Somebody on the Transit forum asked about the energy usage of the water tank and I'm sure glad they did, it forced me to chase down an issue I had noticed but didn't understand. I don't leave the water heater on all the time I just turn it on when I want hot water. But, the hot water seemed to cool off really fast, compared to when I had tested it with the water tank unconnected to the distribution piping. Preliminary electrical test results showed that I'm using at least twice as much energy as the guy on the Transit Forum that asked about it. Here's a one-line diagram of my plumbing system, note the hot water re-circulation loop. This is so you don' t have to run the faucet and waste water to get to hot water:
I think that created a convection loop that pumps heat out the tank since the interconnect valve between the hot and cold water is open when the hot side is cold. The cold water piping coming out of the water heater was hot, which was my first clue what might be happening. When I closed the cold water valve to the water heater the piping cooled off and the time between reheats doubled. I've got a back flow valve coming from Amazon that I'll put in the hot water piping, I think that will break the loop. I'm also going to insulate the cold water piping.
Here's a graph of electrical usage from 11am 5/21 to 6pm 5/22. Wow, shutting off the re-circulation loop had a dramatic effect. The heat was coming on every two hours. Once I turned the shutoff valve to the water tank it didn't call for heat for eight hours.
Bruce
P.S. The water cooling off too fast was what spurred the cozy.
by bdosborn » Sun May 07, 2023 1:56 pm 
