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2015

Review Techluck

100 watt solar panel
Free shipping
Back view                      Front view
Example Renogy mono-crystalline panel

Buy from my affiliate links:
One 100 watt solar panel at Amazon $149
One 250 watt panel at Amazon $350
Two 150 watt panels at Amazon $300
Buy solar panels at Amazon
Branch wires
Mounting brackets
Solar array at Amazon

"90% or so of their original performance after 25 years.  They can easily last longer than that, slowly decreasing output as time goes on."
Solar panel bundle
250W Renogy mono-crystalline panel


Buy Bundles;
4 panels 250 watt at Amazon $1275
6 panels 250 watt at Amazon
10 panels 250 watt at Amazon
20 panels 250 watt at Amazon

Solar panel connectors
Buy solar panels at Amazon
Solar array at Amazon


Plan below uses solar panels

1000 watt system: four 250 watt panels
3000 watt system: twelve 250 watt panels

Specifications of the 250 Watt RENOGY panels
Maximum Power: 250W
Optimum Operating Voltage (Vmp): 30.1V
Optimum Operating Current (Imp): 8.32A
Panel Ideal resistance at 1000W/m^2 solar isolation = Vmp / 1mp 30.1V / 8.32A = 3.617 Ohms (per panel)

Element Wattage = 4500W
Element Resistance: 240 * 240 / 4500 = 12.8 Ohms
Ideal number of panels per single string assuming 1000W/m^2 solar isolation:
12.8 Ohms / 3.617 Ohms = 3.538 panels, round down to 3 panels per string.

System A) 750 watt system, 3 panels, 1 string, Ideal Resistance 30.1 * 3 / 8.32 = 10.85 Ohms
System B) 3000 watt system, 12 panels, 6 panels per string,  2 strings, Ideal Resistance (30.1 * 6) / (8.32 * 2) = 10.85 Ohms.

Element size (resistance) needs to have an approximate match to the PV array (Vmp/Imp)

All costs are energy
Invest in things that make energy!
Everything is on sale today... price only get higher... for wire, solar panels, fuel, aluminum

Review Techluck starts here

This page and everything on it occurred because Techluck caused Dave to email me... and then Dave and I discussed the idea, resulting in several 'new' things to help the solar community
Your contribution is welcome... email at bottom of page
Gene:
What I would like to see from Techluck, or any solar application:
Give us real science, no matter if you are Techluck or AO Smith: Start with fully unheated tank beginning of day. Known gallon capacity of tank. Temperature of water from TP valve and Drain valve averaged together. Specify solar collection specifications. Heat water throughout good solar day.  Measure water temperature at end of good solar. Measure water temperature 2-4-6-8 hours later. No water drawn from tank during experiment. Repeat test marginal solar day. Repeat test summer, and winter.
Dave Dave: Dec 2014
I was going to ask you if you have seen or heard anything about the PV solar controller sold at ...
http://techluck.com/

I have been doing solar as a hobby for 15+ years now and in the time the prices have dropped from 5$ or more/watt to less than 1$/watt.
In doing so there have been a whole lot of technologies and components that have gone by the way side or relegated to niche applications:
Examples:
   Thin film solar
   Active and Passive trackers mounts
   Top of pole mounts

  -Dave
Gene Gene:
A while back the Techluck guy sent his idea for me to assess.

We disagreed, and he stopped emailing.
Inventors are very headstrong... which make them good inventors

I am hyper critical about detail, which makes me a pain in the ass.
I was critical of his initial wiring setup, his sales presentation, and his claim of heating
(No doubt he cleaned up his wiring since he seemed knowledgeable, and his sales presentation seems very nice).

He believes in his invention.
Probably the converter is well-made from off-the shelf parts... but he would never send close-up photo. [for fear of losing his invention?]

Heating... I am skeptical... [update... my conclusion at this point in conversation is not conclusive... keep reading]
He claimed two solar panels heat lower part of his tank during day.
Of course I do not have test facilities, or live in California where I think he does.
He showed me the output numbers
I forget exact Kw rating he gave.

It was very low Kwh arriving from 2 solar panels. [Maybe not enough solar panels?]

I told him the Kwh required to effectively heat water exceeded the solar output he showed.
Memory recalls the amount of Kwh would heat 1-2 gallon in several hours. [update... my conclusion at this point in conversation is not conclusive... keep reading]
So there would be some benefit.
He insisted that the solar panels heated his water. I wanted more details. The conversation ended.
Resources:
Kw needed to heat water
Time table for raising water temperature

Electrical Safety and Techluck



Gene
I remembered a bit more since yesterday.

The problem with the Techluck wiring was connection to water heater.

Warranty:
Water heater warranty: Any connection that alters original wiring voids water heater warranty.
I'm not big on warranties, so this is minor inconvenience.

