What is the easiest way to heat water?

Depending on your space / budget / etc, then there are a lot of good ideas here, and my personal preference would be to try and integrate as many of them as practically possible, because I just don't get the idea that as we are on a boat, we should struggle or "make do" and having options means you can use the most efficient/effective solution at any given time.
Passive heating is great, and can range from simple (shower bag) to complex (piped in system), the limits are only in your space, ingenuity and imagination.
Twin coil calorifier would definitely be on my list (either now or for a future upgrade). If you put in a series of change over / one-way valves you could heat the coils from main engine /genny cooling circuits, passive and diesel/propane heater depending on your need and use. The immersion would still be available
Diesel/propane water heater are the most efficient for instant/semi-instant HW.
In terms of efficiency it's not always obvious. Passive is the winner here, then it could either be diesel/propane OR engine/genny cooling water (this will depend on what you are using those for - if it's engine propulsion or genny is well loaded for other things then the cooling water is otherwise wasted heat, if you are only running the engines for HW then they are incredibly inefficient). Immersion heaters are the least efficient by a long way, but if you are on a dock with shorepower, or are running the genny anyway and have spare load to use then it makes sense in those situations.
Try to think of a way to use the existing passive or waste heat as best as possible first, after that should come heat generation - if that makes sense! You are lucky that you have quite a few options to choose from.
 
Hallberg-Rassy said:
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.
Click to expand...
I'm thinking something like this as a collector....
It's what my man up the Guidiana has. His is smaller.

The only component I have is the existing calorifier. It's fed from the house water so it's under pressure. I could tee into the in and outlets with pre-insulated PEX, but that means the whole solar collector system is under pressure. The calorifier has a more that 40psi blow off valve in it, but it's below that water line. It the collector overheat it will empty the tank.

Moodysailor... good idea, but maybe I could also tee into the engine cooling water circuit, make it an indirect system full of coolant. Um... pros and cons?

I get the 'keep it simple' comments. However, the most unreliable component in the system might be the human being that forgets to turn something off. I'd like to make it as 'fit and forget' as possible.
 
goeasy123 said:
I'm thinking something like this as a collector....
It's what my man up the Guidiana has. His is smaller.

The only component I have is the existing calorifier. It's fed from the house water so it's under pressure. I could tee into the in and outlets with pre-insulated PEX, but that means the whole solar collector system is under pressure. The calorifier has a more that 40psi blow off valve in it, but it's below that water line. It the collector overheat it will empty the tank.

Moodysailor... good idea, but maybe I could also tee into the engine cooling water circuit, make it an indirect system full of coolant. Um... pros and cons?

I get the 'keep it simple' comments. However, the most unreliable component in the system might be the human being that forgets to turn something off. I'd like to make it as 'fit and forget' as possible.
Click to expand...

Thanks, I like that collector idea, looks good.
The reason for suggesting a twin coil calorifier is to enable you to separate the primary engine/gen cooling water circuit and the secondary 'collector' circuit. The biggest risk if you combine the circuits is that a leak in one area renders the other inoperable, so as well as having no HW, you would also have no way of running the engine or gen. Of course, isolation valves should be fitted at each module in the system so this shouldn't be a deal-breaker, but it adds to the complexity and risk (moving away from the KISS train of thought).
It's always a compromise (what isn't), but loads of good suggestions in this thread so far.
 
i get the fit an forget bit (y) ,, i would imagine some simple alarms connected to pumps . elements etc could take care of that .
 
