |
Under-firing will cause rotting Over-firing causes cracks |
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How much static pressure in heat exchanger? |
Very little, so the static pressure inside the exchanger area is usually much higher. If the flame is good but then changes when the blower turns on there might be a crack.
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Permanent repair in commercial and temporary repair in residential. Must be inspected in either case. |
True |
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How do Humidifiers cause cracks? |
If they drip on the exchanger |
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What are the methods for diagnosing heat exchangers? |
• sulphur test, • smoke test, • wintergreen test, • sodium ion test (salt spray test), • water test, • flame monitoring, • visual inspection, • CO/CO2 monitoring, • gas tracer test, • pressure test (external) and • pressure test (internal). |
