HVAC Following Voltage Unit 12

Control Voltage

24v

Red (Control Voltage Wire)

Power

Blue (Control Voltage Wire)

Common

Yellow (Control Voltage Wire)

Cool

White (Control Voltage Wire)

Heat

Green (Control Voltage Wire)

Fan

Orange (Control Voltage Wire)

Reversing valve (only if you have a heat pump)

The 2 types of components in HVAC:

Power Passing (Switch) and Power Consuming (Load)

Power passing

(Switch) Allows power to pass through it

Power consuming

(Load) Anything that gets power and does a job with it

DMM

Digital Multi Meter

VOM

Multimeter (Volts, Ohms, Milliamperes)(Same thing as a DMM)

The 2 checks performed with the system denergized and isolated:

-Ohms

-Microfarads

Capacitors need to be de-energized + isolated + ___

Discharged, because caps. hold a charge

Isolated = ___

No wires connected

De-Energized = ___

No power coming to it

“When in doubt, ___ it out”

Ohm it out

The 2 checks performed with system energized:

-Volts

-Amps

‘Ohming out’

Ensuring there is a path for voltage to follow

OL reading while ohming out means

No path for voltage to follow

A # (any #) reading while ohming out means

There is a path for voltage to follow

How do we check fuses

Inline and energized (Because we’re checking voltage)

A voltage reading while checking a fuse means

Bad fuse (Open line)

A 0 reading while checking a fuse means

Good fuse

You cant read voltage in __

A straight line

Why can’t you read voltage in a straight line?

Because if the circuit is good then the voltage will pass through the DMM and keep going and give a voltage reading of 0. However, if the circuit is bad and has an open line then the circuit will be completed by the DMM and give a voltage reading.

Microfarads = ____

Capacitors (Microfarads are only used in caps.)

What is the only way to determine if a motor is running?

Performing an ampdraw

If something is consuming power it will have a what

it will have an ampdraw

How do you perform an ampdraw

Clamp on either your common or neutral wire, if an amp reading is received then the load is running

What wires are used for amp draws

Common or neutral

Neutral wires = ___ voltage

High voltage

Common wires = ___ voltage

Low voltage

AC Voltage (Alternating Current)

Flows back and forth (Outlets, generators, the power company etc.)

DC Voltage (Direct Current)

Follows in one direction (Batteries)

The 2 types of capacitors:

-Run capacitor

-Start capacitor

Run Capacitors

Metal Body and Oil filled

Start capacitors

Plastic body and Paper filled

which capacitor has a higher mF rating and why?

Start capacitors have a much higher rating than run capacitors, because it takes more energy to start a system than to maintain running it.

Duel Run Capacitors have what

3 terminals. 1 Common 1 Herm 1 Fan

On duel run caps. the common terminal has how many connectors?

4 Connectors

On duel run caps. the fan terminal has how many connectors?

2 or 1 connectors (Depends on manufacturer)

On duel run caps. the herm terminal has how many connectors?

3 connectors

What are the 2 types of breakers?

Single pole and Double pole breakers

Single pole breakers are at what rating

100+ volts

Double pole breakers are at what rating

200+ volts

What is the big # on a capacitor mean?

Common & Herm

What is the small # on a capacitor mean?

Common & Fan

Herm means what?

Compressor

Protons have what charge

Positive

Electrons have what charge

Negative

Neutrons have what charge

No charge

What are some examples of good conductors

Anything metallic (Brass, copper, silver, gold, etc.)

What are some examples of good insulators

Glass, wood, rubber, plastic, etc.

Volt

Unit used to measure the potential difference or the electrical motor force (emf)

Ampere

Unit of measure for current flow

Ohm

Unit used to measure resistance

What is the symbol used for ohm

Ω (Omega)

As resistance ____, current flow ____

Increases, Decreases

As resistance ____, current flow ____

Decreases, Increases

A basic electric circuit needs:

-power source

-Conductive path

-a load

-OPTIONALLY a switch

How are switches and safety devices wired?

In series

How are loads wired?

In parallel

Where do we get AC from

The power company

Ohms law symbols:

E or V - Voltage

I - Amperage

R - Resistance

What is the total resistance in a series circuit

The sum of each resistance in the circuit

What is the total resistance of a parallel circuit

The total resistance will always be lower than the lowest resistance in the circuit

Contactor

One or more sets of contact points controlled by magnetism (for test purposes can be repaired, but not in the field)

Relay

One or more sets of contact points controlled by magnetism that is a smaller scale and enclosed. CANNOT be repaired.

Watt

The amount of power used when 1 amp flows with a potential difference of 1 volt

Electrical power(P) is measured in what

Watts

Watts = __ x __

E x I

1 kW = ___ watts

1000 watts

Power from the electric company is received as what

kWh (kilowatt hour)

Transformers have what

A primary and secondary winding

A larger wire will have lower __ and more __

Resistance and more current carrying capacity

Wire sizes are identified by

AWG (American Standard Wire Gauge)

NEC stands for

National Electric Code

LRA

Lock Rotor Amperage - Amperage pulled at start up, but before the rotor starts to turn. (Typically 5-7x greater than FLA)

Fuses are a ___ device

One time use

Cartridge fuses are found and use where

At the disconnect box

Diodes

Only allow current to flow in one direction

PTC

Positive Temperature Coefficient Thermistor - The resistance increases and temperature increases

NTC

Negative Temperature Coefficient thermistor - The resistance decreases as the temperature increases

Where are thermistors found

Embedded in the windings of the motor

What is the difference between a diode and a rectifier

Under 1 amp = diode, Over 1 amp = Rectifier

Rectifiers do what

Change ac voltage to dc voltage

Heat sinks dissipate heat using

surface area