Direct to water heating.

[Capt Bill]

In wondering about how I might send all or part of my 4000 watts worth of Solar Panels current to a water heating task; ... when my 24v LiFePO4 battery bank is just under fully charged (near cut off set for top voltage:

... I just ordered one of these to play with later:

Amazon.com

I will most likely use this later connected this up to my (overkill 500 amp rated / $40 used) KILOVAC EV200 Series Contactors to disconnect part of my Solar from battery charging task / and at same time switch a good portion of my Solar Array current to Water Heating (maybe for heating my smallish spa/ & then have to consider other option if that tops up nicely without using my natural gas heater). I will soon have 4000 watts of solar panels up and dial in, and might later add an additional 2000 watts (as I have third LV2424 on wall for that easy option). I may switch 2/3 of my PV current at 6 panel Solar Arrays ... or at full Solar Array Current junction IN to each of my LV2424 All In Ones. ... just in brainstorming phase at present.

One person on Amazon with same ideas asked: Want to turn on water heater element once battery bank reaches float voltage and turn element off when voltage drops below X. Can do? ... got a few answers including: Depends on what your "float voltage" is. There are 3 versions of this relay dependant upon voltage monitoring range 12v/24v/48v. I'm thinking you may be looking for a current monitoring relay so when your charger output drops to maintain current vs charge?

So, ... I will also look at current monitoring options (did not find any yet), but think this voltage monitor relay switch may be perfect for my needs at a very ok price.

Wow: Ideas for my creativity basket; with equipment options I can get delivered to my door in California by just pushing buttons on my pc laptop (with a credit card. :+)

 

[Capt Bill]

In wondering about how I might send all or part of my 4000 watts worth of Solar Panels current to a water heating task; ... when my 24v LiFePO4 battery bank is just under fully charged (near cut off set for top voltage:

... I ordered one of these to play with later:

Amazon.com

For Control Option on Heating Water Dump: I just found and ordered one of these too (the price was good) :

Amazon.com: NOYITO 12V 24V Battery Charging Control Board (12-24V MAX30V) Battery Charge Control Switch Auto Power Off Safe and Energy Saving : Patio, Lawn & Garden

Amazon.com: NOYITO 12V 24V Battery Charging Control Board (12-24V MAX30V) Battery Charge Control Switch Auto Power Off Safe and Energy Saving : Patio, Lawn & Garden

www.amazon.com

 

[Santa Fe Big Sky]

Not cheap but the hybrid hot water heaters (essentially heat pumps) might heat more efficiently if you can deliver 30 amps @220v a/c. But I tend to over complicate things. ?

 

[efficientPV]

Are you diverting from your panel array or the lipo battery bank?

 

[Capt Bill]

I am lately taking in this Poz Lesson as I get ready to put 4000 watts of solar panels on my roof. Researching for option to dump excess PV current to water heating.

Matching Water Heater Elements to Solar PV Panels David Poz

Big Insight Lesson: One panel is more efficient than 3 in series or 2 in series. Parallel configuration produces more watts at direct dc connect to a water heating coil! The PVs Poz used were about 36 - 38v / about 350 watt panels.

I would like to figure out a way to divert one full 2000 watt PV array via one or two relay switches directly the proper spec Water Heating Coil Rod in an efficient configuration. At present, taking in David Poz's Insight Lesson; I am re-thinking my 2P/3S PV Out of about 78vdc @29Amps direct to water heating coils when my battery bank is near full. ... Looks like 3 of my PV panels wired in Parallel would equal the heating Watts at a heater coil, and that 3p might equal about same watts of all 6 of my 365 watt PV panels in 2P/3S configuration when put directly put on a heater coil.

Looking at options for how to make efficient use of my panel watts when dc current is diverted to water heating. ... I am Searching for some kind of MPPT or PWM Controller or some kind of In between electronic with capacitor set up; ... that would make more efficient use of my full 2000 watts PV array when its' full dc current potential is diverted directly to a proper choice of one or two water heating coil(s). or maybe I can gt more watts from 6 panels by using two heating coil elements wired in parallel or series ??? Seen some interesting stories, including in this thread or forum, with capacitors mixed in that in between option to make use of more efficient use of solar panel watts when wiring PV panels directly to heating coils. I do not fully understand electronics, or what my best route will be YET.

