Portable Honda Gen to Shore Power- Can this power hot water electrics?

[simonpickard]

Hello all,

I was going to post this in another thread dealing with using Portable Generators such as the Honda to shore power, but they were closed.

As the title says really, can you use these portable generators to plug into the shore power and charge batteries + the hot water?

Or aren’t they powerful enough to do this?

Regards,
Simon

[El Pinguino]

I have a Honda 1000W. Charges the batts quite happily ( 350 Ah approx ) plus house loads but I can't heat water with it....

[simonpickard]

Humm, that’s what I was thinking would be the answer.
Do fixed generators allow for this then? I.e. heating the water. Or is the only way to that via engines or full shore power?

[El Pinguino]

You just need a bigger Honda https://powerequipment.honda.com/gen...odels/eu3000is
but by then you may be starting to think an installed unit woud be simpler to live with...

[mlydon]

It’s all math
The Honda eu2000 is continuos rated for 1600 watts, which equates roughly to 15 amps at 110 volts. Running my battery charger at 60 amps (12 volt) draws roughly 8amps (60ampx13v=780 Watts on the dc side) add in some conversion inefficiencies, and that 780 watts/110 volts = 7 ac amps gets bumped up to 8 or so, on the highest part of the battery charge draw. As the battery approaches charge, the draw goes down. Given this math, you could run a 140 amp charge rate without maxing out the generator.

As for the water heater, they typically have 800 watt coils in them, still well handles by the Honda. It would ne a little bit of a stretch to run both my loads at the same time, but not by much.

So, bottom line it depends on What rate you are charging your batteries, and what coil you are running in your heater. If you reduce you charge rate to 50 amps peak, you could run all day.


Ps I just checked iso temp’s web site - they have a 750 watt coil in their “basic” line.

Matt

[zboss]

This is our primary use for our Honda EU2000 now... heating hot water for showers. 1500 watt heater takes about 20 minutes to heat up the water but we leave it running while we shower so we can also wash dishes with hot water.

20 or 30 minutes leaves plenty of run time to charge the batteries afterwards.

[Pizzazz]

It is always simpler and more efficient to run the main engine to heat water. If you want to run a gasoline generator, you have two options. One is to match the heating element power to the continuous output of the generator. If you have a 1250W element, you need a 2KW Honda. If you have a 700W element you can get away with the smaller Honda 1000 or equivalent. You can always change the heater element, for example on the Rarian heater, the element is 1250W@ 120V. You can replace it with a 220V element and that would reduce the wattage nearly in half. The other option, if you have a marine inverter is to set the current limiter to 5A = 700W, then the inverter will take 700W from the generator and the rest from the batteries. You then need to recharge the batteries. Hugely inefficient but simple.

[mlydon]

Pizazz,

I don’t think swapping elements would give you what you’re expecting...

A 1250 watt 220v coil has a resistance of 38 ohms and a current of 6 amps
Putting that same coil in a 110v circuit with it retaining its resistance (as that’s a physical characteristic of the coil) would only draw 3 amps, and produce only 300 watts - half your expectation

In order to generate 1250 watts, a 110 coil needs to have a 9 ohm resistance, and will draw roughly 11 amps

Now, if you put a 110 coil in a 220 circuit, with that 9 amp resistance, that sucker’s going to draw 23 amps and run at 5000 watts, presumably melting down PDQ.


You can play with the ohms law calculator I used here:

https://www.rapidtables.com/calc/ele...alculator.html

Matt

[GordMay]

Most 6 gallon marine water heaters have a 1500 Watt electric element (12.5A at 120v). Since resistant loads have no inrush current, the HW heater should run on a 1500W generator.
Both a 8A (@ 12V) trickle charger/maintainer & HW heater should run simultaneously on a 2000W generator; but not a larger charger.

[S/V Alchemy]

Originally Posted by El Pinguino

You just need a bigger Honda https://powerequipment.honda.com/gen...odels/eu3000is
but by then you may be starting to think an installed unit woud be simpler to live with...

Two of the newer Honda 2200s ganged together as a "companion" pairing would seem to be a good compromise and should provide more than 20 amps of inverted AC power.

[akopac]

I’ve always run the engine for an hour to put 125 amps in the battery and heat the 6 gallons of water or took a solar shower.

[wannacat]

I disagree with Pizzazz, Our 2000 watt Champion gas inverter/gen has been heating our 6 gal HWT for 9 years now when we're at anchor. Like Zboss said, it takes about 20-30 minutes for scalding hot water and then we can run both our 120 V chargers to top off the batteries. Both are done quicker than running the Yanmar without a load on it which carbons up diesels as we all know. We can also charge computers, tablets, phones, shavers, portable hand lights and handheld VHF's at the same time. It's about 50 lbs and easy to move around to avoid noise and fumes.

[mlydon]

One other consideration - some water heaters have TWO engine loops in them, so you can connect both propulsion and Genset cooling lines through them.

Thus you can run your Genset charging up batteries, and use the heat from the Genset to heat up your water.

I was contemating doing this in my boat, but the Genset is completely aft, at least 20ft from the water heater - too many problems with hose routing, heat loss, etc. If your Genset is near your heater, though, best of both worlds.

Matt

[jmh2002]

Good points. In general some 'big picture' thinking needs to be done to consider the particular needs of this boat and her owners in combination with other installed equipment and overall plans (batteries? solar? main engine? water maker? dive compressor? backup necessary? etc, etc).

[Valmika]

Originally Posted by akopac

I’ve always run the engine for an hour to put 125 amps in the battery and heat the 6 gallons of water or took a solar shower.

At idle or in gear? Mine wont seem to come up to operating temp in neutral.
What about running an inverter at the same time since you are putting a little more of a load on the engine. Then you can run the heating element at the same time.