What is the easiest way to heat water?

[goeasy123]

What is the easiest/cheapest way for me to heat water?

I have a 240VAC water heater and a 240VAC water maker. I currently run these of a 240VAC generator. I’m about to put 350W of solar in because otherwise I’d have to run the generator for hours to get the 420Ah of batteries up to 100%.

With the solar I don’t have to run the generator every day, but I won’t have the ability to heat water every day. So what are my options now heat water?

Also, I don’t have to make water every day, but have to run to generator every few days to do this. It would be nice not to have to do this and just keep the genny on hand for cloudy days.

Any thoughts… most welcome??

 

[vas]

where are you based?
in the Med, I have 600W solar, 220Ah Trojans 24V a 2kW watermaker and a 3000VA Victron multiplus inverter/charger.
I regularly run the watermaker for 20-30mins midday to make water, batteries are not particularly happy, but I do it once they are full and with enough sun to fill them up for the evening.
You could similarly run a 2kW water heater for half an hour a day on solar with my 600W. 350W imho wont cut it, too little.
Also need to know the W of the watermaker and waterheater. If the latter is 4kW, just forget it, use the geny.

And you need a decent inverter as well.

cheers

V.

 

[RupertW]

See this thread. 12 v / 240 v

Post 19 is particularly well written. Well enough that it made no sense to anybody but still heats my water every day.

 

[ip485]

Inevitably it depends how much water, and slightly less, when you use the water most.

I find if you want lovely hot showers in the morning and throughout the day solar is simply not an adequate solution by a long way (I have 800W). In any event the solar is far better reserved for keeping up with your other power needs. Gensets obviously will do the job, especially if you are running the Genset for other purposes - making water for example. Inevitably it is noisy, and you may well not want to run (or need) to run the Genset every day.

For me the solution was an Ebber hydronic heater. I will sing its praise because it has proved the perfect solution. It is very compact, and almost silent. Run it for between 30 minutes and an hour and you have a large tank of piping hot water. Repeat as required. It is thereofore for me the perfect solution off grid while at anchor. The only disadvantage is I guess it isnt ultra green, but it uses a relatively tiny amount of diesel, clearly is more efficient than running the engine and almost certainly a big Genset so I would really recommend this approach.

I tend to use this as the go to means for heating water, but if I am running the Genset for other purposes, whatever they maybe, I will plan to use the electric water heater as I would rather load up the Genset as much as I can while it is running.

The planned solar may or may not keep up with your DC needs. It is well worth doing some calculations and depending where you are it may be marginal, but of course it depends entirely on how much power you need. Obviously if you are short and therefore run the Genset an hour a day to top up the batteries then my suggestion becomes less beneficial as you may as well use the surplus electricity to heat water.

However, it does also give a worthwhile degree of redundancy, given that Gensets are not always the most reliable piece of machinery, but even so I guess running the engine if needs must is always an option.

 

[cherod]

" lovely hot showers first thing in the morning " i would say , adds significant extra demands,, take your shower in the evening for less hassle .

 

[Graham376]

Warm water for shower is easy with camping shower bags left on deck although water can get too hot if left out too long. We hang one through the hatch over the shower tray.

 

[cherod]

Warm water for shower is easy with camping shower bags left on deck although water can get too hot if left out too long. We hang one through the hatch over the shower tray.

try that in the Moray Firth .

 

[Hallberg-Rassy]

Inevitably it depends how much water, and slightly less, when you use the water most.

And how hot you want it?

Whatever system you chose, you'd be using a lot less energy if you pre-heated water using passive solar, eg a bag or tank sitting out in the sun. I can imagine many people don't appreciate Heath Robinson jobs, but you can make a pretty good one using a 4" black drainpipe.

 

[Graham376]

try that in the Moray Firth .

I'd rather not The OP's post mentions watermaker and solar panels, so I assumed (maybe wrongly) he was somewhere with plenty of sun.

 

[goeasy123]

See this thread. 12 v / 240 v

Post 19 is particularly well written. Well enough that it made no sense to anybody but still heats my water every day.

So let me get this right. You put a 240 - 110v AC transformer between the inverter and the water heater to choke the load so that the solar is keeping the battery charging at a reasonable rate? ... in lay mans terms.

 

[Graham376]

And how hot you want it?

Whatever system you chose, you'd be using a lot less energy if you pre-heated water using passive solar, eg a bag or tank sitting out in the sun. I can imagine many people don't appreciate Heath Robinson jobs, but you can make a pretty good one using a 4" black drainpipe.

