Hot water and hot air

[a64pilot]

OK guys let’s just agree that Americans name things differently than other English speaking people. Ask someone in Alabama to open the bonnet of your car and I’m not sure what would happen, but I doubt he would open the “hood” as it’s called in the US.
Neither is wrong, just different.

Anyway only comment I would make is that in my opinion propane’s use inside of a boat can be very perilous and I don’t think any propane water heaters have the safety controls necessary for use in a boat, if it’s outside. Then I assume it’s OK, but who wants a water heater on deck?

[Shaneesprit]

Ok
Well yes I hadn’t seen Johns heater, it doesn’t meet my spec as I want hot water mainly on warm days, and mainly heating on Cold nights. It’s along the right lines though. I could take hot water from the vessel and have the element in the tank for the heating
I have a water to air heat exchanger off of the Engine ( Tax requirement for fuel Tax discount )
That would still work if I submurged it in a water tank,
Gas works better for instant hot water
I don’t feel I am yet ready to commit to an idea

[noelex 77]

Some of the drip feed diesel heaters such as the Reflex brand produce great heaters, but they will also produce hot water. This can be done in two ways.

KISS. This requires a kettle to be placed on hot plate on top of heater, or slightly more complicated with a copper coil inside the heater.

The only drawback is these heaters can be difficult to retrofit. There are specific requirements for the chimney installation as well as minimum clearances from some surfaces.

Here is a photo of our installation, taken during construction of our new yacht, to give you some idea:

[Pete17C]

Originally Posted by a64pilot

OK guys let’s just agree that Americans name things differently than other English speaking people. Ask someone in Alabama to open the bonnet of your car and I’m not sure what would happen, but I doubt he would open the “hood” as it’s called in the US.
Neither is wrong, just different.

Anyway only comment I would make is that in my opinion propane’s use inside of a boat can be very perilous and I don’t think any propane water heaters have the safety controls necessary for use in a boat, if it’s outside. Then I assume it’s OK, but who wants a water heater on deck?

I've seen them for RVs, but a quick search turned up nothing for LP water heater if I included 'marine'. Probably like your saying, LP and boats don't mix well.

That said, people do use LP on boats. Properly vented and drained (maybe it's an environmental concern, the condensate is acidic) these super efficient on demand LP units should be fine on a boat.

One could easily fit in most cockpit lockers, right next to your LP tanks (if you have them)

[Pete17C]

For a group of people that have numerous names for a piece of rope (and get perturbed when one is used wrong), I would think you understand things have very specific names when you're discussing your particular craft.

/when in rome
//it's best to speak roman
///or is that latin?

[wingssail]

Webasto, and presumably others, make diesel powered devices which heat boats (through hot water radiant heaters) and can heat domestic water. They require electricity and possibly some maintenance issues, aside from being expensive for a Cal 25.

For that application, instead, I would recommend a propane powered instant water heater, which is cheap and simple, and a wall mounted diesel heater, which is cheap and simple. (I know, you want one solution, sorry)

You can also heat the boat with a radiator and a fan using engine heated water, but you have to have hot engine water.

Maybe nothing is easy.

[wingssail]

Originally Posted by Pete17C

I've seen them for RVs, but a quick search turned up nothing for LP water heater if I included 'marine'. Probably like your saying, LP and boats don't mix well.

That said, people do use LP on boats. Properly vented and drained (maybe it's an environmental concern, the condensate is acidic) these super efficient on demand LP units should be fine on a boat.

One could easily fit in most cockpit lockers, right next to your LP tanks (if you have them)

We've used propane water heaters for 33 years (first a Paloma, then an Challenger, now a Cinsa, Boshe also makes a good one). They are not approved for marine use. On Wings they have been installed in the head a few inches on the other side of a bulkhead from the galley sink. There is no stack, there is a small hatch a couple of feet from the top of the heater, which is 6" from the overhead. They work. They have not exploded us. There is no condensate. We always have hot water. The Cinsa cost about $125.

[Pete17C]

Originally Posted by Shaneesprit

Ok
Well yes I hadn’t seen Johns heater, it doesn’t meet my spec as I want hot water mainly on warm days, and mainly heating on Cold nights. It’s along the right lines though. I could take hot water from the vessel and have the element in the tank for the heating
I have a water to air heat exchanger off of the Engine ( Tax requirement for fuel Tax discount )
That would still work if I submurged it in a water tank,
Gas works better for instant hot water
I don’t feel I am yet ready to commit to an idea

You need to decide on your fuel. Then pick a heat source.

If you're going to have LP on the boat for other reasons, it may be worth going with an RV style unit.

I wouldn't add LP to a boat for this.

[a64pilot]

Originally Posted by Pete17C

I've seen them for RVs, but a quick search turned up nothing for LP water heater if I included 'marine'. Probably like your saying, LP and boats don't mix well.



