Residential Electrical Inspector (CAE)

HVAC

Lesson 11

Based on the 2014 OESC

Updated: January 2017

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This presentation details the steps involved and the

code requirements for electrical inspection of HVAC

equipment.

After completion of this presentation, the inspector

should be capable of verifying that the HVAC

equipment was installed in line with the electrical

requirements of the Oregon Electrical Specialty Code

and National Electrical Code.

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Introduction

Basic Information

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C

B Disconnect

HVAC

Equip

Typical installation consists of an overcurrent device, wiring

to a local disconnect and wiring and conduit to the

equipment. The disconnect may contain fuses depending

upon manufacturers installation instructions.

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C

B

Disconnect HVAC

Equip

Electrical items to inspect on an HVAC change-out.

1. Is overcurrent protection correct?

2. Is wire size from overcurrent device to disconnect correct?

3. Is the right disconnect installed?

4. Is the wiring method from disconnect to unit correct?

5. Is the wiring from disconnect to the unit correct?

1

2

3

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Applicable Code Sections 2014 OESC and NEC

110.3(B): Installation per manufacturers instructions

110.11: Equipment suitable for environment

110.14: Electrical connections (temperature rating)

110.26(A): Required working space around equipment

210.3: Rating of branch-circuit

210.63: Maintenance receptacle within 75 feet

240.6: Standard breaker and fuse sizes

250.4: Purpose of grounding and bonding

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Applicable Code Sections 2014 OESC and NEC

continued

250.118: Types of equipment grounding conductors

250.122: Size of equipment grounding conductor

T310.15(B)(16): Conductor ampacity table

310.110: Identification of phase conductor (re-

identifying white wire in a cable)

334.12: NM Cable not rated for wet location

348.12: FMC not suitable for wet location

350.10: Uses permitted for LFMC

350.30: Securing and supporting requirements of

LFMC

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Applicable Code Sections 2014 OESC and NEC

continued

356.10: Uses permitted for LFNC

356.30: Securing and supporting of LFNC

424.3(B) Heating circuits are considered to be

continuous requiring a 125% adder

440.6(A): Use nameplate information for install

440.14: Disconnect location (in sight of)

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Caution:

One portion of an HVAC installation often misunderstood

deals with sizing of conductors and their overcurrent

protection. Generally Article 240 specifies that

conductors need to be protected to their ampacity. 240.3

modifies this requirement as it applies to HVAC

equipment. As long as the appropriate circuit breaker

(HACR) or fuse (one time) is used, the conductor may be

smaller than traditionally used for a specific overcurrent

device.

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Definitions: NM Cable: Nonmetallic-Sheathed Cable. A factory

assembly of two or more insulated conductors enclosed

within an overall nonmetallic jacket.

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Service-Entrance Cable A single conductor or multi-conductor assembly provided

with or without an overall covering, primarily used for

services, and of the following types:

Type SE. Service- entrance cable having a flame-retardant,

moisture-resistant covering.

Type USE. Service -entrance cable, identified for

underground use, having a moisture-resistant covering, but

not required to have a flame-retardant covering.

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SE Cable is

generally marked

with the number of

and size of

conductors

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NM Cable

#14 White 15-amps

#12 Yellow 20-amps

#10 Orange 30-amps

SE Cable

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Step 1

Determine Installation

Requirements

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In order to start the electrical portion of the inspection, basic

information is required. The minimum ampacity of the

circuit is needed, the type of and size of overcurrent

protection is needed (fuses and/or circuit breaker)? What are

the environmental conditions, (wet location, corrosion, dust,

etc.)? Are the wiring methods approved for the environment,

(conductors, raceway type, securing/supporting etc.)? Is a

fused disconnect required?

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Look for

maximum size

overcurrent

protection and

minimum

ampacity of the

circuit. Get the

information

from the

nameplate

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Verify that the

HVAC products

are certified and

installed

according to

nameplate

information and

information

instructions

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Occasionally,

there is a

maximum and

minimum

overcurrent

protection

requirement

along with the

minimum

circuit size

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Gas packs

may also

have circuit

and

overcurrent

requirements

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Electric heater packages may have ampacities and

overcurrent values that require large conductors and/or circuit

breakers and fuses. They are also considered to be

continuous loads, 424.3(B).