Moodysailor said:
Thanks, I like that collector idea, looks good.
The reason for suggesting a twin coil calorifier is to enable you to separate the primary engine/gen cooling water circuit and the secondary 'collector' circuit. The biggest risk if you combine the circuits is that a leak in one area renders the other inoperable, so as well as having no HW, you would also have no way of running the engine or gen. Of course, isolation valves should be fitted at each module in the system so this shouldn't be a deal-breaker, but it adds to the complexity and risk (moving away from the KISS train of thought).
It's always a compromise (what isn't), but loads of good suggestions in this thread so far.
Click to expand...
Good point. I wonder if it was plumbed into the engine circuit could it use the engine's control and safety systems. I.e. the thermostat and rad cap to put a upper safety limit on pressure and temperature. Maybe you could leave only enough engin electrical circuit on to read the engines temperature sensor and have an extra circuit to close a valve to the collector. There might be a benefit in keeping the engine warm.
 
goeasy123 said:
It's fed from the house water
Click to expand...
Is that an American term? What we call mains, eg piped supply from the marina?

Are you a liveaboard?

Is it also going to be used as sea? Do you also have a drinking/tap water tank?

My prejudice against propane would be yet another bottle, yet more consumption (eg tendering bottles out to a boat), and where is it or where does it vent to? Propane means condensation and exhaust gases. But, sure, yes, it works. In EU/Britain we have buggers with the bottles; propane, butane, gaz. Don't know where you go.

It sounds like you want some kind of domestic mains hot water on demand set up ...(which means use gas) ... but for what?

Unless I missed a post, you're not really helping us by telling us your full parameters.

A 6' long, 4" pipe would give you 4 US gallons. If it's marina only, fill it up directly from mains, let it run out. Simple. I like the idea of a pipe as it woul be easier to hide/hang on a boat than a large pizza box. See similar idea below.

Or, if you become my Patreon sponsor, I'll send you a link of me having a shower in the nude.

Just joking but, yes, it goes on for real.

Tank Volume Calculator

 
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Hallberg-Rassy said:
Is that an American term? What we call mains, eg piped supply from the marina?

Are you a liveaboard?

Is it also going to be used as sea? Do you also have a drinking/tap water tank?

My prejudice against propane would be yet another bottle, yet more consumption (eg tendering bottles out to a boat), and where is it or where does it vent to? Propane means condensation and exhaust gases. But, sure, yes, it works. In EU/Britain we have buggers with the bottles; propane, butane, gaz. Don't know where you go.

It sounds like you want some kind of domestic mains hot water on demand set up ...(which means use gas) ... but for what?

Unless I missed a post, you're not really helping us by telling us your full parameters.

A 6' long, 4" pipe would give you 4 US gallons. If it's marina only, fill it up directly from mains, let it run out. Simple. I like the idea of a pipe as it woul be easier to hide/hang on a boat than a large pizza box. See similar idea below.

Or, if you become my Patreon sponsor, I'll send you a link of me having a shower in the nude.

Just joking but, yes, it goes on for real.

Tank Volume Calculator

Click to expand...
I mean the boat's water system.... Jabsco pump, accumulator, calorifier etc.

I want to heat water on anchor and on passage. In a marina is not a problem as the calorifier is mains.
 
goeasy123 said:
Good point. I wonder if it was plumbed into the engine circuit could it use the engine's control and safety systems. I.e. the thermostat and rad cap to put a upper safety limit on pressure and temperature. Maybe you could leave only enough engin electrical circuit on to read the engines temperature sensor and have an extra circuit to close a valve to the collector. There might be a benefit in keeping the engine warm.
Click to expand...

No issue or challenge plumbing into the engine cooling water circuit, other than the risks already stated. Caveat Emptor - I'm a low-risk taker on this stuff, so I wouldn't personally do it, but I know others who would without losing any sleep.....
Depending on your engine, you may need an additional expansion tank (at the highest point in the system to bleed correctly) as the additional water volume may overflow otherwise due to thermal expansion. Also, the rad/pressure cap needs to be at the highest point in the system to vent air and the existing rad cap should be replaced with a sealed cap.
Yes, you will lose some heat to the engine so I would be inclined with teeing it into the lines closest to the calorifier with one-way valves. There is probably an easier way :)
 
goeasy123 said:
I mean the boat's water system.... Jabsco pump, accumulator, calorifier etc.

