Isotemp unit drained for winter, shut off engine coolant feed ?

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Meagain

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Hi all
I’m going to drain my isotemp water unit for winter, but will still go out a few more times before it gets cold. Do I need to shut off the engine coolant circuit going into the water unit or is it ok to leave coolant flowing through heating the elements ?
Many thanks
 
It totally doesn’t matter either way. Just take the opportunity to exercise the valves. I would leave them open so the heating coil gets flushed with use, but really it just doesn’t matter.
Remember to turn off the electric element at the breaker and tape it in the off position!
 
I'd shut the engine coolant circuit off, and never open it again.
That's what I did also in my boat right after buying her, because in my experience most of nautical boiler failures are one way or another related to that.
Circulating water at 80+ degrees inside a boiler doesn't make any sense, and unless you use your boat with neither dock nor genset AC supply for longish periods, the electrical heating (which I set around 50deg) is more than enough to guarantee an adequate supply of hot water.
 
MapisM said:
I'd shut the engine coolant circuit off, and never open it again.
That's what I did also in my boat right after buying her, because in my experience most of nautical boiler failures are one way or another related to that.
Circulating water at 80+ degrees inside a boiler doesn't make any sense, and unless you use your boat with neither dock nor genset AC supply for longish periods, the electrical heating (which I set around 50deg) is more than enough to guarantee an adequate supply of hot water.
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Not sure I understand your logic in isolating permantly , would have thought it double ups as a heat sink for one of the engines, plus the benefit of hot water , also 50 deg water temp can allow legionnaires bacteria to survive but not multi ply
 
Thanks all, at this stage I’ll drain the system & disconnect the electric heater while trying to enjoy the last blast of the season! . MapisM I rarely use shore power as we haven’t owned her long and she doesn’t have a galvanic isolator fitted (next job!).
 
dj43 said:
Not sure I understand your logic in isolating permantly , would have thought it double ups as a heat sink for one of the engines, plus the benefit of hot water , also 50 deg water temp can allow legionnaires bacteria to survive but not multi ply
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Well, you can set also the electric heating higher than 50 deg, if you wish.
But I don't think you keep your home boiler at 80+ deg anyway, do you?

Regardless, the double use as heat sink for one engine is precisely where these nautical boilers are intrinsically flawed.

Lets forget the possible benefit of having hot water 24/7 during passages measured in days (if not weeks) rather than hours, because that's a totally unrealistic scenario for the overwhelming majority of moboers.
And for us mere mortals, it's sufficient one night at anchor to lose the benefit of arriving in a spot with the water already warm, and after running out of hot water, you'd rather turn on the genset than the main, obviously.

Anyway, from the engine viewpoint, it doesn't make sense to cool it a bit more or a bit less depending on the hot water usage onboard, and regardless of whether it's already warmed up or not.
Not that I think the short path where cooling liquid goes through the boiler makes a meaningful difference, mind.
But as an engine heat sink, it's pointless by design, so to speak.
 
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Meagain said:
MapisM I rarely use shore power as we haven’t owned her long and she doesn’t have a galvanic isolator fitted (next job!).
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All well and good, but do you keep moving each and every day?
As I previously said, while anchored I would turn the genset on (hence the electrical heater) rather than the engine...
 
Im not getting the turn off the engine water heating permanently either. Here on the west coast of Scotland we regularly hop from one anchorage to another on a daily basis, maybe dropping into a marina every 3 or 4 days or so to replenish water tanks, replenish supplies, dump rubbish & for everyone to take a shower. The water heated from the engine is usually enough for everyone to get washed & dishes washed & the occasional shower, usually taken whilst on the move at displacement speed which means we still have hot water for general use when we arrive.
 
Well, I still hate hot water hoses+joints all around the boat filled with very high temperature water, hence exposed to premature failures/leaks.
But that's me, of course.
 
MapisM said:
Well, you can set also the electric heating higher than 50 deg, if you wish.
But I don't think you keep your home boiler at 80+ deg anyway, do you?

Regardless, the double use as heat sink for one engine is precisely where these nautical boilers are intrinsically flawed.

Lets forget the possible benefit of having hot water 24/7 during passages measured in days (if not weeks) rather than hours, because that's a totally unrealistic scenario for the overwhelming majority of moboers.
And for us mere mortals, it's sufficient one night at anchor to lose the benefit of arriving in a spot with the water already warm, and after running out of hot water, you'd rather turn on the genset than the main, obviously.

Anyway, from the engine viewpoint, it doesn't make sense to cool it a bit more or a bit less depending on the hot water usage onboard, and regardless of whether it's already warmed up or not.
Not that I think the short path where cooling liquid goes through the boiler makes a meaningful difference, mind.
But as an engine heat sink, it's pointless by design, so to speak.
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Here in the uk we do run our heating appliances at 75deg plus , to heat hot water, that is regulated around 60 deg,
Also we don't tend to stay at anchor for any length of time , due to our wonderful weather, in my experience anyway , and are always glad of the hot water when we stop to have a shower to warm up :)
 
Exactly. Hotter water in the tank is not only cleaner but you in effect have a greater volume of it (I mean more total showering time, and super helpful if you have a bathtub).