Wiring:
No way to connect wires to bottom element without drilling 3/4" hole to connect conduit 1/2' connection:

His wires from the converter were tied into the water heater without any box or covering.
His wires, and element and thermostat were exposed to open air.
But he was doing a test, so out-of-code wiring is ok.
Actual real-world connection would have to be covered

NO ECO? Energy cut-off. (red reset button)
-Either he wired directly to the element.... and bypassed thermostat... which means the lower part of tank had no energy cut off.
-Or he connected AC from solar to the lower thermostat... which has no energy cut-off.
I asked for close up photos. My intent was to offer assistance... but I am very critical person... and maybe pushed too hard... or maybe he gleaned enough information from my criticism to move forward, and more conversation would waste his time or reveal his invention.
Safety requires lower thermostat replaced with ECO-protected upper thermostat...
... then the AC voltage from Techluck can be connected to ECO-protected thermostat before feeding lower element

Safety violation:
Two voltages, arriving from two different sources is considered safety violation.
Reason: because unsuspecting person might turn off household 240 volt circuit breaker, and assume power is off at water heater.
BUT the AC solar connection is still present.

No safety cut off:
Techluck did not show a safety cut off to fully disconnect power to water heater
Two different voltages would require a 3-pole cut off, or safety switch located next to water heater.
Three-pole would allow 2 poles for both Hot wires coming from household 240Volt, and then 1 pole for Hot wire from Techluck.
All wire insulation coverings must be rated for 600 Volt AC, as with normal NM-B household wires

Bad science ?

Bad science?
His thermostat was exposed to open air and not covered with insulation
If he wired to the thermostat.... then it shows there is no substantial heating.
This is because water heater thermostat must be covered with insulation to correctly read water temperature through tank wall.
Ordinary water heater thermostat exposed to cool room air temperature will misread water temperature and cause run-away over-heating.
Obviously there was no run-away heating, or his TP valve would release water, or ECO at upper thermostat would trip.

Use 2 tanks instead of one ?

Maybe good way to use his invention:
Connect Techluck to 20 gallon tank. [or 30 gallon]
Then use recirculation pump to supply hot water to larger tank
Note: this would let you feed solar water into gas water heater or electric water heater or hybrid heat pump:

Why use Techluck on smaller water heater, then circulate the solar heated water over to another heater?
Your main water heater is not limited to electric water heater. Main water heater can be gas or electric or hybrid. The small tank must be electric, but is not connected to household electric. Neither water heater warranty is canceled because no alterations are made to either the main heater or small electric heater. Both water heaters are separated electrically and meet safety code easily. You can run Pex pipe between water heaters. No alteration needed for either water heater. Connect recirculation as if it was ordinary recirculation system. Small water heater is not connected to household power. Simply connect Techluck to electric wires at top of small tank; no drilling etc. Small water heater is already rated 120 volt and has 1500-2000 watt element. The main water heater can run at full capacity during low-solar periods, or if Techluck fails.

More options: The recirculation pump can be on a timer, or controlled by reverse photoeye that turns pump on when solar is bright. Or run recirculation pump once per day for certain amount of time, to download contents of small tank into larger tank. There are many untested tweaks available for DIY solar water heaters. everybody will have own idea, unique to their usage and physical surroundings.

Disadvantage of two tanks: More cost? recirculation pump cost money. Pump is 1/25 Hp or 25 watts and draws small amount of electricity. Must buy small electric water heater, and make space for the heater. Loss of heat? Recirculation will lose heat along pipes. Direct connecting Techluck to bottom of electric water heater means no recirculation heat loss.
Resource:
Add another thermostat to gas or electric water heater
Two water heaters
Compare 20 gallon electric water heater
Recirculation systems

Techluck niche product for solar heating?


Techluck not robust?

Dave:
I totally agree Gene.  Using Techluck in a single water heater setup it violates code + warranty and bypasses many of the safety mechanisms (ECO, thermostat misread, wires modified, UL listing gone due to mods).   The idea has merit but it requires two tanks at minimum.  Cold water goes into Solar pre-heat tank with the Techluck and one after on normal grid power.

I hit the same issue with my solar controller.  Originally I was going to modify the wiring to make it simultaneous but hit a brick wall when I could not put an ECO + thermo on the bottom element.
Unlike the severely limited output of the Techluck, my system DOES have the power to easily over heat the tank in the case the thermo sticks closed.

So I left the wiring internally stock (except for the 1-wire remote temp readers). 

I agree that DC power burns out thermostats quickly the same way it burns up normal power relays when they are fed DC power instead of the AC power they are rated at.   Relays can be delicate.

[Gene:, Dave found big amp DC relays for solar water heater]
Resource:
DC relays for solar power

Dave:
 I had an issue with relays in my controller box getting destroyed when I switched elements between 240VAC and 120VAC. I solved the issue by turning off the power relay (DPST relay) feeding the 120/240 selection relay (SPDT relay), then flipping 120/240 relay state, then turning the power relay back on.   I figured the arc flash between the N and Hot side of the DPST relay was being aided and abetted by the armature moving between contacts while under power. 

