Heating water in silence (via inverter)

[CHIEF ENGR BOB]

Originally Posted by s/v Jedi

You should ask the electrician to explain why an 800W load can’t be powered from an 3,000W source.
Spoiler: of-course you can do that

Your battery source of 1300 AH should not be discharged below 50% or 650 AH Forget the the solar. listen to your electrician
The inverter would handle 3000 watts that’s not the problem you don’t have battery capacity to heat water I don’t know anyone who has the hot water heater on the inverter circuit

[Simi 60]

Has anyone mentioned high amp draw down and affect on batteries?

While we do use the inverter and batteries to do our HWS we do have a large solar array that given the right conditions put's in + amps when the HWS is pulling 70 amps.

I tend to freak out a bit when a cloud goes over and we see any more than - 40A for any more than a few minutes.
We have 8 x 220ah @ 12v combined as a 24v bank

[YANDINA]

If you are not yet persuaded that heating water with an inverter is a poor idea and decide to go ahead, there is a much more efficient method.
https://www.google.com/url?sa=t&rct=...AAmhUv17bV8lSS

[Simi 60]

Originally Posted by YANDINA

If you are not yet persuaded that heating water with an inverter is a poor idea and decide to go ahead, there is a much more efficient method.
]

Why is it a poor idea?
We have been doing it for 4 years daily and it works well.

Won't that DC element take all day to heat water due to it low wattage?

[YANDINA]

Poor idea regarding efficiency. 40% for diesel, 90% for alternator, 95% for battery, 90% for inverter, 90% after tank heat losses = .4 * .9 * .95 * .9 * .9 = less than 30% of the diesel energy ended up in the hot water.
I guess the best solution would be a diesel heated hot water.
We used an on-demand propane heater for about 10 years rather than storing heat in a hot water tank. Fortunately we had installed it on deck, they went belly up after killing some people installing it below deck and claiming it was safe.

[Pizzazz]

The most confusing thread ever. The OP has a 220V 800W heating element. If he uses his 110V inverter to heat water, the element will draw 200W or around 17A from his batteries. This will be slow but it is well suited to dump excess solar power. He needs to change nothing in his setup. What else is there to discuss?

[CatNewBee]

Originally Posted by Mantas

Hello,

Before posting I found quite a few posts about running water heaters from the inverter and there are a lot of different opinions about this. So I asked electrician in the boat yard (where I am refiting my first boat) can I run my Sigmar SM40 (220V - 800W) water heater from the Victron Phoenix 12/3000w inverter and he said no and that I need to add one more Victron inverter and connect them both. Can someone explain me why 800W heater cannot be run on 3000W inverter? I will have 1050W solar and 1300Ah gel battery bank. As you may understood already I do not have background in electric stuff.

Please do not turn this discussion in "run your engines or generator - it is more efficient" - my goal is to have morning coffee in silent anchorage while waiting for shower to warm up thanks

It works, no problem. You can run two of them with a 3000W inverter.

[jmh2002]

Originally Posted by YANDINA

Poor idea regarding efficiency...

Most people doing this are using solar energy, or for convenience when using a mixed input of energy sources.

In these cases the questions of efficiency are not valid in the same ways.

[sgtPluck]

Interesting thread. We're also thinking about setting our system up to use excess solar power when batteries reach float-charge state to heat shower water with our inverter. We're looking at this option mostly because it's very simple. We'd just put a 30 minute timer switch to turn on heating element when (only) inverter is on. We know it's not the most efficient option but are curious about real-world experience for how much capacity this actually uses.

Would love to hear more from people who mentioned that they are doing this about the realities vs the theory. Does anybody who does this have a really good sense of how many actual amp-hours get used relative to the theoretical amount needed?

In theory we should be good:

- 1200w 220v 40 litre water heater
- 2000w 220v inverter
- 640 Amp Hours capacity in (new) AGM bank
- 1400 watts of solar - on sunny days we often reach float state of charge (in Caribbean) by noon.


In theory (before Peukert and Inverter waste) our 40L water tank at 1200W should take 33 minutes to heat water from around 75F to 100F, and this should use 646WH of power, or 54 Amp Hours of capacity. We certainly have that to spare on a sunny day.

