Electric water heater with timer and thermostatic mixing valve

magic8192

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Feb 26, 2021
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So here is my current hot water usage per day with the timer.
1616430918566.png

Here is what it was before doing the timer
1616430880796.png
Seems like my total power usage from the hot water heater has gone down a good bit

And just for fun here is total power usage overlapped with solar per day.
1616431174627.png
 

12VoltInstalls

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This is awesome. I love it.
That is my issue with grid-ties: sure the consumer ‘saves’ money but the direct-to-grid is nearly always biased to benefit the grid provider monetarily.
I was talking to someone recently and their consumption is billed as it is used- then the solar ‘credit’ is applied at the lesser wholesale rate. He said in 15-18 years they will break even. That hurt my personal logic motor driver LOL
We don’t even know “where we’ll be” in 15 years. Granted, “stopping the meter” guerrilla-style is generally expensive enough that it doesn’t make sense for a short-term ROI perspective. However, it hurts my head to think of investing big dollars in solar grid-tie that predominantly benefits the utility company not the consumer. One small utility here in Vermont once stated in a public meeting something along the lines of, ‘consumer solar excess fed to our grid will reduce profits below a sustainable level. We have to maintain billing for demand or raise base rates.’

I love this water heater kW workaround!
 

magic8192

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Feb 26, 2021
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This is awesome. I love it.
That is my issue with grid-ties: sure the consumer ‘saves’ money but the direct-to-grid is nearly always biased to benefit the grid provider monetarily.
I was talking to someone recently and their consumption is billed as it is used- then the solar ‘credit’ is applied at the lesser wholesale rate. He said in 15-18 years they will break even. That hurt my personal logic motor driver LOL
We don’t even know “where we’ll be” in 15 years. Granted, “stopping the meter” guerrilla-style is generally expensive enough that it doesn’t make sense for a short-term ROI perspective. However, it hurts my head to think of investing big dollars in solar grid-tie that predominantly benefits the utility company not the consumer. One small utility here in Vermont once stated in a public meeting something along the lines of, ‘consumer solar excess fed to our grid will reduce profits below a sustainable level. We have to maintain billing for demand or raise base rates.’

I love this water heater kW workaround!
This has worked better than I could imagine. I get paid very little for the solar I push onto the grid, so this maximizes my solar power usage and benefits me, not the power company. The power bill stats told me that the hot water heater was 19% of my power bill, but the power bill went down about 25% after installing the timer.

The reason is this got people in my house to start thinking about what they were doing. We try to do laundry and run the dishwasher in the middle of the day now and the kids seem to be thinking about what they are doing more. They don't take long showers, so everyone will have enough hot water.
 

nate_syd

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FYI - my thread may help here: https://diysolarforum.com/threads/half-power-water-heater-setup.22432/
same goal - use my excess solar to heat my water heater.
However I converted the 240v down to 100v, so that it would be effectively a 1000W heater, instead of 4800w. Then I switch it all via relays, controlled with an ESP module (like an arduino). So its home automation voice controlled, it can still use cheap power at night, but i'll have it on for as long as possible when its sunny.
 

Charlesm

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May 27, 2021
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I have one in my shower valve.
Worked well for years, but eventually got sticky.

I knew sediment would come through. I found a high temperature rated strainer for potable water at Grainger (but not that high).
So my problem wasn't chunks, rather deposits.
Be sure to put a strainer before the mixing valve.
I always use a water softener to maintain efficiency.
 

Henrysangret

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Dec 5, 2020
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I have one in my shower valve.
Worked well for years, but eventually got sticky.

I knew sediment would come through. I found a high temperature rated strainer for potable water at Grainger (but not that high).
So my problem wasn't chunks, rather deposits.
Be sure to put a strainer before the mixing valve.
And make sure your aluminum or magnesium Anodein the hot water haven’t dissolved totally, causes a lot of bad deposits in hot water lines .
 

Henrysangret

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I am trying to use less grid power. I hate sending my extra power to the grid because they pay me wholesale for it.
I am getting very confused by this posting. what is it you are trying to do and why are you messing with the 2 heating elements. First heating wateri with electrics is by far the most expensive and if you have an excess in PV as you said, why not using a smaller electric heater connected to your system and any excess power go to the smaller heater and preheats the cold water going to your larger hot water tank. Now your larger tank doesn’t need to stay on as long to heat to temp and you won’t have any accidents with 180 deg water and potential excessive failure modes with messing with thermostats. This works and I have been using this for years with factory water heaters and no surprises. BTW I use propane for primary water heater and a 120vac smaller preheater connected to my system. Once the battery’s are charged they switch over and are redirected to the water heater, my thermal battery.
 

Frick

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The timer is a good way to use low cost power or surplus solar versus high cost power which is all a function of your utility company. the two tanks (one as preheat on solar only) and then a second tank on the grid is another way. I chose to do a solar pre heat tank into a second preheat tank (because I had that many seperate solar circuits and it was simpler) and then through an instantaneous propane hot water heater as a final heat source in case there was heavy clouds or a volcanic eruption or total electrical system failure. Some do direct solar thermal heating as preheat but it seems to be more expensive and failure prone even though it is a simple concept.
 

