The Victron Quattro has an AC2 output which can be configured to turn on under number of different metrics (SOC of battery, not come on if inverter already under heavy load, etc). In order to keep things simple I am wondering why I couldn't connect this to a standard 120V electric water heater tank with a 1500W or 2000W element? The issue with that is tanks that come with 120V elements are fairly small. Otherwise can you convert a 240V tank to 120V? My main concern is dealing with the thermostat.
Dumping excess to 120VAC water heater?
- Thread starter rhino
- Start date
You can put 220 volt, 110 volt or DC elements in any hot water heater tank.
I converted my 50 gal dual element 240v 4500w water heater into 120v 600w by connecting 2 elements in series fed from top thermostat. Works fine so far and makes it possible to dump excess solar via 1000w inverter. I plant to power it via 24v > 60v dc-dc converter in the future to eliminate inverter losses. For that i need to wire 2 elements in parallel and bypass the thermostat. I will use the thermostat to switch dc converter enable signal.
robby
Photon Vampire
- Joined
- May 1, 2021
- Messages
- 4,119
You cannot use the regular Thermostat with DC voltage. It will Arc over and ruin the contacts.
Yeah.. I realize that.. I was wondering about what to do if switching from 240V AC elements to 120V AC elements since everything above 25 gallons appears to have 240V elements.
The original controls should work fine in that situation as long as your amperage is below the rating of the thermostat.
Pierre
Somewhere down South
- Joined
- Dec 21, 2019
- Messages
- 1,125
You can rewire the thermostat to switch a contactor on/off and feed solar directly through contactor to element. Just make sure the contactor is rated to switch DC.
Going from 220 to 110 is ok to use the existing thermostat. It is the switching between AC and DC is the tricky part. I replaced my lower AC heating with a DC heating element on mine and I think I finally figured out what works. For sure you cannot use the AC thermostat though.
SolarHead
50% of people are below average. (Its a statistic)
Not sure if I'm in step with the thread about this but I remember seeing Engineer775 on YouTube show where they hooked the bottom thermostat to a Sol-Ark's smart load (which is excess power once everything else like batteries, loads, etc have been covered), and the top thermostat to the homes main service panel like normal. That way he was getting solar to heat the water, and grid power for the top thermostat which I understand is the recovery element if/when you need to heat water fast. The bottom element is what heats 90% of the water in the tank and is slower to heat since its more water on it (its near the bottom of tank). So, you're heating most of water with solar power, and you have the top element to take you the rest of the way depending on how much water you need or are using. I think bottom element is 120v and top element is 120v. Thats why without solar you have to run 240v to a water heater. No need to change it thermostats, just make sure you are running AC power from the inverter to the lower element. And AC power from your main service panel to the top element. As stated already, and a reminder, do not put DC power to a AC thermostat, it'll burn out almost immediately. I thought I'd mention the idea of practice of sending inverter power to bottom element, and grid power to top element. To me that seems like a good balance.
@SolarHead I'm going to try hooking at least the bottom one to 120V. There seems to be a lot of confusion researching this about people wanting to convert a "240V" water heater to 120V... Many people saying it can't be done but there should be no issue using same elements from other reading. It will use 1/4 the watts. ( 120V / 240V )^2 = 0.25. So 4500W x .25 = 1125W heating element. For the wiring I would exchange the second hot (red) wire for a white (neutral) wire.
References:
www.electricaltechnology.org
References:
How to Toggle Electric Water Heater Between 120V and 240V?
How to wire electric water heater for both 120V and 240V. Toggle Water Heater between 120V and 240V using DPDT and 3-Way Switches. 120 & 240V Heater Wiring
www.electricaltechnology.org
SolarHead
50% of people are below average. (Its a statistic)
I dont know 100% for sure, but seems if you stay with sending AC power to the water heater elements you should be okay. If the bottom element is a 4500 watt element, set your inverter to send 1500 watts to it and I think it should be fine. Will take longer to heat water of course, but that's kind of the deal. Use the bottom element to slow-heat all day while sun in shining. Take showers, wash clothes in the after noons. Take showers in the evenings maybe. The top element is kind of your back-up insurance policy to make sure you don't take a cold shower. If you use grid power for the top element I would think it would be minimal and its 120v so its not like you'll pulling 9000 watts @ 240v from the grid if you had both elements on grid power and no solar system.