Comments Welcome.

 

[efficientPV]

Not exactly the right take on that. There is little difference between series and parallel. Parallel works better in partial shading and with overpaneling. A bad mismatch between panel and heater is just the same series or parallel. I think David and many others just do things wrong in order to make another video. Relays, you go with what you are comfortable with. People will spare no expense or energy to do things the wrong way.

 

[Capt Bill]

taking in David Poz's Insight Lesson; I am re-thinking my 2P/3S PV Out of about 78vdc @29Amps direct to water heating coils when my battery bank is near full. ... Looks like 3 of my PV panels wired in Parallel would equal the heating Watts at a heater coil, and that 3p might equal about same watts of all 6 of my 365 watt PV panels in 2P/3S configuration when put directly put on a heater coil.

Since see how inefficient it might be to switch a full 2000 watt array's dc current directly to a water heating coil (with planned 2P3S configuration that will produce about 28 amps @ 80vdc, that I will most likely stick with); ... I am now studying the option of using a dump controller connected to my 24v LiFePO4 Battery to do that diversion task when my batteries are near full. ... I see the PWM Morningstar Tristar TS60 charge controller/diversion controller as one option, while wonder what less expensive option I might also consider. The TS60 monitors the battery voltage and only dumps what is necessary to hold the voltage steady at the bulk/absorption voltage. The TS60 either works as a 60 amp solar charge controller or a 60 amp diversion controller. It does not do both at the same time. I notice one can select other amp ranges to utilize for diversion too (different units).

Whatever I end up doing, I want to Dump Watts from my 2000 Watts x 2 of Solar Panel Arrays to a Water heating task in an efficient manner as possible (as in getting the most watts of heat out of the diverted current). I Remember one forum member mentioning using an inexpensive PWM Controller to send current to his water heating task at just below full battery charge voltage (wish I could find that again to ask some questions). With 4000 watts of PV going up on my roof soon, I think I will be generating more power than I have normally have used many parts of the year. My Solar Input will be connected to three LV2424 All In One Units already installed and configured on my 1st DIY 24v 280 Ah LiFePO4 build. I am still studying my options for a load dump controller while Learning More All the Time. :+)

 

[Capt Bill]

Considering Options for a Hot Water Dump; & for a specific hardware configuration:

I am looking at options for using part my 4000 Watts (2000 W x 2) of PV Solar Arrays power to heat water via water heating coils
when my 24v 280 Ah LiFePO4 battery is near full. My PV to Battery is handled by 3 LV2424 All In Ones (so I have potential to add 2000 more watts of PV for 6000 w total). I believe I could reliably use an inexpensive volt monitoring switch (have two options on way) to switch current on and off via one of my overkill Kilovac brand 500 amp * 240vdc rated relays ($40 used), or an SSR wired directly from 24v 280 Ah LifePO4 battery bank, or wired directly from my solar panel array; or with a different relay, I could be wired direct from Inverter's 120ac to heater coil(s) for heating water when my battery bank is near full. I will also configure to cut off my water heating task(s) when battery drops to some lower voltage (maybe 1 volt drop or less from full).

I am exploring these options because I will likely be producing more Solar Power for my house than I currently use. I would like heat my small hot tub with solar (thinking may easily be in reach most of the year), when I have excess PV In power, and use that to back off my use of natural gas for spa heating.

From D Poz's recent Youtube lesson: I believe switching one of my 2000 watt solar panel arrays (configured 2P/3S / which is not going to change) to a water heating dump task would be wasting half the potential watts on my PV array. Poz's Experiment seems to show that PV panels wired directly to a water heating coil produces way more watts at a heating coil when PV panels are wired in parallel; while showing significant lost watt potential when wired in series. If there is a simple fix for that, I want to hear about that (?). After taking in Poz's Insight Lesson, I am letting go of my previous idea of switching one of my 2000 watt solar array to a heat dump task (unless someone can give me good reasons to reconsider). ... I am now looking at wiring directly from my batter, or via just using my Inverters 120vac for water heating (as a solar energy dump when my batteries are near full.

