Application Note

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Application Note

When start-up

inspections

pay off for HVAC

F r o m t h e F l u k e D i g i t a l L i b r a r y @ w w w . f l u k e . c o m / l i b r a r y

After years of being a service-

man—slinging ladders, dragging

tools across attics and through

crawlspaces, standing in all sorts

of weather on rooftops—I can

now leave the service work to

one of the younger techs with

better knees and concentrate

on my primary job as company

start-up man. After new equip-

ment is installed, I make sure the

system is operating efficiently

as designed, count the parts

and pieces used on the installa-

tion in order to accurately track

costs, make sure the customer

understands the controls and

operation, and pick up the final

payment. This has gone a long

way in reducing the number

of warranty performance com-

plaints, improving our pricing

structures, almost eliminating

overdue account receivables, and

enhancing our reputation.

Customer profile

Take this job: a furnace replace-

ment in a 25-year-old, two-story

colonial-style home. We replaced

the natural draft gas furnace

with a two-stage, energy-effi-

cient direct vent condensing

natural gas furnace equipped

with a variable speed blower.

We also added a zone control

panel designed to operate with

a variable speed motor that sup-

plies the correct air volumes to

each zone (two zones each for

the first and second stories of the

house) without the need for a

bypass damper. Additionally, we

installed a two-stage condensing

unit, evaporator, heat recovery

ventilator, humidifier and state-

of-the-art air purifier.

Tools

Today, I’m on site to make sure

the new systems we installed are

performing at peak efficiency—

and looking forward to trying out

my new Fluke 902 HVAC Clamp

Meter. I’ve always enjoyed keep-

ing pace with the latest technol-

ogy in multimeters and currently

use a Fluke 87V with several

temperature accessories and an

amp clamp transducer for times

when I want true-rms amp read-

ings. When it’s time for serious

work and diagnostics, I’d be lost

without it. But with features like

true-rms ac volts and amps, dc

volts, microamps, temperature,

capacitance, ohms and continu-

ity beeper, the Fluke 902 could

become my everyday meter.

Systems check

It makes sense to start in the

basement with the furnace so

the house has more load by the

time I’m ready for the air condi-

tioner start-up. I’ll record all my

readings on a start-up form, and

leave a copy in the equipment

document bin for the service

technician to reference during

annual maintenance calls. The

other copy will be filed with the

job jacket at the office.

I measure and record externals

first: gas pipe sizing, vent size

and equivalent length, electrical

wiring including good quality

ground from furnace to service

panel. I’m anxious to put my new

clamp meter through all of its

paces, so I start by checking the

capacitor on the combustion air

Operator: Bill Dove, CM, HVAC trainer

and installation specialist

Measuring tools: Fluke 902

HVAC Clamp Meter, 80PK-24

Air Temperature Probe

Inspections – residential furnace

replacement: Path to ground;

equipment operating values; vent

and duct temperature; flame signal

and combustion air blower/inducer

pressure differentials

Testing

Functions

Case

Study

Summary of content (3 pages)

PAGE 1
When start-up inspections pay off for HVAC Testing Functions Case Study After years of being a serviceman—slinging ladders, dragging tools across attics and through crawlspaces, standing in all sorts of weather on rooftops—I can now leave the service work to one of the younger techs with better knees and concentrate on my primary job as company start-up man.
PAGE 2
blower and measure 7.2 microfarads. It’s within 10 % of its 7.5 MFD rating, so it’s fine. I measure and record 123 volts to the furnace and 28 volts on the transformer secondary. I connect my manometers to the inlet and manifold side of the gas valve. I check the static gas inlet pressure and record 6.5” WC (water column). I’ll watch for a pressure drop when the gas valve opens. Electronics can perform erratically, or not at all, if there is not a good ground path back to the source.
PAGE 3
mocouple Adapter. This adapter interfaces the standard Type K thermocouple mini-pin connector to the standard dual banana plug inputs found on DMMs and clamp meters. This will allow me to use my pipe clamp probes, piercing probes, immersion probes, surface probes and air probes with the Fluke 902. The next measurements I take are important benchmark tests because a definitive initial value is not specified: flame signal and combustion air blower/inducer pressure differential.