Winter Projects - What's on your list?

[Submariner]

Water Heater - Added a temperature probe to tell how hot the water heater is.

Martin, how was the temp probe install on the hot water tank done?

I never stated how well it works as the jury is still out in deliberation. 😀

I picked up two temp sensors for my CerboGX. One sits in the port lazarette which tells me ambient temp. The other I ran to the starboard lazarette and attached the sensor to the hot water output connection, the hot side, using lock wire and some creativity. Not a fantastic solution as I get the temp of that connection which is less than the temp of the actual water. It reads 113 - 116 degrees with 6 gallons of 165degree water inside. But the ambient temp of the lazarette is 48 degrees.

Being that the CerboGX reports up to VRM (Victron's remote management cloud), I get to see the rate at which the hot water tank cools off. I now know how long it really takes to heat up and cool down the hot water heater. I also get to see what temp the outlet connection is at. My hope is that I'll be able to find the offset... 116 degrees is actually 165 degrees, for example. 48 degrees is actually 48 degrees. I'll play with it this season and am hoping I'll be able get to the point where I can say "turn on the hot water heater until the temp reading is 85 degrees. Then go take showers".

It's takes 2 hours to heat the tank from cold to hot. Last season I just ran a stopwatch. I'd turn on the hot water heater and run it for 45 minutes and then go take 3 hot showers. This method worked reasonably well at conserving power and provided us the hot water we wanted. But using a stopwatch doesn't take into account the starting temp of the tank.

To run the hot water heat from cold to fully hot would consume about 1/2 of my battery bank (approx 125amp-hours). But I'd rather not pour amp-hours into my hot water tank just to have that heat evaporate. So by being able to tell what temp the tank is at, my hope is that I'll be able to conserve electrical even more by running the hot water heater for just what we need, when we need it. The hot water doesn't stay hot in the tank for long.

The graphs of temp over time that I have are interesting. All preliminary data.
114.8 degrees at 8:00pm when I turned off power to the heater (fully hot). It starts to cool.
It dropped to 80 degrees by 4:00am.
It dropped to 70 degrees by 8:00pm (24 hours later)

Note: The internal hot water temp will be higher than those numbers as this is the outlet connection and not the actual temp of the water.

I may or may not be chasing perfection. But the cost of the temp probes was minimal as was the install time. I need to wait until the jury comes back with a verdict. A hot shower is usually between 98 and 104 degrees (actual water temp).

 

[Submariner]

The jury came back with a verdict on my hot water temp probe.

My temp probe will read 114-116 degrees when the 6 gallon hot water heater is fully hot at 167 degrees.

I ran the hot water heater until my probe read 90 degrees. We had plenty of hot water for a couple of showers onboard.

Took only 40 minutes of runtime. That’s about 42 amp-hours. To heat the tank fully hot is between 90 and 120 minutes at around 120 amp-hours needed.

This is a significant savings in electrical consumption for me.


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