Electrical--need opinions

[Scott Rosen]

I'm looking for a way to run my hotwater heater while at anchor. I have a five gallon hot water heater which runs from shoreside power (110ac), and also runs off the engine fresh-water cooling side. Unfortunately, the engine doesn't get hot enough to heat the water, unless it is under a load. That means that when I'm at anchor, I can't heat the water because I can't run the engine under load.

I had one thought. Install an inverter just large enough to handle the wattage of the hotwater heater. I have large batteries, and could run the engine to charge them in any event.

Why do I care about this? My wife's enjoyment of cruising is greatly enhanced by hot showers. When she's happy, I'm happy.

[mmd]

I'd go with the inverter. Do a load calc to see if you have enough battery capacity to deal with the extra load without having to run the engine too often, and add another battery if needed.

[TomRobb]

You have to move a lot of electrons to heat anything - water included. If you have to burn fuel to run the engine to spin the generator to push electrons around, why not save all those energy conversion losses and use the fuel to heat the water directly?
Does anyone make a gas or diesel burning water heater? Surely if you can burn diesel in a stove, you can burn it in a water heater.

[Dave R]

Just a question. Probably not much help for your question which I think mmd answered nicely.

Anyway, could you use a solar water heater to to heat water during the day which could then be stored in your water heater tank. At the very least, it could reduce the electrical energy required to make your wife happy.

I am thinking of a box that might be stowable which could be laid out on dack and attached to the water supply into the water heater with some sort of quick connect fittings.

[Tom Lathrop]

I'm with Tom Robb. Fuel to engine to alternator to batteries to resistance elements to BTU's is a very inefficient way to get hot water, not to mention the noise and extra wear on the engine. A flame water heater is a far more efficient and faster way to heat water.

[Scott Rosen]

I appreciate the inefficiency of using an inverter. But I already have my hotwater heater installed and working. My boat is relatively small, and the amount of hot water is even smaller. It takes about 5 to 10 minutes to heat the tank and it stays hot with no futher electricity for 24 hours or so. So I'd probably be running the inverter for no more than 10 to 20 minutes every 2 days, at most. My electrical use is extremely small--lights, water and bilge pumps, nav--and my battery capacity is large. I can easily go a week at anchor on my house battery without needing a charge. In any given season, I probably spend less than 30 days at anchor.

I'm not looking to replace or overhaul my water system.

[Torna]

Pardon me for being the newbie here, but why can't you run your engine under load at anchor? Presumably sitting there at moderate throttle in reverse for a few minutes wouldn't hurt enything and would set your anchor nicely. Or am I missing something completely stupid?

-leif

[Dan McCosh]

Sounds as if you either don't have a thermostat on the engine, or it's not working. I looked into a similar system and gaveit up mainly because I use a raw-water cooled engine without a thermostat, and the tanks that are mainly aimed at a closed-circuit cooling system with a thermostat. If you don't have a closed-circuit system, you might consider setting up a separate loop with a valve that recirculates a portion of the water through the engine block and through the heater in a closed loop. (you could bypass the normal cooling process altogether until the water in the tank heats up). This is sort of a manual way of doing what a thermostat would do. Of course, you would need to watch the temperature while this is going on.

There is another thing going on here, which is that it sounds as if your engine is running too cool a lot of the time. This causes engine problems as well, and you might find if you can keep the operating temp up, it would both give you hot water and be better for the motor.

Problem with an inverter is the old problem with current. A hot water element would draw in excess of 100 amps on the battery.

[Scott Rosen]

leif,

In theory, that would work. However, the Westerbeke 4-107 combined with the three blade prop and the full keel make for some problems with what you suggest.

The stern of the boat "walks" when the engine is in reverse, and will not respond to the helm. I tried that once, and the boat went riding on the anchor rode, uncontrolably. Depending on the wind and tide, the boat could easily run over the rode and foul it. It could more easily bang into other boats. It's a dangerous thing to do in an anchorage.

There is also a lot of power when the engine is run hard enough to put a good load on. I don't want to add that strain to my boat or my gear unnecessarily. I've never had a problem getting a good anchor set.

Finally, I do not think the engine, transmission and mount are designed to handle the stresses of lengthy running in reverse. It pulls all the stuff that's designed to be pushed.

[ 03-31-2003, 12:01 PM: Message edited by: Scott Rosen ]

[Scott Rosen]

Dan,

I have a closed, fresh-water cooling system with a thermostat, and there's a loop that runs through the heater.

For those of you not familiar with the old Westerbeke 4-107, it will not get hot enough to open the thermostat unless there's a load on. And most of you probably already know that it's not good for a diesel engine to run it for any length of time without a load.

