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Old 01-05-2014, 08:16   #16
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Re: heating hot water with engine

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Originally Posted by RunawayC47 View Post
I was told by a major Volvo parts distributor that a thermostat can stop the flow of coolant to the water heater. He said the system works different than what we are accustomed to. He said if the thermostat stayed closed or either the thermostat or tube with small holes was installed backwards there could be no flow.
True, the thermostat on my volvo 2003 which I changed last weekend clearly controls the water flow to the calorifier not the engine temperature.

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Old 01-05-2014, 08:27   #17
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Re: heating hot water with engine

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Originally Posted by djmarchand View Post
First of all, running your propulsion engine at anchor to charge batteries and heat water is not a good idea. Operating for a long time at low load is bad for the engine- carbon build up, glazing of cylinder walls, etc.
I used to hold this opinion too but last year I dove more into it and realized that it's not necessarily true. While you can build up some carbon and glaze the cylinder walls, it's largely an overblown concern. Here is a link to the discussion here, and at Sailboatowners.com and on my blog.

The glazing concern is mainly during the initial break in period. After that it's not that big of an issue.

When running the engine while on anchor you do have a load because the alternator is putting a load on the engine to charge the batteries.

So to the OP, IMO running the engine for an hour a day or so at 1200 RPM or so to charge the batteries and heat up some water is not a big deal and something that cruising boats have been doing for years without ill effect provided to do a couple of things that are advisable anyways. Most significantly, move your boat under engine power often (like maybe once a week) and when you do that bring it up to WOT for a period of that time.

As the water heater manufacturer pointed out to you, the engine might need to run long enough to open the thermostat for water to flow to the heater (depends on the motor and the setup of hosing). So my advice is to get a IR thermometer and read this article. You can then check the hoses with the IR and know when the water is hot enough to turn off the engine.
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Old 01-05-2014, 08:55   #18
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Re: heating hot water with engine

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Originally Posted by JK n Smitty View Post

So to the OP, IMO running the engine for an hour a day or so at 1200 RPM or so to charge the batteries and heat up some water is not a big deal...
Good advice, thanks.

One thing to note: the engine rpms obviously affect the alternator output. I suggest that your battery monitor will and should be able to tell you the alternator output, so often 1200 rpm might give you 25 amps while 1500 will give you 35 or 40 amps. Big difference if you want to minimize run hours when not moving. Check output at different rpms, which will, of course, be affected by house bank size and battery state of charge and acceptance.
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Old 01-05-2014, 09:16   #19
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Re: heating hot water with engine

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That's a very good idea. I use a Sun Shower, just easier to handle.
So do I on the current boat. Works great.

On the next boat (still waiting to close) it has a engine and 120V water heater, but I'm thinking the solar part might be a nice addition. No more showering on deck in a crowded anchorage... Sometimes you get funny looks from folks! The new boat has shower set up in the head

*Side not always use biodegradable soaps when showering aboard. If it goes out into the water its good to be as friendly as you can with no waste water treatment ect. We're on the Great Lakes and love them dearly. It amazes me how many sailors just dump thinks like cleaning chemicals, dish soaps, body soaps and shampoo. There's a lot of chemicals in the "regular" store shelve items that are filtered or caught in the land based wastewater treatment facilities. After all your literally swimming in it when you dive over the side. Thread drift over, sorry*
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Old 01-05-2014, 09:42   #20
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Re: heating hot water with engine

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So do I on the current boat. Works great.

On the next boat (still waiting to close) it has a engine and 120V water heater, but I'm thinking the solar part might be a nice addition. No more showering on deck in a crowded anchorage... Sometimes you get funny looks from folks! The new boat has shower set up in the head
The sunshower heats up on deck. I take it below and hang it on a hook inside on the head door. No reason to have to use a sunshower up on deck, the water's hot already.
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Old 01-05-2014, 09:54   #21
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Re: heating hot water with engine

Technically speaking, running the engine in neutral while charging batteries IS running under a load.

