Water Heater Sizing Formula

H out q ρ dt c p 1 where.

Water heater sizing formula.

Rd total gallons of 120 f water required tw total number of washers 1 2 conversion factor 160 f to 140 f c2 diversity factor for 20 minute cycle c3 diversity factor for 30 minute cycle sr minimum storage requirement. Sizing storage and heat pump with tank water heaters. 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. To select the right state water heater for your home try our xpert product selector for personalized estimates of the performance and estimated energy cost.

The higher the btu the more water it is capable of heating. Water heater sizing heating water is the second biggest energy expense in your home. Getting a heater that is too small will create havoc in your household but getting a heater that is too big will cause you to waste money on the initial purchase and costs to. Once you have your total flow rate and the required temperature rise you can find the right size tankless water heater for your home.

Smith pro size sizing program is a tool that can be used to estimate water heater requirements for many common applications. The first hour rating is the number of gallons of hot water the heater can supply per hour starting with a tank full of hot water. Pro size is intended to assist in selecting water heaters or boilers that best meet the specific job requirements. Input heating capacity of a domestic hot water system.

Btu is a measure of how much energy is needed to heat water. Establish peak demand measured in gallons per hour gph. Rise x 1 0 btu input gph x 8 25 x temp. Below we ve highlighted what size water heater you would need in our example of 6 5 gpm at a 63 f temperature rise.

Rise x 1 0 btu hr. Output heating capacity of a domestic hot water system. Then evaluate tank water heaters on the same gph basis to determine how many gallons of storage are needed to meet this demand. Sizing tank water heaters.

After sizing a tankless water heater and evaluating your needs it may become clear that a tankless water. The formula goes like this. Knowing your family s first hour water usage will help you get the right size heater. H out heating capacity output btu h q flow rate gph ρ 8 34 density of water lbs gal dt temperature rise o f c p 1 0 specific heat of water btu lb o f input heating capacity.

1 btu is equivalent to the amount of energy it takes to raise 1 lb of water by 1 f. Various formulas for water heating calculations efficiency gph x 8 25 x temp.