The big problem I see with the Techluck is that the max PV you can put into is like 1250 watts PV nameplate rating and even then Techluck very much cautions that the user should not overdrive the controller
I suspect that the Techluck product does not last long at its max rated wattage. 
Recommending like 750 is a good number to hit so it doesn't burn out before the warranty period is over.

Problem is I typically burn through 10-15Kw of hot water on a daily basis.  A 1250 watts max setup at a average 6 hours (I'm being generous) direct sun equivalent is only 7.5Kw yield.    Derate that by non-ideal solar conditions and a more sustainable 750watt array and now its only about a quarter of my needs.

So I just need another Techluck controller and a second PV array right?  Not so fast.  The controller inverts the DC from the panels into an AC waveform.  The AC waveform from two controllers will not be in phase sync and if the outputs are connected together they will probably fry each other like connecting a genny output to the grid.  

So more yield requires a separate water heater for each Techluck controller or hack to make the water heater unsafe as you have stated and feeding top and bottom with separate Techluck.

So Techluck is a niche product.  Someone that likes the idea of solar and wants a system to marginally assist in water heating.  It does not provide any other facility to make usable power for any of the few zillion electrical devices in my house.

Techluck efficiency?

Dave:
Have you seen any stats on the efficiency numbers for the Techluck?  Its got to be less than 100% because there is heat generated, enough to require the heat sink effect of a large metal enclosure.  I assume 95% if I don't see  otherwise.  Also any indication of the efficiency of yield?  The electronics have a good chance of getting 98-99% because of the high frequency switching and I am assuming good MPPT seeking algorithm but I don't know because I haven't tested it.

Gene Jan 2015/
I guess the Techluck is less than 95% if there is heat sink. But otherwise, I don't know. You would need Kwh meter to measure actual output.
If Techluck requires heat sink... aluminum is best metal for heat dissipation, but maybe not best for grounding. Heat is killer of all electrical devices... if heat sink is required, then Techluck is vulnerable to failure. Maybe a fan; for example like used on desktop computer... but then that adds another energy cost for fan.
We really need to know how hot the Techluck product gets to make guess at efficiency loss. Maybe use bigger #6 wire between Techluck and water heater. Wire is expensive, and it is an energy cost too.

Gene
Basically, physics says that it takes .0002931 Kwh to raise 1 pound of water 1F....  Resource/ Kwh
Elements are generally 99% efficient due to  immersion of elements in the water.
Efficiency will drop if elements are coated with sediment, or sediment/sludge fills bottom of tank, or if wires are undersized causing heat loss along wire (use 10 gauge or larger wires), or water heater too distant from power source causing voltage drop and energy loss and lower element output/ How to clean out tank and replace element
*** So water heater elements must be clean, and tank cleaned out, wires have to be #6 or #10, and best if water heater is located close to solar panels and close to Techluck, or efficiency will drop... Techluck efficiency calculation uncertain

Techluck Heating calculation/ discussion


Yes Techluck heats 'some' hot water on good solar days


Gene
Double-check some quick numbers below and see if you think they apply to Techluck.
Water weighs 8.33 lbs per gallon/ 40 gallon tank 332 lbs water. To raise 40 gallon water heater 1 degree requires .097 Kwh. Raise 10 degrees .97 Kwh,.
Let's round off to 1 Kwh needed to raise 40 gallon by 10 degrees.

Wattage is just a rating that does not measure heating power.
Wattage over time, or watt-hours or Kilowatt-hours (Kwh) is measure of heating power.
If you have 1250 watts for 1/2 hour, then you have 625 watt-hours or .625 Kwh.
If you have 1250 watts for 2 hours of the day, and 750 watts for 3 hours, then you have 4.75 Kwh... which should raise 40 gallons of water from 75 to 120
***This rough estimate shows that Techluck will heat water on good solar day if solar panel array can fully clock Techluck @ 1250 watt for 2 hours and then run at Dave's suggested rate @ 750 watt for 3 hours.
My numbers are approximate from non-mathematician and do not factor Techluck efficiency, nor factor .92 energy-rated electric water heater that suffers standby loss over 5 hour period. Nor does the calculation anticipate real-world condition of hot water usage: For example if you take shower at 9 pm, some of the solar heating has been lost to standby?... implying that Techluck is paying for standby heating during the day? Resource: Read; maybe standby loss is not issue with solar ... In any case, the tank should be well-insulated, and maybe suggest adding mixing valve used to keep heat inside tank Resource/ mixing valve]. Obviously reducing temperature and using less hot water is good strategy, and these DIY actions action cost nothing to implement.

