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Heating water with excess power
#21
This is interesting. I could keep the existing ac elements in the water heater and use the drain and pop off valve to make the sidearm with the dc element in it.
I wonder if it would make the pop off valve (that’s extended out beyond the sidearm) to pop if the element would heat the water in the sidearm to over the 150 degrees that the pop off pops.
That pipe around the element would probably get really really hot. Which might be a problem if someone touches it. Could pipe insulate it I guess.
I wonder if the water convection would stop once the water (in the tank) at the top of the sidearms outlet was the same temp as the dc element is set to, therefore not heating all the colder water at the bottom of the tank.
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#22
The pipe that holds the element I had thought to use 2" diameter. Then reduce before it elbows into the top port.
but yeah, it would need to be insulated with something like fiberglass batting.

I'm not sure i'd mess with the pop valve. The water flowing past it would be hotter than 150F
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#23
Note that if the element is to high powered you will get a to high circulation and cause disruption in the water heat level (what the heck its called in english). You need to strive towards a very slow change.

Like the system i got here it can easily be 90C in the top and 20C in the bottom... And its only 2 meters high Wink

I have roughly 3m3 heated water that i heat my house with during the winter.
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#24
There's no difference between the AC or DC water heating element. You just have to size the element to your voltage otherwise it will be only tenths of the actual wattage. There's a davidpoz spreadsheet somewhere that does that. I would use a pre-heater if your main heater has only one element or is a gas model. I have a gas version so one of my to-do things is to put a pre-heater in my setup. I already got a 120V 10 gallon heater and my goal is to run it off the 120VAC. Reason is it's easy to get a AC wifi controlled outlet (in my case a x10 unit) that I can control. Then I don't have to figure out how to adapt another temp controller.

If you have a large heater with two heating elements then yes you can use one of the elements and probably the easier choice. Here's another youtuber that's done it using solid state relays. https://www.youtube.com/watch?v=2nEfElD7B5s
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#25
(08-31-2020, 09:53 PM)not2bme Wrote: There's no difference between the AC or DC water heating element. You just have to size the element to your voltage otherwise it will be only tenths of the actual wattage. There's a davidpoz spreadsheet somewhere that does that.

For matching power to heating elements - See @DavidPoz's research visually by https://youtu.be/kVaxAfXQPDU and the tool (Excel download) at https://www.davidpoz.com/
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#26
(08-31-2020, 08:42 PM)daromer Wrote: disruption in the water heat level (what the heck its called in english)

I think you want "stratification" so that all the hot water collects near the top of the tank ready for consumption, and the cold water falls to the bottom.
Vs mixing/circulation, resulting in lukewarm water throughout the tank.
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#27
(08-31-2020, 09:53 PM)not2bme Wrote: There's no difference between the AC or DC water heating element. You just have to size the element to your voltage otherwise it will be only tenths of the actual wattage. There's a davidpoz spreadsheet somewhere that does that. I would use a pre-heater if your main heater has only one element or is a gas model. I have a gas version so one of my to-do things is to put a pre-heater in my setup. I already got a 120V 10 gallon heater and my goal is to run it off the 120VAC. Reason is it's easy to get a AC wifi controlled outlet (in my case a x10 unit) that I can control. Then I don't have to figure out how to adapt another temp controller.

If you have a large heater with two heating elements then yes you can use one of the elements and probably the easier choice. Here's another youtuber that's done it using solid state relays. https://www.youtube.com/watch?v=2nEfElD7B5s
I do have a water heater with 2 elements. like I explained above, if the bottom element is connected to a battery, then if I didn’t have enough excess solar that day due to clouds etc. then all the water in the tank wouldn’t heat up all the way. I’d need to be able to heat all of the water in the tank with ac so everyone could get a hot shower but I couldn’t do that if the bottom element is wired to the dc battery instead of ac. This would lead to the battery being drawn from to power the ac element via the GTIL2 when someone is taking a shower after the sun goes down.
Thanks for the video

(08-31-2020, 10:17 PM)OffGridInTheCity Wrote:
(08-31-2020, 09:53 PM)not2bme Wrote: There's no difference between the AC or DC water heating element. You just have to size the element to your voltage otherwise it will be only tenths of the actual wattage. There's a davidpoz spreadsheet somewhere that does that.

For matching power to heating elements - See @DavidPoz's research visually by https://youtu.be/kVaxAfXQPDU and the tool (Excel download) at https://www.davidpoz.com/

Thanks for the link. I seen that episode when he talked about doing that so we could easily figure out which elements to use
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#28
A preheated tank might be the way to go. As others have suggested. Many would suggest a smaller tank as a reheat tank, but I would go the same size tank. If you can raise the temp of the water in preheat tank 20 - 40 degrees F with excess power you are no longer using power from the grid/gtil2 to heat it from tap cold. might only use 1/2 the power maybe less. You don't have to heat the preheat tank to the same temp as the main tank.

Later floyd
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#29
(09-01-2020, 12:04 AM)floydR Wrote: A preheated tank might be the way to go. As others have suggested. Many would suggest a smaller tank as a reheat tank, but I would go the same size tank. If you can raise the temp of the water in preheat tank 20 - 40 degrees F with excess power you are no longer using power from the grid/gtil2 to heat it from tap cold. might only use 1/2 the power maybe less. You don't have to heat the preheat tank to the same temp as the main tank.

Later floyd
If I used a preheating tank then the first couple people showering would only receive the water temp that the main hotwater heater cooled to overnight. Korishan suggested a blanket to help keep the tank from cooling overnight.
Right now I fully heat my tank with the GTIL2 usually in the middle of the day, after battery is full. Then the hotwater heater is shutoff till the following day when battery is full. Problem is there could be other loads on at that time that could be using the pv power. Another problem is I’m not using all the excess throughout the day once battery is full. I want to use that excess to heat water automatically so I don’t have to wait to turn on the hotwater heater everyday once battery is full.

Right now Once all 4 of us shower it is then night time and most of the water in the tank is tap cold. so the water in the heater couldn’t be heated back up (with pv power) from tap cold till the next day. Right now I don’t use grid power to heat my water

I guess to solve all of this I could just add more panels to assure I have enough excess pv power everyday to fully heat the water heater everyday via the bottom element that’s connected to a dc battery. But then I’d need another charge controller because mine is maxed..
but I’m remembering a recent thread-post about that the Op oversizes the array wattage in respect to the charge controllers capacity
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#30
The water would cool no matter if preheat tank was used or not. By using an insulated preheat tank and insulate the piping from the insulated water heater to the shower you would minimize the cooling of the water.

Extreme -->You could make a giant vacuum bottle to eliminate as much heat loss as posibble.

Later floyd
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