When I'm under way, under power, the water will heat just fine.

[paladin]

welll...I can crunch numbers for you on the inverter idea if I know what the amp hour rating of your batteries izz, and the power requirements of the heater (amps at 115 v a.c.) but it might be easier and cheaper to install a 115 volt a.c. alternator on the engine...then you could charge batteries, heat water, run the automatic coffee maker and breadmaker in just a few minutes at anchor with the engine running..............send e-mail if you want me to do this..I don't get on the forum much regularly anymore.....

[Bob Adams]

Use the inverter in conjunction with the engine.The alternator will replentish the batteries while the engine will preheat the water reducing the temp rise required from electrical elements.That's one thing about a diesel, less waste heat than gasoline.

[ 03-31-2003, 12:40 PM: Message edited by: Bob Adams ]

[Torna]

Thanx for the clarification Scott, another day, another browse, another lesson.

-leif

[Figment]

If this is all you're going to use the inverter for, it sounds like you're going to be cooking some VEEEERY expensive hot water.

for such limited occasional use, might a small carry-on generator be more appropriate?

those little honda models are not so expensive, and they've come a long way in terms of noise suppression. My guess is that you could pick one out of the bargainnews for less than the cost of your inverter, and there'd be no installation hassle.

EDIT- ok, so I got curious and checked the bargain news. There's nothing that small listed right now. Still, this portable genset thing is the route I'd pursue.

$.02

[ 03-31-2003, 02:53 PM: Message edited by: Figment ]

[Dan McCosh]

I'm not familiar with the installation, but it sounds as if the water heater is running on the same line as the intercooler, hence it gets no hot water unless the thermostat is open. Dunno if it's possible, but the water heater ought to be on the same circuit as the block, getting the water flow from the engine as it is warming up with the thermostat closed. Even with the engine idling, the water ought to be reasonably hot before the thermostat opens. I wouldn't think it would take a long time to warm the water to 120 degrees or so. (usually a thermostat opens at about 180 degrees) All this assumes that there is some choice in where to plumb the water heater.
Truth is, I use a tiny 110 volt heater at the dock, which was warmly welcomed by the mate. Anchored, I'm now looking at a gallon tank with a hose that sits on the stove. (The sun shower also works--we run the hose down through a hatch.)

[Dale Genther]

Taking a quick look at the number involved with using an inverter for heating your hot water: The typical hot water heater has a 1500 watt element in it. This is about 13 amps AC at 115 volts. If you try to pull 1500 watts thru an inverter you will pull at least 125 amps at 12 VDC. This does not take into account losses in the inverter. This is quite a load on your batteries. In 20 minutes you would use at least 42 amp hours. Also an inverter capable of supplying a minimum of 1500 watts is pretty expensive. So essentially you can do it but your batteries will take a pretty good beating.

[Matt Middleton]

Hey Scott- something doesn't sound right about this:


For those of you not familiar with the old Westerbeke 4-107, it will not get hot enough to open the thermostat unless there's a load on. What's keeping it cool, if there's no water flowing?

Based on no knowledge whatsoever of your particular engine, it sure sounds like a thermostat that's always open, like Dan said. Please forgive me if there's something obvious I've overlooked, and good luck!

Matt

[Scott Rosen]

I have a 145 or 150 degree thermostat, I forget which. When idling or running without a load, the temp will move slowly to 145 and then stop. That's the point that the tstat starts to open. However, my raw water cooling side is very effective, so the coolant in the reservior doesn't get hot enough to touch.

It might eventually heat my hot water, but it would take hours.

If I run the engine under load, it will get to about 150 to 160 depending on how hard I run it. At that point, the tstat is open, the raw water side gets hot and hotwater heater gets hot pretty quickly at that point.

If I recall correctly, the loop to the hotwater heater is taken from the engine coolant reservior. My engine mechanic said that these engines simply don't generate enough heat unless under load.

[Scott Rosen]

P.S. These engines are amazing in some respects. They run very cool when idling or at low rpms, and much hotter under load.

Once, my raw water impeller failed. At 2000 rpm's the temp climbed quickly to over 200 degrees. I throttled way down to about 1100 or 1200 rpms, and the temp came down to about 190 under load, and stayed there for over an hour while I motored back to the dock. In other words, even without the raw water pump working, the engine can run for quite a while, under load, at low rpms, without overheating.

[Matt Middleton]

That is amazing that the engine keeps as cool as it does, particularly considering what's going on inside the cylinders.

I suppose that you've already looked into the option of a higher temp. thermostat?

