Tankless water heaters

[john61ct]

Originally Posted by Connemara

Dunno if this applies to onboard systems, but.... We have a tankless water heater in the house, which we like a great deal; the drawback is that you have to run it a while before you get hot water. On board, that would mean going through a lot of fresh water, unless the marine versions are built with some sort of recycling system.



Connemara

Which is why a mixing container is used, can even be a bucket. Just recirculate the in/out together if too cool, add cool if too hot. Of course nothing to do with **how** the water's being heated, works with any method.

@Noelex may have a link to his elegant example.

[CF32907]

Originally Posted by john61ct

Which is why a mixing container is used, can even be a bucket. Just recirculate the in/out together if too cool, add cool if too hot. Of course nothing to do with **how** the water's being heated, works with any method.

@Noelex may have a link to his elegant example.

In your house is not the reason for the length of time, you do not need a recirculating system. The heater puts out hot water within 5 seconds of coming on line. The closer the heater is to the faucet is what relegates how long it takes to get hot water. If you put the tankless where the tank water heater was, it still has to push water 20 - 30 - 40' before it gets to the sink, this was the same with your old tank type WH. Can't change that no matter what you use for heating. You have to put the heater closer to the service fixture.
If you have the TW heater in the boat and it's within a few feet, you will get hot water virtually instantly, they do not require pre-heating time. I've used them in homes and boats for 50 years, there the best thing since sliced bread for heating water.
The main downside up north, most of these on demands will raise temp about 35-40 degrees, if your ambient tank water temp is 50 degrees you will only get a rise to 90 degrees at the faucet. We don't have those problems here in Florida. Happy showering all, Capt. Vince Rakstis, Ret.M.S. St.Petersburg, Fl.

[john61ct]

All that is fine and good, but I stand by what I wrote,

a recirculating / mixing container is a very inexpensive, simple and IMO elegant way to get exactly the temperature you want, no matter which of the many possible heating methods you are using at that time,

no matter ambient conditions, and most importantly

not wasting even a drop of precious fresh water.

Especially for minimalistic extended living aboard in primitive locations, simplicity to me is critical.

[drcat]

I know your original question was for switching to a tankless water heater for space saving purposes and you have received a lot of opinions on all types of water heaters. My input deals with the current 6 gal heater you have now which I assume has a 110v calrod heating unit for when you have shore power and has a water coil loop from the engine.
Below are 2 alternatives that keep your 6 gal tanks but heat water without 110v or running your engine. The alternatives assume you have or plan on having PV solar panels.
1) System from green-yachting dot com where the 110v calrod is replace with a 12v 310 watt calrod combined with a controller that knows when your solar panels are generating excess electricity that can be directed to the calrod to heat water. I believe you can still have the 110v calrod and engine coil loop.
2) System from custommarineproducts dot com where a flat black plate with water filled channels is placed directly in back of the solar cells themselves (sandwiched between the cells and the white plastic backing seen on most PV solar panels) . When the sun heats up the cells and the heat is transferred to the plate, water is pumped thru the plate heating the water and cooling the cells and heated water then pumps thru coil in water heater. The system is self powered as the water pump is solar powered.
I have nothing to do with either co and have not used either system.

[wingssail]

Originally Posted by Dockhead

I mentioned the Lord Trenchard case only because it was the subject of a full MAIB accident report, which has a lot of important detail in it, relevant to this discussion. There are previous threads on CF with references to dozens of accidents, if you care to do a search. As I said, someone gets blown up almost every year.


The Lord Trenchard case is particularly interesting and particularly relevant because the boat was a Royal Navy training vessel which was exceedingly well run, much better than any cruising boat I know, with great care taken with gas safety, much more care than taken on any cruising boat I know. This degree of care went so far as to require the crew to pump out the bilges every morning -- pump out gases using the diaphragm hand bilge pump.
I read the Report, I didn't read anything about daily pumping of bilge to exhaust any gas which might have been there.

Despite all this care, they blew themselves up, and one cadet lost a leg, and the boat was blown to smithereens. The gas locker on Lord Trenchard of course drained overboard. The problem happened because of a tiny flaw in the sealing where the gas pipe left the locker, and that was enough to allow a fatal quantity of leaked gas into the hull volume. Remember, propane has twice the explosive power by weight of TNT. It only takes a little bit.

