new tankless system

Stan123

I'm considering installing a tankless system as part of a home renovation but don't know how big of a unit i will actually need.  Will have a pretty active household using hot water in 3.5 baths, dish washer and laundry.  How many GPM's will I really need?  Should I be considering multiple units with point of use heaters as well? I'm located in the North East, so temp, rise, as I understand it, is also going to be a concern.  thanks  for  the input

TonyS

Try here

http://www.navienamerica.com/unit/step_01.aspx

CMadatMe

Tankless Sizing

Here is the formula

GPM Required x Temp Rise x 500 = Btu's needed

What's in those 3.5 baths? Basic 2.5gpm shower heads? Body Sprays? Any whirlpools? How many of those showers are running at once. Let's say 2 of them and they have basic heads.

2.5 x 2 = 5



Now let's add another 2.5gpm in case the wife decided to run the dishwasher or someone turns on a kitchen sink. That gives us 7.5gpm. Most laundry is done in cold water so we won't worry about that.

7.5gpm x Temp Rise

Temp rise is the difference between the incoming cold water temp coming from the street or well (IN THE WINTER) and the water temperature I want to make.

Let's say the incoming temp is 50 and I want to make 110 degree water. My temp rise is 110-50 = 60

7.5gpm x 60 x 500 = 225,000 btu's an hr. I need an on demand water heater that has the ability to produce 225,000 btu's an hr when every fixture calls for hot water.