What Size Tankless Water Heater To Replace A 50 Gallon

Tankless water heaters are rated past the maximum temperature rise possible at a given menses charge per unit. Therefore, to size a demand water heater, you need to determine the flow rate and the temperature rise you'll demand for its application (whole house or a remote awarding, such as just a bathroom) in your domicile. It is of import to note that you should never endeavor and save money by undersizing your tankless water heater.

Step i:

Decide the maximum number of devices yous want to run and their total flow rate. Then, add up their flow rates (gallons per minute). This is the desired flow charge per unit you'll desire for the demand water heater.

For case, allow'south say yous expect to simultaneously run a hot water faucet with a flow rate of 0.75 gallons per minute and a shower head with a flow rate of ii.6 gallons per minute. The flow charge per unit through the need water heater would demand to be at least 3.26 gallons per minute. To reduce flow rates, install low-flow water fixtures.

Stride 2:

Determine required temperature rise. To determine temperature rise, subtract the incoming h2o temperature from the desired output temperature. Unless you know otherwise, assume that the incoming water temperature is fifty°F (By using a depression temperature assumption y'all ensure that you will not undersize your tankless unit.

If you live in a warm climate your water temperature volition probable be much higher.) For almost uses, you'll desire your water heated to around 105–115°. In this instance, you'd need a need water heater that produces a temperature rise of 55°.

Step 3:

Sizing Example: An average shower volition be between 104–106° and uses 2.6 gallons of water. Bold your water temperature is 40° coming into your habitation, and y'all want to produce enough hot water to run 2 showers at the same time, what temperature ascent would you need to produce to attain this?

Respond: You'll demand to raise the incoming water temperature from xl degrees to 105. Yous'll demand to exist able to heat at least 5.2 gallons of water. So y'all'll demand a tankless water heater that can produce at least a lx degree ascent in temperature at 5.ii gallons per minute.

Catamenia Rates

How much hot water do you lot need at one time? Do y'all need to run 2 showers at the same time or maybe a shower and a couple sinks? The chart beneath shows the range of water usage range and boilerplate water temperatures for various fixtures. We suggest using two.5 gpm for a shower and 1.0 gpm for a bathroom every bit a reference point in determining your total simultaneous water needs.

Fixture	Boilerplate Flow GPM	Boilerplate Temp.
Tub	4.0 GPM	102°F
Shower	ii.5 – 3.0 GPM	104°F
Washing Machine	2.0 GPM	120°F
Dishwasher	1.5 GPM	110°F
Kitchen Sink	one.5 GPM	110°F

For example, if you are running 2 showers at the same time, yous volition need 5 gallons of hot h2o per minute from the tankless water heater. If yous were running a shower and the washing machine at the same fourth dimension, y'all would need 4.5 gallons per minute from the water heater. In either of these situations, you lot volition want to size the unit that meets or exceeds how much hot h2o yous demand at the same time.

Note: tankless water heaters are intended to heat beverage (drinking) h2o simply and the inlet water to a tankless unit should non be pre-heated.

Other Sizing Notes

Gas tankless water heaters are able to produce a larger temperature rise per gpm than electrical models. Well-nigh demand water heaters are rated for a variety of inlet temperatures. Typically, a lxx°F water temperature ascension is possible at a catamenia rate of v gallons per minute through gas-fired need water heaters and 2 gallons per infinitesimal through electric water heaters. Faster menstruum rates or cooler inlet temperatures can sometimes reduce the h2o temperature at the about distant faucet.

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