Comparing Electrical Tankless Water Heaters.

 I had one of the staff members ask me about tankless water heaters, so I created a unit on the topic.  I was looking at both electric and liquid propane tankless water heaters but the electrical ones had the most data so I shoe those.  Tankless water heaters are also known as 

Today you are checking out three different “On Demand” or Tankless Water Heaters.  They are all electric, small and fit on the wall.  The size was chosen to meet the needs of family with 6 members at least.

Time to do some calulations.  GPM is gallons per minute while the flow is based on the temperature of the incoming water.  Notice that as the temperature of the water flowing in increases, the more water you get each minute.

1. Find the volume of the water heater. You will multiply height x width x depth.

2.   Find the percent increase for each increment of increase in temperature.  To find it, you will subtract the (new temperature - old temperature) divided by the original temperature and multiply the answer by 100.

Example for the Rheem going from 4.2 at 37 degrees to 5.1 at 47 degrees.

(5.1 - 4.2)/4.2 = .21 x 100 = 21 percent.

Do this for all the GPM for each brand.

3.  What is the percent difference between the highest and the lowest for each temperature.  So for the flow at 37 degrees, the percent difference between the Rheem and Ecosmart.

We use the same formula from step 2.

(4.2 - 3.6)/3.6 = .16666 x 100 = 16.7 percent.

So you’d repeat it for the 47 degree, 57 degrees, and 62 degrees.

Then you’d do the same thing fo the 47 degrees, 57 degrees, and 62 degrees.

Fill out the following table.

Brand	Rheem	Ecosmart	Black & Decker
Volume
Percent increase 37 to 47 degrees
Percent increase 47 to 57 degrees
Percent increase 57 to 62 degrees
Percent diff at 37 deg
Percent diff at 47 deg
Percent diff at 57 deg
Percent diff at 62 deg

4.  So based on all the information printed in the table at the top, which would you recommend your family buy.

I had fun creating these.  My principal suggested I put these exercises in my sub binder for next year, if I'm every suddenly absent.  I hope you like this.  Let me know what you think, I'd love to hear.  On Monday, I'll share the last activity I created for the last part of school.  It will be on furnaces.  Have a great weekend.