Water Heater heat exchanger hook up question

EO32 · #1 (**permalink**) 08-19-2008

I have a 1200 watt 110v small water heater. I works good and my inverter can power it. It only takes about 15 min to get to 120 degrees.

On our last trip, I found the inverter shutting down when the batteries fall off. I really need fully charged batteries to make this work.

I noticed that my water heater has a dual 1 inch pipe thread inputs with nothing connected, which makes me think it has a heat exchanger built in, but not hooked up.

So I'm thinking about running the engine raw water cooling circuit over and back. Not sure if my Yanmar will support this, but I'm looking for input from the experts.

Any clues?

Thanks
Chris

sailingdog · #2 (**permalink**) 08-19-2008

That is typically how a marine hot water heater is setup, with the engine cooling water running through the heater's internal heat exchanger. Why you'd be using an inverter to power the thing is beyond me...especially if you're motoring.

Sailormann · #3 (**permalink**) 08-19-2008

If the fittings are on the engine the Yanmar will certainly do it. You loop it into the cooling system. The idea is that when you're underway the engine can provide hot water, and when you're alongside the shore power system does it. Just replaced my heater, but have a Volvo so can't help with the Yanmar situation.

Make sure you check your hoses regularly. We had a some frightening moments when we found water coming in to the boat a couple of weeks ago -took a few minutes to determine that it was coming in through one of the heat exchanger hoses that was underneath the engine and had deteriorated where we couldn't see it.

I'm a little surprised that your heater is wired through your inverter. Doesn't it drain the batteries quickly ?

sander06 · #4 (**permalink**) 08-20-2008

We have an engine-heated hot water system on our boat. I took a look at the plumbing requirements and have decided to yank the engine-heat portion out. Too many possible leak points and we don't need hot water while we're underway. We still have our shorepower hook-up to heat the water for washing dishes.

sailingdog · #5 (**permalink**) 08-20-2008

When you're out cruising, having an engine-heated hotwater solution is a good one, since anchorages and mooring balls generally don't have shore power.

Quote:

Originally Posted by sander06

We have an engine-heated hot water system on our boat. I took a look at the plumbing requirements and have decided to yank the engine-heat portion out. Too many possible leak points and we don't need hot water while we're underway. We still have our shorepower hook-up to heat the water for washing dishes.

capttb · #6 (**permalink**) 08-20-2008

Quote:

We have an engine-heated hot water system on our boat. I took a look at the plumbing requirements and have decided to yank the engine-heat portion out. Too many possible leak points and we don't need hot water while we're underway.

Kinda like removing the heater from your car so it can't leak ? Personally, hot water from a tap at anchor is the difference between cruising and camping in the boat.

robfinora · #7 (**permalink**) 08-20-2008

Chris -

What kind of Yanmar engine do you have? If its raw-water cooled, you may not get enough heat from the raw-water discharge water to heat the water in the tank. Raw-water cooled engines are set (via the thermostat) to run cooler to avoid the salt in the water from crystallizing in the engine block. I have a YSM-12 and it did not get hot enough so I disconnected it form the HW exchange. That is why perhaps the PO set up your system with the inverter....maybe if you run the engine while the inverter is running you can maintain enough charge to keep things going.

- Rob

SteveInMD · #8 (**permalink**) 08-20-2008

I agree. You typically plumb the hotwater heater into the freshwater cooling loop.

Quote:

Originally Posted by robfinora

Chris -

What kind of Yanmar engine do you have? If its raw-water cooled, you may not get enough heat from the raw-water discharge water to heat the water in the tank. Raw-water cooled engines are set (via the thermostat) to run cooler to avoid the salt in the water from crystallizing in the engine block. I have a YSM-12 and it did not get hot enough so I disconnected it form the HW exchange. That is why perhaps the PO set up your system with the inverter....maybe if you run the engine while the inverter is running you can maintain enough charge to keep things going.

- Rob

EO32 · #9 (**permalink**) 08-20-2008

Quote:

Originally Posted by sailingdog

Why you'd be using an inverter to power the thing is beyond me...especially if you're motoring.

It's not hooked up currently, so my inverter is my only choice.

I have a Yanmar 2QM20 and the service manual so it might so the connections in that.

EO32 · #10 (**permalink**) 08-20-2008

Quote:

Originally Posted by Sailormann

I'm a little surprised that your heater is wired through your inverter. Doesn't it drain the batteries quickly ?

Yes is does, and yes I added the inverter and yes I understand the electronics.

The heater is wired to the AC panel and my inverter can be switched over to power the AC circuit.

BTW, it does work, but since I already have a heat exchanger water heater, I might as well hook it up to the motor.