If the batteries don't need charging, the solar shower works great (saving fuel and money). Don't leave it in the sun too long, I got burnt taking a shower from one I left in the sun for over 4 hours.
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Old 01-05-2014, 15:38   #22
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Re: heating hot water with engine

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Technically speaking, running the engine in neutral while charging batteries IS running under a load.
Since it's not zero, technically speaking, it IS a load. However, practically speaking and realistically speaking, it's NOT a load because even a maxed out 150A alternator won't be using more than about 2 or 3 horsepower, less than 10% of what a typical marine diesel is capable of. That's not considered operating it "under load."

I had a discussion with a Northern Lights tech supervisor about my 5.5 kW genset and some problems I'd been having with it. Before he even asked me any questions, he said that I'd been operating it intermittently and at too low a load and that was the reason for my issues. I (rather indignantly) replied that I always operated it for about 2 hours at a time and took care to keep it loaded up to as close to the 30A breaker limit as possible. He said that even 2 hours a day was considered "intermittent use" and since it was a 5.5 kW genset and I was using only a maximum of 30A X 120V = 3600W, that was too low a load so of course I was having problems. Once warmed up, diesel engines DO like to be loaded up to about 80% of their max load for as much of their operating time as possible, so making it a habit to use your main engine just to charge the batteries or make hot water while anchored or moored will shorten the engines life, but who knows by how much? At least that's what the tech supervisor who handled my genset problem said.

It sounds like the OP doesn't have a lot of choice other than a sun shower on days that it happens to be sunny. If my boat didn't have a genset and I wanted some hot water, I'd still probably just operate my engine at the mooring, knowing that since it wasn't under much load it would take quite awhile to open the thermostat to start making hot water, and also knowing that it would be better for my engine to try to plan my hot water usage so I could make the required hot water while actually underway with the engine pushing the boat.
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Old 01-05-2014, 16:31   #23
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Re: heating hot water with engine

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Originally Posted by jtsailjt View Post
Since it's not zero, technically speaking, it IS a load. However, practically speaking and realistically speaking, it's NOT a load because even a maxed out 150A alternator won't be using more than about 2 or 3 horsepower, less than 10% of what a typical marine diesel is capable of. That's not considered operating it "under load."

.........
Faulty thinking. How many HP is the diesel putting out at say 1200 rpm? What percentage of that HP is the alternator? You definitely can hear a 50 hp diesel reduce rpm when you turn the Alternator on. (I usually put a switch in the field wire) A 25 hp even more so.
At any rate, ALL my cruising boats have been alternator charged systems. I don't think I've had any more engine problems than anyone else. Actually... knock on wood!... I've not had any engine problems in sailboats.
I'll agree with JK and Smitty on that one...
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Old 01-05-2014, 17:14   #24
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Re: heating hot water with engine

All you have to do is jut put her in reverse,thats a load
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Old 01-05-2014, 17:29   #25
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Re: heating hot water with engine

I should add, the perfect setup for me was a high output alternator, engine drive water maker and hot water heater. For an hour a day you run the engine, Make up to 25 gal of water, charge the batteries and have hot water until the next am. Simplicity, nothing hanging outside the boat. Cheap. What more could you want?
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Old 01-05-2014, 18:36   #26
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Re: heating hot water with engine

Makes sense to me. I don't plan on a generator.
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Old 01-05-2014, 18:49   #27
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heating hot water with engine

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Originally Posted by jtsailjt View Post
Since it's not zero, technically speaking, it IS a load. However, practically speaking and realistically speaking, it's NOT a load because even a maxed out 150A alternator won't be using more than about 2 or 3 horsepower, less than 10% of what a typical marine diesel is capable of. That's not considered operating it "under load."

I had a discussion with a Northern Lights tech supervisor about my 5.5 kW genset and some problems I'd been having with it. Before he even asked me any questions, he said that I'd been operating it intermittently and at too low a load and that was the reason for my issues. I (rather indignantly) replied that I always operated it for about 2 hours at a time and took care to keep it loaded up to as close to the 30A breaker limit as possible. He said that even 2 hours a day was considered "intermittent use" and since it was a 5.5 kW genset and I was using only a maximum of 30A X 120V = 3600W, that was too low a load so of course I was having problems. Once warmed up, diesel engines DO like to be loaded up to about 80% of their max load for as much of their operating time as possible, so making it a habit to use your main engine just to charge the batteries or make hot water while anchored or moored will shorten the engines life, but who knows by how much? At least that's what the tech supervisor who handled my genset problem said.

