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  #1   IP: 71.16.159.194
Old 09-17-2007, 02:06 PM
Jesse Delanoy Jesse Delanoy is offline
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re-plumbing for hot water heater operation

I purchased a Moyer-rebuilt Atomic Four at the end of last season, about a year ago, and had it installed in my 1977 Catalina 30, replacing a thirty-year old original engine that finally gave up the ghost. Getting somewhat cocky with such a well-functioning engine, I decided to follow Donís instructions on re-plumbing the raw-water cooled engine to provide hot water to the heater core in my hot water heater. Since Iíve owned the boat, the water heater has never been connected to the engine, so it has only functioned electrically, when plugged into shore power. This means that on cruises, we only get hot water for the first day or so, and then a series of cold showers (not always a bad thing on Chesapeake Bay in the summer!).

Shortly after completing the project, we embarked on a two-week cruise. I thought I would write up a report on the performance, for anyone considering the change, and pose some questions that have arisen. See Donís FAQ No. 19, under Cooling System for details about the plumbing.

Prior to the modification, the engine ran at about 172 degrees under load, fully warmed up, just under 2000 rpms, with very little fluctuation up and down due to nominal thermostat operation. I interpret this to be just slightly above optimal 160 - 170 degree range, and completely acceptable.

The modification worked quite well. We had hot or warm water at all times during our trip.

As expected, the plumbing change makes the engine run hotter, due to the added resistance in the cooling water line. As Don instructs, I installed a ball valve in the bypass line, to restrict the bypass water a bit, so as to run more water through the engine block, and keep it cool. However, I found that I have to keep the ball valve virtually closed to get the engine back down to about 172 at 1700 - 1800 rpm, and it rises to 180 degrees at 2000 rpm, which is my hull-speed cruising power setting. The note in Donís FAQ about not closing the ball valve too far, to avoid overcooling, is a non-issue.

In addition, I note that the amount of water exiting the stern of the boat is reduced significantly, and there is a notable amount of steam exiting the exhaust port in its place. I attribute this to the fact that, without the cooler bypass water being reintroduced into the manifold, much of the water is raised above the boiling point in the exhaust line, and exists as steam rather than liquid water.

At this point, my question then is: Since Iíve already blocked off my bypass, and the engine is still running somewhat above optimum temperature, am I better off just blocking off the bypass entirely and removing the thermostat, and letting all of the water pass through the block unimpeded? Iím aware that this might cause overcooling, as I ran an engine this way for a full season (at about 140 degrees) before I realized that there was no thermostat installed. If this is the case, I could re-install the ball valve in the cooling water line upstream or downstream from the block, to create some restriction and force the temperature back up to a proper level.

Assuming that overcooling can be controlled this way, are there any other problems that could occur with this configuration? Is the steam exiting the exhaust an indication that the bypass water needs to be restored? Perhaps if the overall system is cooled (if indeed it is), by removal of the thermostat, and warmed up to the minimum acceptable operating temperature by use of the ball valve, the steam condition may resolve itself.

Iíd hate to have to go back to taking cold showers.

As always, I appreciate any thoughts by Don and others.

Jesse Delanoy
s/v Agapť
Baltimore
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  #2   IP: 38.118.52.41
Old 09-18-2007, 06:44 AM
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Jesse,

As soon as Brenda wakes up, I'll ask her to scan a sketch of this plumbing modification which should assist folks in better understanding what we're talking about. Meanwhile, I'm attaching a "text-only" set of instructions in case anyone has a problem accessing our FAQ.

In a nutshell, I interpret the reduced water flow out of the exhaust and the steam you're observing with the ball valve closed (step 7 & 8) to be clear indications of a restriction somewhere that is limiting the amount of water entering through the "T" fitting, or through the hot water heater itself, or (perhaps more likely) that the thermostat is not be opening normally.

I would follow through with your instinct to remove the thermostat and then see what effect this action has on temperature and the function of the ball valve. If you can force the engine into an overcooling condition by closing down on the ball valve, it would seem to me that it would confirm the lack of a restriction anywhere in your system and finger the thermostat.

Don
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File Type: pdf Replumbing raw water engines for hot water heater.pdf (10.0 KB, 1572 views)
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  #3   IP: 71.16.159.194
Old 09-18-2007, 09:16 AM
Jesse Delanoy Jesse Delanoy is offline
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Thanks, I'll give it a try. I don't think there is a restriction in the hot water heater since, before I did the re-plumbing, I hooked a garden hose up to the intake and ran water through the system, just to make sure of this very point. The water appeared to exit the water heater outflow hose normally, i.e. at about the same rate as the garden hose.
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  #4   IP: 66.161.32.165
Old 09-18-2007, 10:36 AM
luvmyi36 luvmyi36 is offline
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somewhat related question....

