Domestic Hot Water Return Pump Sizing

Sizing any pump is challenging.

Domestic hot water return pump sizing. The system includes an alpha 15 55 circulator pump with a permanent magnet motor a temperature sensor and two push button controls. The friction loss for this diameter supply pipe will be about 1 4 ft per 100 ft according to the system syzer. Size the recirculation return line. All circulator pumps are typically sized based on the heat load and head loss pressure drop for a given zone.

Fitting a pump to manage this amount of the load should give you 90 95 percent of the hot water needs for your home. A sizing calculator i e. For 1 87 gpm we would choose a copper pipe. Part 1 find the pump gpm determine the heat loss of the total supply pipe using tables or rules of thumb.

Domestic hot water recirculation steps. Knowing the heat load in btu s for a given zone allows to calculate the required circulator pump s flow rate in gallons per minute gpm. The alpha 15 55 hwr d is a recirculation system that delivers hot water in homes at the push of a button and can save thousands of gallons of water each year. Circulating pumps should be sized to meet around 60 percent of the heating load which is the calculation you have performed including water needs leakage and pressure.

Domestic water systems are constantly getting brand new oxygen filled iron munching water. Determine the hot water needs of the household. Typically for systems where the distance from the hot water heater to the consumption fixtures exceeds 25 30 m. With a hot water recirculation system you can guarantee your customers the luxury of hot water in an instant becoming an increasingly scarce resource we waste millions of m3 every year as we wait for hot water when we turn on the tap.

Literature general brochure. A return circulation pipe is sometimes provided in a hot water system where it is desirable to have hot water available continuously at the fixtures. System syzer can be used to size the return line. Calculate the gpm required using a 10 f δt or other value as determined by the engineer.

Ashrae pipe sizing guide chapter 22 in ashrae fundamentals suggests using an approximate 50 to 100 addition to the estimated pipe length to account for fittings. Using a hot water recirculation pump eliminates instantly this expensive and annoying wait. Pump selection is a function of pipework layout affected by lengths of straight pipe and fittings during the design phase of a project the actual pipe route is unknown. Time for hot water to reach fixture without circulation pump.

For most residential systems the simple charts provided by manufacturers are sufficient. Determine pump head select pump. If the system has 140 degree water in the water heater then the sizing method maintains 130 degree hot water at the end of the system and then back at the cold water inlet to the water heater the temperature would be approximately 120 degrees. Hot water recirculation pumps can save water and energy.

Compare that to gpm times the number of balance valves and choose the larger value.