12v water heating setup

[kenbo]

If you want to be self sufficient AND not use diesel, you circulate the hot water through a small solar water heating panel like this, https://heliatos-solar.myshopify.com...r-heater-panel

I sailed on a boat with one of these and it was very effective. They had it installed on a arch along side the PV panels.

[kenbo]

Originally Posted by belizesailor

Solar dump load.

This is a project on my list too. Aux Out from my solar controller is 20A max which I think will drive a 220V element just not very hot...no problem, only need to take the chill off here in the tropics. I think my existing t-stat will handle it too, but need to research/test that. Tank already has over pressure protection.

Definitely test your tstat, many don't work with 12VDC but some do.

[Jubilee39]

Originally Posted by kenbo

Definitely test your tstat, many don't work with 12VDC but some do.

Don't know how you plan on wiring into solar, I am using a relay to dump wind and solar into the HW when battery is charged. With this setup if you are concerned about the thermostat you could break power to the heater that way. Me, I just wired through the T stat

[kenbo]

Originally Posted by Jubilee39

Don't know how you plan on wiring into solar, I am using a relay to dump wind and solar into the HW when battery is charged. With this setup if you are concerned about the thermostat you could break power to the heater that way. Me, I just wired through the T stat

That could work, have verified that the tsat is in fact working?

[kenbo]

And I'm not wiring 12vdc to my water heater I was only responding to the OPs questions.

[belizesailor]

Originally Posted by Jubilee39

Don't know how you plan on wiring into solar, I am using a relay to dump wind and solar into the HW when battery is charged. With this setup if you are concerned about the thermostat you could break power to the heater that way. Me, I just wired through the T stat

The wiring is simple, many solar controllers have a dump load connection which outputs excess solar power. Just wire it up with a suitably sized/fused circuit. My Blue Sky 3000i controller has an "aux out" dump load connection rated at 20A.

Caution: you have to isolate the AC input to the water heater. Ive read of installs using relays to isolate, but I rarely hook up to shore power, so I plan to disconnect and cap the AC connection at the water heater. On the rare occassions when I need it, I will just hook it back up. A simple manual switch would work too, but I dont want to complicate things with relays and I dont need the convenience.

[Pete7]

Originally Posted by JimMann

Good point, I did consider running it into the bilge but I remembered there was 2 expansion copper pipes coming out of my old 2 water tanks (plastic 240L barrels) I haven’t investigated yet but they seemEd to be heading out up toward the the pilothouse. I’ll have a look this weekend but I’m sure there’s a hole one each side of the pilothouse

Thanks

If you do pressurize the tank, the pressure relief valves (PRV) have a habit of leaking after a while. You wouldn't want to pump all the freshwater over the side and not notice. So perhaps discharge into the cockpit. Hopefully the crew will notice their feet getting wet and do something about it. It also avoids a wet bilge.

Pete

[JimMann]

Originally Posted by kenbo

Mike,

Just install the T&P valve first at the top of the tank. My only concern from what you stated as your plan is using the 300W element rather than the 600W combined. I haven't done the BTU calculations but your recovery time (° rise from incoming water temp) will be fairly low.

Have you considered installing a switch, Off/300W/600W, to give you an option?

I just did a quick calculation, it will take 35 watt-hrs to raise your 30 liter tank 1°C. Or said differently, 300W will raise 30 l of water about 8.6° C in one hour assuming 100% efficiency. You'll have to decide if that's OK.

Hi,

Sorry for my late reply! I’m stating to realise this more complicated than expected and a little over my head but I want to understand and make it happen as I really do want a 12v water heating system.

I’ve realised I will need it pressurised in order to refill the tank. Does this mean the water will start cooling down as I use it because it will be refilling at the same time? Would there be a way so it didn’t start the refill until it was nearly empty I.e just above the element?

Do you know of any diagrams for such a system?

Thanks

[GILow]

The tank should self-stratify across the temperature gradient provided you introduce the new water at the bottom and collect the hot water from the top.

But I think you’ve got a lot more homework to do because I suspect you are greatly overestimating the capacity of your solar to heat the water to a SAFE temperature.

Storing warmed water is extremely dangerous. It must periodically be taken to a high enough temperature to kill some of the deadly bugs that can grow in it.

Do some research/reading on legionella and similar bugs.

[JimMann]

Originally Posted by GILow

Wow, you must have a lot of solar. I’ve got 760 watts and I can’t make the maths work to heat water from the batteries on my boat.

Whatever you do with this setup, I suggest you leave provision for a heat exchanger just in case you want to boost it later with something like a diesel heater or perhaps engine heating.

Incidentally, how thick is the insulation on that tank?

Hi,

I have over a 1000w plus I’m looking for a decent wind generator. I’m always looking to reserve energy and I’ve managed to keep my consumption very low due to mainly only using 12v where possible. I also try to use the engine and less as possible with it being a large 3.8.

The insulation is very thick, seems to be verywell done

Thanks

[JimMann]

I have enough solar (1000w and will shortly have a wind generator as well) plus lithium batteries. I’ve already been looking into inline filter systems to solve that issue

Thanks

[GILow]

Originally Posted by JimMann

I have enough solar (1000w and will shortly have a wind generator as well) plus lithium batteries. I’ve already been looking into inline filter systems to solve that issue

Thanks

I don’t THINK filters will work for the nastier warm-water bugs. Check the literature but I suggest it will be much safer to make sure the system can be periodically made hot enough to kill them all.

Or have a look at how CF user, Typhoon/ColdEh solved the problem by storing only treated coolant and extracting hot water on the fly using a copper coil heat exchanger.

I am using his design, fired by diesel, and it is brilliant.

If you really do have enough solar then you could use electric instead of diesel in his design quite easily.

But I think you’ll find that 1000 watts is not remotely satisfactory. The energy required to heat meaningful amounts of water will shock you. (Pun unintended).

[GILow]

Originally Posted by JimMann

Hi,

The insulation is very thick, seems to be verywell done



Thanks

Just curious, how thick is “very thick” and what is it made of? I’ve yet to find a well insulated water tank, most seem to have maybe an inch of rockwool or similar.

[belizesailor]

Originally Posted by GILow

The tank should self-stratify across the temperature gradient provided you introduce the new water at the bottom and collect the hot water from the top.

But I think you’ve got a lot more homework to do because I suspect you are greatly overestimating the capacity of your solar to heat the water to a SAFE temperature.

Storing warmed water is extremely dangerous. It must periodically be taken to a high enough temperature to kill some of the deadly bugs that can grow in it.

Do some research/reading on legionella and similar bugs.

Good point. With a conventional marine water heater with a heat exchanger, that problem should be addressed by occassional engine run. For example, we typically run the engine about once a week either just to give the batteries a good full charge or to move to another anchorage.

[JimMann]

Originally Posted by GILow

Just curious, how thick is “very thick” and what is it made of? I’ve yet to find a well insulated water tank, most seem to have maybe an inch of rockwool or similar.

It seems to be foam but it’s 2-3 inch thick, I’m just waiting on guy who built it to get back to me with more info. If it’s not upto a good standard, I will redo myself

Thanks