Sense appears to be over reporting usage by hot water heater


#1

Ok, Hopefully someone can figure this out. Sense found my hot water heater early on. As you can see it is showing that it is using 5759 watts, only problem as you can see from the name plate the elements only draw 4,500 watts and t!hey don’t run at the same time. What is going on?


#2

Is it possible that the water heater is older? Maybe the elements are corroding and requiring more energy to heat to the the desired setting?


#3

It is barely two years old and we have a water softener.


#4

Check the real-time power consumption in the sense app, and make sure it matches what the individual device screen is showing. If so, one of your elements has a problem (low resistance) and needs to be replaced.


#5

@pswired would I really care if one of the elements is pulling more power? Wouldn’t all of that power be dissipated as heat which is the desired outcome anyway? The heat would go into the water which would mean it would just heat quicker. As long as it is not tripping a circuit why would I care???


#6

I don’t think it would be a huge problem. Assuming your heater is wired with 10AWG cable on a 30A circuit, 5800W still puts you within the 80% continuous rating of the circuit. The wiring inside the heater, the controls, and the element itself may be a different story, though. I would probably monitor those for overheating. Generally, cheap residential appliances are designed with components that just barely can handle normal operating conditions, and not a 30% overload condition.

Energy-wise, yes, all that power is being dissipated as heat in the water, so you’re not losing anything there.


#7

Just got a reply back from tech support that they checked and each leg is pulling almost exactly half the reported load, so they seem to feel the draw is correct. I find it strange that both elements ( they don’t operate at the same time) would each pull this much over the rated wattage. I could see one being off, but both seems odd?


#8

Do you have a meter with a current clamp? That would answer your question quickly.

Alternatively, do you have a reference load that draws a known power that you can use to check against your sense realtime data?

Finally, you could figure this out using some math and a heating cycle between two known water temperatures. That would be a bit more work but the only tool needed is a thermometer and a stopwatch.


#9

Thanks, all good ideas. The water temperature one sounds like a real pain in the rear, but it would work. The only reason I asked about this is this device has a big old name plate that says 4,500 watts so when it shows up as 5700 it made me think. I guess I could look and see what else might have such a name plate and see what Sense says about it. Unfortunately my meter with current clamps seems to have died :frowning:


#10

You might also try disconnecting power and measuring the element resistance with an ohm meter.


#11

Do you know if this water heater has ever had the elements replaced? One or both?
The thread sizes for all elements are the same. If someone installed 5500 instead of 4500, this would explain the discrepancy.
The sense may have just identified a serious safety issue for you
@pswired had good advice and using his suggestion would confirm.


#12

Haven’t visited here in a while and just saw some more replies. I solved the problem, which was an ID10T problem. Turns out the device was not the hot water heater, rather it was a heater for a spa. Water heater was recognized later and shows that it draws on average 4768 which is more reasonable, especially since our voltage is a little on the high side of normal.


#13

Glad you figured it out @32259fl
Something that shocked me about warmer heaters is the energy guide people state a water heater is on 3 hours a day on average.
That lines up with what sense tell me about ours but what surprised me is it coming on for 5 minutes every hour.
So 2 hours or 120 minutes a day is just to maintain temperature. Only 1 hour a day of it running is for showers, laundry and dishes.
Two thirds of the cost for maintaining temperature hurts to know.


#14

If 2/3 of your water heating energy is going to standby losses, there is a problem. A modern electric tank with typical usage should have much less than 10% standby losses.

Do you have a recirculation loop to keep the hot water supply piping warm? That could account for such high standby losses.


#15

I do have recirculating loop but it’s insulated very heavily. I turned it off for several days and it didn’t change enough to notice. If I’m right at 3 hours runtime a day as what is considered average, then I don’t know. But I know for a fact about energy loss from my loop.
I did heat loss calculations when I designed it and expected bigger loss that’s I have. I was quite surprised that it was about 10-15 minutes more on time per day when loop was on.
Keep in mind the loop pump and valves are on timers and aqua static control. I don’t keep the lines exactly the same temperature as the tank itself. Tank is 135 and loop circulates at 115 until it gets to 125.
The water heater rarely turns on while the loop is running. The capacity of the loop is close to only 3 gallons.


#16

My hot water usage is showing it was on 221 times for the month with an average on time of 6m 46s. That comes out to an average run time of just under 50 minutes a day. I too have a re-circulation system, but not a loop per-se. I have a Watts circulating pump that works in combination with a by-pass valve under a far sink. The valve is thermostatically controlled so when the water temp drops below 95 degrees it opens connecting the hot line to the cold. Normally nothing happens when the system is idle as the pressures are equal. When the pump is running a small flow of warm water is pushed into the cold lines which then forces hot water out of the tank to provide a flow of hot water to the far end. We only have this run when we need it rather than have it always on or even on by a timer. I hooked a TP-Link HS-110 Energy up to the pump so we can use Alexa to turn it on and off. I found that I only needed to run it for six minutes to get hot water at the far end. So now instead of running the water for 2-3 minutes wasting water to get it hot we just run the pump. To further automate it I wrote a Routine in Alex to turn it on and then after six minutes turn it off. I tied that routine to one of the battery operated Alexa button devices that sits on the bathroom counter. When we want hot water we just push that button.


#17

I think what you are seeing is accurate. Mine shows on for 183x this month. I didn’t go with the bypass valve (although it was included with pump) because it wastes hot water by pushing the warm water into the cold supply. It also doesn’t have a control fronthe temperature I want the line to be kept. It is far less plumbing though.
Average on time for us is 3 hours a day. According to energy guide, that is what it should be.
2 baths, 4 people, lots of laundry and the dishwasher runs 2 times a day.

Recirculating loop with Taco pump