nate ac service test

what is the recommended external static pressure used for heating and cooling equipment with blowers for 5 tons of cooling or less

.5 IWC

the continuity reading on a functional fuse will be

0 ohms

a 120v x 24v step down transformer has a rating of 40va. must not be connected to more than

1.7 amps 40/24=1.666777

for indoor air quality purposes the minimun distance between and economizer and a plumbing vent iut

10ft

which microfarad value indicates a good start capacitor rated at 145/175 mfd a)130 b)160 c)180 d)190

160

load across T1 & L1 when compressor contractor is de-energized and compressor windings in tact.

230v Springs are used to open the contacts when the magnetic field is de-energized. The coils of a contactor are energized by the control voltage of the system. This voltage is typically 24, 120, 208/230, or 460 volts.

with the thermostat set to on which of the following measurements indicates a call for residential indoor blower operation

24v at load side of relay **** not sure

according tot the generally accepted national code, what size should the condensate be.

3/4"

cfm per ton of cooling

350-450 cfm

a duct 36"x24" with an average of 600fpm is handling what cfm

3600

what is the maximum acceptable supply voltage tolerance for a 120v circuit

5%

an air conditioner refriderant circut should be evacuated to a minimum of

500 microns

Electronic air cleaners can operate with internal voltages as high as?

5000v

a system is supplied with a factory charge of 5 pounds 10 oz for a 15 ft line set. and requires .6 oz per additonal foot. what is the total charge if the lineset needs to be 25ft in total.

6lbs

A technician has determined a supply in a flexible duct system is leaking. What should be checked?

All connections inner and outer layers.

What is the component that reduces sound transmission and prevents water leaks of a package heat pump installed on a roof?

Curb Gasket

Why do some electromechanical type thermostats require connections to both the hot side and common side of the low voltage transfromer

Display lights must be powered using both sides of the line

According to fire protection codes, when should fire dampers be used

In any air duct that passes through a two hour fire rated wall or partition of a light commercial installation

which of the following are the first two checks typically made on a electronic control>

Proper input voltage and proper output voltage.

The following conditions exist in a circuit that supplies power to three parallel loads.One load is resistiveOne load is capacitiveOne load is inductiveHow do you find the total current?

The sum of the currents through each load.

During a service call on a unit the technician finds that the wiring diagram is missing from the access panel. The technician may begin troubleshooting by:

Tracing the circuits either mentally or on a sketch pad

which of the following can casuse lower than normal suction pressure

a restriucted drier

what does a test of the compressor oil after a burnout indicate

acidity

which of the following should be done to reduce vibratiion transmission in sheet metal ductwork

add isolations collors

In a low voltage circuit, a corroded wire-to-terminal connection acts in the circuit like an

additional resistor

what is the effect on supply airflow using a psc blower motor when adding a ducted return to a previously non ducted return

airflow will be increaded

what will refrigerant oil in a hose cause when a technician is checking the pressure in an operating system with manifold gauge

all readings will increase in value

which mesures duct static pressure

anemometer

electronic air cleaners do not remove

animal fur

where should a technician check voltage to an energized compressor

at the load side of the compressor contactor ** not sure

outdoor condensing units that are installed in areas where flooding is possible must

be mounted above flood level

in an economizer system the enthalpy control is used to measure

both temperature and moisture content

what factors should a technician determine when replacing a contactor

coil voltage coil amp draw wire sizes and nmumber of poles

a high pressure limit control is used to shut down a compressor is condensing pressure becomes excessive, is typically installed to sense:

compressor discharge line pressure

to achieve a specific seer rating which components must be matched

condensing unit and evaporator

the technician believes that a hermetic compressor has a permanently openn internal overload protectio the technician should test the compressor while it is?