This is a very interesting topic. Raised a couple questions for me as I do not have a water heater now, but have kicked it around. Do you actually use the water that runs through the engine? Or is there a heat exchanger in your heater that uses the heat of the engine water to heat fresh water? Just curious.
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  #5   IP: 71.16.159.194
Old 09-18-2007, 11:31 AM
Jesse Delanoy Jesse Delanoy is offline
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I have a 5 gallon hot water heater in my cockpit seat locker. It heats the water in the tank electrically, when plugged into shore power (and will keep the water hot for an indefinite period when disconnected). It has hoses to connect to the hot water exiting my engine. These hoses lead to a heater core in the device, which heats up the fresh water in the hot water tank when engine exhaust water is run through them. As hot water is used, it is replaced by cold fresh water from my pressure water system. Without some way to heat the water while under way, there would be no hot water once the initial five gallons was used up.
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  #6   IP: 66.161.32.165
Old 09-18-2007, 01:35 PM
luvmyi36 luvmyi36 is offline
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Very nice Jesse. Thank you for the response. I am clear as a bell now!
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  #7   IP: 38.118.52.41
Old 09-22-2007, 09:40 PM
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Jesse,

Here is the schematic I promised to add to your thread when Brenda woke up. Clearly, sheís a late sleeper.

Don
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  #8   IP: 70.90.87.69
Old 04-17-2008, 12:34 PM
Jesse Delanoy Jesse Delanoy is offline
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After having had the winter to think things over (and discuss them with the Admiral), and testing my thermostat in a pan of water on the stove (it seems to work fine), I've decided to abandon the plumbing modification, and I have returned the engine to its standard plumbing configuration, and reinstalled the thermostat.

However, not liking to have things around that don't function, I'm still kicking around ideas about how to use hot engine water to heat up my water heater while under way. I had the following thought that I put out for comment:

Suppose I intercept the hot water where it exits the rear of the manifold, and using an arrangement of ball valves create a situation where I can divert the water into my hot water heater core, or alternatively let it go directly through the anti-siphon valve, water lift muffler, and out the rear of the boat.

It seems to me that, with this kind of arrangement, I can select at any time whether I want to run hot engine water through the water heater, to warm up my shower water (knowing that the engine will run warm as I do this), or whether I want the engine water to exit the boat normally, bypassing the water heater and keeping the engine within a nominal temperature range.

Under this arrangement, I can use engine water to heat the water heater only during the limited times when I want to (and can probably keep the engine temperature under control during such times by limiting cruising speed), and not have the overheating issue during the majority of the time when I don't care if I'm heating shower water or not. This way, I hopefully would not have to put a restriction on the bypass to keep the engine running cooler while cruising at speed, and would not have the problem of too much steam and too little water flowing through the exhaust.

I welcome anybody's comments or observations on this thought. As always, thanks.

Jesse Delanoy
s/v Agape
Baltimore
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  #9   IP: 75.40.230.184
Old 04-19-2008, 07:18 AM
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Another idea

My idea for hot water is to have a completely separate system, so a failure in the hot-water system does not effect the supply of engine cooling water.

What I was thinking was to use copper tubing wrapped around the hot portion of the exhaust and a small electric pump. I haven't started on this project, so if anyone does something similiar I would very much like to hear about it.

Mike

Last edited by marthur; 04-19-2008 at 07:22 AM. Reason: clarity
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  #10   IP: 38.102.16.123
Old 04-19-2008, 05:27 PM
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Hi, Mike:

Unless you are aware of some commercial application of the idea which would serve as "proof of principle," the mechanical engineer in me says this is not something I'd set out to invent.

The traditional exchanger (with one tube nested inside the other and the flows in the two tubes opposing one another) goes back a hundred years, or at least as far as my ninth grade chemistry class (not sure what predates what). Managing the heat transfer in your model is going to be a bear. Too much and you'll be generating steam, and you'll have to worry about dangerously high pressure and temperature. Too little and you wasted your time.

I'd discourage you, especially in the face of long proven technology. I can't shake the vision of things melting, hoses blowing off fittings, steam and scalding water all over the place, etc.

HTH.

Bill
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  #11   IP: 75.40.230.139
Old 04-21-2008, 08:05 PM
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Your points are well taken, Bill.
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