I don't mean to keep badgering you on this option, but it does seem to be the simplest solution.

Matt

[Bob Cleek]

Well, the two obvious solutions are clearly not cost effective (i.e. getting an inverter or losing the wife.) There are some nice little Taylor, etc. diesel water heaters. There are diesel stoves that have a hot water coil in them as well. (Check out the Toplicht catalog if you spreken Deutch.) All of these options would be to costly, IMHO, for hot water, particularly when you already have two heating options in place.

So, it doesn't seem like anybody's suggested what to me was obvious at first glance... why don't you just close your raw water intake valve enough to run the engine temp up at idle? You'd have to keep an eye on it, and make sure you'd opened it up again when you wanted to run the engine at load, but I'd expect restricting the raw water flow (leave enough running to keep the impeller lubed) would increase the heat at idle enough. If you have problems with the raw water pump impeller not getting enough to keep it cool, then put a bypass loop and valve on the system so you can redirect the water pump flow past the heat exchanger and directly back into the exhaust discharge. Just a wild thought... I could be wrong... don't blame me if she overheats and siezes up while Mom's taking a 45 minute shower! LOL

[ 03-31-2003, 05:20 PM: Message edited by: Bob Cleek ]

[Scott Rosen]

Bob. Your post brought a huge smile to my face. That was first thought many moons ago. Why not partially close the raw water intake?

But it just doesn't seem like a good idea, if you know what I mean. I could try it . . . but if my impeller blew to bits, I'll have to blame you. LOL

Matt, I used to have a hotter tstat, but the engine would run too hot. For reasons that only Westerbeke could know, the engine will run about 10 to 15 degrees hotter than the tstat. So if I put in a 180 tstat, I've got problems. Although that was before I got the hotwater heater . . . hmmm.

[imported_Conrad]

I think the cheapest, simplist, solution is to mount a 120 volt a/c alternator. And then you can also provide a hair dryer, hot coffe, toast, and a blender for those evening drinks. If it were me, I'd look around for an inexpensive used home generator and salvage the generator head, then hook it up using an automotive 12 volt A/C compressor electric clutch so you don't have to mess with anything except switches when you're interested in making 110. $300 total?

[Gaff]

To heat 1 kg water from say 15 deg C to 50 deg C requires 146,510 Joules. This equates to approx 41 Watt hours. Now if you what to heat say 20 litters (approx 5 US gallons) from 15 deg to 50 deg C in say 30 minutes, 1640 Watts is required. At 12Vdc this equates to 137 Amps. Assuming the inverter has an efficient of 80%, the battery needs to supply 170 Amps for 30 min. This is the equivalent of draining a 165Amp hour (C10) down to 1.7 volts per cell. If the installed batteries have a very large Amp hour capacity then you would not drain the batteries as much. It is not a good idea to discharge batteries to such low volts per cell on a regular basis as this will shorten their life as they have a limit to the number of times you can do this. Some batteries are better then others, flooded cells tend to be better then Gel or AGM and manufacturers data with respect to the number of discharge cycles their batteries can be misleading or even extremely optimistic. Fitting an AC generator as mentioned previously may be the better option. Saves the expense of a large inverter and reduces the cycling of your batteries which will make them last longer.

[Ken Baker]

The only bugger about the AC generator option is that your 60 Hz is controlled by the engine rpm. When the hot water heater turns on the engine rpm will drop due to the load placed on the generator. The heater element might work OK with the frequency drop that will occur (or increase if the load turns off) but if you have something else running on AC, it might not like it. Hense, you may be doing a bit of running back and forth to the cockpit to tweak your engine throttle back and forth to keep producing 60Hz. There maybe some electronic gizmos out there that can compensate for the frequency changes but I haven't seen any lately. The (expensive) AC gensets available have governors to adjust the throttle to maintain the engine at the appropriate speed when an electrical load is applied.

Another issue is that most AC generator windings are designed to run at 1800 or 3600 rpm so you will have to decide what engine rpm you want to run at and design you pulley ratio to suit. Be cognizant of the maximum rpm the generator can handle in the pulley ratio design otherwise your generator might self destruct when your in a hurry to get into a harbor some night.

Good luck,
Ken

[Concordia..41]

Scott
At what point on the engine cooling water system did you connect the hot water heater?

Dave

[Scott Rosen]

Good question, Dave. I don't remember exactly. I'll be going down to take a look this weekend and will report back.

[Cedarhill Boatworks]

Seems like Dave is on the right track. Assuming that all you need is hot water from the engine to run through the heat exchanger in the hot water heater, find a hose that is on the engine side of the cooling system(inside the t-stat loop) and tap it. Thats how mine works.