Gene:
We can make another estimate: Techluck suggests using 1500 watt 120 volt element:
Compare: 4500 watt element under full 240 Volt AC output, heats about 20.7 gallons per hour... unknown rise in temperature See water heater recovery chart
Compare: 1500 watt element under full 120 Volt AC output, heats about 6.9 gallons per hour.... unknown rise in temperature See water heater recovery chart
What does this mean for Techluck?
If maximum output is 120 volt at 1250 watt for 2 hours, then you would get about 11.5 gallons. Add 120 volt at 750 watt for 3 hours, 10.3 gallons
Add 11.5 gallons and 10.3 gallons for total 21.8 gallons fully heated by Techluck
***Again, this rough estimate shows that Techluck will heat water on a good solar day if solar panel array can fully clock Techluck @ 1250 watt for 2 hours and then run at Dave's suggested rate @ 750 watt for 3 hours.
****You will not overheat water or get a lot of hot water from Techluck

Dave:
My water is 60F on average.  55F in winter.  65F in summer

0.0002931 Kwh to raise 1 pound of water 1F
0.0024444 Kwh to raise 1 gallon of water 1F
0.146666  Kwh to raise 1 gallon of water 60F (60-120F)
5.866689  Kwh to raise 40 gallons of water 60F (60-120F)

My rule of thumb for solar is 5x to 6x the panel rating during a really sunny day. 
1250 watts of PV should make about (1250watts x 5) = 6.250 Kwh

*** So yes!  Techluck can probably do that if it is half decent efficient on a really sunny day. But we don't know the efficiency of Techluck

But 5 to 6Kwh of hot water isn't enough for me.  I burn more like 10 to 15Kwh of hot water per day.  Sometimes more if its a heavy laundry day or have to run two loads in the dishwasher.

***Also, if its a less than stellar solar day there will not be nearly enough for average joe.
Take today for instance.  I will be lucky if I get 30Kwh as compared to the 66Kwh I harvested yesterday. 

*** Techluck is a good solution for a small PV array.  I still would not drive that thing at max 1250W.  Maybe 1000W would be a good compromise between reliability and system capacity.

Conclusions

General math above shows:
**1) We cannot determine efficiency factor for Techluck, which affects our estimated amount of hot water produced, and failure rate of Techluck

**2) Techluck claims his unit heats water during the day. True.
Yes this is true. We estimate Techluck will heat 20-40 gallons hot water depending on solar output, actual-world efficiency of Techluck, initial temperature of water, standby loss, temperature expectation, condition of tank and element, size of wire, and other factors.
... and will heat water IF solar array provides enough power ... without exceeding 1250 watts Techluck maximum.

**3) Dave's assessment of Techluck is correct.
Techluck is 'niche product' that provides some hot water.
Techluck needs to be bigger capacity to meet full needs of average home
Running Techluck at full 1250 watts will probably burn it out quickly. 750-1000 watts might be better target for long-term.
Techluck product might not be robust longterm product.... comments on this topic welcome... email at bottom of page.

**4) Possible best way to use Techluck:   Connect Techluck to stand-alone 20-30 gallon water heater that supplements regular tank heater.
This strategy lets you integrate Techluck with ordinary gas or electric heater without voiding warranty on ordinary heater
This lets you direct connect Techluck to smaller 120 volt tank, that has 120 volt 1500 watt element, without voiding small tank warranty, or requiring modifications
Note: 120 volts can be connected safely to any 240 volt electric water heater, without modifying the water heater. Suggest changing element to 120V.

**5) Handy rule of thumb for solar is 5x to 6x the panel rating during a really sunny day.  1250 watts of PV should make about (1250watts x 5) = 6.250 Kwh

**6) The full DC solar water heater design (shown lower on this page) can produce same or more solar heating than Techluck... and DIY parts for the full DC solar design means lower cost, longer life than Techluck. The full DC solar water heater design can be expanded with more options, and will definitely support more solar panels and heat more water than Techluck with various wiring versions. But Techluck is pre-packaged with minimal DIY installation. Techluck allows person to experiment with 3-4 solar panels, and folks often want pre-packaged instead of full DIY tinkering that is required with the full DC solar water heater shown lower on this page.

Resources:
Two water heaters
Compare 20 gallon electric water heater
Convert 240 volt water heater to 120 volt
Add another thermostat to gas or electric water heater
review techluck
Larger image
Local code requires direct bond (ground wire) from solar panel frames and metal conduit to nearby ground rod using #6 copper wire. Ground rod must meet local specifications. Additionally, code requires all ground wires from solar, telephone, satellite, etc to be bonded (connected) to household ground system.