That said, people do use LP on boats. Properly vented and drained (maybe it's an environmental concern, the condensate is acidic) these super efficient on demand LP units should be fine on a boat.



One could easily fit in most cockpit lockers, right next to your LP tanks (if you have them)

The issue I believe is the potential for a propane leak.
It could build up in the bilge and go boom, and this does sometimes happen.

Marine stoves etc have thermocouples that will stop the flow of propane if the stove goes out, same stove meant for an RV will not, but of course there is no bilge in an RV.

I don’t know why there is no Marine on demand heater. I assume one could be built and instant hot water is pretty desirable.
I have no idea really what standards a Marine instant water heater would have to meet.

[GILow]

Originally Posted by Shaneesprit

Ok
Well yes I hadn’t seen Johns heater, it doesn’t meet my spec as I want hot water mainly on warm days, and mainly heating on Cold nights. It’s along the right lines though. I could take hot water from the vessel and have the element in the tank for the heating
I have a water to air heat exchanger off of the Engine ( Tax requirement for fuel Tax discount )
That would still work if I submurged it in a water tank,
Gas works better for instant hot water
I don’t feel I am yet ready to commit to an idea

I understand your concern with John's design, I was also slightly concerned about heat leakage into the boat on warm days. But as I fabricated mine I have come to realise the leakage is relatively minor. As John remarks, his system loses 10 degrees over 24 hours. The numbers will tell you that this is only 4 KJ which is hardly significant and therefore unlikely to be noticed in the cabin.

In return for this minor heat leakage you get instant hot water on demand and instant cabin heating on demand. Just to be clear on this, I say again, both are INSTANT.

Clearly you have to be comfortable with whatever you fit to your boat, but it is important to quantify the trade-offs.

For me, I was more than happy to throw my existing instantaneous gas hot water unit in the bin and go to 100% diesel heating because I really do not like having gas on the boat. I do understand that others may not be as concerned about such things as I am.

One final pair of points about diesel vs gas that you may wish to consider. I am not sure what the costs are like in your part of the world, but the cost of heating with diesel here in Australia worked out to be less than half the cost of heating by mains electricity when I did the calculations for marina use, and about one fifth of the cost of heating by bottled gas. And THEN there is the inconvenience of transporting and refilling the relatively low capacity gas bottles in contrast to just tapping into the existing boat diesel tanks. Depending on your use and your diesel capacity this may or may not be significant.

Anyway, that's enough from me. Any more and I will just sound like a zealot, and that is not my intention. But I do think it is important to be clear on the facts of John's design, and the associated numbers.

Good luck with your choice, I know how nice it is to have a warm boat here in Australia, goodness knows what it is like in your part of the world.

[Dymaxion]

I have a small 5,000 btu LPG powered instant water heater for my VW camping that I hang outside off the rain gutter. In my last house I had a NaturalGas Combi boiler, massive 200,000 btu output. Also instant on type.

For boat use I've considered a slightly larger LPG unit mounted in the cockpit. Pressurized cold water in, on the outlet hot side 2 lines, to galley and head PLUS a recirculation loop back to the cold water inlet. The recirc loop will include a recirc pump obviously, but also a bus heater (rad+fan). Open up either hot tap and the water flow triggers the water heater. Or if the cabin thermostat calls for heat it turns on the recirc pump, also triggering the water heater. Combi unit, as mentioned. I've seen small LPG units in stainless for under $200. HTH

[GILow]

Originally Posted by Dymaxion

... but also a bus heater (rad+fan). Open up either hot tap and the water flow triggers the water heater. Or if the cabin thermostat calls for heat it turns on the recirc pump, also triggering the water heater. Combi unit, as mentioned. I've seen small LPG units in stainless for under $200. HTH

The bus heater will also have to be stainless or it will rust out fast. Those things are designed to be used with coolant containing a corrosion inhibitor.

[Pete7]

Given your location and space / cost requirements, I think you have a couple of options.

Air blown diesel heater, probably a Chinese copy like this:

https://www.ebay.co.uk/itm/3KW-Air-D...gAAOSwYwFbmM-n

We have the Webasco 2kw version and it works really well even during a UK winter when we lived on board for a while. However, no hot water, we use the kettle or hot water from the engine, occasionally from mains electric if we are in a harbour or marina. The diesel blown air heaters will use 30-40AH per night at 12v.

