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Off grid water heating project
frackers:
I also use an oil filled heater on my 24v system, ripped the original 2500w element out of it and put in a pair of 28v 1000w elements. No way can it overheat as it designed to dissipate 2500w and the max I can push into it is 2000w.
Works well (now I've fixed the leak!!)
Wolvenar:
I to have used these oil filled heaters.
As long as you don't cover them up or anything like that they should be fine.
The oil is just being used as a non corrosive means to spread heat though convection I believe.
It keeps the overall temperatures lower where anything touches them while still dissipating the energy.
Unlike the marketing says there is nothing more special about them.
A lot of solar concentrator heating systems use mineral oils as well, so I am not sure why the fears.
Am I missing something?
dochubert:
I'm now using 2 of the oil filled heaters in the basement, sometimes 1 heater only or both on with 1 element, sometimes all elements on on both. These are hooked to the 48v bank and I only run these during sunny days Measuring 5-6a at 55-56vdc for each heater with both elements on. No problems after a couple weeks of running all day.
Also installed one of the 400w ceramic panel heaters in the bathroom. It is also currently running off of the 48v bank. That one I've been leaving on 24/7. It only draws about 3 amps at 55-56vdc. Gets mildly warm and stays that way. All good until we get some no-sun days, 2 or more in a row and battery power becomes too scarce to waste.
Originally I had planned to connect that one to either 2 or 3 150w 95v solar panels. Maybe I should stick to that. Only warm in the day but no battery drain.
solarnewbee:
Hey guys!
Here’s my home made dump load for my windmill. Haven’t gotten that up yet. That’s next trip. Philippines is a long way off.
I believe Pete drew a mud map of this delta arrangement. I was thinking 3 phase would work best with a delta and he confirmed that and 1 ohm was the smallest I could get. They are 100 watt and with the heatsink compound and huge forced air cooled heatsink it should work. I have a 24v battery charger now so I guess I could test that theory. These were 5 for $4 so pretty cheap. 2nd set kicks in to halve the resistance if necessary. Heatsink came off an inverter control board for a mini split hvac unit. I used to get lots of these but they don’t send the heatsink anymore. Hell they don’t even give you new isolation feet for the replacement compressors either.
Maybe someone could line up some of these in a row on a heatsink like this from a scrap yard find until they get the right resistance and wattage and strap on some fans. I used nylon all thread and nylon nuts. Had more fans on it but those little fans don’t have a drop height if you know what I mean.
Good luck experimenting!
If it’s there, may as well use it, right?
dochubert:
Hello Posterity!
I haven't updated this in quite a while so guess its time.
Now that spring has sprung here in Idaho, we're getting a reasonable amount of sun about half the time. The hot water system works fine on moderately sunny spring days, and passably well even on mostly cloudy days. The regular hot water heater runs off of that 24v/8kw powerjack, powered by (4) 200ah batteries, which are charged by eight 320w panels. The pj puts about 110v ac at about 2500w into the original 240v water heater elements. Additionally, there is a timer that limits water heating to between noon and sundown. The water heater is 50 gal and well insulated so it holds temp well overnight. Of course if one uses all the hot water after sundown, that's all folks! (I can override the timer as necessary or switch the water heater over to grid as for example when we had company for a week) Normally with just my wife and myself, we have no issues.
Then there is the preheat tank. It is also a 50 gal water heater. Its hot water output feeds the cold water inlet to the main water heater. If there is sufficient sun to keep the 15kw powerjack running the house loads happy and the main battery bank is full, a dc controlled ac relay (dump load controller) powers up the elements of the preheat tank. It has 120v/2000w elements. A moderately sunny spring day easily heats up the preheat tank, sometimes before the main water heater is up to temp itself. When the preheat tank reaches a set temp, a circ pump kicks on circulating hot water through both water heaters and through the whole house piping, which allows the main heater's elements to shut off sooner.
So on days with any decent amount of sun we have at least 50 and usually more than 100 gal of hot water. If it will do that in early spring, then late spring, summer, and early fall should be no problem. Late fall and winter will have to use grid power most days. But thats no more than a quarter of the year so not bad. Even then we get some good sun days.
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