# Water Heater heat exchanger hook up question



## EO32 (Jan 7, 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 (Mar 19, 2006)

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.


----------



## TSOJOURNER (Dec 16, 1999)

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 (Sep 18, 2003)

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 (Mar 19, 2006)

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. 


sander06 said:


> 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 (Dec 13, 2003)

> 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 (Apr 25, 2001)

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 (May 11, 2007)

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



robfinora said:


> 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 (Jan 7, 2008)

sailingdog said:


> 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 (Jan 7, 2008)

Sailormann said:


> 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.


----------



## robfinora (Apr 25, 2001)

Chris - It looks like you have a closed-loop cooling system with an exchanger. You should be fine. This is easy: The cooling line coming off the engine head that runs to the exchanger is going to be the line you tap into. Redirect this line from the head to first run through the hot water tank loop and then from the hot water tank to the raw-water heat exchanger. So you are just adding 1 hose to the system and its still a closed system when you are done. Again - the cooling line from the head connects to one of the fittings on the tank (either one)....a new hose is added from the other fitting on the tank to where the head-cooling line was previously connected on the exchanger. You are going to loose antifreeze when removing the lines so make sure you catch and replace any lost fluids....also you may need more now that you added hose to your closed system. Also - your tank should be mounted at about the same level as the engine so the flow of water through these lines is consistent.

I would recommend getting a manual for your engine so you can see exactly what i am talking about. Try this link for an online version:
http://www.gomarine.dk/files/QM-QMOperationManual_3.pdf

Good luck- Rob


----------



## SteveInMD (May 11, 2007)

Once you add the antifreeze loop to the heater it can be hard to remove air from this loop if it's higher than the motor. It can be done, but you may have to add a T and valve to let the air out.


----------



## TSOJOURNER (Dec 16, 1999)

Since others have said you have a closed loop coolant on this Yanmar, (I'm not familiar with that model) it is just a matter of connecting the plumbing as described above by Rob. For anyone who has a similar situation with a raw water cooled engine, sure, the engine runs cooler than antifreeze cooled engines. That means your water will not get as hot. But the thermostat on the water heater will shut down at the normal temp (I think 140 F) and it will take a lot less battery to heat water from 100 to 140 than it does to heat from 70 to 140! If you don't use the inverter, warm water is better than cold when you wash up. And by the way, if you have the closed loop cooling system, be careful of the hot water! I think my Perkins diesel runs at 180 degrees, so after several hours of run time my hot water is REALLY hot!


----------



## EO32 (Jan 7, 2008)

I have the 2QM20(h) which does not have a fresh water cooling system.

I do have the service manual, but it's on the boat now. I was down at the boat the other day replacing the rear motor mounts when I noticed the connections on the hot water tank and that got me thinking about hooking it up.


----------



## robfinora (Apr 25, 2001)

Chris - tough call then. It also depends on how you use your boat. If you run the AC to heat the tank...depending on conditions, it could stay hot for 24 hours. Raw water running through the hot water exchanger is going to take a very long time to get warm. I had mine connected for a while and then disconnected as I didn't want all the extra and unnecessary lines that could just over complicate my cooling system.

- Rob


----------



## camaraderie (May 22, 2002)

You need to add shut off valves to the hose at the exchanger connections. This way... if the hose or heater busts a leak, you close the valve and refill your coolant and motor on.


----------



## EO32 (Jan 7, 2008)

I'm going to look to see if there are connection points on the motor. If so, then for a few bucks I can run lines over and back and see what I get.

I really only need about 110 degree water once a day, which I can get to in about 10 min of Inverter running while the Alternator "tries" to keep up (Yes. I realize that 1200 watts = 100 amps) but running the motor for 20 min makes up the loss.

On our last and first overnighters, I found we would run the motor in the morning to get out into wind, then run it again when coming up to anchor, so we would have hot water at those times.


----------



## robfinora (Apr 25, 2001)

Chris - You will not find any connection points on the motor - you will need to tap into the line as I described above - that is the point where you will find the hotest water. Try it out and let us know how you do.....you may get it.


----------



## EO32 (Jan 7, 2008)

Piece of cake.

My Yanmar has a 3/4" ID tube going from the head to the mixing elbow via a thermostat. When the motor gets to 42c it opens and settles at 52c.

These are right on top of the front of the motor.

I should be able to run from there to my water heater and back. I'm not putting in any shut offs, because I never want this shut off by accident.

I am going to put a nipple/nipple union in so I can bypass easily for winterizing or failure.

Endless Hot water here we come.