Question: Has any one seen test results showing which route would be more efficient in using excess Solar Watts for heating water? ...as in comparing wiring directly from battery bank vs using my 120 vac options from my Inverter(s); ... for heating water?

Added Note: from just studying Direct to Water Heating thread: and reading: about forum member finding reasonable success with a dc-to-dc boost converter. It takes 20-60 VDC, and converts it to 120 VDC. Of course, it is pulsed DC, but the element doesn't care about that. The best part is you can use the existing thermostat without burning out the contacts. (and finding one for $25 on eBay) ... I am wondering if there way to get fuller watts power of one of my 2000 Watt Solar(in 2p/3s config) arrays when wired directly to a water heating coil by wiring some inexpensive in between Pulsed or MPPT type hardware. So still exploring that option because I can think of easy relay switch config for that.

Learning More All the Time by Wondering :+)

 

[Capt Bill]

The magic box is a small circuit that modifies the DC solar into rough AC suitable to be directly plugged into an existing electric water heater

Re: that: Solar Direct Hot Water Controller: w NOTICE: 10-14 Day Lead Time for $259.95 :
Here is an Alibaba option for a way lesser price (but can only handle a Maximum input current of 15A

11.15US $ |DC DC 600W 10 60V to 12 80V Boost Converter Step up Module Power Supply In Stock good price|Integrated Circuits| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Maybe I could wire three of these together to handle my 27 amp step up needs ??? Its' specs say: The input voltage to 60 V: maximum output power P = 60V * 10A = 600W (my PV array might be too high for it? / while experiment might cost $45 plus my time and wiring.

I am searching for the Alibaba option that can handle my 2000 watt solar panel array configured 2p/3S ... outputting about 76vdc @ up to 27A as in between solar panel array wire directly to water heating coil(s) ... when relay switching my full PV array to water heating coils as a dump task when my 24v 280Ah LiFePO4s are near full. I want to get the most watts I can at the water heating coil (most efficient use of my electric current options, plus the most bang for my buck!

 

[efficientPV]

I tried one of those to boost 60 to 80. Your best bet is to stick that inside the tank, it sure gets hot. At higher power the efficiency really drops. End result was a gain of only a few watts. Totally not worth doing. Input voltage was held closely at 60V and one of the capacitors still blew up. Your money.

 

[Capt Bill]

I tried one of those to boost 60 to 80. Your best bet is to stick that inside the tank, it sure gets hot. At higher power the efficiency really drops. End result was a gain of only a few watts. Totally not worth doing. Input voltage was held closely at 60V and one of the capacitors still blew up. Your money.

I have searched Alibaba Express for a 2000W version; but I have not found one yet. RE: your: "stick that inside the tank, it sure gets hot." ... Maybe I want a 3000 Watt version if they get that hot. Appreciate the personal reference :+)

 

[Craig]

I would just buy a few water heater elements and hook them to your AC out of your inverters with a ac switch being controlled by battery SOC or whatever you want to use . I hooked heating elements up to straight 24v from my battery and it does heat but not very well hooking them up to the inverter works about 5 times better. I think i got 3 amps at 24 volts and 3 amps at 120 as well. You may lose some efficiency but who cares it is a dump load afterall

 

[Capt Bill]

I would just buy a few water heater elements and hook them to your AC out of your inverters with a ac switch being controlled by battery SOC or whatever you want to use . I hooked heating elements up to straight 24v from my battery and it does heat but not very well hooking them up to the inverter works about 5 times better. I think i got 3 amps at 24 volts and 3 amps at 120 as well. You may lose some efficiency but who cares it is a dump load afterall

Thank you Craig :+) ... I appreciate the heck out of your personal reference story. I think I will use that idea. I now think AC will likely be my easiest and most efficient route. Be awhile before I put that online.

