If a 1,500-gallon spa has a starting temperature of 91 degrees, how many BTUs are needed to raise it to 102 degrees?

To determine the BTUs required to raise the temperature of the spa water, you can use the formula:

BTUs = Volume (in gallons) × Temperature Change (in degrees Fahrenheit) × 8.33

First, calculate the temperature change needed. In this case, you need to increase the temperature from 91 degrees to 102 degrees, resulting in a temperature change of:

102 - 91 = 11 degrees.

Next, take into account the volume of the spa, which is 1,500 gallons. Now, substituting the values into the formula gives:

BTUs = 1,500 gallons × 11 degrees × 8.33.

Calculating this step-by-step:

1. Multiply the volume of the spa with the temperature change:

1,500 × 11 = 16,500.

2. Multiply this result by 8.33:

16,500 × 8.33 ≈ 137,445 BTU.

This calculation demonstrates that raising the temperature of 1,500 gallons of water by 11 degrees requires approximately 137,445 BTUs, making this the correct option. This type of calculation is essential for pool and spa contractors to effectively determine the heating demands