Water Heater Calculation Formula

Tankless water heater sizing calculator.

Water heater calculation formula.

Calculations for heating air in a duct. Also we can use this formula as the basis of similar calculations for heating oil. Rise x 1 0 btu hr. Formula i apartments hotels and motels designed for family or transient living rd tu x fr x af x c x 0 8 sr rd x 25 for minimum formula ii convention type hotels and motels rd tu x fr x af x 0 8 sr rd x 33 for minimum note.

Calculate the kilowatt hours kwh required to heat the water using the following formula. Once the volume of air in standard cubic feet per minute scfm and the required temperature rise in f δt are known the required kilowatt rating kw of the heater can be determined from the following formula. Hi john it takes the same amount of energy to heat water from 48 degrees to 52 degrees as it takes to heat water from 58 degrees to 62. Generally oil heats up in half the time of water due to its density.

98 c to 102 c this does not hold true any more. Input specific heat btu output gph x 8 25 lbs gal. Pvi strongly recommends insulating all hot water lines and all calculations in this guide are. To properly size a storage water heater for your home including a heat pump water heater with a tank use the water heater s first hour rating.

Various formulas for water heating calculations efficiency gph x 8 25 x temp. Rise x 1 0. Pro size is intended to assist in selecting water heaters or boilers that best meet the specific job requirements. Convert the flow rate to scfm using the formula given.

Smith pro size sizing program is a tool that can be used to estimate water heater requirements for many common applications. T 2 final water temperature. We already covered gpm. Pt is the power used to heat the water in kwh.

However oil needs a much lower watts density element than water as described in the how to choose an oil heater article. T 1 initial water temperature. Now you need to understand what temperature rise means. 2 c to 2 c or from fluid to gas e g.

Before we get to how to use the calculator to size a tankless water heater let s talk about the factors that go into understanding what size inline water heater you need. Sizing storage and heat pump with tank water heaters. Visit the solar water heaters page for more on these calculations. Hence the required power to heat the different temperature formula can be written as p kw 4 2 x l x t 2 t 1 3600.

The first hour rating is the number of gallons of hot water the heater can. Pt 4 2 l t 3600. But when the state of water changes from solid to fluid e g. L is the number of liters of water that is being heated and t is the difference in temperature from what you started with listed in degrees celsius.