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Tankless Water Heater, CNG?

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cng users
11K views 25 replies 12 participants last post by  remetau 
#1 ·
Anyone tried any of the less expensive tankless water heaters? Has anyone installed one to CNG? My old 110 tank is dying. I don't have a heat exchanger on my S2 9.1 either, so hot water away from dock and less weight (we also race) would be good. I have CNG for cooking and like it.
I'm looking at installing one of the small tankless water heaters out there and running it off my CNG. Has an ignition system that runs off of 2 D cells and is only on when water runs through it. I mostly use the hot water for dish washing and the odd twice a decade shower.
Any thoughts on installation? Anyone done this before?
 
#2 ·
why don't you use the engine to heat HW? it's not that difficult to do. Then even if you had a sea water cooled engine, to convert it to a RW cooled heat exchanger is also not that difficult.
I used to do tankless systems in my land based business they don't work well on boats because they need venting,
 
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#3 ·
My Yanmar 2 GM runs quite cool with our Puget Sound water. Not much heat with a raw water system. Looked at conversion a while ago--fairly expensive plus weight.
Why is venting a problem? I was considering mounting it on a custom bracket where my existing water heater is now and running the venting aft and out of the boat.
 
#4 ·
Well I did a bit of looking up. It seems there are a number of tankless units that meet ABYC guidelines. CNG and LPG are very differen't but the safety guides are not very differen't.
where will you make "another hole in your boat" ? for the vent?
 
#5 ·
Since hot rises on its own ,I'd bet it wouldn't breath well out the transom. CO could be an issue. Any way the pressure inside has to be greater than outside or it inhales to your peril.One way to a bi annual shower is a black solar water bag with a small connection thru deck head into washing area. control valve inside. Unless you run some pipe either shower at the galley sink or pile the dishes in the head.
 
#7 ·
I've got an old Wolter. The installation venting issue was that you needed at least a foot of flue pipe before the mushroom vent. The vent needed a foot of clearance from other stuff like dorade vents hatches etc. that could cause a downdraft. This ensures that the flow goes out the pipe and not back into the boat. For the unit itself you needed about four inches of clearance on the side and eight above. There needed to be an air supply about 20 sq inches. While tankless units are lots better now the same principles probably apply
 
#15 ·
Now I don't want to be spreading miss information, but I contacted Precision Temp about the ShowerMate M-550. I specifically asked if it was ABYC approved and they said yes it is. He did not provide any documentation at all though. I do know they are not legal at all in Canada on boats.

Another option would be a hydronic heater and they offer a heat loop for the hot water but they run on diesel. It is kind of pricey.
 
#16 · (Edited)
The last time I looked into a Precision Temp they were not "sealed combustion". In order to meet ABYC standards they must be sealed combustion.

Perhaps they've added one to the line up but the web site does not show it... As far as I know these are exhaust only to exterior of vessel not exhaust & intake to/from exterior....

This is what the manual for the Showermate M-550 "marine" unit says..

"At least 20 square inches of incoming air is necessary and the power vent of the unit should always be vented to the outside with 2" approved duct."

That is not sealed combustion. The ABYC standards are not difficult to read or understand but apparently PT missed the part about it needing to be sealed combustion for use on boats...
 
#17 · (Edited)
if the portable shower ones support electric they may be compliant as they don't have any exhaust when operating in electric mode, though admittedly it is 11KW or 100amp.

Alternatively there is also the Soviet shower method -- how people took hot showers in the soviet-union and post-states where hot-water is either intermittent or completely absent. I remember it from my childhood.

The method is to have a bucket or some container which holds liquids, fill it mostly with cold water, then set the kettle to boil, pour in boiling water, stir and test is appropriate warmth (exact proportions of hot-to-cold depend on water temperature), then use a measuring cup or some such to pour it over yourself in the shower.

Washing dishes is same deal, make sure either container wide enough, or dishes small enough to fit.

I was thinking that if you happen to have a gravity-fed solar-shower assembly, then in winter or relatively cold times, can simply top it off with some kettle water. Though admittedly solar-showers and gravity-fed ones do have "tanks". Could even consider a bucket to be a "tank", though bucket very handy item, since can also use it for laundry, and many other uses.