Hot water heating via radiators and hot water, then:

https://www.butlertechnik.com/uncate...4117864a-p2755

Surejust > Surecal Calorifiers

These sorts of kits were fitted to Rover and Landrover cars, the bits often appearing on e bay. You would need to have a calorifier for the hot water and radiators for heating the boat. This is the cheap DIY option, but likely to need some form of charging for the batteries as they do use more electrical power than blown air heaters.

https://www.ebay.co.uk/itm/Webasto-H....c100008.m2219

Final option is diesel air heating Webasco or Chinese copy with caravan water heater on demand. Now these are caravan type units which vent outside. However, with a cat, you may be able to locate it in such away that the exhaust gasses vent over the side. The instructions say not for boats, so you are on your own with this one. Very difficult to do on a mono hull and I have looked, but a cat has lots more space venting options.

https://www.ebay.co.uk/itm/PALOMA-WA...IAAOSwHLJZkb1X

Final solution is:

https://www.ebay.co.uk/itm/Refleks-S...sAAOSwFQBdDVMM

Needs chimney to vent through the deck and will take up cabin space. Some versions can have a hot water coil inside to heat water in addition to cabin heating.

Other option for hot air heating is a gas heater, but will use a lot of gas hence why diesel air heaters are popular in the UK.

https://www.ebay.co.uk/itm/PROPEX-HE...MAAOSwTM5Y6qKj

[Dockhead]

Originally Posted by GILow

I understand your concern with John's design, I was also slightly concerned about heat leakage into the boat on warm days. But as I fabricated mine I have come to realise the leakage is relatively minor. As John remarks, his system loses 10 degrees over 24 hours. The numbers will tell you that this is only 4 KJ which is hardly significant and therefore unlikely to be noticed in the cabin.

In return for this minor heat leakage you get instant hot water on demand and instant cabin heating on demand. Just to be clear on this, I say again, both are INSTANT.

Clearly you have to be comfortable with whatever you fit to your boat, but it is important to quantify the trade-offs.

For me, I was more than happy to throw my existing instantaneous gas hot water unit in the bin and go to 100% diesel heating because I really do not like having gas on the boat. I do understand that others may not be as concerned about such things as I am.

One final pair of points about diesel vs gas that you may wish to consider. I am not sure what the costs are like in your part of the world, but the cost of heating with diesel here in Australia worked out to be less than half the cost of heating by mains electricity when I did the calculations for marina use, and about one fifth of the cost of heating by bottled gas. And THEN there is the inconvenience of transporting and refilling the relatively low capacity gas bottles in contrast to just tapping into the existing boat diesel tanks. Depending on your use and your diesel capacity this may or may not be significant.

Anyway, that's enough from me. Any more and I will just sound like a zealot, and that is not my intention. But I do think it is important to be clear on the facts of John's design, and the associated numbers.

Good luck with your choice, I know how nice it is to have a warm boat here in Australia, goodness knows what it is like in your part of the world.

Everyone will have to weight the various pros and cons, and make his own conclusions, but I cannot really understand why people heat boats with gas. Is it because you can buy gas heaters for $125? That seems to me the only point in their favor.


Gas heat cannot be made ABYC compliant unless you have a place outside the hull volume to mount the heater. If you blow yourself up with one of them, your insurance company will have an air-tight reason not to pay you.


Then there's cost, and humping the fuel.


I heat with electrical power when it's available. It's almost always unmetered where I sail. At anchor or underway, I use a 12kW Eberspacher Hydronic heater which runs three fan coils and heats domestic hot water.


The Eberspacher/Espar/Webasto type hydronic heaters have certain drawbacks -- expensive, not easily user serviced, and need a fair amount of service. Also, they use electrical power. But the advantages are no flue through the deck, no soot on sails, and easy distribution of heat throughout the boat. They are extremely compact so quite easy to install compared to most other types.


On a smaller boat I would look hard at a pot-type heater like Noelex's. Drawback is the stack, but huge advantage is great simplicity and total owner serviceability, plus no electrical power needed. You can heat domestic hot water with a coil and circ pump.



If installing a new system from scratch, I would look seriously at something like John's system with a heat accumulator. You can collect heat from engine and generator with heat exchangers too.


Another thing to consider: In many weather conditions you might not really need heat in the cabin, but you would sure like to warm up and dry out the heads, towels, etc. Consider a heated towel bar and radiator in the heads which can be operated separately from the rest of the heating system.



I sail in cold places and good heating is mission critical. A cold and damp boat can ruin a cruise in cool or cold weather; whereas a dry and toasty boat can make it a delight.

[Shaneesprit]

Hi thanks for all of your replies ( even the ones arguing about the names of said equipment [emoji12] ) ok wingssail - you have the answer there is no solution, the Air heating is so much better for heat and the LPG so much better for water - It’s actually the lightest solution to fit both ( water just for a heating circuit - crazy on a boat ) when the diesel heater is lighter than the water and extra fuel only carried when needed - so I already have a diesel Engine and LPG cooker and Fridge ( I have never used the fridge other than as a cool box )
On the Gas not I have an alarm but Gas is lighter than air and I have an alarm fitted, as a child I saw a boat blow up I don’t remember to much just we went to rescue the people but a RIB that was out of our site pasted us going balls out before we managed to set sail, don’t even know if the boat was a sail or a motor it was long gone before we arrived - Gas i guess