If there was a leak in the gas line from the locker to the cabin then that is a) a flaw which should have revealed itself by the smell of gas. b) the gas valve would properly have been in the locker. If it was shut off then how did it leak out through the pipe.If there was a leak in the gas line from the locker to the cabin
Moral of the story -- gas on board is bloody dangerous and is not "absolutely safe" even if you are really careful. "Reasonably safe" -- perhaps. But how reasonably safe is a boat where safety rules are flaunted and derided as something produced by gnomes in offices?

Wait a minutes, you detect leaks by smell? If you ever smell propane on your boat, it's too late, you're already sitting in a bomb.

It goes like this: In the morning (or at any time) when we turn on the gas and light the stove for our coffee, the lower pressure of the mostly empty gas bottle causes the flame to burn less completely, and we smell it. It still burns and heats the water for the coffee but we know it's soon going to run out.

Simply smelling gas in a boat does not mean it's a bomb. In order to ignite, the propane/air mix must contain from 2.2 to 9.6 percent propane vapor. If the mixture contains less than 2.2 percent gas, it is too lean to burn. If it contains more than 9.6 percent, it is too rich to burn. However, the human nose can perceive propane in the air before it is within this range.


And what are you smelling when you are "telling it is getting low" -- combustion products? You don't even vent it? Have you ever heard of carbon monoxide?

It is always vented, it is always off when not in use, The entire locker is vented. We have most often smelled it when transferring it outside or when a tank is heated and vents. Even a slightest leak, OUTSIDE OUR BOAT, IN THE GAS LOCKER, is perceptible in the boat. It takes an way less than the amount that can ignite to be able to smell it.


That is precisely what the Lord Trenchard crew thought! That's exactly why I posted that report.

Be safe, man. A really good start to being safe with gas on board is scrupulously following the ABYC rules, which are very sensible and very effective.

I follow ABYC rules when they make sense. I am not slavish about it.

[ncohen226]

We sail in Georgian Bay and have had a tankless propane hot water heater on our sailboat for 10 years. We're avid sailors and have never had a problem with the unit, except for spiders. It's been an incredible add-on to our sailing life as we like to stay out for as long as possible and not go to a marina to fill up with fresh potable water.

We have two water systems installed. One which uses the boat water heater that was in-situ when we purchased it. The other is a lake freshwater propane system that we use for showers and dishwashing. That way we keep our potable water for longer.

IMPORTANT: We called our boat insurer to make sure it was okay to add the propane in-line heater and their only request was to have the unit installed by a gas-fitter. We got a certificate stating this for the insurers. We had our marina complete the second plumbing to all the showers and sinks. It works well and we have ample pressure to shower but not dishes and shower at the simultaneously.

It works regardless of the heel angle of our boat.

We bought the ECCO unit from Walmart for $125 CAD and bought a second one as a spare which we keep on board. The unit is hung on the outside of our transom pushpit so it takes up zero room on the boat and was plumbed with hot and cold so we get whatever temperature we want.

hope this helps

[Macblaze]

The two most irritating, finicky things in my life that I can't fix for myself are my webasto hydronic heater on the boat and the hot water on-demand system in my house. Electronics make me crazy. I doubt I would ever give up my engine fired waterheater

As for the explosive power of propane I used to be ultra paranoid. These days I am just overly cautious. It's mostly due to the Yachting Monthly video where they try to blow up their boat—It just ain't that easy.

https://www.youtube.com/watch?v=Yxm3uMy6MPI

[GrowleyMonster]

Propane, in spite of it's dangerous nature, has a fairly good safety record. Nevertheless I will admit to having a very keen prejudice against it. I won't have it on my boat apart from the possible exception of a gas grill topside, with topside canister storage. Stuff happens. I like diesel for cooking. Or electric, pierside.



