water heater installation

[capz]

I've had my 2000 270 for one season now and I need a new water heater. I bought a Force 10 6 gallon to replace the Atwood ehm6. The Force model has the heat exchanger to run off the engine cooling (raw water-cooled). Before I get into plumbing, what do I need to do on the electrical side to run it off of DC while underway? Right now there's just the AC switch on the main panel.
On a side note, after reading through my documentation, I realize how little I understand my boat's electrical system. Example, I don't understand why my refrigerator, an a/c appliance, can run under DC but my microwave can't. But that's a topic for another day. Any info much appreciated.

 

[Dave S]

First off welcome to CSR.

Relative to hot water heaters, I am not aware of a marine water heater that runs off of straight DC voltage. That's why they are supplied with a heat exchanger so the water heats up from the water off your engine. The heat exchanger does a pretty good job of heating the water but naturally the longer you are at rest and not plugged into shore power, the colder the water gets.

If you don't have a generator, with adequate battery power and a DC inverter, you could run your water heater, microwave or A/C sytem off of batteries. But this is not necessarily easy to do or cheap either. We have had a few threads on this subject. If you wish to learn more about it, just do a search on "inverter". Here is one thread where it was discussed. http://www.byowneryachts.com/forums/phpBB2/viewtopic.php?t=582&postdays=0&postorder=asc&start=45

 

[Sea Gull]

First you will have to check the specs on the water heater. I have never seen one plumbed to a raw water engine cooling system. They are usually designed to work on the fresh water side. Second, I doubt that it runs on 12volts DC, again, check the manual but all that I have seen run on 110v AC only.

The refrigerator is likely a dual voltage design which will run on 110v AC when available and 12v DC otherwise.

 

[goblue]

First you will have to check the specs on the water heater. I have never seen one plumbed to a raw water engine cooling system. They are usually designed to work on the fresh water side. Second, I doubt that it runs on 12volts DC, again, check the manual but all that I have seen run on 110v AC only.

The raw water cooled 1990's era SRs all had heat exchangers and made very hot water.

 

[capz]

So the function of the exchanger is just to reroute the heated raw water to heat the fresh water in the tank. So the heater doesn't have to be powered while underway. Thanks Dave for clearing that up. And thanks for the welcome. Plenty of experience and knowledge here.
I'm still not sure where to connect the hoses to the engine. The mercruiser manual offers recommendations but the pictures aren't too clear. As you can see I'm still in the "getting to know her" stage. I'll keep you updated.

 

[capz]

goblue I found the manual for the Atwood. The heater has a heat exchanger but it's not hooked up on my boat. All I can see are two hoses, hot/cold, and one for the relief valve. I don't see any reason why it wouldn't work with raw water, besides long term corrosion. I'll dig a little deeper.

 

[Dave S]

You can see from this picture of my hot water heater there are two black hoses running from the engine. In all likelihood you will have to determine how to create the same setup off your engine and purchase the hoses and couplings you will need. Your dealer is probably the best source to go to first so you can see what you need.

 

[never monday]

Because of the amount of energy required to heat the domestic water, you won't find a DC unit. Water heaters are either 120v and heat exchanger or just 120v. When I install one in a sailboat I typically lengthen the last section of hose between the engine and the manifold/riser. This will work for a good while in salt water. Like everything else exposed to salt it will corrode over time.

Microwaves and refrigerators. Fridges are typically 120V and 12v. They automatically switch over with 120v being the preferred and default setting. Microwaves are 120v only. You can run one on an inverter with a large battery bank. Doing this will require running your engines more to replace the used volts. Or getting a genset.
Think of your electricals as dual parallel systems. Some of the appliances can use both systems.
Pat

 

[secret agent]

replaced hot water tank with new Atwood EHM6. Hooked all up exactly as before
and only get hot water from heat exchanger.
When hooked up to shore power no hot water.

Brand new water tank from a recommend source on this site.

Anything I should look for before contacting the seller back??
I'm hoping its not the element on a brand new unit!!

Thank you in advance for any advice you can give

 

[smittyasc3]

Whats that white piece between your engine and water heater???

You can see from this picture of my hot water heater there are two black hoses running from the engine. In all likelihood you will have to determine how to create the same setup off your engine and purchase the hoses and couplings you will need. Your dealer is probably the best source to go to first so you can see what you need.

 

[Zorba]

I don't think Dave is around very much anymore, but my guess would be he fabricated something to hold his cockpit table in the bildge.

 

[Air O'Nautical]

So the function of the exchanger is just to reroute the heated raw water to heat the fresh water in the tank. So the heater doesn't have to be powered while underway. Thanks Dave for clearing that up. And thanks for the welcome. Plenty of experience and knowledge here.
I'm still not sure where to connect the hoses to the engine. The mercruiser manual offers recommendations but the pictures aren't too clear. As you can see I'm still in the "getting to know her" stage. I'll keep you updated.

Will work with raw water, my last boat was like that.
Expect it to rot out every few years.
I replaced three in 10 years on that boat.

 

[Handsome Transom]

Will work with raw water, my last boat was like that.
Expect it to rot out every few years.
I replaced three in 10 years on that boat.

I am thinking about bonding a couple if thin strips if pressure treated strapping in the bilge with a good silicone and mounting my new water heater to them with stainless screws I am thinking the 3/4" space created might keep it from deteriorating so quickly