[Carl Simmons]

Thinking outside the box, what about mounting
a POS (point of service) hot water heater on the dock and run a hose to the boat. The units are fairly inexpensive and you could put it in a small box enclosure to keep the elements out. This way you don't have the losses in the inverter or wasted gas from running the engine.

Carl.

[Dan McCosh]

Somehow, this reminds me of the electric car that runs on the ten-mile-long extension cord.

[Scott Rosen]

Originally posted by Dan McCosh:
Somehow, this reminds me of the electric car that runs on the ten-mile-long extension cord.That's exactly what I'm hoping to avoid. :D I'm looking for a simple, elegant solution. I'll check into Dave's idea.

[Scott Rosen]

I checked into Dave's idea. No go. The inside of the t-stat loop is entirely in the engine--no hoses. Right now, the hotwater heater is tapped into the system at the hotest possible point, where it goes into the heat exchanger.

[gaffman]

I would call a fellow named Fred at Hanson Marine, which is a Westebeke Distributor. He has been there a long time. Phone is 781.631.3282. He has always been very helpful with me and is a wonderfully knowledgeable fellow when it comes to these motors. He may have come across this issue. Note also that they have a good parts department.

[paladin]

Scott, The engine rpm is not a problem,Fabco uses a belt driven hydraulic motor that you plumb over to the alternator. The entire package with install hardware, wire, hoses, control panel and hydraulic bypass valve will run about $1600 for a 3000 watt unit....a heck of a lot less than a comparable inverter, more efficient, more bulletproof and you get more bang for the buck....

[Bob Cleek]

Well, Scott, in the wintertime at least, it might help to push her overboard before she takes her morning shower. That way, whatever comes out of the shower will feel warmer! Seems like there's WAY too much brain power getting invested in a honey-do job here. You'd better tell her to lump it, Scott, or you'll be on your way to buying one of those big floating Winnebago houseboats before you know it! LOL

[Concordia..41]

Scott

The Westerbeke 4-107 uses a Perkins engine with Westerbeke marine conversion. The exhaust manifold, heat exchanger are Westerbeke. I do not know why a Westerbeke with fresh water cooling would use a 150 degree thermostat. I do not have a Westerbeke manual but the Perkins manual calls for a low temperature 125 to fully open at 150 degrees on a raw water cooled engine only. It is also a bellows type thermostat instead of a wax capsule used on the fresh water cooled engines.

I do have a engine manual for the Westerbeke L-25 that I have in the shed. It uses a 190 degree thermostat. It also says that if you are connecting a water heater that you have to replace the 4 # pressure cap with a 12-15 # pressure cap. You also have to bleed the system at the highest point.

Perkins engines in our area use a 170/185 thermostat. The 36’ Heritage that I had at one time had 4-107 Perkins and I had no trouble with the hot water. The 36’ Watkins we now have has a 4-108 Perkins and it also uses a 170/185 thermostat and no problems with hot water.

I do have a Westerbeke 4-107 out back under the shed that came out of Sarah and if I get a chance I will pull the thermostat and check it. As I said it came out of Sarah and we believe it is a 1983 model. Sarah does not have a hot water heater but the engines should be the same set up. Right now we are busy getting the Watkins ready for sale but give me a few days and I will pull the thermostat.

I also have heard that is bad to idle a diesel but someone forgot to tell all those over the road truckers that idle their diesels while they sleep at the rest areas. Ever pull in and try and get a nap with 20 diesels sitting there running? They only expect to get 300,000 miles between rebuilds so I guess they don’t care. Seriously I have never had a problem running a diesel at low speed with out a load to charge may batteries or heat water.

If you can not correct it where you can heat the water with the engine they do make a propane heater. There is a steel schooner here in town that I helped bring up from South Florida several years ago that has a Path Finder diesel. (VW diesel with marine conversion.) It has a demand type propane heater and it is a lot better than the engine heated water. It also uses very little propane. It would be a lot more efficient that trying to use a converter.

The price of comfort is not cheap but may well be worth it to keep the wife happy. You may also have to install a larger water tank as it is on demand and you will run out of water before you run out of propane.

Check this site for the heater.

http://www.gaswaterheaters.com/boatsandrvwaterheaters/showermate/index.htm

Dave

[Scott Rosen]

Dave,

We installed a cooler thermostat because the engine was always running too hot with the 170/185 thermostat. First we completely cleaned the raw water side, including removing and acid-dipping the heat exchanger. It's an old engine, but it's always run hot. With the 150 thermostat, the engine runs at about 160 to 165 under load. I suppose it's possible that the temperature senson and gauge could be wrong, and the engine ran okay.

