SolarHead
50% of people are below average. (Its a statistic)
yet another good point
I think basically theres about 1,538 ways to configure solar and heating water so whatever floats your boat and doesnt sink mine may be the idea.
Dumping excess to 120VAC water heater?
- Thread starter rhino
- Start date
I think basically theres about 1,538 ways to configure solar and heating water so whatever floats your boat and doesnt sink mine may be the idea.
I have 3 separate controllers with 4 panels on each controller with battery backup and inverters. I also have 6 extra PV panels, 3 on the south east and 3 on the south west. These extra panels are connected directly to a dual probe DC water heated element. This is a 36 volt, 1200 watt element that is replacing the bottom 240 element in my 50 gallon hot water heater. I always have people tell me that this does not work but it has been producing hot water for a couple of years now. I have a DC temp thermostat that shuts the collection of PV off when water temp hits 150 in the tank.
Pierre
Somewhere down South
- Joined
- Dec 21, 2019
- Messages
- 1,122
I do not agree. The heating element is resistive in nature and does not care if it is fed AC or DC. You can connect PV directly to the element but the thermostat must be re-configured so that it switches the coil of a contactor ( small DC current ) and the DC heating current will go through the switching contacts of the contactor , which must be rated to switch DC.
sparrowhawk
Christian Prepper
sparrowhawk
Christian Prepper
sparrowhawk
Christian Prepper
I left the 240 volt heating element in the top of the water heater. The dc element is in the bottom of the water heater. It is also on timer to come on 5 to 7 am and then 5 to 9 pm if needed. So even if i have no sun we can still have hot water. I am married.
For hot water, very simple and less expensive than running it through pv to batteries and then inverter. All you really need is pv and dc element to heat water.
sparrowhawk
Christian Prepper
robby
Photon Vampire
- Joined
- May 1, 2021
- Messages
- 4,116
With your inverter you can just put in a transfer switch on the Gen/Smart load breaker.
Normally you would have smart load on and it would dump excess 240v power to the connected heater.
If you need the generator then configure it back to Gen mode, throw the transfer switch to the generator and start it.
SolarHead
50% of people are below average. (Its a statistic)
Really I think the idea of using solar for heating water , I think we're all kind of right in our opinions and experiences/knowledge, so in a way we're all saying the same thing. It really depends on your current situation, if you have an inverter (or not), how many solar panels you have, if you have grid available (or not), how much hot water or number of showers and dirty dishes and clothes you need to wash, there's a lot of factors that goes into what do you want to do and what do you have to do it with, and how much money or trouble do you want to spend getting there. Some inverters don't have smart loads like the Sol-Ark where it manages excess power and utilizes it. Some people don't have an inverter at all. As I mentioned earlier, there's a lot of different approaches here, but the main thing is to realize heating water is a HUGE load for an electric solar system, and you have to be aware of what you can or cannot do with DC power, as well as AC power, and if you want to use 120v or 240v going to your water heater and which and type of heating element(s) you have or want to use. There's other things to think about such as do you want to have a tempering tank which is nothing more than a solar-connected water heater placed in-line before your grid-tied water heater so that you heat water to some temp (whatever you can get based on sunlight and capability of your solar system), and the grid-tied (or gas-fired) water heater takes the water the rest of the way up to 120F.
As long as you don't burn up anything, hurt yourself, or cause a fire, then any amount of water you heat is headed in the right direction in my opinion. But you do need it hot (120F) and enough to be usable otherwise you're farting in the wind. Kind of all depends on the multiple factors that I mentioned (if inverter or not, how many panels, etc etc etc) that dictates your approach to heating water with solar power.
As long as you don't burn up anything, hurt yourself, or cause a fire, then any amount of water you heat is headed in the right direction in my opinion. But you do need it hot (120F) and enough to be usable otherwise you're farting in the wind. Kind of all depends on the multiple factors that I mentioned (if inverter or not, how many panels, etc etc etc) that dictates your approach to heating water with solar power.
Daddy Tanuki
Solar Wizard
well said, I have had this discussion on several different forums with mixed results, some folks claim i am a heretic as i will not group think with them, others who knows.
it boils down to what you have, what you want and what you are willing to do to achieve it. I am currently prototyping a simple latching relay/circuit that will turn on my water heater and a dedicated HF 5kw inverter during the hours of highest production, and only if my batteries are at 53.9 volts or higher. (I am massively over paneled due to my winter requirements.)
I could try matching heating elements against the MPPT of the panels but then I would need to replace all four SCC's with ones that have diversion load capability, and that would cost more than an inverter does.
if you can do with solar panels, or the vacume tube styled water heaters or any combination of both is great. Many folks don't know it but down on Okinawa they heat water in big fiberglass tanks on top of the roofs that are nothing more than large tanks painted black and yet they heat enough water for a family of four to take a reasonable length shower for free, and all it is is a big black FRP tank, yet it works, its cheap, and it follow the KISS principle to a T. some folks cannot think out side of their own echo chamber.
ken
Attachments
SolarHead
50% of people are below average. (Its a statistic)
Yep, its like asking if you can jack up a car using a log to change a flat tire broken down somewhere remote. Everyone you talk to says "Use a car jack" like you're an idiot for not doing it the way it should be done or the way they'd do it, but they don't realize you're out in the middle of BFE with no car jack and it's getting dark and cold. Sometimes you just use what you got.