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Step 2

Verify that ampacity of the conductors

and overcurrent protection meet the

nameplate information

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When looking at conductors, environmental conditions may

come into play. Heat is the biggest issue associated with

conductors. As heat increases, the ability of a conductor to

carry a specific load (amps) drops. The ampacity table found

at T310.15(B)(16) is based upon an ambient temperature of

86F. If the conductors are installed on the side of the

structure facing the sun, the temperature can increase beyond

the 86F range. Also, the lugs that the conductors are landed

on may only be rated for 60C. A location outside is

considered to be a wet location. NM Cable (Romex) is not

approved for this application.

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The conductors that run from the disconnect to the unit

should have a marking along the side of the conductor. The

marking identifies the insulation (outer jacket) of the

conductor and identifies what type of environment the

conductor is rated for. The marking should be THWN-2 or

equivalent. The “W” designator indicates the conductor is

rated for wet locations and the “-2” indicates a starting

temperature rating of 90C.

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Note the difference in operating temperature from wire

insulation to wire insulation.

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An HVAC unit indicates a minimum circuit ampacity and OC

of 35-amps, if NM Cable is used, a #8 conductor is required

from the panel to the disconnect and a #10 THWN-2 could be

used from the disconnect to the equipment. 27 of 46

NM Cable is always rated upon the ampacities found in the

60C column of Table 310.15(B)(16). If SE Cable is used to

supply a heating unit and the SE Cable is installed in

insulation, then the SE Cable ampacity is also based upon the

60C column. Ampacities of free conductors in a raceway are

based upon the insulation rating and the termination ratings

of the lugs. If the lugs have no markings or the disconnect or

equipment is not marked, then the 60C column is used for the

ampacity.

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Typical disconnect

used with heat

pumps outside.

There may be fuses

located behind the

cover. Verify the

nameplate

information.

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Non-fused

disconnect,

conductors are not

landed correctly

nor identified as

required by Section

310.110

Should be

moved

Should be

re-identified

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Approved re-

identification of

white conductor

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Local disconnect and

overcurrent protection

as required by Section

424.19

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Fused disconnect,

white conductor needs

re-identified.

Note lack of

grounding.

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HVAC

overcurrent

protection

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Step 3

Wiring Methods

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Typical installation;

individual conductors

rated for a wet

location are installed

in liquid-tight

flexible non-metallic

conduit. (LFNC),

Article 356. Check

for proper securing

and supporting, tight

connections and

proper sizing.

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Disconnects are

required to be in sight

of a heat pump (Section

440.14) and lockable.

The gate blocks the

view of the disconnect.

In sight of means:

visible and within 50

feet.

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Note the

disconnects are in

sight of but not

marked to

indicate which

unit they

disconnect

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Verify that the raceway

is connected to the

equipment and properly

supported and tightened

in place. This is liquid-

tight flexible metallic

conduit (LFMC).

Generally an EGC is

also required.

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This unit has a heat

pack and needs two

circuits, one for the

blower and the other

for the heat strips.

Local disconnects are

located behind the

plastic cover at the

bottom.

Nameplate

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Same situation

as the previous

slide but the unit

is laid on it’s

side.

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NM Cable used outdoors

in a wet location. This is

a violation of Section

334.10 and 334.12

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FMC and

metal box

are

required to

be

grounded

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Copper SE cable used for

a temporary connection to

a heat pack

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#10 NM Cable in the

wall, THWN-2 is used

outside in the

raceway. Note the

EGC’s and bonding to

the enclosure.

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Many inverter type units have

a main unit and at least one

additional remote unit.

The same requirements apply,

use the nameplate information,

verify the wiring methods to

the unit and to the remote head

or heads and ensure the

disconnect shuts off the main

unit and any remote heads.

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