I want to heat water on anchor and on passage. In a marina is not a problem as the calorifier is mains.
Click to expand...
If you have spare solar capacity then that is a fit and forget solution, basically if you don’t mind having your hot showers and washing up in afternoon/evening and you probably have enough solar if your batteries reach absorbtion by midday-ish. So for us 400w solar does it.
Much more efficient if you don’t have lots of spare solar capacity to go piped and passive as others have suggested but that will add to your deck clutter.
 
RupertW said:
If you have spare solar capacity then that is a fit and forget solution, basically if you don’t mind having your hot showers and washing up in afternoon/evening and you probably have enough solar if your batteries reach absorbtion by midday-ish. So for us 400w solar does it.
Much more efficient if you don’t have lots of spare solar capacity to go piped and passive as others have suggested but that will add to your deck clutter.
Click to expand...
RupertW, I think we have the same situation as you... capacity, kit and requirement. I just need to work out the numbers and see what transformer I need. Possible issues are:

1. Mastervolt Dakar Combi, Inverter, Charger 12v/1500/65. I think the numbers mean it's 12v 1500VA 1.5Kw output 65A
2. Sigmar 60ltr hot water tank – 800w/22 1 ¼”, 285mm immersion and main engine heated. Only 800w so that makes things easier.

Any thoughts?
 
goeasy123 said:
RupertW, I think we have the same situation as you... capacity, kit and requirement. I just need to work out the numbers and see what transformer I need. Possible issues are:

1. Mastervolt Dakar Combi, Inverter, Charger 12v/1500/65. I think the numbers mean it's 12v 1500VA 1.5Kw output 65A
2. Sigmar 60ltr hot water tank – 800w/22 1 ¼”, 285mm immersion and main engine heated. Only 800w so that makes things easier.

Any thoughts?
Click to expand...
As others have seen my thoughts probably over-explain how I decided on things as there are so many options at each stage so here goes.

Well your element is lower power so assuming you are ok with how long it takes to heat water under mains I would actually consider not stepping down the voltage as that would give you just 200w at 110v. I’d be tempted to replace the element eventually with a higher powered one if you are often on mains but that’s not important to this discussion.

The other parts of the circuit needed depend on how much you are happy to do manually and how much you want to just switch it on and forget it for weeks.

1) Solar/Mains switch over - this is on the supply side before your mains hot water on/off switch and the tank. You either want input from mains or invertor but not both. This element I was happy to have as manual as I only ever switch on the mains side for water (even at a marina) if we are doing a lot of washing clothes etc. So I went for a DPDT 10amp switch which is the cheap option compared to detecting mains and switching automatically. My other issue with a mains detector is where electricity is charged for and I don’t need lots of extra hot water I would keep with solar water heating even with mains connected for other things.

2) Control mechanism to only use solar to heat water when batteries nearly full.
You could switch the invertor manually on and off all afternoon depending on your battery monitor or MPPT readings but I preferred an automatic option and there may be far better ones that I didn’t think of.

Alas my Victron 100/50 doeesn’t have a Load output so I have to approximate when the batteries are full enough to start heating water and stop and start the water heating depending on sunlight. The first question is whether your batteries get to absorbtion voltage (say 14.4v depending on your settings) by lunchtime-ish. If they do then you have all afternoon to heat the water and with using a bit here and there as it goes I needed about 1kwhr before sunset. If they don’t reach that before mid or late afternoon then you need a fair bit more solar (or less overnight electricity use) for this to be reliable - in that circumstance I would look at passive piped water systems as well.
So I used a properly programmable VSR (allows you to adjust not just on and off voltages to any level, but also timings before on, timings before off etc) and this then switches on a high load bog standard VSR connected to the invertor. Then you adjust the programmable VSR to whatever works for you and your solar/battery balance - taking into account the that low voltage will be the voltage under considerable load so the battery state will not really be that low. It will vary from every set up but what worked for me was:
- ON after 120 seconds at 14.2 or above
- OFF at 13.0v (under a load of normal boat usage plus 375w)

Then it just cycles on and off all day - much longer on if sun is shining and above 300w (of 400w rated) solar output, and shorter if not.

