Diverting excess solar power to water heater

Mark's dual element rod that fits Suburban water heater drain plug and two wires to the diversion load terminals on the solar controller would be the easiest for me.
I am also thinking about hydronic heating as a supplement so where a water heater element fits in with that system, I'm not sure. I may also launch an element into my fresh water tank, it's steel, is **** cold in the Winter, and could be a big passive heat sink.

Kayteg1 wrote:
Changing RV wiring is not that difficult, although sometimes require flexible body.
I rewire most of my RV with my mechanical skills just fine.
But the main issue here is that with lack of 12V heating element (who doesn't care if it gets 14 or 4 volts) - the inverter route require reliable and controlled power supply, that "excess" will never give.
The linked topic where somebody was able to manufacture such element is fun to read for hobbyists, but when you consider that average RVer spend $5 or 10 a year for water heating, the economy of such project is senseless.
I might have couple more ideas to check.
One would be for 12V electric blanket inserted under WH insulation. Such blankets exist for bed, question is can you get them to come to 100F temperatures?
Other option for WH having engine coolant option is to install ceramic resistor inside it, what would give some effect. Such resistor heaters are popular for freezers defrosting and even they are design for 120V, they will give more power than hooking up 12V to original 120V heater. Beside having independent 12V heater, you can still use original 120V at convenient time.

If I was going to pull the WH to make modifications, I think the simplest thing to do would be to modify the tank by adding a 1" port in it to handle any of the many 1" 12V heater elements out there ranging from 200W to 700W.

***Link Removed***

On Edit - why are my links being removed? This was a link to a 700W 12V element on Amazon.

MH

Changing RV wiring is not that difficult, although sometimes require flexible body.
I rewire most of my RV with my mechanical skills just fine.
But the main issue here is that with lack of 12V heating element (who doesn't care if it gets 14 or 4 volts) - the inverter route require reliable and controlled power supply, that "excess" will never give.
The linked topic where somebody was able to manufacture such element is fun to read for hobbyists, but when you consider that average RVer spend $5 or 10 a year for water heating, the economy of such project is senseless.
I might have couple more ideas to check.
One would be for 12V electric blanket inserted under WH insulation. Such blankets exist for bed, question is can you get them to come to 100F temperatures?
Other option for WH having engine coolant option is to install ceramic resistor inside it, what would give some effect. Such resistor heaters are popular for freezers defrosting and even they are design for 120V, they will give more power than hooking up 12V to original 120V heater. Beside having independent 12V heater, you can still use original 120V at convenient time.

i agree with Bob
easy to say wire it this way
easy to draw it up mentally or on paper
NOT so easy to cut splice disconnect and change the 120v wiring in the RV

smkettner wrote:
Here is the thread:

> TEST RESULTS: 12Vdc Water Heating As Diversion Load

good job

GordonThree wrote:
I still don't get the need to make it complicated by changing heating elements, etc.

It does make it simple as the heater is on when there is excess solar.

Using the inverter requires self management or some sort of automatic cutoff as you suggest. The inverter needs to be adequate size and on my rigs the HW is not connected to the inverter for obvious reasons so that would need to be changed. 1400W is a 100A+ battery draw and very few rig solar systems have that capability. So you draw the battery down and hope there is enough remaining solar that day to recharge them.

The appeal of free hot water is understandable but for me and I suspect many the overall complications are undesirable.

I still don't get the need to make it complicated by changing heating elements, etc.

If there's so much excess power, run the water heater off the batteries and let the excess power charge them. Yes the 1400watt element will exceed instaneous output of the solar, but what is the average over time? The element does not heat continuously.

Put a relay on the solar controller status output, closed when charging, open when idle, connect to AC feed for water heater. Sun goes away, heater shuts off.

Bend wrote:

road-runner wrote:
In case you missed in it GordonThree's post, you do not need to dump excess solar power. The charge controller can simply not draw the power from the panels.

Need has nothing to do with it.

The batts are full, the sun is still shining, what more can I/we do with the solar provided wattage? Heat water!

Got it!

road-runner wrote:
In case you missed in it GordonThree's post, you do not need to dump excess solar power. The charge controller can simply not draw the power from the panels.

Need has nothing to do with it.

The batts are full, the sun is still shining, what more can I/we do with the solar provided wattage? Heat water!

Here is the thread:

> TEST RESULTS: 12Vdc Water Heating As Diversion Load