Hot Water Heater

Hi Folks,
My wife & I have been living aboard for about
6 weeks, now. Our vessel is 24 years old and I
Believe our water heater is the original one,
I looked for a date on the tag, could not find a
date. It is an Atwood, out of Rockford, Ill.
It is 120 volt, so we realize that limitation, but
We just aren't much hot water, so I figure it's just
plain WORN OUT!
Does anyone out there know anything about Atwood
units?
We're planning to install a new unit, probably a 17
gallon unit (provided it fits).
Any recommendations for or against any particular
Manufacturer?
Thanks alt,
JIM'N'I III

For What It's Worth: After going through 3 marine (120v and heat-exchanger) units in as many years, I threw in the towel and followed a friend's advice. Purchased a Whirlpool 20 gallon unit at Lowe's for $245. That was one month ago. So far, so good. My friend's water heater (also a Whirlpool) is 8 years old and still going strong. Good luck!

I'm replaceing our 23 year old Rartian 6 gal w/h with a Seaward 6 gal w/h at $ 255 - at that price it's less then half the cost of a Rartian - ( $ 701 ) - if it only last 12 years, I can replace it again & still save money - and with 6 gals of hot water, we find we have plenty of hot water and the 6 gal size takes up less space in the engine room - with a non - marine w/h you will need shore power or a gen/set to heat the water as there will be no heat exchanger, IMHO

tracie said:

I'm replaceing our 23 year old Rartian 6 gal w/h with a Seaward 6 gal w/h at $ 255 - at that price it's less then half the cost of a Rartian - ( $ 701 ) - if it only last 12 years, I can replace it again & still save money - and with 6 gals of hot water, we find we have plenty of hot water and the 6 gal size takes up less space in the engine room - with a non - marine w/h you will need shore power or a gen/set to heat the water as there will be no heat exchanger, IMHO

Click to expand...

I had a Seaward totally fail after 10 years due to Al tank rotting out. Atwood or Torrid is my choice. The last few years all sorts of Al gunk was getting into hot water lines, I didn't know from where until the tank failed.

Use a domestic one unless you really need the heat source from the main engine. Another consideration is water heater heat exchangers can fail or trap air, causing damage to the main engine.

I have investigated two Yanmar engines that cooked due to the water heater. In both cases, air trapped in the heater made it to the engine, air bound the circ pump, and the high temp sensor did not pick up the heat without coolant flow.

On my boat, I installed a 3gal water heater, even though I have room for a larger unit. This was done to keep crew from taking long showers and using up (very limited) water. When shower gets cold, they stop!!!

From research and experience, Isotemp is the gold standard for boats. We replaced a Raritan on our sailboat with one. They are super efficient and well insulated, so your water will stay hot much longer when on the hook. That said, we had to go with another brand when we recently replaced the original one on the tug. This was becuase of the location - the Isotemp wouldn't fit without major surgery. I am not happy with the quality of our replacement and will be surprised if it last more than a few years. However, it was about 1/3rd what we paid for the Isotemp on the sailboat. Practical Sailor did a review of waterheaters a few years ago and Isotemp was on the top of their list.

There's no question that there's better quality marine w/h's out there other then Seaward and Atwood - by adding an Anode ( $ 60 ) to a $ 300 heater, that will extend the life considerable - some consideration to the " kitty " is another one - if money was not part of the formula, my thinking would perhaps be different -

JMCD... we have an 11-gallon Atwood, model EHM11, and it works well enough.

You can see product features here:

Marine Water Heaters - Atwood Mobile

And you can get a copy of the manual, such as it is, here:

http://www.atwoodmobile.com/manuals/waterheaters/MPD 93757 PS 11.19.07.pdf

It's about 11 years old, now. I've replaced our thermostat and ECO switch (parts 2B/3, in the manual diagram) a couple times, easily and inexpensively available at RV stores. I also replaced the heating element once (part 8, also from an RV store), but don't know for sure it was strictly necessary... I haven't had to change the pressure-temperature relief valve, but that's a routine service item, too.

Before you do major surgery, on your boat you may find it useful to a) check water flow rate through the unit, and b) flush the thing anyway with something like vinegar and water, to clear out any lime deposits that may have built up over time.