This means Techluck conduit, metal box, safety switch etc should be bonded to nearby ground rod, and bonded water heater tank, and water heater ground wire connected back to main breaker panel that is connected to proper outdoor ground rod. Connecting ground wires to metal water pipes is no guarantee of ground, and can cause deteriorated water pipe.
This information covers all metal components that are connected to this water heater and solar panel system.
In addition to information above, solar PV power is DC, with a positive leg and negative leg. The negative leg of solar power should also be grounded, and this is not covered here. Uncertain what Techluck product offers for grounding the negative leg of solar power.

Surge protection against nearby lightning strike is aided when all grounds are bonded together, and bonded to neutral busbar in main breaker panel. Do not use ground wire as a neutral since this increases risk of surge destruction, and fire.
No surge protection is available for lightning strikes within 90 feet.
Use lightning rod system in areas where lightning is common.
Risk of lightning is higher when home is near pond, high elevation, or sitting alone. Higher structures or multiple structures nearby, will reduce lightning risk.

Local specifications for grounding are based on conductivity of local soils. Dry, loose, rocky soils are less conductive than tightly packed wet soils. Example: Ground rod in Mississippi wet clay may not need to be as deep, or as large diameter, as ground rod in California dry rocky soil.

Recommendations for Techluck install

tapered drill bit

Tapered drill bit for any size hole in metal

Drill 3/4" Hole for 1/2" conduit connection from solar
Buy
tapered drill/ step drill bit for any size hole
Step drill bits at Amazon
Neiko tapered drill bit 1/4"-1-3/8 holes
safety switch

3 pole safety switch
3 pole non-fused safety switch wiring

120-240 Volt 3-pole safety switch

House power and solar power must have safety shut off to protect anyone working on water heater. Use fusable or non-fused. Clearly label, and locate safety switch next to heater. Local codes vary, and generally require another cut off for solar located outside near the solar panels
Connect all household & solar ground wires together
Buy:

3 pole 60 amp non-fused safety switch
3 pole 100 amp non-fused safety switch
30 amp AC cartridge fuse at Amazon
20 amp AC cartridge fuse
30 amp DPDT shut off switch
Resource:
How-to-wire-safety-switch.html
      thermostat terminal protector

Wiring diagram for ECO thermostat

ECO thermostat and terminal protector

AC from Techluck must be wired to ECO-protected thermostat in event the thermostat sticks open. Thermostat at top of tank still has ECO, but it is not connected to Techluck solar power, and will not shut off Techluck in event of overheating. Wiring diagram for ECO thermostat
Buy:

Therm-o-disc terminal protector
Camco 90-150 F thermostats at Amazon
Resources:
More thermostats
Elements
Add another thermostat to water heater
1500 watt element

Wiring diagram for element and thermostat

Use new element/ lower part of tank

1500 watt 120 volt element:
Buy:
1500 watt 120 volt element at Amazon
Resource:
Read about / choose water heater element + how to clean out tank and replace element
Insdulation under screw plate
Larger image
Both wires MUST be same gauge
Straighten each wire
Tighten screw very tight against copper wire



Larger image
Never use stranded wire under screw plate for heavy-amp loads. Ok for table lamp, but not ok for any application over 1-2 amp.
Connect stranded and solid with wire nut and run jumper to screw plate.
Or add solder to stranded wire to make solid.
Or crimp terminal onto stranded wire.
See example image

Fire safety

Use only solid copper wire, and no insulation under screw plate.

Max 2 wires under screw plate

Both wires same gauge

Do not use stranded wire, it will come loose with heat expansion and overheat and cause burning. Turn stranded wire into solid wire by soldering stranded wire.

Always keep enclosure covered
Gene;   
    Techluck and I disagreed, and he stopped emailing.
    Inventors are very headstrong... which make them good inventors

Dave;
I wouldn't classify myself as an inventor but I do "invent" things from time to time.  I'm more of a builder / system integrator.  I like running systems, open to whatever comes along.  I do notice trends a lot when it comes to technology. 

I see tech diverging recently.   On the one hand there is tech for stupid people (Google Nest thermostat are now selling in Home Depot).  And on the other hand there are more SOC system-on-a-chip like the Arduino and Raspberry Pi ($35) that allow people to run their own custom gear that is not cloud-based.   The data need never leave the confines of the local area network.

Gene:
    I am hyper critical about detail, which makes me a pain in the ass.
    I was critical of Techluck's initial wiring setup, his sales presentation, and his claim of heating
    (No doubt he cleaned up his wiring since he seemed knowledgeable, and his sales presentation seems very nice).

Dave:
My take is when it comes to electrical and plumbing.  Code is code.  Its that way for a reason.    Water heaters have blown up peoples houses and that's why they are built with triple safeties (thermo -> ECO -> T&P).
As example, code is no threads on the T&P pipe, not because smart people will cap off the T&P but because stupid people might.     Techluck guy needs more emphasis  on his website on how to install his gear and do it so its safe and preferably to code.