The reality of course is that there are inefficiencies including from inverter and Peukert factor to account for in determining how much battery capacity we'd actually be using up. Although, if we're doing this with the mid-day sun beating down on 1400W of solar panels and float-charge state batteries, maybe Peukert is not a major factor?

Would love to hear some real-world experience on the reality vs the theory.

[CatNewBee]

We do it with lithium batteries, but not automatically. 30 minutes with 1200W heat up the 40l boiler sufficiently for showering or washing dishes (using about 50Ah). For really hot water from cold it takes about 1h or 100Ah

[markcouz]

If you are at float around midday then your water heating on a good day in a good area will be almost entirely via your solar array (probably delivering around 1kw).

If you keep other loads low while heating water you will have little to worry about.

[FlyingScot]

For one 6 gallon water tank from ambient (Caribbean) to the hot cutoff it takes approximately 100ah @12v nominal.
Dishes and showers for two. This is through the inverter with specification of approximately 94% efficiency.

[WizardOfTheWind]

Originally Posted by sgtPluck

Interesting thread. We're also thinking about setting our system up to use excess solar power when batteries reach float-charge state to heat shower water with our inverter. We're looking at this option mostly because it's very simple. We'd just put a 30 minute timer switch to turn on heating element when (only) inverter is on. We know it's not the most efficient option but are curious about real-world experience for how much capacity this actually uses.

Would love to hear more from people who mentioned that they are doing this about the realities vs the theory. Does anybody who does this have a really good sense of how many actual amp-hours get used relative to the theoretical amount needed?

In theory we should be good:

- 1200w 220v 40 litre water heater
- 2000w 220v inverter
- 640 Amp Hours capacity in (new) AGM bank
- 1400 watts of solar - on sunny days we often reach float state of charge (in Caribbean) by noon.


In theory (before Peukert and Inverter waste) our 40L water tank at 1200W should take 33 minutes to heat water from around 75F to 100F, and this should use 646WH of power, or 54 Amp Hours of capacity. We certainly have that to spare on a sunny day.

The reality of course is that there are inefficiencies including from inverter and Peukert factor to account for in determining how much battery capacity we'd actually be using up. Although, if we're doing this with the mid-day sun beating down on 1400W of solar panels and float-charge state batteries, maybe Peukert is not a major factor?

Would love to hear some real-world experience on the reality vs the theory.

Your setup is similar to ours with 3000W Victron inverter, 900Ah AGM batteries, 850W solar and a 40L 1200W Quick hot water system.
I manually run the inverter once we get to about 100% (usually about 10am) for about 30mins and we get quite hot water for the next morning showers. The power generally goes down to about 92% after this but we have then plenty of opportunity to get back to 100% before the end of the day. Have not really checked the amperage but believe it is about 60A.

[coopec43]

Duoetto MK2 Digital Dual Voltage (12v/240v) Electric 10L Storage Water Heater


The Australian designed and approved Duoetto MK2 offers selectable temperatures between 30-75ºC on 240v and up to 70°C on 12v so that you can shower, wash, cook, clean and enjoy abundant hot water.
Whether visiting the Outback, adventuring on one of Australia’s many waterways, or travelling for business or pleasure, this unique product will provide sufficient hot water for you and another to shower in comfort.

$425.00

[WizardOfTheWind]

Originally Posted by coopec43

Duoetto MK2 Digital Dual Voltage (12v/240v) Electric 10L Storage Water Heater


The Australian designed and approved Duoetto MK2 offers selectable temperatures between 30-75ºC on 240v and up to 70°C on 12v so that you can shower, wash, cook, clean and enjoy abundant hot water.
Whether visiting the Outback, adventuring on one of Australia’s many waterways, or travelling for business or pleasure, this unique product will provide sufficient hot water for you and another to shower in comfort.

$425.00

This is a well respected unit, although it is quite small in caoacity and would not fit well in a boat that has an existing 240V water heater but would satisfy many people who do not have an installed unit already or do not have the need for greater capacity.