 

[Fred S]

If you have the inverter capacity, especially at 240v, that certainly is the easiest approach. To Craig's point, you have to account / be prepared for the drain on batteries at night or in low light conditions, such as using a LVD to remove the heater load. (The problem with a LVD for such a large load is that it can cause a vicious cycle of on and off triggering, due to the load turning off, causing the voltage to increase without the load, then causing the LVD to trigger the load back "on" again, and so on.)

A method I use is what I call an "insolation panel", using the idea suggested by efficientPV. I placed an old 5w panel out with my main array, and added a continuous load of 200 ohms to it (using power resistors because the load gets up to 3w). Because of the load, the voltage from the panel is fairly linear with light intensity. I send this voltage to a LVD gadget to turn on items only when there is adequate light. This approach avoids the normal fluctuations of a working array influencing the LVD.

For heating water without using your inverter, the best efficiency will come from using a mppt controller designed for this heating purpose. Here is one I installed:
https://actii.pl/en/ladowarki-prost...240073919.html?SubmitCurrency=1&id_currency=2
it works well, but it is a risk, as it has no support at all.

Whether you use an mppt-type controller or not, when you tie to an array directly you have to match the array's "equivalent resistance" (working voltage / working amps) to the heating element's resistance. E.g., a common 4500 watt 240v element has 12.8 ohms resistance, so for that element you'd set up your array to provide [working volts/amps] = as close to 12.8 ohms as possible. This is what David Poz eventually discovered. (And series or parallel is not really relevant, except that generally you do want to get voltage as high as possible while balancing the equation, so to speak.) But, even when you do this balance, without mppt the performance will become terrible when the light decreases. This is because the [volts/amps=equivalent resistance] value of the array changes. Anyway, my controller gives me 800-950 watts in good sunlight, from a 960 watt array, and 150-300w in overcast conditions.

A boost converter does not work nearly as well, but it does work. As a test I have had one set up on a 12.8 ohm element for a couple of months, with a supplemental cooling fan. In good sun I get in the low 400-watt range getting to the element, at a 50-60v array voltage and 8-9 amps draw.

Amazon.com: Drok Numerical Control Regulator DC 8V-60V to 10V-120V 15A Boost Converter, Constant Step Up Module Adjustable Output 48V 24V 12V DC Power Supply with Led Display : Electronics

Buy Drok Numerical Control Regulator DC 8V-60V to 10V-120V 15A Boost Converter, Constant Step Up Module Adjustable Output 48V 24V 12V DC Power Supply with Led Display: Power Converters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Side FYI note: The boost converter may have "pulsed" output, which you mentioned in a post. As another test, I tried leaving the water heater's stock thermostat in line with the heating element when I wired up the converter output. It did not work - the thermostat contacts arced badly when the contacts opened.

 

[Capt Bill]

(The problem with a LVD for such a large load is that it can cause a vicious cycle of on and off triggering, due to the load turning off, causing the voltage to increase without the load, then causing the LVD to trigger the load back "on" again, and so on.)

Thanks for sharing info. from your personal trials, and testing different configurations. I certainly would want to avoid excessive on and off cycles (unless on purpose via one of those PWM Solar Controllers) when activating a LVD cycle (low volt disconnect/ had to look up those intials). I appreciate the lesson. ... RE: that mppt controller designed for this heating purpose that you installed. I saw one of those on ebay recently, and noticed it handles panel current of up to 10 amps. I would be much more interested when If I saw one that could handle up to 27 amps that my 2000 watt solar array might sometime reach (even though I could imagine volts and amps shifting around when connecting a full PV array to a water heating coil), if it was not too costly. I did notice your link had a lower price than those on ebay's.

RE: your: "I send this voltage to a LVD gadget to turn on items only when there is adequate light." Cool idea. I once used a $10 thermal disc in a black can or a jar with black inside lid facing sun, ... to turn on a small 120vac circuit for circulating my hot tub water through 3 water filled solar panels. I also had a high temp disconnect at my hot tub set at may 105 degree F, so it was set up to run on automatic. That was cheap and dependable. I obtained that idea from my imagination.