Gene;
    Techluck believes in his invention.
    Probably the converter is well-made from off-the shelf parts... but he would never send close-up photo for fear of losing his invention.

Dave:
Techluck is probably a custom board but I haven't seen it in person. Buddy at work might buy one and I will get to see it up close.  Apparently its easy to have PCB boards printed, populated and soldered these days.  Just need the volume to make it cheap.

Gene
    Heating... I am skeptical...
    He claimed two solar panels heat lower part of his tank during day.
    Of course I do not have test facilities, or live in California where he does.
    He showed me the output numbers
    I forget exact Kw he gave.

    It was very low Kw arriving from 2 solar panels.

    I told him the Kw required to effectively heat water exceeded the solar output he showed.
    Memory recalls the amount of Kw would heat 1-2 gallon in several hours.
    So there would be some benefit.

Dave:
The idea has merit but realistically it needs the ability to handle more power like 2x or 3x as much.   Needs to be more honest about having a second tank.   Buddy at work has got lots of space for a second tank to go along side is newly refurbished 50 gallon electric Bradford White.    He used the trick off your waterheatertimer.org site to vacuum out the crud at the bottom after his bottom element went boom.  
Resource:
How to replace element and clean out sediment

He is thinking using the 105 marathon as the primary grid powered and the 50 gallon using a Techluck preheat.    I'm interested to see how the whole thing will work.

Whats the deal with Marathon fused upper elements???   Do I really need them if I am smart enough to never dry fire the upper element.   Seems to me its just another part to fail.
Gene:
marathon fused upper elements:
Resource:
Marathon-water-heater-elements
Gene
Let me know what you discover about Techluck... if you can invent or prove a useful product, I will display it on my website in detail.
... make you into a thousandaire
[And here's where Dave and I began working on a DC solar water heater... but discussing Techluck actually caused our conversation and subsequent invention]
Dave
LOL.   Ill take you up on that. :)   I could use a couple thousand bucks.

I think the big problem is that a Techluck style system that inverts DC->AC waveform with a decent level of power (3 to 4 kW of PV solar) will cost a lot of money.   My inverters that I run are rated at 3600W continuous and cost around 1700$ each.   I'm sure his gear isn't nearly as beefy as my outbacks so it needs to be limited to 750watts for long lifetime.    And what is more the whole DC->AC thing is really not needed because DC elements can heat water just fine.  The issue is the thermostats and the ECOs burning out with DC power.    Its possible to buy standard fitting DC powered water heater elements that run on 48VDC but they are a specialty item and they have low wattage.  They are also really pricey.

[Gene says: We both confirmed later that AC elements work fine with DC solar power. The problem is water heater thermostat burn up with DC. So the problem with connecting DC directly to electric water heater is the thermostats, not the elements]

Dave:
The whole idea of lets just use standard elements and drive the water heater with high voltage (120 to 240 VDC) power does have merit.   PV is cheap.  Standard electric water heaters with standard elements are cheap.  The trick is the power control to not burn the delicate AC rated relay/switches inside the ECO and thermos.

Dave
Here is an idea:   I know it removes the UL listing because it mods the UL listed water heater but consider:

Have a small 120 or 240 AC power source.  Feed the water heater with it so that the ECO/Thermo  receive the 120 or 240 VAC that they want but then use the 120 or 240VAC supplied at the bottom of the thermostats to drive a 120 or 240VAC coil relay(s) with *DC* rated contacts so its possible to switch the PV DC on and off and feed that to the water heater elements.  

For a typical water heater with two elements.  Two relays will be required.  One to switch the upper and one to switch the lower.

End result:  The ECO and thermos that come stock standard with the water heater are not themselves modified (just their wiring).   They are never exposed to DC and therefore not driven by power they were not speced for.    The DC is switched by a device that is UL rated to handle that power.

There is no fancy shmancy controller that inverts the wave form that is power limited to 1250Watts.  There is no loss of efficiency in converting the DC -> AC.  

Techluck really needs two water heaters. 

DIY alternative to Techluck: see illustration below

Now we go to Dave's solar idea.. and how to wire it (Dave's invention, Gene assistant & illustrator)

The key is supplying low voltage DC to lower thermostat that is used to control heavy-amp DC relay. This diagram, and several direct DC solar water heater designs evolved over period of one month of intense work between the DC solar guru Dave and AC waterheatertimer guy.

See all the DC water heater wiring options/ and more info:
Convert-AC-water-heater-to-DC-water-heater
DC solar water heater
Dave: This is for a small system: For a user that does not require a lot of on demand stand-by hot water the "Simultaneous DC water heater" shown here will work well.