I think some people think you can hook at DC solar panel directly to a water heater, it doesn't work unless you change the AC element out and install a DC element(s). But if you did go direct from solar panel to water heater element, you're getting power only when sun in shining. If you have an inverter and battery bank, you should be able to push 1500watts to that bottom element more steadily and for a bit longer each day. My 2 cents.
I think some people think you can hook at DC solar panel directly to a water heater, it doesn't work unless you change the AC element out and install a DC element(s). But if you did go direct from solar panel to water heater element, you're getting power only when sun in shining. If you have an inverter and battery bank, you should be able to push 1500watts to that bottom element more steadily and for a bit longer each day. My 2 cents.
The wiring is such that the 240V (red, black, white in my case being used as the ground) comes right into the top of water heater to wire nuts which are then routed inside the water heater down to the top and lower elements. So I don't think I have choice to separate out top from bottom without hacking into bottom panel. For the 120V line I'll replace black with black, red with white and the white with bare copper ground.
SolarHead
50% of people are below average. (Its a statistic)
Correct, you'll have romex going into the bottom panel (I think one screw holds it on) to the bottom element. Would be best to use flexible metal conduit from your inverter over to the water heater
sparrowhawk
Christian Prepper
When I was originally planning my solar setup I read everything I could on here about the different ways people used solar to heat water. Most were either inefficient, complicated or beyond my capabilities so I opted to just use a timer to turn my water heater on around noon and off around 4pm. I also changed my heating elements to 2500 watt ones to reduce the needed power and allow more headroom on my inverters.
It originally worked kinda mediocre which had to do with inadequate battery storage. I got plenty of hot water but when it was the least bit cloudy my battery storage suffered and sometimes I couldn't make it through the night with my normal loads.
I started out with two 3 kilowatt inverters in split phase, 6 kilowatts worth of panels and 14 kilowatts of battery backup. But I have since doubled my batteries size and haven't had one instance in 6 months where I have run out of battery despite lots of cloudy days.
I found out the reason for this was I was not able to take advantage of all the solar production that was available. It now appears I have a very well balanced system. It's also obvious that trying to heat enough water after fully charging my batteries wouldn't work well for me for the same reason as having to little battery storage, I just couldn't take full advantage of the available solar power.
The simple reason for this is these commodity cells I bought from china just won't take a charge fast enough without going way out of balance so I have to keep the charge current low which keeps them from being completely charged while there's still enough sun to heat a tank of water. But at peak sun hours there's enough power to heat water, charge batteries and run all my typical loads and when the water heater timer kicks off there's still more than enough sun to top off my batteries.
In the end the KISS method of heating water has worked out pretty well for me.
It originally worked kinda mediocre which had to do with inadequate battery storage. I got plenty of hot water but when it was the least bit cloudy my battery storage suffered and sometimes I couldn't make it through the night with my normal loads.
I started out with two 3 kilowatt inverters in split phase, 6 kilowatts worth of panels and 14 kilowatts of battery backup. But I have since doubled my batteries size and haven't had one instance in 6 months where I have run out of battery despite lots of cloudy days.
I found out the reason for this was I was not able to take advantage of all the solar production that was available. It now appears I have a very well balanced system. It's also obvious that trying to heat enough water after fully charging my batteries wouldn't work well for me for the same reason as having to little battery storage, I just couldn't take full advantage of the available solar power.
The simple reason for this is these commodity cells I bought from china just won't take a charge fast enough without going way out of balance so I have to keep the charge current low which keeps them from being completely charged while there's still enough sun to heat a tank of water. But at peak sun hours there's enough power to heat water, charge batteries and run all my typical loads and when the water heater timer kicks off there's still more than enough sun to top off my batteries.
In the end the KISS method of heating water has worked out pretty well for me.
Why deplete your batteries when you can just connect directly from PV to a DC water heater element? I have "0" problems going from cold to 150 degrees by 4 in the afternoon. This is truly the KISS method. No batteries or inverter just Straight PV.