If that doesn't improve your hot water supply, changing the thermostat and high-temp limit switch may solve it. It's inexpensive enough -- and easy enough to do, if you have decent access -- that it could be worth the effort. Even replacing the heating element is easy enough, if you have access. (The latter is a 15-minute job, on the bench; took me a few hours because of our specific bozo installation.)

Some folks plum engine coolant lines to these, to capture heat from an engine's cooling system. Ours is not installed like that, but it looks easy enough to do.

-Chris

Thanks everybody....

Ranger 42C.... How do you check 'flow thru rate'?

You mentioned a 17 gallon hot water heater. Do you live aboard in a marina or at anchor? At anchor the 17 gallon tank would be more difficult to heat up. We are able to heat up our 6 gallon Raritan in 15 minutes at anchor and the 6 gallons lasts us for our showers and washing dishes.

Regardless of which water heater you install it will last for many more years if installed properly. Less than 10% of the units I see are installed correctly.

Most of the conventional marine units are aluminum tanks wrapped in fiberglass batting, inside a metal box. If you mount this box (as most do) directly on a deck, any drips condensation etc. will get trapped under the box where the fiberglass will wick it up. Holding moist fiberglass against the aluminum (or stainless steel) tank will greatly speed up corrosion. The tank should be mounted on non-absorbent cleats with about 1/2" airspace underneath to promote air flow . Running hoses from the pressure relief valve and the drain tap to the bilge will also help as these two items leak often.

Using a domestic unit is certainly cheaper but you will get no hot water when off the dock unless you run your generator. The same installation tips apply to the domestic units.

We lived aboard for 16yrs with a 6 gallon unit and never had a shortage of hot water as with such a small unit and the same wattage as larger units, the water heated almost as fast as we could use.

jmcdboater said:

Thanks everybody....

Ranger 42C.... How do you check 'flow thru rate'?

Click to expand...

Ummm... use shore water to feed the boat, attach a hose to the drain valve and open it.... see if what goes in comes out at about the same rate.

Perhaps slightly more precisely, use that to fill a bucket and time it. Then use another faucet to fill the same bucket, time that. Compare times. Doesn't have to be exact or perfect, just getting a sense of whether you've got some kind of deposit build-up in the HWH.

Comparing from two different boat sources (HWH and another faucet) lets you take into account the pressure regulator you probably have on your shore water inlet.

-Chris

Nor too small but RHEEM has a line of house units that have GRP inner tank that is warenteed almost forever.

They do not have the marine co generation built in but that can be added to any heater .

Their other advantage is excellent insulation , loosing only 5deg over 24 hours of non use.

OF course they are pricy , but not compared to most yachty stuff.

Marathon Water Heaters by Rheem

www.rheem.com › Products › Water Heating‎Rheem


Marathon Water Heaters are the most durable water heater made, with a warranty to ... The filament wound fiberglass outer tank is designed to be more flexible and ... for Residential use providing years of hot water for you and your family.

Boatpoker - thanks - very good point about raising the tank 1/2 inch off the base -

boatpoker said:

Most of the conventional marine units are aluminum tanks wrapped in fiberglass batting, inside a metal box.

Click to expand...

The Seaward unit that failed on my vessel was indeed an Al tank - painted. Destined to fail just sitting there with hot water in it.

The Torrid unit I replaced it with is Al too, but glass lined and powder coated on outside. Think thermos jug lining. A world of difference.

The Torrid's frame keeps the tank off the wooden support base so little chance of water wicking, any leak at the base would be noticeable. The devil is in the details.

Try Marinetec, their Solaris are top of the line, the inner tanks are copper.

Solaris Marine Heating

Expensive, but quality cost..

Is you boat a gasser? Is the WH in the engine room? If yes to both, stick with the marine units to avoid creating an ignition source.

Ski in NC said:

Use a domestic one unless you really need the heat source from the main engine. Another consideration is water heater heat exchangers can fail or trap air, causing damage to the main engine.

I have investigated two Yanmar engines that cooked due to the water heater. In both cases, air trapped in the heater made it to the engine, air bound the circ pump, and the high temp sensor did not pick up the heat without coolant flow.

