FC Furnace Installation Techniques 2

Question 1

What is the minimum clearance required between a furnace and combustible materials on the sides, unless the manufacturer specifies otherwise?

Accepted Answer

1 inch

Answer

Most furnace manufacturers require at least 1 inch of clearance from combustible materials on the sides, but always defer to the installation manual for model-specific requirements.

Question 2

When installing a furnace in a closet, which code requirement applies to the combustion air supply?

Accepted Answer

Two openings must be provided — one near the top and one near the bottom

Answer

NFPA 54 requires two permanent openings in confined spaces — one within 12 inches of the top and one within 12 inches of the bottom — to supply adequate combustion air.

Question 3

During a gas furnace installation, the technician discovers the supply gas pressure is 0.25 in. W.C. at the manifold under full load. What action is required?

Accepted Answer

Contact the gas utility to increase line pressure

Answer

Natural gas manifold pressure should typically be 3.5 in. W.C.; 0.25 in. W.C. indicates severely insufficient supply pressure requiring the gas utility to investigate the supply line.

Question 4

What is the purpose of a furnace drip leg (dirt pocket) installed on the gas supply line?

Accepted Answer

To trap condensate and debris before they reach the gas valve

Answer

A drip leg is a short capped vertical drop installed upstream of the gas valve to catch pipe scale, moisture, and debris that could damage the valve.

Question 5

A high-efficiency condensing furnace is being installed. Where must the condensate drain line terminate?

Accepted Answer

Into a sanitary drain or approved neutralizer

Answer

Condensate from high-efficiency furnaces must drain into a sanitary drain; if the condensate is acidic (pH < 5), local codes may require a neutralizer before it enters the drain.

(FC) Furnace Installation and Maintenance Certification Practice Test

(FC) Furnace Installation and Maintenance Certification Practice Test

FC Furnace Installation Techniques 2