Chris


----------



## TSOJOURNER (Dec 16, 1999)

My engine is raw water cooled. The heat exchanger sems to do a fair job of heting the water - although we've only tried it a couple of times to deteremine if it does work. We are on fresh water. It may be that our engine thermostat is set a bit higher than might be the case in salt water. Or perhaps Volvos run hotter than Yanmars ....


----------



## TSOJOURNER (Dec 16, 1999)

> I should be able to run from there to my water heater and back.


If you ran a hose between the two then you wouldn't have to scoot around all the time...


----------



## EO32 (Jan 7, 2008)

Sailormann said:


> If you ran a hose between the two then you wouldn't have to scoot around all the time...


Plus burning yourself slopping pans of hot water between the two.



Sailormann said:


> The heat exchanger seems to do a fair job of heating the water - although we've only tried it a couple of times to deteremine if it does work.


I don't have success yet. But 52c is a hell of a lot hotter than 90f. If I can heat up the motor, heat up the water and wait for the wind to heat up, it's one more thing off the "make this work" list.

I'll take some pic's of the setup so you can see how easy (he say's before it's done) it is.


----------



## SteveInMD (May 11, 2007)

Chris -

The most difficult part of the job may be removing the air-lock from the coolant loop. On some boats it's easy and on others it can take hours. Good luck.


----------



## PBzeer (Nov 11, 2002)

Running the hot water heater as you run the motor prior to anchoring would seem to be one way of approaching the situation. If the WH is in decent shape, it should keep the water hot enough until you're ready to use it. I have a hookup for the heat exchanger on my boat, but it doesn't get the water much past tepid (raw-water cooled Yanmar).


----------



## gc1111 (May 13, 2004)

I have a Raritan heater and a Westerbeke 4-107 engine. The heater installation recommendation for the engine heat is the only valid use for a gate valve on a boat that I have seen. 
Because the engine cooling water gets too hot to use for domestic hot water, you can control this by installing two tee's with a gate valve between them. Put this into the engine cooling line running to the heat exchanger. Run hoses from the tees to the hotwater heater. Now you control the amount of water flowing through the heater by the amount the gate valve is closed. Just watch out for the fittings - they get hot!!
Also the install instructions recommend a direction of flow for the engine water (I have forgotten which direction now). I think this partly addresses the issue of clearing any air bubbles from the lines. But I also had to install a tee with a plug in the branch into the top hose going into the heater since it is higher than the engine. When changing coolant I can crack open the plug to let the air out.


----------



## deniseO30 (Nov 27, 2006)

Replaced the Raritain for an atwood on my boat about a week ago. I've a Universal diesel, the hoses are 3/4 ID the connections to the new at wood are 5/8 id, other then that and and burping the air from the lines from the Htex loop it works great. Don't forget to be sure the water heater is secure because when it has water in it it's heavy 6 gallons alone are close to 60 lbs.


----------



## EO32 (Jan 7, 2008)

I am not tapping into a closed system, so there is no need to worry about air in the lines.

I had thought about a bypass valve, but 52c is 125f which is perfect temp. A little too hot, but with losses in the hot water heat exchanger it should be fine.

The tank is original and mounted about 50 inches from the engine in the sail bin, but the heat exchange was never hooked up.


----------



## SteveInMD (May 11, 2007)

I must have missed something. I though you said you did have freshwater cooling. Maybe you mean freshwater cooling as in the lake.


----------



## EO32 (Jan 7, 2008)

Thanks for all the input. I picked up all the parts yesterday and should be able to put them in tomorrow.



SteveInMD said:


> I must have missed something. I though you said you did have freshwater cooling. Maybe you mean freshwater cooling as in the lake.


I am in fresh water, but I thought I was clear.



EO32 said:


> 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.





EO32 said:


> I have the 2QM20(h) which does not have a fresh water cooling system.


Chris


----------



## SailorByFate (Feb 6, 2007)

gc1111 said:


> Because the engine cooling water gets too hot to use for domestic hot water, you can control this by installing two tee's with a gate valve between them. Put this into the engine cooling line running to the heat exchanger. Run hoses from the tees to the hotwater heater. Now you control the amount of water flowing through the heater by the amount the gate valve is closed. Just watch out for the fittings - they get hot!!


In my home hot water system, I plumbed in a thermostatic mixing valve that allows me to turn up the water heater as high as I want, but limits the temperature to 120 degrees at the tap by mixing in some cold water. A higher tank temperature effectively gives me more gallons of hot water.

As I recall, the valve was less than $100.

I plan to do the same thing when we convert to engine-heated water on our sailboat.