On my boat, I installed a 3gal water heater, even though I have room for a larger unit. This was done to keep crew from taking long showers and using up (very limited) water. When shower gets cold, they stop!!!

Click to expand...

Poseidon smiles upon this one, he is very wise..

If you kept it switched off most the time, when you do power it up you will have hot water fast, also. I like the way you think.

FF,

How would you add the heat exchanger to a non exchanger heater? I would be esp. interested in the Rheem PROE6 1 RH POU you mentioned.

Rob

Datenight said:

FF,

How would you add the heat exchanger to a non exchanger heater? I would be esp. interested in the Rheem PROE6 1 RH POU you mentioned.

Rob

Click to expand...

You wouldn't

They do sell home type water heaters with heat exchanges for homes with solar systems....

but I think you will find the sizes and prices to not be advantageous.

If I had 24 years of service with a marine water heater, I think I would replace it with the same make and model. Most likely, you won't still have the boat 24 years from now so let someone else worry about it. Also, replacing the heater with the same make and model is far simpler than rerouting or extending water and electric lines.

I think it would be a big mistake to use a non-marine water heater on a gasoline powered boat and it would be a big mistake to use a water heater without the heat echanger feature if you plan to anchor out or use hot water underway without running a genset.

After a day's travel, I still have hot water the next morning because of the heat exchanger in my water heater.

The Atwood website says their marine units are ignition protected. The instruction manual says to "locate the switch in an area where ignition protection is not required."

Ours is installed in the engine room (diesel boat), and the controlling breaker is on the AC/DC distribution panel in the saloon. There is no other "switch" on the unit, so I'm guessing (hoping) this installation suffices.

I know the boat manufacturer moved the unit out of the engine room in later models, but was told that was at least partly for space concerns, so they could also install a slightly larger generator (ours is just adjacent to the HWH).

I'm satisfied enough with our unit, but if I were replacing and wanted to use an Atwood model, I think I'd have a conversation with them about that "switch vs. ignition protection" thing anyway, just to understand better what they think they mean.

-Chris

Ignition protection is as simple as a screen...like on alternators or back-fire flame arrestor on carbs..nothing magical...

Not sure what would be required to "ignition safe" a water heater but it wouldn't be much I'm sure....but I know the "sea lawyers" will wince at the suggestion and worry about voiding their insurance.

The OP has a 44 Sea Ray...can't be sure but it may be a diesel anyway.

I have a 11 gallon Attwood that is 27 years old the only part I've had to replace is the safety pop off valve, if I ever have to replace it the same thing will go back in.

boatpoker said:

You wouldn't

Click to expand...

Easily done and inexpensive as well:

B3 12A 10 Plate Heat Exchanger 7 5" x 2 9" w Studs Stainless Steel Copper Brazed | eBay

RickB said:

Easily done and inexpensive as well:

B3 12A 10 Plate Heat Exchanger 7 5" x 2 9" w Studs Stainless Steel Copper Brazed | eBay

Click to expand...

And that is going to heat the tank how? Add a circ pump, design a thermal siphon??

That'll work. Or just put it on the cold water inlet

Seaward Aluminum Tank

This tank was 13 years old when it failed. Seaward sold me a replacement tank and suggested I include a anode which would in their opinion prevented this rupture. They were prompt and friendly.

I currently have glass lined residential 20 gal which provides me with hot water at least 24 hrs without power. I run the generator to recharge my battery bank first thing in the morning. Cooking is electric as well as heat, or cooling so we try to time power usage while charging the batteries. Plenty of hot water for showers or laundry if needed. I haven't missed using engine coolant to make hot water. Or for that mater the scalding from super heated hot water. The engines do run at about 180 deg.

One concept to avoiding a ruptured tank might be to use a FW pump that has much lower pressure.
And cycle the overpressure valve on the heater tank more often.

Might make the dishwasher or washing machine unhappy but normal living should never notice.

The larger the supply tubing , the easier it is to live with 20 - 30 PSI instead if 55psi.

Be sure to use a rebuildable and adjustable pressure regulator if you run dock side water aboard to the boats FW system.