4500 watt element is fine, but you can experiment.
If solar is not as intense, use smaller 3000 watt element
If solar exposure is high, use 5500 watt element
Element size (resistance) needs to have an approximate match to the PV array (Vmp/Imp) which are ratings shown on your solar panel
Resources:
Identify and test and select elements

See all the DC water heater wiring options/ and more info:
Convert-AC-water-heater-to-DC-water-heater

Direct connect AC water heater to DC solar panel

Simultaneous DC water heater/ direct connect solar panel to heater

This wiring diagram does NOT by-pass water heater safety features

This DIY solar water heater probably performs similar to Techluck, except off-the-shelf parts are more reliable since DIY repairs and tweaks and variables can be made. Long term cost will be lower than Techluck. Solar output can be higher than Techluck. The basic parts can be expanded to make full DC solar water heater.
The number of solar panels is undetermined, but you can run full maximum 240V DC 26 amps through the DC-DC relay... and that will match 240V 4500 watt element See DC power relays
With this illustration, showing simultaneous operation, the power supply is ON at all times, unless ECO reset button on upper thermostat is tripped.
Lower thermostat has 24 volt DC power available at all times, unless ECO on upper thermostat is tripped.
Water heater thermostats are mechanical and will operate fine with 24V DC. No problem with melting.
Ordinary lower element is resistive load, and will work fine with high voltage DC power
When lower part of tank is cool, solar power turns ON.
When lower part of tank is hot, then upper part of tank is also heated (because hot water rises to top of tank)
When lower part of tank is hot, DC-DC relay turns OFF, and solar power cannot reach lower element.
Upper part of tank heats normally using 240V household power. Or add 30 amp switch or timer to the black wire that feeds voltage into upper thermostat.. Adding switch or timer means tank is heated using only solar. Adding timer or switch on black wire, as described, does not by-pass ECO, and ECO will turn off solar if tank overheats.
ECO (reset button) on lower thermostat is not needed. Use ordinary lower thermostat because the upper ECO controls entire water heater, just like any ordinary water heater.
Same as Techluck, this design voids water heater warranty.
Same as Techluck, hot water from this design can be recirculated another tank, gas or electric See recirculation
Safety: This illustration requires DC circuit breaker or fused safety switch (as shown in drawing). DC breaker must be clearly marked and located next to water heater. Also requires safety switch for 240V AC household power located next to tank.
All safety features discussed about Techluck also apply to this diagram, including conduit, safety switch, circuit breaker, clear labeling, solid copper wire only, no stranded wire, and all electrical connections covered inside contained space, proper wire size and grounding as per local code. etc.
See all the DC water heater wiring options/ and more info:
Convert-AC-water-heater-to-DC-water-heater
DC to DC relay
240 volt 26 amp DC Load
With 24V DC coil
This is one of the big boys

DC to DC relay/ mechanical type

DC power relays with 12-24 VDC coil

Mechanical relay will fail open, so in event of relay failure, solar will be OFF, or in event of overheated tank, ECO will trip and solar will be OFF. Relay must be contained inside box with cover.Buy:
24 VDC coil 250VDC electromechanical DC-DC G9EB-1 relay
G9EB-1-B-DC24
24 VDC coil and 400 VDC/ 200 amp contacts

Resource with more information on DC relays
DC relays for solar water heater
power supply

Power supply

Input 90-265 Volt AC / output 12 volt DC.
Must be safely contained inside box with cover...

Buy:
12 volt DC 3.5 amp power supply at Amazon
12 volt DC 20 amp power supply at Amazon
      thermostat terminal protector

ECO thermostat and terminal protector

Not required with this installation, but nice to have extra thermostats and elements on hand.
Buy:
Therm-o-disc terminal protector
Camco 90-150 F thermostats at Amazon
Resources:
More thermostats
Identify and test and select elements
How to add another thermostat to water heater
30 amp DC safety switch

DC safety switch

Heavy Duty 250 V Dc Voltage; 30-60 Ampere
Use 10 gauge wire with 30 amp fuse
Use 6 gauge wire with 60 amp fuse
Buy:
Square D 30 amp DC/ outdoor/ fusable/ HU361RB
Square D 60 amp DC/ outdoor/ fusable H222AWK
100 amp non-fusable/ outdoor/ at Amazon
100 amp 3-pole non-fused safety switch

Resource:
DC safety switches
How to wire safety switch
Convert AC water heater to DC water heater
DC relays for solar power
surface mount fuseholder

Surface mount ANL fuseholder

Buy:
e2 fuseholder with platinum plating
ANL fuses
photovoltaic fuseholder    DC fuse
Fuseholder                         Fuse

Photovoltaic fuseholder/ DC fuseholder/ 1000 volts DC/

DC fuse/ photovoltaic fuse: use 20-25 amp fast-acting for designs on this page

Not waterproof... mount inside Nema 3R enclosure
Mount on din rail/ change fuse with flick of finger
Install 25-30 amp fuses
Use 10 x 38 DC fuses

