FC Load Calculations & Equipment Sizing 3

Question 1

Which building characteristic most significantly increases heating load in cold climates?

Accepted Answer

Exterior wall area with low insulation R-value

Answer

Interior partition wall area

Answer

Number of interior doors

Answer

Floor plan shape (rectangular vs. L-shaped)

Question 2

What is the effect of a slab-on-grade foundation on a home's heating load compared to a basement?

Accepted Answer

Slab-on-grade can increase perimeter heat loss if not properly insulated

Answer

Slab-on-grade reduces heating load because the ground provides insulation

Answer

Slab-on-grade has no impact on heating load calculations

Answer

Slab-on-grade always results in a lower heating load than a basement

Question 3

What does 'internal heat gain' refer to in a load calculation?

Accepted Answer

Heat generated by occupants, appliances, and lighting within the conditioned space

Answer

Heat produced by the furnace itself during operation

Answer

Heat recovered from flue gases by a secondary heat exchanger

Answer

Heat transferred through the ground beneath the foundation

Question 4

A technician is sizing a furnace for a 2,000 sq ft home in a cold climate with a calculated load of 35 BTU/h per square foot. What is the approximate total heating load?

Accepted Answer

70,000 BTU/h

Answer

35,000 BTU/h

Answer

105,000 BTU/h

Answer

17,500 BTU/h

Question 5

Why is using a simple 'rules of thumb' (e.g., BTU per square foot) discouraged as the sole method for sizing furnace equipment?

Accepted Answer

Rules of thumb ignore critical variables like insulation, windows, and climate, leading to inaccurate sizing

Answer

Rules of thumb are not recognized by ASHRAE or ACCA

Answer

Rules of thumb always result in undersized equipment

Answer

Rules of thumb are only valid for commercial buildings, not residential

Question 6

What is the relationship between a furnace's 'input' rating and its 'output' (or delivered) heating capacity?

Accepted Answer

Output capacity equals input rating multiplied by the furnace's AFUE efficiency rating

Answer

Input and output ratings are always identical for gas furnaces

Answer

Input rating is always lower than output capacity

Answer

Output capacity is determined solely by the blower motor size

Question 7

When selecting a two-stage furnace to meet a heating load, how should its high-stage output capacity be sized relative to the design load?

Accepted Answer

High-stage output should be sized to meet or slightly exceed the design heating load within Manual S limits

Answer

High-stage output should match the design load exactly with no margin

Answer

High-stage output should be sized at 200% of the design load for redundancy

Answer

High-stage output only applies to cooling and is irrelevant to heating load sizing