Then when the thermostat reaches it’s set temp (at the hotter end of the settings for me), the invertor no longer has a load, the MPPT comes out of absorbtion to Float and the daily cycle is over.

The circuit diagram I drew is on the boat as otherwise I’d post that which would be far simpler to see.
 
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RupertW said:
As others have seen my thoughts probably over-explain how I decided on things as there are so many options at each stage so here goes.

Well your element is lower power so assuming you are ok with how long it takes to heat water under mains I would actually consider not stepping down the voltage as that would give you just 200w at 110v. I’d be tempted to replace the element eventually with a higher powered one if you are often on mains but that’s not important to this discussion.

The other parts of the circuit needed depend on how much you are happy to do manually and how much you want to just switch it on and forget it for weeks.

1) Solar/Mains switch over - this is on the supply side before your mains hot water on/off switch and the tank. You either want input from mains or invertor but not both. This element I was happy to have as manual as I only ever switch on the mains side for water (even at a marina) if we are doing a lot of washing clothes etc. So I went for a DPDT 10amp switch which is the cheap option compared to detecting mains and switching automatically. My other issue with a mains detector is where electricity is charged for and I don’t need lots of extra hot water I would keep with solar water heating even with mains connected for other things.

2) Control mechanism to only use solar to heat water when batteries nearly full.
You could switch the invertor manually on and off all afternoon depending on your battery monitor or MPPT readings but I preferred an automatic option and there may be far better ones that I didn’t think of.

Alas my Victron 100/50 doeesn’t have a Load output so I have to approximate when the batteries are full enough to start heating water and stop and start the water heating depending on sunlight. The first question is whether your batteries get to absorbtion voltage (say 14.4v depending on your settings) by lunchtime-ish. If they do then you have all afternoon to heat the water and with using a bit here and there as it goes I needed about 1kwhr before sunset. If they don’t reach that before mid or late afternoon then you need a fair bit more solar (or less overnight electricity use) for this to be reliable - in that circumstance I would look at passive piped water systems as well.
So I used a properly programmable VSR (allows you to adjust not just on and off voltages to any level, but also timings before on, timings before off etc) and this then switches on a high load bog standard VSR connected to the invertor. Then you adjust the programmable VSR to whatever works for you and your solar/battery balance - taking into account the that low voltage will be the voltage under considerable load so the battery state will not really be that low. It will vary from every set up but what worked for me was:
- ON after 120 seconds at 14.2 or above
- OFF at 13.0v (under a load of normal boat usage plus 375w)

Then it just cycles on and off all day - much longer on if sun is shining and above 300w (of 400w rated) solar output, and shorter if not.

Then when the thermostat reaches it’s set temp (at the hotter end of the settings for me), the invertor no longer has a load, the MPPT comes out of absorbtion to Float and the daily cycle is over.

The circuit diagram I drew is on the boat as otherwise I’d post that which would be far simpler to see.
Click to expand...
Excellent. If you can remember and when you get to it I'd really appreciate the circuit diagram.
 
Hallberg-Rassy said:
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.
Click to expand...

I like mine at about 45C! I also like a shower in the morning and sometimes in the evening.

I think this can be over thought. Unless you are set on not burning a drop of diesel more than necessary, a diesel water heater is by far the best way to go and probably the most efficient short of solar, and maybe even then if you are using a lot of your solar to heat water and then end up running the Gen. you are probably no better off.

The hydronics are very compact and actually work really well if you want unlimited hot water like me.
 
goeasy123 said:
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??
Click to expand...

I dont see a problem here.

You might well have to run your genset for a long time to bring the batteries right up but you can heat a calorifier full of hot water an an hour while giving the batteries a bit extra at the same time with the genset.

We run our genset every morning for an hour or so to give a tank of hot water for showers when not on shorepower. Also puts a bit in the battery bank.

That is why we have it.

Use you new solar to keep the batteries up and heat water with your genset.

Simples.............................
 
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