Friday, April 21, 2017

the new water heater

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(click graph to enlarge)

I had previously determined that my hot water heater was one of my top five largest electricity uses.

So I recently replaced my old electric water heater with a new electric heater of the same type, but 23 years newer. I now have data which shows less electricity to keep my water hot than before. The red line is the new water heater, the blue is the old.

I didn't get anything special. Mine is a GSW (AO Smith) base model but I will treat it with a bit of extra insulation. Even without the insulation I will add, so far I can see that the new heater has better insulation than did the old heater from 1994. It is ON less often.

The graph shows the percentage of the time that the water heater is ON. The new heater has the same standard 3000 watt heaters as did the old so it uses the same amount of energy when it is ON. The difference is that it is not ON as much as the old heater as shown by the %.

I am measuring the duty cycle % in the same manner that I did in the old water heater article then plotting the data points as I make them. The red regression line of the new heater data should grow towards the right as the temperature in the basement gradually rises with the coming summer.

A water heater will work harder when the temperature around it drops (lowering the ambient temperature). My water heater is in the basement quite close to the furnace which causes the temperature in the basement to vary by a few degrees as the furnace goes through its cycle so I have a fair amount of scatter in the data points the more the furnace runs.

Here is the new water heater on a sort of pedestal that I made from wood and 1-1/2 inch Styrofoam sheet that I hot wire cut to a disc shape to sit between the heater and the wooden base.

The old heater was sitting directly on the cold concrete floor. The base and insulation will help reduce heat loss through the bottom of the heater.

I plan to wrap the heater with a blanket layer of insulation. I have another circular disc to close the top.

Both the new and the old set points are the same, the recommended 60C / 140 degrees F to prevent bacterial growth. The new water heater is also controlled with an electronic timer to prevent it from operating during peak rate periods.

Thanks for your interest.

George Plhak
Lion's Head, Ontario, Canada

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