Adding engine heat for hot water

[Nomad Willy]

My Willard has that feature and the domestic water gets too hot.

 

[psneeld]

I guess I dont get it, most places I use shower or faucet handles work the same. Right cold, left hot, a little of both, warm. Adjust to pleasure.

If I cant handle that setup, hard to believe the state allows me to drive both a car and boat.

 

[CaptTom]

I guess I dont get it, most places I use shower or faucet handles work the same. Right cold, left hot, a little of both, warm. Adjust to pleasure.

If I cant handle that setup, hard to believe the state allows me to drive both a car and boat.

I'm with you 100% on this. But I went and installed the tempering valve anyway just to shut people up. Also, it extends the hot water at anchor.

I do miss being able to use that really hot water when I need it. I'm always tinkering with my potable water system. The valve may come out at some future upgrade.

 

[wkearney99]

A few engine mechanics have said to me that they do not like to see the engine coolant running to a hot water heater due the possibility of failure of one of these hoses. If you overheat a very expensive diesel engine the cost to rebuild is very high. If you are running a generator anyway like we do in Florida most of the time for air conditioning, they say it is not worth the risk for hot water. Shut off valves might be a consideration to have on the extra coolant lines closed when not needed.

Exactly what happened during delivery of my 47 Eastbay. Coolant loop from starboard engine failed due to a brass elbow at the engine with a valve hung off it. Hose was supported, so it wasn't bearing the entire weight of the valve at the elbow... but still a lesser design than I'd chose.

Upside was the engine immediately reported the alarm and we shut it down. Fortunately this was as we were coming into a marina to refuel AND they had the ELEVEN gallons of C-12 coolant (@$20/gal) necessary to refill the system. Bilge pump work quite well, hardly any sign of the coolant remained, save for the catch pan under the engine itself. Marina shop also had just the right threaded fitting to plug the line at the engine. The trick will be in removing/replacing that without losing too much coolant when the final repair gets done.

We will likely run the generator a lot and I may consider not re-connecting the loop. One less thing to puke out $200+ worth of coolant...

 

[ranger58sb]

A few engine mechanics have said to me that they do not like to see the engine coolant running to a hot water heater due the possibility of failure of one of these hoses. If you overheat a very expensive diesel engine the cost to rebuild is very high.

Our builder apparently routinely did NOT use the extra coolant loop in their models. Perhaps similar as David described about Mainships. (And I don't remember our '87 Mk III usig the loop, either.)

Very good point, but with a proper set up and hoses check, as well as the hot water heater, how high is the risk? I'd hope very low.

If this was really a risk, you wouldn't see heat exchangers in water heaters and boat manufacturers wouldn't manufacture them this way. The risk of a hose breaking is pretty slim if you use quality hose suitable for the purpose and route it in a safe manner.

I'd think risk is low, but... water heater manufacturers wouldn't necessarily care about the risk to a propulsion engine (doubt they could be found liable for a hose-up), and boat manufacturers maybe vary. Different focus from engine manufacturers...

I did once have a hose fail in a water heater coolant loop, and it did drain most of the coolant into the bilge. A support had come undone and the hose fell to where it was chafing on the tiller arm.

Exactly what happened during delivery of my 47 Eastbay. Coolant loop from starboard engine failed due to a brass elbow at the engine with a valve hung off it. Hose was supported, so it wasn't bearing the entire weight of the valve at the elbow... but still a lesser design than I'd chose.

Upside was the engine immediately reported the alarm and we shut it down.

So hose-ups do apparently happen. Probably just a matter of understanding the risks and then deciding whether that's within the comfort zone... or not.

-Chris

 

[wkearney99]

I don't think there's excessive risk to the loop being present. There's already a ton of hoses and fittings involved with heat exchangers and the like. So as long as they're part of a regular maintenance check it would seem reasonable to use them.

What concerns me is the placement of the shutoff valves. Especially if they're for 'hurry up and get it done' winterizing situations. As in, some bilge monkey yanking on the handle in late November. Too much force on the lever translating into excessive torque on the fitting. Do it often enough over a decade and that likely explains how ours failed. That and engine vibration. Always important to make sure all of your shutoff valves are working smoothly and completely open/close.