cool

how would a technician repair a 1" hole in a section of duct board

cut out the hole, and fabricate, staple and tape a plug in place to fill the hole

return air leakage in a hot attic will

decrease capacity

which of the following is a likely problem if the air across the evaporator of an air conditioner has a high temperature differential

dirty filter or evaporator

in a simple refrigeration system the refriderent boils in the

evaporator

on a three ton unit installation, the measured airflow euals 1550 cfm,what does this indicate

excess airflow

what does a red or orange glow from the resistance elements in a duct heater indicated

flow of air is insuffient

a delay on make relay delays load from

from energizing after a fixed time after a cycle

a delay on break relay delay load

from energizing for a fixed time after a cycle starts **not sure

a system air flow check is used to diagnose

humidity problems

on a residental no cooling call, typically the first check would be

if the thermostat is calling for cooling

which of the following is a typical use of an outdoor ambient thermostat in a split commercial system air conditioner

increase blower speed in high ambient

what effect does overcharging have on sub cooling

increase sub cooling

benefit of a media filter vs a fiberglass air filter

indoor air quality

the slab of a packaged air conditioner at grade level should be

isloated from the structure to minimize noise

what is the typical method of staging a two stage compressor in a air conditionoing system

it is based on the deviation from the thermosetpoint

a technician finds a R-410a system with a suction pressure of 105 psi. this indicates that

it is undercharged

what precautions need to be taken with a packaged ac system with ductwork installed outside

it must be insulated and weatherproofed

other than using a two-stage compressor what is another method for capacity control

liquid line receiver

to properly check the compoerssor and its line volatage wiring, the technicain should mesure resistance at the

load side of the compressor contactor

the lubricating oil primarily ised with r-22 is

mineral oil based

the suction line instulation is important to control condensation and what?

minimize heat transfer

will a capacitor start capacitor ruun motor that has an open run capacitor start

no it would be unable to start without the run capacitor

what is the purpose of the grounding conductor?

not sure, but i think personal and equipment protection

the continuity is checked through what measurement

ohms

When a split system air conditioner has a counterflow air handler, what are the best locations for return air grilles?

on a sidewall next to the ceiling

the purpose of a sequencer in an auxiliary 20kw electric heater is to energize

one or two elements and the blower motor simultaneously followed by remaining elements in timed intervals

The airflow path of an outdoor unit pull through coil is air moves from the

outside to the inside.

what would cause a voltage reading across a closed contact in a 24v control circuit

pitted or dirty contacts

the purpose of flux is to

reduce oxidation

a residential supply diffuser that is noisy because of a loose vane is best serviced by.

replacing the diffuser

how should a mercury bulb be disposed of

return to approved recycling facility

S.E.E.R stands for

seasonal energy efficiency ratio

what steps are necessary to clean a two row curved condenser coil

separate the two rows of coils, spray all surfaces with proper coil cleaner and water flush

most safety controls are wired in

series with the load

When performing a cycle check during a preventive maintenance call, the technician should:First, check with owner for equipment performanceNext, turn the unit off at the thermostat system switch then:

set fan switch to ON and check that the blower is running

electronic type leak detectors typically have a push button or knob for setting a reference level, this is useful for

setting the detector for use in environments with ambient refrigerant vapor

how would a technician check a three phase blower motor to determine that it is rotating in the proper direction

start the motor briefly using the disconnect to verify proper rotation

thermostatic expansion valves meter refrigerant flow to a coil to maintain

superheated refrigerant leaving the coil

when an air conditioner with a thermostatic expansion valve is installed is overcharged, the excess char sgould be removed by recovering some charge and checking

system pressure

hard start kits are typically required on

systems with reciprocating compressors and TXV metering devices

which of the following is a proper operation for a packaged air conditioning system using an electric control board

the blower condenser fan and compressor comes on at the same time

during an annual service check up, it is discovered that there is a moderate amount of resistance on a bellyband crankcase heater. what does this condition indicate

the crankcase heater will operate

if an air conditioning system needs to operate in a low ambient condtion, the condenser may become to effiecent

the head pressure becomes too low and the condenser fan motor needs to be slowed or stopped

The blower wheel used by a direct drive blower will have an rpm that is:

the same as the blower motor.

service site condtionms

the system blower is operating normally but the supply registers are to restrictive

when a disc type close on rise pressure control is being used a s a loss of charge limit control on the liquid line has its setpoint drift lower

the system is less likley to shut down as a result of a small leak

what effect does insuffiecnt voltage have on a solenoid valve

the valve will vibrate or chatter**** not sure

an important consideration when installing a motorized economizer is to check to be certain that

the vanes operate without binding

two 90 degree short radius elbows are added to an air conditioner suction line

there will never be an effect on the system performance

What condition can cause a reduction from design capacity in a heat pump?

undersized suction line

supply ducts running through unconditioned spaces should be insulated and have

vapopr barrier