Twin coil calorifier, a circulating pump powered from panels and a solar water heater or even coiled hose, will provide lots of free hot water.

 

[cherod]

So let me get this right. You put a 240 - 110v AC transformer between the inverter and the water heater to choke the load so that the solar is keeping the battery charging at a reasonable rate? ... in lay mans terms.

it took 4 pages and 66 posts to get to that yesterday , dont think you are getting it in 10 posts ,, ( but yes , i think that is it ,, there are some other numbers as well like size of elements and inverter , i think )

 

[RupertW]

So let me get this right. You put a 240 - 110v AC transformer between the inverter and the water heater to choke the load so that the solar is keeping the battery charging at a reasonable rate? ... in lay mans terms.

Exactly - I added in a control mechanism as well so it only happens when the battery bank is near full charge but the load choke is what makes it roughly balanced.

 

[goeasy123]

And how hot you want it?

Whatever system you chose, you'd be using a lot less energy if you pre-heated water using passive solar, eg a bag or tank sitting out in the sun. I can imagine many people don't appreciate Heath Robinson jobs, but you can make a pretty good one using a 4" black drainpipe.

Not so fast with the 'people don't appreciate' Mr classy boat owner. I met a dutch man up the Guadiana just last week that had boiling water coming out of a PEX tube coil in a 2 foot square frame. Great idea if I can work out how to plumb it into the existing insulated tank.... free hot water on tap 24 hours a day.

Issues: How do you 'themostat' the temperature?
What happens to the PEX coil when the water stops flowing?
How do I insulate the pipes between the solar heater and the tank?
Can I make it passive thermosyphon or does it have to be pumped? What pump?

 

[Graham376]

does it have to be pumped? What pump?

DC 12V 24V 800L/h 5m Solar Hot Water Circulation Pump Brushless Motor 5m Lift | eBay

 

[Hallberg-Rassy]

OK, I was thinking more about dealing with Moray Firth temperatures.

Do you want to give us more of a design brief then? What equipment do you have where?

Off the cuff, I'd say use the passive solar system more like a calorifer and plumb the existing hot water system through it. How about something like running a long copper coil, from your present tank's intake, along the inside a long, 4" (100mm) sealed drain pipe, then back, with a simple manual valve to control it?

Something like 8mm microbore tube that already comes in coils? Do you have a pump, pressure release valve etc already?

A black metal cylinder would probably be more conductive, but I'm thinking cheap, low tech, easily made/repaired. Whatever you can find locally.

With a little brain power, you could even build a passive solar desalination unit (very impressive). If you are on the Moray Firth, consider using anti-freeze in your master cylinder.

 

[thinwater]

A propane water heater works for me. Any amount, any time, limited only by the water supply.

 

[DownWest]

Not so fast with the 'people don't appreciate' Mr classy boat owner. I met a dutch man up the Guadiana just last week that had boiling water coming out of a PEX tube coil in a 2 foot square frame. Great idea if I can work out how to plumb it into the existing insulated tank.... free hot water on tap 24 hours a day.

Issues: How do you 'themostat' the temperature?
What happens to the PEX coil when the water stops flowing?
How do I insulate the pipes between the solar heater and the tank?
Can I make it passive thermosyphon or does it have to be pumped? What pump?

Thermosyphon only works if the storage is above the panel. Also, spiral coils won't thermosyphon.
Pex will withstand boiling, gets little more flexable.. but a relief valve might be an idea.
Insulation: foam tube from B&Q.
Of you are anywhere near the Guadiana, too much heat is usually the problem. If you live on board, then a temp guage that indicates when the useful max is reached (light/beeper) then shade it. All simple stuff.

As for the Moray Firth, I thought that kilt wearers didn't shower in the cold months

 

[cherod]

Thermosyphon only works if the storage is above the panel. Also, spiral coils won't thermosyphon.
Pex will withstand boiling, gets little more flexable.. but a relief valve might be an idea.
Insulation: foam tube from B&Q.
Of you are anywhere near the Guadiana, too much heat is usually the problem. If you live on board, then a temp guage that indicates when the useful max is reached (light/beeper) then shade it. All simple stuff.

As for the Moray Firth, I thought that kilt wearers didn't shower in the cold months

No but the misses does

 

[goeasy123]

Just found this.... Kit - Radiant Solar Water Heating System Integrated with the Boat Fresh Water System

But I seem to recollect someone saying it stops the PV from cooling properly. And I wonder why they don't just have direct sun on a solar collector.