But we are talking about water heaters. Different critter altogether, because nobody is watching it like a cookstove. I don't care if it is allowed or not, I won't have a propane water heater on a boat. At the dock, electric is the way to go. There are tankless heaters that will run on 120v and pull 30a or less. At sea, run the diesel. There are a lot of schemes for using waste heat from the engine to make hot water. Then use it while you got it. Another simple way to get clean in cold weather is to heat water on the diesel burner and take a ho bath. On anchor if it isn't cold and the sun is shining bright, a black plastic bucket will give you enough water to bathe with that is at least nice and warm. The campers' "solar shower" bags are not very durable and can't tolerate a lot of chafing against mast, shrouds, halyards, etc but it is a handy thing to have in reserve.



On a big enough boat in higher latitudes, a wood/coal stove can be pretty sensible. It has its drawbacks, to be sure, but it is pretty simple to wrap copper tubing around the flue for making a couple of gallons of hot water. Or make a proper waste heat boiler to install inline with the flue. And you can burn your paper waste in it, to reduce the trash you have to store until you reach port.



No matter what, no matter how many folks think it is perfectly okay, no matter how many insurance companies will sign off on it, no propane water heaters OR propane cookstoves for me. You guys can do what you like, I won't throw rocks at you.

[Paul L]

We sure enjoy our tankless, on-demand diesel hotwater heater. ITR Huricane Zephyer.

As far as religously following ABYC propane standards is concerned. Boats that are ABYC compliant often fail the Australian and New Zealand standards.

[Pete7]

Originally Posted by wingssail

I follow ABYC rules when they make sense. I am not slavish about it.

The RN practice on yachts was to pump, by hand, the bilges on the hour every hour and record the number of pumps required to empty the bilges, then pump for one more minute to remove any gases. This gave you a heads up if there was a problem even a small one if the number increased. The log of course kept a permanent record even when the watch handed over.

Pete

[undercutter]

Originally Posted by Paul L

We sure enjoy our tankless, on-demand diesel hotwater heater. ITR Huricane Zephyer.

As far as religously following ABYC propane standards is concerned. Boats that are ABYC compliant often fail the Australian and New Zealand standards.

In Australia and NZ it is against the law to install your own electric water heater in your house. These countries are the leaders in Nanny states. You can't even buy R134a for your fridges unless you have a refrigeration license.



They say it is for safety but it is only too protect the tradesmen and it results in some of the highest costs in the world because these guys know that you have no choice.

[Paul L]

Originally Posted by undercutter

In Australia and NZ it is against the law to install your own electric water heater in your house. These countries are the leaders in Nanny states. You can't even buy R134a for your fridges unless you have a refrigeration license.



They say it is for safety but it is only too protect the tradesmen and it results in some of the highest costs in the world because these guys know that you have no choice.

Of course true. But ABYC allows soft hose for the long propane runs, while other countries require hard piping.

[Matt Johnson]

Originally Posted by GrowleyMonster

But we are talking about water heaters. Different critter altogether, because nobody is watching it like a cookstove.

I've yet to see anyone with the propane tankless water heater install it out of sight. Typically it's installed right at the use point (galley or shower) and only runs when needing hot water. How is that more unsupervised than a stove? At worst you have shampoo in your eyes and can't see for 10 seconds

We don't have one on our boat, but I've happily used them on other people's boats and felt perfectly safe. You flip a switch to open the propane solenoid, turn a tap, and the heater engages to make hot water. Seems to me that it is just as safe as a stove.

Matt

[john61ct]

The various standards are not compatible.

Do not mix & match unless you're an experienced professional.

Stick to one, do scheduled checklisted inspection / testing, replace proactively especially rubber hoses.

Use detectors, test & replace regularly.

And odds are good you'll be fine, safer than getting cars going highway speeds.

[GrowleyMonster]

Originally Posted by funjohnson

I've yet to see anyone with the propane tankless water heater install it out of sight. Typically it's installed right at the use point (galley or shower) and only runs when needing hot water. How is that more unsupervised than a stove? At worst you have shampoo in your eyes and can't see for 10 seconds

We don't have one on our boat, but I've happily used them on other people's boats and felt perfectly safe. You flip a switch to open the propane solenoid, turn a tap, and the heater engages to make hot water. Seems to me that it is just as safe as a propane stove.

Matt

There, I fixed it for ya.



Not telling anyone not to use propane. Just that I won't. I don't like it and I don't trust it and I won't have it. That should make propane users happy, due to demand for those things being reduced by one unit.