Buy:
Photovoltaic fuseholder / DC fuseholder/ ultrasafe/ at Amazon
Ultrasafe fuseholders at Amazon
600 volt DC fuses at Amazon
Mersen 600 volt DC fuse
waterproof DC fuse holder

Waterproof Solar fuseholder/ 1000 VDC/ 2 amp to 30 amp

Buy
Solar fuseholder at Amazon
Fuse holder plus 20 amp DC fuse
Fuse holder plus 30 amp DC fuse
DC circuit breaker
DC circuit breaker

DC circuit breakers for Solar/ use 20-25 amp for designs on this page

Buy from my affiliate links:
DC circuit breakers
High voltage DC circuit breakers at Amazon

Combiner boxes at Amazon

Resource:
How to set up solar array
Din rail

Din rail for mounting Breakers, fuse-holders, timers, relays

Make your own breaker box, combiner box
Buy:
Din rails for mounting
Combiner boxes at Amazon

Resource:
How to set up solar array


Resource:
DC circuit breakers
For example, if a single cell can provide 5A at 35.5 Vd.c.,
in order to reach the level of 100A at 500 Vd.c.,
it is necessary to connect 20 strings in parallel, each of them constituted by 15 cells.
Photovoltaic plants can supply currents from a few dozens of Amperes (domestic applications and similar) up to several hundreds of Amperes (service industry and small industry).
Direct current presents different problems than alternating current with regard to interrupting high value currents since the arc extinction is particularly difficult with DC.
Alternating current, there is natural passage of voltage to zero with each half cycle as the current changes direction 60 times per second.
With DC, the voltage is constant. There is no passage to zero volts as with AC.
This means that DC wants to keep arcing when switch contacts are pulled apart. The continuous arc causes heat which causes burned contacts and failed switch
Circuit breaker for DC: In order to guarantee breaking of a short-circuit current in a d.c. system it is necessary to employ circuit-breakers which can ensure:
- rapid tripping with adequate breaking capacity;
- high fault current limiting capacity;
- overvoltage reduction effect.
https://www.youtube.com/watch?v=kRB7Z66brO0
http://www.solar-electric.com/installation-parts-and-equipment/midnite/cipr1/stfubr1.html
Compare AC and DC ratings
600 volt AC @ 30 amp fuse/ 300 volt DC @ 15 amp
600 volt AC  @ 600 amp/ 120 volt DC @ 60 amp
6000 volt AC @ 6000 amp/ 300 volt DC 2000 amp
Time delay fuse passes surge currents without sacrafice short circuit limitation
AC rating for 200 kA is reduced to 20 kA for DC
kA is max surge capability... if too much surge is on the fuse, the fuse will not trip and fuse can melt onto the contacts, feeding high voltage into the wire causing possible fire
"The value of the kA rating determines how much current the circuit breaker can withstand under fault conditions. The circuit breaker only has to withstand this for a brief period of time, usually the time it takes for the circuit breaker to trip. For example, a value of 6kA means that the circuit breaker can withstand 6,000 amps of current during the brief time it takes to trip.

Why is the kA rating so important?

Under fault conditions (such as a short circuit) much more current flows through the circuit than what it was designed for. A circuit that was designed for a maximum of 20A may suddenly be drawing hundreds, if not thousands of amps. The circuit breaker will trip if this occurs.

However, what if during a short circuit there is more current flowing through the circuit than the kA rating of the circuit breaker? In this case the circuit breaker will fail, often in either one of two ways. One possibility is that the contacts in the circuit breaker will weld, thus preventing the circuit breaker from tripping. The best case scenario for this is that the cable in the circuit is damaged. The worst case is that a fire is started. Another possibility is that the circuit breaker explodes, as a result of the copper in the circuit breaker overheating and turning into dangerous plasma. This could be very dangerous to people nearby, for example the electrician turning the circuit breaker on after a fault.
Conclusion

The kA rating of a circuit breaker is a very important safety aspect to consider when designing a circuit. Without it, there is a good chance that a serious accident will occur. It only takes a few minutes to do the calculations when you have the correct tables.

The author has personally seen an incident where an incorrect kA rating caused a man to receive burns to 60% of his body. It could happen to you. Be safe and always consider the kA ratings in your design."

AC rating for 200 kA is reduced to 20 kA for DC
kA is max surge capability... if too much surge is on the fuse, the fuse will not trip and fuse can melt onto the contacts, feeding high voltage into the wire causing possible fire
Resources:

http://mandrelectrical.com.au/karatings.php
http://www.cooperindustries.com/content/public/en/bussmann/electrical/products/surge_protectiondevice/pv-spds.html

Gas and electric water heaters Support the economy:
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water heaters  from my associate links:
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Resources:
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Troubleshoot gas water heater
Troubleshoot electric water heater
Point of use water heaters
Gas and electric water heaters Industrial electric at Amazon

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Control water heater w/ Z-wave
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Control water heater with countdown timer
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