Henrysangret

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The timer is a good way to use low cost power or surplus solar versus high cost power which is all a function of your utility company. the two tanks (one as preheat on solar only) and then a second tank on the grid is another way. I chose to do a solar pre heat tank into a second preheat tank (because I had that many seperate solar circuits and it was simpler) and then through an instantaneous propane hot water heater as a final heat source in case there was heavy clouds or a volcanic eruption or total electrical system failure. Some do direct solar thermal heating as preheat but it seems to be more expensive and failure prone even though it is a simple concept.
I dont know about volcanic eruptions but am an electrician engineer for over 30 years and me understand failure modes and effects and reliability indexes and do believe in the saying KEEP IT SIMPLE and AC and DC are not the same. My system is off grid and has been running flawlessly for 3+ years.
 

efficientPV

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It is astounding the resistance to technology in solar and the encouragement given to remaining technology backward.

I just watched a video that was 5 minutes long with this guy up on a ladder switching solar panel connections to adjust for the weather heating his water. That is keeping it simple! Heating water can be technically advanced, simple an reliable. Given a worldwide audience you would think a few people could figure it out.
 
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Henrysangret

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If you think about it, big industry has for years been squashing this technology to line their pockets. Now foreign markets who have been doing technology with the thought basis of customer have or have not ( have power or no power) are marketing their product overseas now the big manufacturing and technology companies have to jump on the bandwagon supporting technology but undermining it back channel in the government offices with new taxes and permit requirements and then getting the government to impose new and larger import duties which basically double the product costs to the consumer to support a internal manufacturing market that doesn’t exist.
 

efficientPV

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A friend of mine owns an industrial HVAC business. He says one quarter of project budget is used by automation controls. Business is well advanced of the consumer market. They are spending where the best return is. Payback, not simple. It is an education process.
 

Frick

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It’s fantastic when it all works right, has a guy you can call, has parts availability... every application has its ideal. I use to be in that world, one of the most advanced plants of its kind, fully automated from my desk, my dreams and the boss mans money. It was limitless what I could do with that system. Good times.

my new home is very removed from civilization, and has different needs. My new grain mill is hand powered and is a work of mechanical art. one Day i might add an electric motor, eventually it will run it from the river that runs next to me.

I know an old friend from those years, works as a caretaker for a smart home. Mansion and estate really. It’s so smart it needs a full time tech person at 60k a year, and they are hiring a second one soon. This is just to maintain the ‘smart home’, not the grounds. Reprogramming light switches and updating fridge code (maybe, I laughed so hard when he described his normal week I don’t remember exactly) and constant annoyances of the occasional squirrel or mouse appearing and eating a wire.
 

Cheap 4-life

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I’m fairly certain all water heaters have a pop off valve. It usually pops off at 150f.

I used to use that same mechanical timer. I have switched to using my chargecontrollers 12v aux output. I have that 12v wired to a double pole relay that the water wires go through. The aux allows the 12v to go to the water heater when the batteries reach float voltage. When battery reaches float there’s excess power because the batteries are full. I changed my water heater elements from 4500w each to 3000w each. The 3000w element allows my 2 inverters to fully cover the element. At night the batteries come out of float and then the water heater can not turn on till the next day when batteries again reach float. It’s been working great. I haven't paid money to heat any of our water for years.
 

Hedges

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I know an old friend from those years, works as a caretaker for a smart home. Mansion and estate really. It’s so smart it needs a full time tech person at 60k a year, and they are hiring a second one soon. This is just to maintain the ‘smart home’, not the grounds. Reprogramming light switches and updating fridge code (maybe, I laughed so hard when he described his normal week I don’t remember exactly) and constant annoyances of the occasional squirrel or mouse appearing and eating a wire.

I'm known as something of a Luddite. Still, when I needed a replacement kitchen faucet and saw a Moen at Re-Store that had IR sensors as well as a lever, I went ahead and got it. Two annoyances - it is "fly by wire", the lever is encoded with a few discrete steps, so if the batteries are dead you ain't getting water (no solar panel like the commercial ones I've seen). Doesn't have the nice analog behavior of a valve. Second, the sensor facing sink turned on the water every time I reached for something. Tried putting tape over the sensor, but that didn't work.

I had to read the owner's manual to program my kitchen faucet!

And I have an EE/CS degree. I built a computer as a kid. As in, wire-wrapped sockets between ICs. Built a bit-slice computer out of SSI/MSI ICs in college. Designed computers for HP (as in full custom ASIC design, on a team designing microprocessors. We wrote our own CAD tools). I automate test with bench instruments.

But I don't know how to program a VCR, and I just bought a replacement computer when I couldn't successfully install drivers for RealTek HD audio after XP SP3 on a "Media Center" PC. It was mute.

Falling back to a hand-crank grain mill and building a water turbine sounds appealing to me. I may solve Black Arts problems like EMI emissions and susceptibility, but levers and gears are much easier to understand.
 

