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35 Cards in this Set
- Front
- Back
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How to make maxitrol go to high fire (probably not on test) |
Remove 4 for high fire Remove 7 (or 8) for low fire |
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Direct fired is 100% efficient? |
True |
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When are they designed to turn on PPM? |
1000 ppm will turn it on |
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In the winter time? |
Take your filters off |
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Indirect differences between it and direct? |
Has: Heat exchanger, roll out switch Doesnt have: profile plate
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Isolation dampers are usually parallel? |
True |
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What is the purpose of a V-Bank filter configuration? |
Allows for more filter surface area. Magnehelic gauge measures static pressure across the filters to know how plugged the filters are. |
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Rate of flow across the burner?
How does variable airflow MUA work with variable airflow? |
2500-3200 fpm Low pressure proves above 2500 fpm High pressure trips if above 3200 fpm
Variable airflow uses a modulating profile plate |
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Dont need to know |
Back (Definition) |
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What is a common temperature rise? |
Direct Fired Burner • Most direct gas-fired MUAs have a supply-air temperature between 50°F and 100°F (10°C and 38°C) • Temperature rise ranges from 0°F to 100°F |
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If you open the profile plates then open both? T/F |
True, if you open them then the velocity will increase |
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Service call: Blower Not Running Name some causes.. |
Blower Not Running • If the blower is not running: • Check power supply to the unit and motor Verify that freeze protection has not activated • Make sure dampers are operational • Make sure end switch is working properly. Normally the switch closes when the damper is open • Check Exhaust fan is on • Check air Filters. •motor running backwards |
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Where are the ports located to measure low velocity or high velocity |
Low port is after the profile plate
High port is before the profile plate |
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The pressure switches sense static pressure, when should you test your switches? Heat on or off? |
Heat must be on |
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What is the maximum allowable voltage drop across the contactor? |
No more that 3% voltage drop across the contactor |
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Name three types of MUA heat exchangers? |
3 Types of Heat Exchangers -Clam Shell -Tubular -Drum and Tube |
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What is a reverse interlock? |
A reverse interlock is when the MUA will shut down the EF if the MUA fails. |
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What are the 2 types of burners for MUA? |
Burners • The two main types of burners used in indirect fired MUA units are upshot and in-shot • Depending on the age of the MUA, most have in-shot burners. • When diagnosing an ignition issue, be aware that few things can go wrong with the burner itself other than becoming misaligned or dirty. |
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What is the temperature of a HSI? |
Hot Surface Ignition Direct Spark Ignition • Ceramic materials with an electric heating element • When 120 V is applied to the igniter, current flows through the element causing it to glow red. • The surface temp may exceed 980°F • An HSI is only energized for a few seconds. |
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What is the voltage of an ignition transformer? |
Its in the thousands.
1/8 inch away from surface. Hold it with insulated wire |
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flame sense question and diaphragm question on TQ? |
Not sure what they are.
Bleed tube goes from diaphram to the pilot flame (standing flame) Removes excess gas from diaphragm. You need a bleed line so the solenoid can open.
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How to make maxitrol go to high fire (probably not on test) |
Remove 4 for high fire Remove 7 (or 8) for low fire |
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How many fins on a cooling coil for a MUA? |
6-12 fins per inch |
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If the unit is a direct fire the DX coil is down stream of the burner? T/F |
True, If it was upstream and there is a refrigerant leak then you are going to have issues |
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Dont need to know the acronyms for the BMS systems |
Blah |
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Direct fired MUA btu/hr? |
94,000-18 million |
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Mua temp rise? |
50-100F |
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What are the three types of heat exchangers? |
Drum and tube Tubular Clam shell |
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When should the burner on off set point? |
10-20F below discharge setpoint |
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What is the temperature range in Celsius? |
55C max temp rise |
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What is the discharge head of a MUA? |
The outlet |
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Where is the evaporator on a MUA? |
After the fan |
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2500-3200 units? |
Feet Per Minute!! |
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High pressure is before profile plate? |
Yes! |
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F = (C x 1.8) + 32? |
Yep Fpm = 4005 * (root (vp)) |