efficientPV
Solar Addict
- Joined
- Sep 24, 2019
- Messages
- 1,341
Heating water today is like when solar used relays to charge batteries. MPPT came along and everyone said who needs that technology. I swear MPPT only became popular when they figured out a bunch of panels could be strung together, connected to any battery and they didn't need to know anything about solar. All these diversion threads are from people who have way too many panels and apparently alcohol is involved. True diversion takes whatever excess power and uses it without adding an extra load on controller, inverter or battery. Using a battery in diversion requires purchasing an extra KW of battery. Real diversion is a beautiful thing to watch and even small systems have enough excess power to heat water without buying more panels. A timer isn't diversion. It is just a hope everything will turn out alright. There apparently is no performance metric in solar. The major criteria is easy. Everyone just gets a plastic trophy for participation.
Daddy Tanuki
Solar Wizard
Wow aren’t we so special , snotty and childlike today
robby
Photon Vampire
- Joined
- May 1, 2021
- Messages
- 4,116
Good lord are you a Ham Operator? You sound just like the guys on the Ham Radio forums who argue that the only Real Radio Operators are those that use Morse Code and know how to build a Radio from Bamboo and coconut shells.
Times have changed, Panels are now super cheap, no need to do it old school anymore.
sparrowhawk
Christian Prepper
For me I treat heating water as just another load and have hot water everyday. My system is a very modest size, yet it's simple enough for most DIYers to get good results from. I factored in my water heater when I designed my system because I didn't want to try and design another water heating scheme on top of a system that could do the job.
I over paneled so I would have more power when it was cloudy. What I didn't factor in was how my batteries would react when charged & discharged and a high c rate. Sure I could have bought some battery balancers to try and mitigate that but they add another level of complication.
Because I was over paneled I had excess power to heat water but only when it was sunny so if I had a cloudy day I didn't have much hot water. But with 6 kilowatts of solar and now 28 kilowatts of battery backup I have gone 3 days with hot water and still have some usable battery power.
I'm not trying to say my system is the best for anybody but myself. My system wouldn't work for a household that needs lots of hot water. In a household like that it probably works best staying connected to the grid and only boosting with solar.
I actually have two 80 gallon water heaters plumbed in series but I'm currently only using one. I could certainly benefit from diverting power to the first water heater. A less complicated way of doing it would be to also install an upper thermostat in place of the lower thermostat in the water heater I currently have hooked to solar and when the lower is satisfied it will divert power to the other water heater and preheating my water.
My other idea is to feed both water heaters with 120v instead of 240v and run them longer during the day and double the amount of hot water. Haven't needed that much hot water so haven't tried it yet.
SolarHead
50% of people are below average. (Its a statistic)
Wait a second guys, I had to read what he typed twice. I get it. I think everyone can learn something from anyone and that's something I have done or tried to do my entire life (I've learned valuable stuff from a HS drop-out just as much or more than I have from an MBA in some of my lifes journeys). What I gathered from this post is that, we as newer generation of solar minded people, tend to think we're diverting extra load and I think all he is/was trying to say is that "true" diversion is what comes before the controller and inverter and I kind of get that. However, in todays world, the newer technology of MPPT and inverters and all of this filtered and controlled power we have once it comes out of our systems is not really considered TRUE diversion since the origin of the power is in fact the solar panel modules themselves (or the sun if you want to take it back that far). I guess if you wanted to get technical, "diversion" is one thing, and another different thing is "excess power" (which comes after the mppt/inverter). I think that's where he/we got off track or disconnected a bit , if I had to throw my 2 cents in. The difference in diversion at the solar panel module, versus excess power that has been already processed is something to ponder. Maybe I'm off track?
I think some are trying to heat water with PV direct to a WH. Some are using 120v power from the inverter to a WH. Some are using 240v power from inverter to WH. There's a lot of different configurations of varying types of equipment we're discussing here in this thread. Easy to get all balled up in conversation due to this fact. Really, we should all list our equipment, system sizes, on or off grid, etc, all within our signature IMO. Not knowing where the other is coming from is adding confusion and varying opinions. Kind of like real life eh?
To add some more confusion just to possible make things clearer....
I no longer like the terms excess or diversion when applied to solar as they seem to cause a counter productive reaction in most people.
If something can be seen as worthy enough to be the target of any excess then surely it must be worthy enough to have solar resources built just for that purpose.
Eg: This thread is about water heating with solar.....If we want 100l of water heated to 60C then build the solar for that with the provision for an alternative heating source for those cloudy days. That alternative heat isn't going to come from excess solar somewhere else because its cloudy there too. That's the nature of solar! If your non hot water solar system consistently over produces then add some panels and hws to fulfil that in the first part of this paragraph.
What does a solar panel leaning up against a fence do in full sunlight?...nothing until a load is connected.
The same thinking can be applied to a country's grid once things are better understood. There will never be excess solar.
I have a 80 gallon solar water tank (4 inlets and outlets) that my roof Solar Hot water system feeds (SHW). Then it flows into a 40 gallon natural gas water heater . I have taken the Sol arcs smart load (extra power) and feed a top element (3500 watts )with that power to preheat that tank the past year . No other elements are in the tank. Works great
Sol Arc says maximum watts is 3500.