Frick

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I'm known as something of a Luddite. Still, when I needed a replacement kitchen faucet and saw a Moen at Re-Store that had IR sensors as well as a lever, I went ahead and got it. Two annoyances - it is "fly by wire", the lever is encoded with a few discrete steps, so if the batteries are dead you ain't getting water (no solar panel like the commercial ones I've seen). Doesn't have the nice analog behavior of a valve. Second, the sensor facing sink turned on the water every time I reached for something. Tried putting tape over the sensor, but that didn't work.

I had to read the owner's manual to program my kitchen faucet!

And I have an EE/CS degree. I built a computer as a kid. As in, wire-wrapped sockets between ICs. Built a bit-slice computer out of SSI/MSI ICs in college. Designed computers for HP (as in full custom ASIC design, on a team designing microprocessors. We wrote our own CAD tools). I automate test with bench instruments.

But I don't know how to program a VCR, and I just bought a replacement computer when I couldn't successfully install drivers for RealTek HD audio after XP SP3 on a "Media Center" PC. It was mute.

Falling back to a hand-crank grain mill and building a water turbine sounds appealing to me. I may solve Black Arts problems like EMI emissions and susceptibility, but levers and gears are much easier to understand.
If you feel the need, I can honestly say I have never been more impressed by a product. Yes it is a simple device, but spectacularly executed in purpose and finish. I will always find something to critique in a product (or nearly all of it), but from the way the box was assembled, taped, stacked and protected I knew they were doing something out of pride of craftsmanship. The mill itself is beautiful, the finish perfect. The bearings are intentionally chosen to be overkill and replaceable at any auto parts store if need be. It’s guaranteed for your life and then some. Literally found not one single reason to fault it, add not one Thing I would change. Also, they are decent and helpful people, a family run business in Montana.

as for the water heater, I think I’ll start at 140deg with the mixing valve, it that’s with my 2x30 gal tanks and the propane instant catch all, if that ever becomes insufficient and I start burning up too much propane, I’ll likely go to 180 on both tanks with the thermostatic valve.
 

jsbc

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Jun 26, 2021
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The only thing that gives me pause is the 180°F. That just seems too dang high.

IMHO, usability will be impacted. If it's just you, you can probably manage it, but I wouldn't want the uncertainty of getting 120 vs. 180°F water out of my hot faucet for anyone else in the home.

EDIT: DERP... missed the mixing valve.

Have you considered using the timer to allow normal operation only during solar PV hours and upping the temperature to something like 140° on both thermostats?
I don't think its wise to run water heater at less than 60c (i'm metricated )you can end up with legionella. The previouse post mentioned tempering valve holds temp to about 60c which is hot but not so hot "the reaction on contact is to pull your hand away it is not hot enough to scald you instantly".
I live rurally in New Zealand and am thinking of installing solar water heating via solar storage tank for winter heating with the hot water tank supply via a heat exchanger to feed the hot water cylinder reducing heating costs. The reason to use a heat exchanger is I would like to use water from the house supply you dont' know what will breed in the solar storage tank.
 

pinkeng

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I would recommend no more than 140 degree temperature. Reason being at 180 degrees, you're going to get a massive amount of calcium build up very quickly on your heating element. And a fair amount of heat loss thru the wall. 140 degrees will produce about 20% of the lime, and have lower standby heat loss. I might also recommend, only wiring and using the bottom element the top element is for a quick recovery, it does not do much. But as your are on solar the bottom element will do all the heating you need. while the commercial heater will do 180 degrees. It will wear out faster at 180 degrees due to liming.

I designed a lot of water heating systems in 40 years including a few that did a thousand gallons a minute.
 

Frick

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I would recommend no more than 140 degree temperature. Reason being at 180 degrees, you're going to get a massive amount of calcium build up very quickly on your heating element. And a fair amount of heat loss thru the wall. 140 degrees will produce about 20% of the lime, and have lower standby heat loss. I might also recommend, only wiring and using the bottom element the top element is for a quick recovery, it does not do much. But as your are on solar the bottom element will do all the heating you need. while the commercial heater will do 180 degrees. It will wear out faster at 180 degrees due to liming.

I designed a lot of water heating systems in 40 years including a few that did a thousand gallons a minute.
Good to know. Thanks, I hadnt thought of calcification yet, I was more thinking of ways to increase capacity to meet demand on full cloudy days. We won’t have grid service where we are, so the thought of using the top element for quick recovery isn’t possible. We opted to go full solar only.

I also havent decided on which water source on the mountain we will be using and run any tests of it, so that will play in later.

as for the heat loss, if I have the excess solar available, and it’s turning off after topping the batteries and hitting the thermostat at 140, then the power is potentially lost by failure to collect. If I run a higher temp and the mixing valve and it never reaches 180 but always falls between 140 and 180, then I will have collected the maximum solar available, if I lose it in thermal loss from the tank after that, it’s probably still better than never having had it in the first place.
 
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