Alternative Wiring for Water Heater

[spadaforaj]

Looking for alternative wiring scheme for a Seward Water Heater (F700 with heat exchanger). Much to my disappointment, my 1981 Hunter 33 old Yanmar engine does not have a heat exchanger, and we would like to have the capability of having hot water when not in port. Right now it is wired to the ac panel and works fine when in the dock. I have a 2500 watt inverter system, the specs say it requires a circut with a minimum of 1500 watts.

1) I assume there is no way to use the fresh water cooling system through the water heater's heat exchanger system ?

2) Is it possible or advisable to simply change the electrical inputs from the ac panel to to the inverter ? Use only when the engine is running

3) Is there way to wire this to select between the AC panel when in port and the inverter when under power (best of both worlds) ?


Thanks

Jim

 

[Maine Sail]

Looking for alternative wiring scheme for a Seward Water Heater (F700 with heat exchanger). Much to my disappointment, my 1981 Hunter 33 old Yanmar engine does not have a heat exchanger, and we would like to have the capability of having hot water when not in port. Right now it is wired to the ac panel and works fine when in the dock. I have a 2500 watt inverter system, the specs say it requires a circut with a minimum of 1500 watts.

1) I assume there is no way to use the fresh water cooling system through the water heater's heat exchanger system ?

2) Is it possible or advisable to simply change the electrical inputs from the ac panel to to the inverter ? Use only when the engine is running

3) Is there way to wire this to select between the AC panel when in port and the inverter when under power (best of both worlds) ?


Thanks

Jim

Your alternator will never keep up with a 1500 watt load off an inverter and you can't physically install one that will on that motor. You'll literally kill your batteries even with the engine running.

You would need a 175+ amp alternator, minimum, just to stay even. A 1500 watt AC load through an inverter is about a 165 amp load to the batteries.

Watts = Volts x Amps

Battery size is expressed in terms of amp hours. Batteries usually give a 20 hour Ah rating. A 12V Group 27 battery may have 85 Ah's at the 20 hour rate but if drawn down at a load greater than what the 20 hour rate was, eg: 165 amps, the battery may only be able to supply 40 Ah's or less. The higher the load drawn beyond the 20 hour rating, the less available Ah's you will have.

With a 12V inverter, each 100 Watts of AC supplied requires approximately 10 DC Amps from the battery. 1500 Watts + a 10% inverter inefficiency = 165 amps for the water heater.

 

[Don S/V ILLusion]

The only practical way of making hot water with your heater is to run it (the boat) off a portable generator which is what many folks do as it can serve multiple purposes. To run the HW heater, you would need a genset capable of 1800-2000 watts and cost anywhere between $400 for a cheap one to $900 for a Honda 2000e which is one of the most popular choices.
About the only alternative is a camping type solar shower.

 

[Steve Dion]

I believe that you can add a heat exchanger to your engine.

http://www.sen-dure.com/

 

[alexco38]

You should be able to find a way where the RAW cooling water goes from the engine to the exhaust elbow. And T-it off to the water tank. That's how a RAW water cooled Volvo engine works. The pic shows how it was done with copper pipe elbows. The straight part is not thru. There is a copper plug inside that force water out to the tank and return to exhaust mixer. Volvo sells a part for pretty big $$$, so I made one.

 

[alexco38]

It isn't simple to add a heat exchanger to a RAW water cooled engine. You need a coolant recirulation centrifical pump, new belt, expansion tank and a host of pipes bend to shape that fits around the engine. The kit for my Volvo runs about $1500.

You don't need a heat exchanger to have hot water. Raw water engine can do that too.

 

[Chuckbear]

1) I assume there is no way to use the fresh water cooling system through the water heater's heat exchanger system ?




Thanks

Jim

Jim, Actually, every boat I have ever been on that has a heat exchanger on the HW tank runs off the fresh water side of the engine coolant system. Our Yanmar was plumbed like that as we cruised for 17 years on our sailboat. There will be a plug somewhere just past the fresh water pump to tap into, run a heater hose to the hot water heater and back to the engine and reroute the water back into the coolant system . It is not a good idea to use the raw water side for this. If in doubt as to where to make your connections then contact your local Yanmar dealer. We just replaced the plumbing from the engine to our hot water heater and posted it on our website, http://tinyurl.com/yjfjt8x , ours is a Ford Lehman so the configuration is different but the principle is the same. Chuck

 

[alexco38]

Tap right off the raw water pump is just cold water. You need to tap into the heated engine water just before it enters the exhaust water lifter.

 

[spadaforaj]

Freshwater Cooling to Water Heater - Photo

Thanks all. I went down to the boat last weekend and it looks fairly straightforward (except for the contortionist act) - if anyone has an experience with this engine (2QM15, I believe - freshwater cooled) I'd appreciate the confirmation - the photo shows where I believe I should tap into - divert the black hose in this photo from the far end of the photo to the heater, then back again to the exhaust manifold in the foreground - seem correct to you ?

 

[Ed Schenck]

It is how my 2QM20 was plumbed to the water heater. In the pictures the hoses have been removed just prior to pulling the engine.