@mm on reliability, in 20 years of boating I have never had a failure of the engine coolant heating loop. I have had failures of electric heating elements though :)
 
Beamishken said:
Have you never heard of thermostatic mixers?
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I didn't want to dig further into these technicalities, but yes, I have.
Otoh, I've also owned (and seen) several boats without it.
In fact, I'd be curious to hear how many folks know whether they have it on their boat or not, and if yes where it is and at which temp it's regulated.

Anyhow, by the same token, may I ask if you ever heard of pressure limiters, expansion vases, relief valves, drain pumps?
If you wish to keep water in the boiler at very high temp (which btw is something you can do also with the electric heater anyhow, so we are a bit at cross-purposes now vs. dual heating through engine), they are all components that should be included in a kosher installation.
Unless you accept to have water constantly leaking in the bilge, that is (I don't).

Btw, in my current boat I've got all the above bits, thermostatic mixer included, but I consider them as unnecessary complications, being a fan of the principle that the only bit you will never break on a boat is the one you don't have.
That's why I keep the engine feed permanently closed, the electric heater at 50 deg, and the thermostatic mixer at 40 deg.
As a result, I never have any water out of the relief valve, and the drain pump only runs when I remember to test it, since its box is always bone dry. :encouragement:
 
jfm said:
@mm on reliability, in 20 years of boating I have never had a failure of the engine coolant heating loop. I have had failures of electric heating elements though :)
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Good for you J, but I suspect that this has also something to see with the fact that you often owned brand new boats, and you didn't keep them for long.
Anyhow, I never said that the electric heater is more reliable than the engine loop.
Otoh, while you can live without the latter, you can't live without the first, for very obvious reasons.

Besides, trust me, a sudden hose failure in the heating loop while the engine is running and its cooling circuit is hot and pressurized is something you don't want to experience.
Not that I did first hand (thanks God!), but I saw the aftermath of such occurrence in the e/r of an old neighbor boat, 15 years ago or so.
And it wasn't a pretty sight, on top of the disabled engine!
Btw, the yard who made the repair assured me that they saw it happening several other times.
I always kept engine heating loop shut on my boats since then - and never missed it for one minute.

Then again, I'm not cruising in Scotland, so I appreciate that it might be a convenient feature for other boaters!
 
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MapisM said:
Besides, trust me, a sudden hose failure in the heating loop while the engine is running and its cooling circuit is hot and pressurized is something you don't want to experience.
Not that I did first hand (thanks God!), but I saw the aftermath of such occurrence in the e/r of an old neighbor boat, 15 years ago or so.
And it wasn't a pretty sight, on top of the disabled engine!
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What damage did it do?
 
Not much real damage actually, but cleaning the e/r mess took the yard 2 full days, IIRC.
And you could still find blue drops in some corners also after the thorough cleaning, if you looked carefully.

When I mentioned the disabled engine, it's just because in that silly installation the rubber hoses were directly connected to the engines with no valves, so they had to come back with the other engine alone.
Luckily, they had an e/r camera and when the image got blurred they realized that there was something wrong and went down to check.
Otherwise, they would have risked an overheat as well.

Coming to think of it, that's one of the things pretty high in my "nice to have" list, too.
I must find the time and mood to fit it, sooner or later... :o
 
I doubt there is much greater chance of the water heater hoses failing than any other of the many water hoses on the engine. Certainly on my boat the hoses to the water heater are a far thicker wall thickness than the origional engine coolant hoses.
In all my years boating I've never seen a water heater hose burst either & my boats tend to be significantly older than JFM's boats.
Disabling a usefull function in the hope it prevents a failiure is probably not reducing your overall likelyhood of a problem by a very high percentage given all the other dozens of items that can fail on a boat engine working hard.
 
Beamishken said:
Disabling a usefull function in the hope it prevents a failiure
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Non sequitur: preventing this particular failure is clearly a certainty rather than a hope, if like in my boat you've got valves directly screwed on the engine outlets/inlets of the heating loop, and you keep them closed.
And as I said, the usefulness of the disabled function is absolutely none, with my type of boating.
I already acknowledged that this can be different for yourself and/or other boaters, though.
Can't see why you shouldn't accept that it's different for me too.

Lastly, of course I agree that there are dozens of other possible problem sources on a boat engine - that's stating the obvious.
But I don't think there's any way to get rid of them all, other than give up boating altogether.
To get rid of this one, I just had to close a couple of valves, with zero drawbacks (for me).
Pretty much a no brainer: unlikely as it might be this problem (but tell that to the chap who experienced it in open sea!) it still means dozens minus one... :encouragement:
 
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