Alternative to Bosch ES2.5 Water Heater - AusJ 12V/120V

[WCF]

Not trying to convince anyone of anything, or sell anything, just sharing something I found that is going to work well for me. The maker of this water heater doesn't seem to do much marketing and I couldn't find a lot of info about it.

I found this heater with US stock at a reduce price, unfortunately they are sold out now. Still pretty reasonable direct from Australia:

https://ausj.com.au/products/duoetto-gen-3-dual-12v-120v-water-heater

I don't have it fully installed yet, but I did run it through a long bench test. I previously had the Bosch.

For context, I have around 400Ah (usable) of LiFE4PO batteries, 300W bifacial solar, and charge DC-DC around 15A.

Some advantages of the AusJ Duetto 3 for me:

- Runs on 12V at 25A (Or 120V at around 13A), meaning on my system it is practical to run it on DC. Obviously many/most folks may not be able to take advantage of the 12V side. On 12V Warm water in about 45 minutes, seems ready for a shower in an hour. I'll use it as a "dump load" when there's solar or DC-DC and the batteries are already topped off.

- Exact-adjustment of the water temperature, and a display showing current temperature. A remote replicates the same controls and includes a surface-mount box.

- Automatically switches between 12V and 120V when available. On the 12V side it has a built in relay, simplifying wiring if you want to use a timer or remote switch at the helm.

- The form factor is MUCH easier to deal with in my opinion; it can be bolted directly to the shelf under the sink in the 25, or in the original location. The pipe fittings are at the END of the tank rather than on top. This also means a valve can be added to gravity-drain the tank and winterize, unlike the Bosch which seems like it has to be blown out or removed and dumped.

- It seems to heat faster on 120V and stay warmer longer; the unit is significantly larger even though the water volume is almost exactly the same as the Bosch; I assume the AusJ is better insulated. It averages 10F gain per 3.5 minutes on AC.

The AusJ is obviously more expensive than the Bosch. There are also other options; I have seen that many small water heaters (Not the Bosch) can be modified with lower power "12v" elements. Some folks get the dual 12/120 heating by adding a silicone 12V heating pad against the inner metal tank. A lot of RV/Van folks are also making and insulating their own poly tanks in a form factor that works for them.

Just wanted to throw this out there in case anyone is looking for options.

[thataway]

Ausj has on the same website, if you scroll down a 240V/12V model for $200 less than the 120V model. There actually may be an advantage to use this on a C Dory, in that a 1000 watt 120 Volt generator may run this same element at 1/2 the amperage of the 240 volt use. The 240 volt unit is 1000 watts, so that the 120 Volts will draw 500 watts. Both the 12 v (300 watts) and the 120/240 500 watts will heat slower than the 240 volts, but still a very good option, and perhaps more realistic for the C Dory.

[WCF]

Yes, but, it would depend on how the controller is wired/works. AusJ seems like a small company that may be willing to help.

[ssobol]

They also have a 6L 12V unit. About 1 foot sq.

https://ausj.com.au/products/aqueous-water-heater-6l-12v?pr_prod_strat=jac&pr_rec_id=6ead492ae&pr_rec_pid=7557154767091&pr_ref_pid=7904675791091&pr_seq=uniform

[Donald Tyson]

That is incredibly small. Pretty cool. Ran by a Sureflo Style Pump.

[WCF]

I appreciate you guys mentioning the other heaters - I didn't actually look at their other units because the importer/retailer in the US (Which is going out of business) only had the Duetto 3.

The 6L 12V only unit draws half the amps at 13A - I think it's safe to assume it would take quite a bit longer to heat and re/heat incoming water. It would probably be a good option for getting some warm water for washing the dishes.

I think all of this is a balance between performance, cost, complexity, and energy use/density, and how it integrates into the boat.

If you really want off-grid hot water the diesel hydronic heaters seem like the way to go; the only thing that scared me off of diesel-hydronic was the number of hours I'd have to spend setting it up inside the galley cabinet