# FREE Certified Energy Manager Motors and HVAC Questions and Answers

#### At a flow rate of 6750 cubic feet per minute, air with a relative humidity of 50% and a dry bulb temperature of 69°F is heated to 90°F. How much BTU per hour is needed for this process? Don't consider duct losses.

#### There are roughly how many cooling degree days in a calendar year if the outside temperature stays constant at 75°F:

" 65 Degrees F is the “target” outside temperature. If the average temperature is 75, then we are 10 degrees “off target”. For 365 days, the Cooling Degree Days would be:

(10)(365)

=3,650 CDD per year"

#### The COP of a 250-ton chiller is 4.2. What is the chiller's load (in kW) while it is operating at full capacity?

Power input divided by Powermoved is the Coefficient of Performance. This machine can move 250 tons of cooling using a 250 ton chiller, hence the power input would be:

#### How much can you afford to spend for the waste heat exchanger (total installation cost) if your company's MARR is 30% and it saves $1,000,000 year and lasts for 7 years?

In this problem, we are given A and must find P. Logically, for this project to have a positive NPV, we know the P (from the positive cash flows) must be at least equal to the Cost. Thus, let's find the P and then that is the maximum we can pay for the installed cost. The PV of the Annual Savings of $1,000,000 per year:

= $1,000,000/year (P/AIN Factor)

= $1,000,000/year (2.8021)

= $ 2,802,100

Thus, we can pay $2,802,100 for the Waste Heat Exchanger and still have a positive NPV.

#### The US industries and structures with the highest installation rates of electric motors are:

Induction of Alternating Current The most common form of motor used in buildings is a motor.

#### Pick the most accurate estimate of electric motor efficiency (in percent) when motors are appropriately loaded in the absence of additional data:

An appropriately loaded motor typically operates at 90% efficiency.

#### What are HP savings if a motor has a Variable Speed Drive (VSD) fitted that slows down a 200 HP motor by 20%?

Use the “Fan Laws” HP2=HP1 (RPM2/RPM1)3. Therefore, if the new speed (RPM2) is 80% of the old speed (RPM1), the new power load (HP2) will be:

HP2=HP1 (.8)3

HP2=200HP (0.512)

HP2=102.4 HP