Using low-voltage water heating elements as a diversion load.

[Cadence]

The only thing I can see a low voltage element doing is " possible " maintaining already warm water warm a little longer? Raising ambient water more than a couple of degrees is unlikely unless your speaking a cup or so.

[SV FlyingSpirit]

Originally Posted by jtsailjt

I don’t understand what’s to be gained by heating water via an inverter if you’re going to have a DC element too. Why change your DC power into AC to make hot water rather than just sending it right to your DC element? You’ll have to get a pretty big inverter unless you have a small AC element. Are you thinking of using both elements at the same time so it’s OK if they both are small? If you don’t have a genset or spend much time on shore power so can’t use a big AC element anyway I guess that could make sense. Just curious about the logic you used to arrive at your plan.

You are probably right. I had been looking at the 12v element purely as an alternative to a shunt for the reasons explained, mostly heat and lost energy when and if load diversion is warranted. I had plans to modify the wiring to run the boat mostly off DC. I have a Promariner 40 amp charger but the 4 AC outlets, each with dual USB 5 v plugs I planned to power from the inverter. It seems to me that having a manual timer for the water heater would work fine for making water hot when I need it. Still working through the final setup.

[Locquatious]

Excess solar energy is easily controlled using a regulator. It essentially disconnects the solar array from the battery when the batteries are charged.
Excess wind energy is best controlled by stopping the wind generator when the batteries are charged. The wind generator goes silent and there is no wear on the generator components. This is what the Kiss Extractor does for a Kiss wind generator.
Diverting excess energy to a diversion load because you want to dump energy as waste heat is not necessary.
But if you want to use solar and wind energy to heat water for useful purposes, then use a diversion load device.

[jtsailjt]

Originally Posted by Locquatious

Excess solar energy is easily controlled using a regulator. It essentially disconnects the solar array from the battery when the batteries are charged.
Excess wind energy is best controlled by stopping the wind generator when the batteries are charged. The wind generator goes silent and there is no wear on the generator components. This is what the Kiss Extractor does for a Kiss wind generator.
Diverting excess energy to a diversion load because you want to dump energy as waste heat is not ninniecessary.
But if you want to use solar and wind energy to heat water for useful purposes, then use a diversion load device.

You are right that a dump load isn't necessary if you are going to be there to turn off your wind gen, but a circumstance when a dump load would be necessary is if you are off the boat so not using any electricity but your wind generator is left on and the wind blows a lot. The dump load serves as your "safety valve" to prevent overcharging the batteries.

As has been discussed, there are a couple of problems with using a secondary, DC element in your water tank as your dump load, such as forcing you to have a smaller than desirable AC element if using a dual element in your existing tank, or the expense of buying a new tank that's set up for two separate elements. If I could find a dual element that would screw into my existing tank that had a 1500 Watt AC element, I'd buy it in a heartbeat, but I haven't been able to find one of those and it doesn't make sense to me to have to run my genset for over an hour just to make enough hot water to take a shower. Also, I think that there are very few of us who get our batteries so full when are aboard, running all the DC equipment (lights, instruments, refrigeration, fans, water maker, stereo, etc.) we typically use each day that the dump load will ever be used and if we are off the boat so none of those things are being used, thus allowing the batteries to get completely full, making hot water is no more useful than making hot air.

[john61ct]

Originally Posted by Locquatious

But if you want to use solar and wind energy to heat water for useful purposes, then use a diversion load device.

That is the topic at hand, so links about known good versions would be most appreciated

[john61ct]

With an LFP bank, there is no long tail of declining amps, they'll take all produced.

Soon as target voltage is reached, isolate the bank and all the charging output can be used for whatever useful loads you like.

[foggysail]

Yeah-- LFP is the way to go

Lifepo4 cells catch fire! - Battery Vehicle Society

[john61ct]

Yes, plenty of stupid DIYers out there, but if you had to dig to almost a decade ago that's a pretty good endorsement.

No installer would skip using a BMS.

[foggysail]

Really? I doubt that ALL installers would insist installing a BMS. And those involved in the fire had installed a BMS which may or may not have functioned properly.

[NRbar]

I emailed John Gambill at Hotwire Enterprises about a dual voltage water heater element. I told him I would post his answer, so here it is:

Our 12/120 water heater element is only rated 500 watts on the 120 volt side. It would take about twice as long to heat a tank of water as a 1200 watt element. The 12 volt side is 360 watts. It has a one inch thread which fits the Raritan water heater and most other US made water heaters.

So far as I know, ours is the only water heater element that has both 12 and 120 volts (two in one). The 12 volt side can be used with any diversion type charge controller (Xantrex C-series, Morningstar TriStar, and others.

John

Hotwire Enterprises
102 W. Fulton St.
Tarpon Springs, FL 34689
(727) 943-0424

Rob

[john61ct]

Seems like a tank that takes two separate elements would be the better way to go?

[jtsailjt]

Originally Posted by NRbar

I emailed John Gambill at Hotwire Enterprises about a dual voltage water heater element. I told him I would post his answer, so here it is:

Our 12/120 water heater element is only rated 500 watts on the 120 volt side. It would take about twice as long to heat a tank of water as a 1200 watt element. The 12 volt side is 360 watts. It has a one inch thread which fits the Raritan water heater and most other US made water heaters.

So far as I know, ours is the only water heater element that has both 12 and 120 volts (two in one). The 12 volt side can be used with any diversion type charge controller (Xantrex C-series, Morningstar TriStar, and others.

John

Hotwire Enterprises
102 W. Fulton St.
Tarpon Springs, FL 34689
(727) 943-0424

Rob

That's what I found out when I was researching this a couple of years ago. I wish they had a dual element with more AC watts but I'm sure there must be a good reason why they went with such a small one. It would be interesting to learn why.