 

[Ski in NC]

Have seen a couple of engines wrecked due to water heater loops. One a fitting with a valve was cantilevered and broke off at thread roots. Used a brass nipple where it should have been steel, or valve located after a section of hose.

Other one a mechanic changed coolant, and water heater drained too. When refilling, a large air pocket was in water heater and once up at power the air slug moved into engine, air loading the pump. The temp sensor did not sense the heat as the flow had stopped. Finally alarm came on but by then engine was cooked.

On my personal boat with single engine, no loop to water heater. Much cheaper water heater (domestic type) and I run the gennie in the morning and pm anyway. I don't miss the feature.

I do use engine coolant for cabin heat, but on winter runs I use that for hours on end, so pretty valuable. I close the valves off in the spring.

 

[siestakey]

Exactly what happened during

We will likely run the generator a lot and I may consider not re-connecting the loop. One less thing to puke out $200+ worth of coolant...

We eliminated ours because of the same reason engine alarm caught it we shut down turned off the valve and topped off the system.

new water heater going in soon I will remove the old lines to the port engine

 

[Lou_tribal]

Have seen a couple of engines wrecked due to water heater loops. One a fitting with a valve was cantilevered and broke off at thread roots. Used a brass nipple where it should have been steel, or valve located after a section of hose.

Other one a mechanic changed coolant, and water heater drained too. When refilling, a large air pocket was in water heater and once up at power the air slug moved into engine, air loading the pump. The temp sensor did not sense the heat as the flow had stopped. Finally alarm came on but by then engine was cooked.

On my personal boat with single engine, no loop to water heater. Much cheaper water heater (domestic type) and I run the gennie in the morning and pm anyway. I don't miss the feature.

I do use engine coolant for cabin heat, but on winter runs I use that for hours on end, so pretty valuable. I close the valves off in the spring.

Ski,
As I am about to change my heater with a new one what would be your advice to avoid air locking the pump?
I plan to fill up the heater with coolant by gravity feeding it, any other thing I should be careful with?
Also I will add shutoff valve at the engine block, as the block is cast iron what type of fittings are the best, steel, brass, bronze?
I will replace the engine fittings as they show some sign of aging.
Lastly if I put shutoff valve will the coolant bypass internally or do I need to add a loop between in/out coolant fitting on the engine?
And for hoses, regular rubber hose for coolant? Silicon hoses? Any advice for these?

Sorry for the slight thread hijack

L

 

[FF]

One advantage to plumbing the coolant from the noisemaker is the electric can be used at the same time if guests have large demands, usually for showers.

 

[wkearney99]

Ski,
As I am about to change my heater with a new one what would be your advice to avoid air locking the pump?
I plan to fill up the heater with coolant by gravity feeding it, any other thing I should be careful with?
Also I will add shutoff valve at the engine block, as the block is cast iron what type of fittings are the best, steel, brass, bronze?
I will replace the engine fittings as they show some sign of aging.
Lastly if I put shutoff valve will the coolant bypass internally or do I need to add a loop between in/out coolant fitting on the engine?
And for hoses, regular rubber hose for coolant? Silicon hoses? Any advice for these?

Sorry for the slight thread hijack

I'm sure it'll vary by engine but I think most have ports for this that are normally blocked, so you don't necessarily have to bypass anything. Mine has shut off valves at the engine for both the in and out flows.

Where you often want a bypass is mounted ON the actual potable water fittings of the water heater tank. Bypass the cold input over to the hot output and then drain the heater tank. This allows saving quite a lot of antifreeze for the winter. No sense in putting that many gallons of pink into it, provided you drain it completely. I typically bypass the tank, winterize the system, and then re-open the bypass to run a bit into it.

Putting in a bypass on the engine coolant would seem like unnecessary overkill unless the coolant system design required it.

 

[Airstream345]

Hmmm, we have a loop off the port engine which is used for the Hurricane hydronic heater and the Hurricane loops through the hot water heater.

I'll be sure to quadruple check the hoses and fittings as part of regular maintenance and checks.