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 > Feedback on 12V water heater element as solar diversion load

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pianotuna

Regina, SK, Canada

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Posted: 02/19/23 10:28am Link  |  Quote  |  Print  |  Notify Moderator

I too just used the inverter, but powered it from twin #8 wire from the chassis battery and solar.

I'd disconnect the charging path when the starting battery reached 12.3 volts (which took about 20 minutes), and then reconnect 40 minutes later, when the chassis battery had recovered.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

ewarnerusa

Helena, Montana

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Posted: 02/25/23 06:59pm Link  |  Quote  |  Print  |  Notify Moderator

Check this thing out. 300 watt 12V element that is swappable with the hot water tank drain plug. It dry fit well in my tank. Hopefully with thread tape it seals up perfect. The white plug is one of my spares.
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ewarnerusa

Helena, Montana

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Posted: 03/05/23 12:06pm Link  |  Quote  |  Print  |  Notify Moderator

I did some "bench" testing on the heating element today. It pulled 24 amps and got nice and hot. I had the element in a mug of water and it heated it up quickly.


Aspen Trail 2710BH | 470 watts of solar | 2x 6V GC batteries | 100% LED lighting | 1500W PSW inverter | MicroAir on air con | Yamaha 2400 gen

ewarnerusa

Helena, Montana

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Posted: 04/09/23 09:06pm Link  |  Quote  |  Print  |  Notify Moderator

Spring projects weekend. I got 3 projects done: installed auto transfer switch for the inverter, replaced main 12V feed to control center with 4 gauge wire, and got the diversion load water heater element wired in. No testing yet, 2 full days of crawling around on the floor and ground and I am done working for the weekend! I'll do some testing some evening this week or next weekend.

pianotuna

Regina, SK, Canada

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Posted: 04/10/23 04:17pm Link  |  Quote  |  Print  |  Notify Moderator

ewarnerusa,

I for one, will be waiting with baited breath on the results!

ewarnerusa

Helena, Montana

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Posted: 04/11/23 09:10am Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

ewarnerusa,

I for one, will be waiting with baited breath on the results!

I've got a test scenario all rigged up right now! Should be a nice sunny morning but clouds and wind forecast for later. Sun has not yet crept over the trees and hit my panels yet, so nothing to report.

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When I first got to wiring up the diversion load circuit to the SCC, it wasn't what I expected since I had not read the manual for that part carefully yet. I know, I know, RTFM... But I got it figured out now. It requires connecting the panels directly to the batteries and the former panel input to the SCC is now the diversion load output. Thankfully I had purchased a pack of several Anderson style connectors and could make several convenient disconnects for swapping back and forth between normal setup and the new diversion load setup.

ewarnerusa

Helena, Montana

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Posted: 04/11/23 11:12am Link  |  Quote  |  Print  |  Notify Moderator

Wow, it is working great! I'm shutting this test down as the water is getting hotter than expected and I'm not available for continuous monitoring. 66F to 130F in a couple hours. I realize this is just a tiny volume compared to 6 gallons, but this little sucker is cranking out heat just using current that the battery isn't needing for absorption charging. Panels are harvesting 15 amps, looks like between 7-10 amps are going to the diversion load element, the remainder is going to maintaining the batteries at absorption setpoint, the laptop charger to run the laptop in order to monitor stuff, and any other camper parasitic loads (not that there is much, it is sitting in storage at home).
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Laptop hooked to the SCC to monitor things. Interesting that when wired up for diversion load, the charge current shows 0. I believe this is because the panels are not actually hooked to the SCC in diversion load mode. They are hooked directly to battery and SCC monitors battery voltage, allowing anything in excess of charging setpoints to flow to the diversion load.
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Full current from panels right now is 15 amps:
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StirCrazy

Kamloops, BC, Canada

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Posted: 04/12/23 08:04am Link  |  Quote  |  Print  |  Notify Moderator

ewarnerusa wrote:

Wow, it is working great! I'm shutting this test down as the water is getting hotter than expected and I'm not available for continuous monitoring. 66F to 130F in a couple hours. I realize this is just a tiny volume compared to 6 gallons, but this little sucker is cranking out heat just using current that the battery isn't needing for absorption charging. Panels are harvesting 15 amps, looks like between 7-10 amps are going to the diversion load element, the remainder is going to maintaining the batteries at absorption setpoint, the laptop charger to run the laptop in order to monitor stuff, and any other camper parasitic loads (not that there is much, it is sitting in storage at home).
[image]
[image]Click For Full-Size Image.

Laptop hooked to the SCC to monitor things. Interesting that when wired up for diversion load, the charge current shows 0. I believe this is because the panels are not actually hooked to the SCC in diversion load mode. They are hooked directly to battery and SCC monitors battery voltage, allowing anything in excess of charging setpoints to flow to the diversion load.
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[image]Click For Full-Size Image.

Full current from panels right now is 15 amps:
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[image]Click For Full-Size Image.


It's too bad we can't get a water temp gauge into the hot water heater. When you finally hook it all up, I would recommend putting a temperature operated shutoff in line with the heater. The last thing you want is it to get too hot and blow your safety relief valve.


2014 F350 6.7 Platinum
2016 Cougar 330RBK
1991 Slumberqueen WS100

ewarnerusa

Helena, Montana

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Posted: 04/12/23 09:08am Link  |  Quote  |  Print  |  Notify Moderator

StirCrazy,
It has definitely crossed my mind from the start of this little project. I admit that I have been hoping that the 6 gallons of water as a heat sink will never be able to reach the blow off valve setpoint with this diversion load. Assuming I am leaving the propane water heater burner off. But if the diversion load gets disconnected, then I have all my panels directly wired to the batteries with no control. Which scenario is worse?

I also don't know why my sig won't show up? The box is checked.

pianotuna

Regina, SK, Canada

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Posted: 04/12/23 07:40pm Link  |  Quote  |  Print  |  Notify Moderator

ewarnerusa,

These figures might help a bit.

The ten gallon unit in my rv takes 90 minutes before it cycles the first time.

There after, if no water is drawn, it will cycle on for 15 minutes every 4 hours.

It has a 1400 watt electric heater built in.

From that I can infer that heat loss is about 350 watts over the 4 hour time frame.

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