1/3 fothermo PV Solar Free Hot Water Heater Review
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- Опубліковано 6 тра 2022
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Fothermo
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420w solar panels
www.paidonresults.net/c/56084...
I've been designing PV water heating electronics for years. Here are a few observations from my experience.
Heat is the killer of capacitors. The capacitor used to store energy to make it efficient will be in a 24 hour hot environment with no thermal isolation from the tank. Capacitors operated at rated temperature only have a life of 4,000 hours, that is just half a year.
While operating at lower temperatures greatly extends the life, operating in a hot environment should be avoided to prevent premature failure. This won't be a catastrophic failure. Rather a degradation in performance.
In that design the capacitor always sees maximum pulse current into the heating element which is about 2 ohms, a 16A pulse. That capacitor likely is rated at only one amp. That will stress the capacitor from internal resistive heating and could open internal welds. The techluck, now out of production, has this problem as it uses three capacitord rated at 0.68A in a bank. There are reports of these failing causing a drop in daily production. My board has a capacitor bank rated at more than 20A.
A large capacitor bank in needed in order to have efficient adiabatic capacitor charging. This increases the RC time constant of the system and the voltage differential change of the capacitor bank. This voltage differential should be kept to 5%. That board likely has a conversion loss of 50%. That isn't as bad as it seems. A majority of the heating happens around the two hours of midday which in which it will be near direct connect. The rest of the time, 50% is very much higher efficiency than the lost power of direct connect.
The problem always is with those days when there is no intense sunlight at noon. Nobody wants to talk about those and the excess number of panels needed to get reliable hot water. Conversion efficiency really matters. I worked at a company where costs really mattered. I'd agonize
for days over whether to add an extra 1/3 cent resistor to get a little better performance. Adding extra parts for a market that doesn't know the difference doesn't pay. I want to add that the idea of PV panels used only for hot water is a odd concept to me. Anyone with a PV
system already has excess power which is needed to recover from bad days. This excess is usually just wasted. I tap that excess power directly from the panels and heat water with it. Reliable hot water can often be had without adding any extra panels. The suggested additional PV panels from the manual is much higher than I would expect from my experience.
It is not doom and gloom. This is a good turnkey unit for those who want PV hot water. It is Plug & Play and at these low voltages quite safe for neophytes uncomfortable with voltages over 60V. Thermostat contact arcing is a problem that many experience when they build their own in direct connect. Overall efficiency for this all in one is much better than a direct connect PV system and expected lifetime of electronics for most will be the same as the tank starting to leak. Chances are an external capacitor bank could be added to improve performance. Can't say for sure without seeing the heater waveforms. The ability to provide external DC power is a nice feature. In the current market there is little competition for this product and high performance is not a factor. The provided video is for reference ow what a real efficient PV hot water control should look like if cost is not a factor. In resistive water heating, voltage is your friend. Low voltage systems have a lot of power loss just getting power to the heater element. The board shown has arc interrupt allowing heating elements to be daisy chained. This allows heat stratification in tall tanks which greatly improves apparent performance in low light conditions. For those with electronic experience these power point circuits are relatively easy to build. There are also modules which can be added to existing water heaters which have a lower total system cost. Below is what a board looks like with properly sized components. ua-cam.com/video/iaLbLYhPLtw/v-deo.html
What a winner product. Hope larger capacity units are available or retrofit units to standard house immersion, say 1kW
fothermo has currently placed 1.6kW 200l / 300l Water Heaters on the market with 3x MPP trackers you are very flexible with PV module orientations :)
Hi great video . What bar is the preset of the pressure relief valve ? Does the supplier also provide spares like the anode?
I'd like to see more of the circuit board to see what they are actually doing.
Sorry, I did not include this. I normally so when I review products like this.
any chance you could do a tear down video of the wattsunde or ective lifepo4 batteries?
Thanks for watching. If someone want to send me some I will be happy to 😁 I have a limited channel budget. Products on this channel are pretty expensive.
Im a bitt confused. Does the water go directly into the tank, and then again directly to the fosset? Is this not dangerous because of the dangerous legionella bacteria? Is there no special liquid for heating?
Thanks for watching. The water is always being turned over in the tank with mains water which has chlorine in it. Yes it goes directly into the tank. It's also being heated everyday to 65 degrees. This is no different to a traditional heated water tank. This tank is heated with a heating element so no special liquid for heating. Hope this helps.
I bet you wish you were connected to them 👍are you conectting it to your own hot water system?? Will this be also supplying your heating?? How long does it keep water hot for???
I will find out soon. Yes connecting it to my own hot water system, just in the process as I write this. This won't be heating just got water. I used a log burner for heating. I will be sharing how I'm installing alongside my combi boiler.
I've been heating water for years efficiently with PV. Except, I share existing solar panels that charge my off grid batteries and only take excess power which would be wasted. I have so much hot water that the garage has its own 40 gallon tank just for laundry and all cycles use hot water. Even the LG washer operates with no batteries. ua-cam.com/video/XJ3iDQnRFt0/v-deo.html
You disassembled and video all that is kind useless.... the board is what is interesting, all the rest is standard.
Why those designs are bad... Cause you hook up panels directly... When water is hot, those panels are still hooker and useless.
Surplus is the way to go....
Stay tuned.. 👍
they actually just released a switching device where you can connect a second priority device like a small inverter (Hoymiles HM600, NEP...) or Battery MPPT charge controllers for batteries which can feed into your home when the fothermo Water Heater is "charged"