It sounds like the OP doesn't have a lot of choice other than a sun shower on days that it happens to be sunny. If my boat didn't have a genset and I wanted some hot water, I'd still probably just operate my engine at the mooring, knowing that since it wasn't under much load it would take quite awhile to open the thermostat to start making hot water, and also knowing that it would be better for my engine to try to plan my hot water usage so I could make the required hot water while actually underway with the engine pushing the boat.

Totally different animal. A genset is not variable speed and has different operation requirements.

As for the putting your transmission in reverse while at anchor, why? That risks unsettling your anchor. Plus show us some evidence of running diesels just for charging batteries being an issue. As discussed on the other threads I provide there are a lot of examples of cruising boats charging their batteries at anchor from their diesels with out issues. In addition to all of the construction equipment that have diesels running at idle for 20-40 hours a week, every week without issue.

Again, the theory that running diesels without load will damage the engine makes sense at first but the evidence is just not there.
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Old 01-05-2014, 19:18   #28
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Re: heating hot water with engine

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Originally Posted by djmarchand View Post

At the very least put the transmission in reverse gear (at anchor) and rev up to at least 1,200 rpm. That will put enough propeller load on the engine to heat it up to operating temperature (open the thermostat) in 10-15 minutes rather than 45 as Seaward says (and they are probably right).

Most high output alternators need at least 1,200 rpm anyway to put out decent amps. If you don't have a high output, externally regulated alternator get one. Otherwise you are pissing into the wind trying to charge batteries with the OEM alternator.

Once the engine starts heating up feel the hose going to your water heater. It should start to get hot and build temperature as the engine warm. It takes about 1 hour of running at these conditions to fully heat a hot water tank.

It doesn't matter whose hot water heater. All of the marine water heaters have the same hot water coil that can be plumbed to the engine and a 120V electric element. You can replace the 120V element with a 12V element if you want to heat water that way. Another way is with an inverter.

David

Pretty much correct. We have high output alt with a Balmar regulator. 900 rpm before the alt runs well; 1100 is better. Under lazy cruising load we see the engine temperature hit 195 after about 15 minutes & 7 knots. The variable pitch prop lets us choose the engine load/boat speed. We have hot water after about an hour of motoring. The 110/220 element is gone; I don't care. The engine/glycol heat loop is a pleasant surprise but mostly unnecessary for us.
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Old 02-05-2014, 05:14   #29
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Re: heating hot water with engine

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Faulty thinking. How many HP is the diesel putting out at say 1200 rpm? What percentage of that HP is the alternator? You definitely can hear a 50 hp diesel reduce rpm when you turn the Alternator on. (I usually put a switch in the field wire) A 25 hp even more so.
At any rate, ALL my cruising boats have been alternator charged systems. I don't think I've had any more engine problems than anyone else. Actually... knock on wood!... I've not had any engine problems in sailboats.
I'll agree with JK and Smitty on that one...
Where's the faulty thinking you refer to? You may think it's OK to operate your diesel engine regularly at low or no loads but that's a whole different issue than an alternator being a "load" for a 50 hp engine. You ask what percentage of that HP is the alternator and actually I even did the math for you in my previous post, 2 or 3 HP or about 10% of a 20 hp engine and even less % for a bigger engine. Using 2 or 3 hp that it takes to run the alternator isn't enough to bring the 50 hp up to its normal operating temp and according to everything I've read, that's not good for the engine when you do it regularly.