Of course there is also the option to take cold showers, which are supposed to be good for you. In Russia snow bathing is one (fun) way to get clean during the winter. Winter swimming is also great fun :), good for circulation, and heat-generating ability (assuming you have enough dietary-iodine).
 
#18 ·
I'm looking for help. I had one on my old boat for eight years and loved it.

I just got a used Wolter that was never installed. I tested it and it is working fine. It has a flue hood with the 3" vent.

I'm looking for a manual and I found part of one online, but it was missing some pages. One thing in particular I'm trying to figure out is how the optional flue fan was connected and what type of fan it was. I had put the fan option into my Wolter on my last boat. I liked the power venting as it assure proper flueing. It looked like just a normal muffin fan and I remember hooking it up to the terminal strip, just not exactly where.

Would anyone have any information, like a manual or information on the fan connection or type, like CFM for the flue vent option?

Please e mail me tcdunlap(at)gmail.com

Thanks,
Tim
 
#19 ·
Oh, as far as being "compliant, last I checked ABYC is a voluntary standard that is mainly forced onto boat owners through problems with surveys, and subsequently insurance companies that will not insure your boat. I'm not saying we should not have some standards, but from my 35 years of boating experience, it is a rare builder that builds boats that meet all ABYC standards. Then there are problems with the standards differing from those in Europe, something else to be aware of.

Surveyors do sometimes misinterpret rules, and this has resulted in people, myself included, in having to modify boats to get insurance. Meanwhile they miss things all over the place. I was just aboard a boat that had the fuel tank vented in the bilges (diesel), and batteries installed in the bilge on their side, and not well fastened down. The survey did not even mention these things.

As far as gas water heating, if done right, I think it is very safe. With systems that have vents, I don't see a problem; I do like power venting ones best, as they assure proper draft. I would not use an unvented heater, but I think some unvented ones can be modified to have vents. I know some boater have done so.

The few instances of problems, and some were quite serious and involved deaths, were the result of people not following installation instructions or common sense. One happened near where I live. The person involved had installed the flash water heater in the head shower without a vent. This was a live aboard situation, and the person used it in the winter, with the hatches close up, with disastrous consequences. You can hardly fault the equipment for the result.

I don't like to see these heaters mounted in living spaces. A cockpit locker would be a better choice. If you have the room and are really concerned, I think you could make any one of these heaters ABYC complaint by building a gas tight locker to put it in. Supply outside air and a flue and you have it. Maybe this is more than most people are capable of, but it's not impossible. The Precision Temp would be ideal for this, as it is power vented. If done this way, you are not taking combustion air from inside the boat. I think the Precision Temp is plenty safe even if using inside air for combustion.

I would also argue that a flash water heater is an attended appliance. It is not left on when no one is on board. Even if power was left on to it, it should not cycle on. I don't see any reason for it to be on except when one is right there using it. In this regard it is no different than a galley stove.

You ought to have a smoke and carbon dioxide detector on your boat too. Common sense, but I don't think this is required by ABYC.

All-in-all, even with all the modern convinces being added to boats, boating has never been safer. Very few people are injured or die from this activity. The number of deaths has fallen over the years. Remarkable when you think of things like Jet Skis showing up on the water with hundreds of horsepower. Your chances of becoming a statistic are much greater in a boat with no motor and less than 16 feet. More people die falling on their front steps than boating. I'm growing tired of all the "safety police" trying to tell me how to conduct my business. No activity is without risk, but people will jump in a car and think nothing of it, while people are flying past them driving with less thought than they use brushing their teeth!

Anyway, I say these units can be installed in a safe and effective way. The risk can be mitigated. They are no worse than the galley stove. When gas stoves fist started showing up on boat, many people said they were unsafe. It turned out insurance company clams fell, as compare to older technologies like fuel oil or alcohol stoves. Suddenly they were no problem.

Does it take some thought and careful planning, sure, but I think they are a great idea for increased comfort. I used one everyday for over eight years living aboard without a problem of any sort. Make up your own mind; I'm just a guy with an engineering background, and a licensed 100T CG captain with thousands of hours on the water. What do I know?

Cheers,
Tim
 
#26 ·
We have been using our vent-less Excel for 5 years without any problems. We have a dedicated LPG system for it along with a water solenoid that opens the supply to it when the LPG solenoid opens. This keeps the system from trying to ignite when the water is on, but the gas is not.
 
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