Thanks for sharing real life experiences, ohm related lessons, and comparing notes. I intend to heat water in some automatic fashion when I have extra PV panel current not otherwise being utilized. :+) Bill

 

[Craig]

Seems to me if you sized your load properly it wouldnt necessarily draw down the battery if it did you can make the reset voltages far enough apart that it wouldn't cycle too often. I would do say run a load that is 50-75% of your expected solar output. this way the battery is not drawn down by the "dump" load I'm just brainstorming here with you. Seems like a fun side project.

 

[Fred S]

- Ha, the snap disk in a can was a good idea!
- If you have a lot of battery capacity, the "cycling" on and off due to voltage swings may not be a problem at all.
- For the controller that I linked -- it says it will handle up to 2,000 watts, but I recommend that you not exceed 1,000 watts. You could give it a try, the unit supposedly can handle up to 400 volts input. But I wouldn't even do 200v at 10a (2,000w).

If you use a 2nd water heater as a preheater tank for your main water heater, which is what I did, then you could split the array into two, buy two controllers and send 1,000w to each element. Then you'd also have redundancy for the times that something fails.

 

[Fred S]

Seems to me if you sized your load properly it wouldnt necessarily draw down the battery if it did you can make the reset voltages far enough apart that it wouldn't cycle too often. I would do say run a load that is 50-75% of your expected solar output. this way the battery is not drawn down by the "dump" load I'm just brainstorming here with you. Seems like a fun side project.

Yep. And with a big battery capacity you'd probably not have the cycling problem I mentioned. You could swap in, say, a 1,500w heating element, and with a large battery and inverter, and a 2,000w or greater array, and a LVD and/or timer to give the battery priority charging, it should work.

You just gotta plan for the other loads that need power while the water heater is on.

 

[EricBarbour]

if this helps at all, I ran an experiment recently (late May), after learning that it was possible to purchase 12v, 24v and 48v standard heating elements for water heaters.

Bought this 20-gallon water heater, which I judged to be large enough for our use. Took out the 120v element and installed this 48v 600 watt element. Already had a number of 230w Sunpower panels purchased from a nearby surplus dealer. (He has THOUSANDS of them. They were removed from a giant solar farm in Arizona that bought newer, slightly more efficient panels. All the panels I bought worked perfectly, putting out 42v at about 5.5 amps in full sun.) Looking at the specs and thought, "if it's getting full sun, why bother with any electronics?" So I wired three of those panels in parallel to get 42v at about 16 amps or thereabouts. Then connected that directly to the heater's 48v element and thermostat.

Filled the tank with cold water and put the panels in direct sunlight. It took about 6 hours for the panels to bring the water to the set temperature, about 50 deg C or 122 deg F. So it DOES work, at least for one tankful per day--and you don't need a charge controller or regulation if the panels put out the same voltage the element needs, or a little less. The thermostat built into the water heater will shut off the current when it reaches set temp. (I live in northern California which gets good insolation for at least half the year but is "questionable" during the 4 months of winter weather.)

Most home water heaters are 40-50 gallons and usually have two 3800 or 4500 watt 240v heaters, which usually run one at a time as each has its own thermostat. You would need a LOT of 300-watt panels in series-parallel to run a heater like that, although it would heat the water much faster than 6 hours. I figure if you have 300w 32v panels that are typical of commercial solar installations, it would take a minimum of 7 x 2 = 14 panels in series-parallel to run it. No batteries, no electronics.

Something to mull over for a while.

 

[EricBarbour]

PS, I asked a local plumber about running a water heater element on DC. He said it is okay since most tank heating elements are only rated to last 5-10 years anyway. So keep a spare element.

Also asked a couple of local electricians. They both said running tank elements on DC should not be a problem, the thermostats are "very conservatively rated". Plus they pointed out that very similar small water heaters are routinely used on RVs, and the 12v element is connected directly to the 12v DC power circuit. The thermostats are "the same" as the ones used on AC power.