There's been a lot of mention of all the time you see diesel trucks idling at truck stops while the driver eats dinner or even spends the night, but that's just where you see them. What you didn't see is the hour after hour every day that they are run at much higher loads before he got to your local truck stop. There's also been mention of commercial fishing boats that operate for many hours at low loads out at sea but that same marine diesel is also run hard for a few hours on the way in and the way out to the fishing grounds. Both of these examples are much different from a sailor on a mooring or at anchor operating his engine at low loads for an hour or two a day and then the engine just sits until he does the same thing the next day, and the next day.

There's also been a lot of talk about "I've been doing that for years and have 3000 hours on my engine with no problem" as if 3000 hours (or even 6000 hours) on a diesel engine is a lot. Yes, a diesel engine will run quite awhile even if it's mistreated but there's a reason why those of us in the boating community tend to think that a diesel engine with 3000 or 4000 hours on the engine is starting to get up there in age, whereas in most other uses, a 3000 hour diesel is considered to be just a baby. You say that you don't think you've had any more engine problems than anyone else but you haven't exactly done a survey to know if that's true and many of those you are comparing yourself to are probably operating their engines similarly to the way you are so of course they have about the same amount of problems you do. But you aren't comparing yourself to the similar diesel engine that is operated at a higher load on a regular basis without any trouble for many times those hours without any trouble. If you did, you'd notice that the life expectancy of a marine diesel in a sailboat is much less than that same diesel engine that was regularly operated as it was designed to be operated, at a higher load and for much longer periods of time between shutting it down.

Luckily for boaters who regularly operate their engines at low loads (low temps) for relatively short periods ( a few hours) without also regularly operating them at high loads, diesel engines are a tough animal to kill so even using it as you describe, it will probably last for many years and there's a good chance that it will even outlast your ownership of the boat, but that doesn't change the fact that it would be better for your diesel engine if you avoided repeatedly running it for any significant length of time at low loads such as is commonly done for making hot water or charging batteries. It would be MUCH better for your engine, after a short warm up period, to leave your mooring and go for an hour or two long cruise with your engine running at about 80% of capacity.
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Old 02-05-2014, 05:38   #30
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Re: heating hot water with engine

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Originally Posted by JK n Smitty View Post
Totally different animal. A genset is not variable speed and has different operation requirements.

As for the putting your transmission in reverse while at anchor, why? That risks unsettling your anchor. Plus show us some evidence of running diesels just for charging batteries being an issue. As discussed on the other threads I provide there are a lot of examples of cruising boats charging their batteries at anchor from their diesels with out issues. In addition to all of the construction equipment that have diesels running at idle for 20-40 hours a week, every week without issue.

Again, the theory that running diesels without load will damage the engine makes sense at first but the evidence is just not there.
The fact that the diesel engine in a genset runs at one consistent speed doesn't make a "completely different animal" at all. It's still a diesel engine that will survive longer if it is regularly run as designed, at operating temperature and for longer periods of time between shutdowns, just like your main engine will.

There are two issues here, low load and short periods of time. It's true that on construction sites you see diesel engines operating for long periods of time at low loads but if you stuck around you'd also see them run at higher loads for a good part of each day. That's different than how we sailors tend to use our engines on the mooring, which is also at low loads the entire time, but also for shorter periods of time between shutdown and starting another cycle of cooldown and veeeerrrrrry gradual warmup the next day. So, your diesel engine on your mooring spends half its running time not even up to its optimum operating temperature and that happens day after day and that's not good for it. I understand why boaters do it and given the space constraints on a sailboats it probably makes sense because it allows you to use the space/weight where a genset would sit for something else, and modern diesel engines will still operate a long time (by boaters standards) before failure, but don't kid yourself that you are doing your engine any favors by operating it that way on a regular basis without also regularly operating it at high loads.

I do agree with you that putting your engine into reverse often isn't a great idea, especially in a crowded anchorage or mooring field because it can result in your boat swinging in a wide arc, or even entire circle, and that can make gelcoat repairs to your boat and your neighbors boat become necessary, not a good thing. Also, while 1200 RPM in reverse will help your engine eventually come up to something at least close to operating temperature, it would be better to warm it up for just a couple of minutes and then take your boat out for a cruise that would allow you to operate your engine up at the temp where it was designed to be operated.
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