----------



## Trekka (Jul 16, 2006)

gc1111 said:


> I have a Raritan heater and a Westerbeke 4-107 engine.


I'd love to know more about exactly where and how you tapped off of that engine - and returned flow back to it after the water tank run. I have a 4-107 and believe the PO did a poor kludge job of it. If you could be very specific, even take some pictures, I'd be very grateful.

Thanks


----------



## gc1111 (May 13, 2004)

Here are some pictures of my heater install plumbing. The flow is from left to right. It comes off the exhaust manifold, through the tee-gate-tee setup and exits on the right side to the main heat exchanger. I'm in a bit of a rush now so I don't have time to annotate the pics, but ask any questions you have.


----------



## Pub911 (Oct 25, 2007)

ok, i was going to remain quiet, but now you have me worried. Is that water heater upside-down? That's just what made me type....the rest of the thread is a little concerning, too. Be VERY careful if you're going to interrupt the engine's "fresh water" cooling cicuit - that's the one with antifreeze in it - not the one that takes in 'fresh' lake water. If you block the flow of that cicuit, you could overheat, and BLOW YOUR ENGINE. This can happen very easily due to air in the new hoses, as mentioned above.

Now, if what you're doing is interrupting the 'raw water' circuit - the one that suck water from the outside of the boat - there is also risk. The risk of using THIS circuit is that salt-water, to the extent you boat floats in it, MAY corrode the guts of your water heater. If this happens, you could end up pouring raw water into your bilge at a rate that overcomes your bilge pump. The potential result? - glug glug glug, bye-bye boat.

Happy to clarify if you wish.


----------



## Trekka (Jul 16, 2006)

gc1111 said:


> Here are some pictures of my heater install plumbing. The flow is from left to right. It comes off the exhaust manifold, through the tee-gate-tee setup and exits on the right side to the main heat exchanger.


Ok, I think I see what you're doing. And your Perkins somewhat resembles mine - which helps! (I've seen _so_ _many_ variations so unlike each other). I'm on the boat tomorrow so I will look at what I might do. The PO had a tap off the top of the block near the back which I think is where the temp sensor alone was supposed to be. I disconnected the hose and closed off the tap when I took the hot water system out. Plumbing was so weird I decided to start over rather than fix what he had done. I like that you are diverting the main flow and then returning it just a few inches down the path. I guess if you turn the gate valve to "open" that the full flow pretty much goes direct to the heat exchanger? Do you screw it down to full "close" for the bypass or only partly?


----------



## Sapperwhite (Oct 21, 2006)

Pub911 said:


> ....the rest of the thread is a little concerning, too. Be VERY careful if you're going to interrupt the engine's "fresh water" cooling cicuit - that's the one with antifreeze in it - not the one that takes in 'fresh' lake water. If you block the flow of that cicuit, you could overheat, and BLOW YOUR ENGINE. This can happen very easily due to air in the new hoses, as mentioned above.....


This isn't a big issue. When you plumb a water heater into the fresh water side from the engines heat exchanger YOU DO GET AIR in the system. The plumbing and heater were dry, so you can expect quite a bit of air actually. Just run the engine for a few minutes to draw antifreeze/water mix into the system, then top off with more antifreeze/water mix. Repeat as nessecary. Get to the point where you are maintaining a normal cold level in the heat exchanger with the engine and heat exchanger actually cold. I do this every so often with maintenance like freshwater pump impeller change (get lots of air in every time).

Hopefully someone would respond to the overheat audible alarm and indicator lamp (provided you have that) before you "BLOW YOUR ENGINE".


----------



## gc1111 (May 13, 2004)

Pub911 said:


> ok, i was going to remain quiet, but now you have me worried. Is that water heater upside-down?


I wondered if anyone would pick that up. No the heater is right side up, just the access cover plate is upside down. I did that at one time because I had trouble getting a screwdriver at the screw holding in on. But since then I have changed other things and that is no longer a problem.


----------



## gc1111 (May 13, 2004)

> I like that you are diverting the main flow and then returning it just a few inches down the path. I guess if you turn the gate valve to "open" that the full flow pretty much goes direct to the heat exchanger? Do you screw it down to full "close" for the bypass or only partly?


If I recall the install instructions correctly, start with the valve full open, bring the engine up to operating temp, then close the valve and watch the engine temp. When/if the temp rises, back off a little. Then keep an eye on it under usual operating conditions. If the engine runs hot, open the valve a little. Just remember that it is HOT at that point.

It takes relatively little flow to heat the water in the heater. More flow just increases the rate of temp recovery when new water is drawn in or at first engine start.


----------