I could always reinstall a 170/185 when I commission the engine this Spring and see what happens. What do you think?

[Dan McCosh]

If the water heater is on the line with the intercooler, what you want is a cooler thermostat, rather than a hotter one. Seems backward, but the low-temp unit will open sooner than the high-temp thermostat, allowing the water to flow through the heater with less load on the engine. Actually, you might consider removing the thermostat altogether, and putting a manual control valve on the line to the intercooler. You then adjust the coolant flow with the engine operating under load until the temp is correct. This works well enough as long as the temperature of your local waters stays the same--when you go to a cooler or hotter climate, you manually adjust it again. Coolant then always goes through the water heater and intercooler. A manual control valve is all that I've ever had on my engine.

[ 04-03-2003, 10:02 AM: Message edited by: Dan McCosh ]

[Scott Rosen]

Dan, I understand that a cooler thermostat opens earlier. But that means that the temperature of the water that circulates into the hotwater heater is also cooler. I'm thinking that with a hotter tstat, it may take a little longer for it to open, but when it does, the circulating water will be hotter.

Am I wrong?

[Figment]

I may be missing the forest for the trees here, but to my way of thinking, the thermostat issue is irrelevant.

1) Under a given load condition, an engine will produce a given amount of heat.

2) Thermostats aren't full-open vs. full-closed valves. they open gradually more and more until the temperature of the coolant stablizes. When the engine is under heavy load and producing lots of heat, the thermostat allows far more coolant to flow than when at idle.

installing a higher-setting thermostat will allow the coolant water to heat more before it begins to flow, but LESS FLOW will be required to keep the engine at that higher temperature.

to put it another way (inventing quantities for sake of explanation)...... if in 60 seconds of running your engine cycles through 10 gallons of water at 140 degrees, then it will cycle something like 7 gallons at 195 degrees.

The 10gallon and the 7gallon buckets of water described above both contain the same amount of heat energy, just at different "concentrations".

It's a fixed equation. heat input = heat output (minus efficiency factor). To get more energy out, you need to put more energy in. The heat/energy is produced by the engine. The thermostat simply regulates the concentration of that energy it by adjusting the volume of coolant.

I'm sorry I can't seem to formulate simpler mathematic terms. I guess George's "Learning is Tough" thread burned the math side of my brain yesterday. ;)

[Concordia..41]

Scott

I use a Fluke 80T-IR infrared temperature probe on a Fluke model 77 digital multimeter to read temperature at the sending unit to compare the gauge reading. A lot off times I find the gauge to be way off. I also use it to check other parts of the engine such as the exhaust riser and to compare cylinder temperatures. Yanmar engines down here are bad about stopping up at the exhaust riser and causing the engine to over heat. Scale and corrosion build up in the riser and restricts the flow of raw water.

When you commission the engine this spring, see if you can find a mechanic or surveyor with an infrared temperature probe to check out your engine.

Dave

[Stephen Hutchins]

Hi Scott. Personally I like your inverter idea. But an alternative solution could be to put a Y fitting on the heat exchanger line and use two thermostats with valves in front of each.

[Matt J.]

Scott, can I ask a newbie question?

Where, on a wooden boat, do you shower? Really, I'm wondering where the water goes? Just runs into the bilge to be pumped overboard?

Simple minded question, I know, but I never considered running a shower aboard a wooden boat - the idea of pouring gallons of fresh water on the sole seems... I don't know, odd?

Sorry for the lame question, and thanks for an answer.
:rolleyes: -Matt

[Dale Genther]

Matt, Your concern about a shower in a wood boat is the same one I had. I did however want a shower, so what I did was: In the area of Boreal between the hanging locker (to port) and head (to starboard), with the v-berth to forward and the main salon aft, there is about a 30 in X 30 in. space. Buy closing the doors to the V-berth, main salon and head I cound make a small shower stall. I built a teak grate to replace the teak/holly sole piece there. To the bottom of this grate I attached a "pan" made of hypalon inflatable dingy materal. This pan is sloped to the center. In the center is a drain fitting which drains further aft, via a 1/2 inch hose, into a small box containing a little bilge pump. This pump can be turned on via a switch mounted in the "shower" area. The whole assembly just lifts out if you need to get under it. It works great! I had to do it this way because I did not want frest water in the bilge and there was not enough clearance below my shower grate to put a pan with integral pump.

[Scott Rosen]

Matt,

We shower in the head. We have a hand-held nozzle that attaches to the sink faucet. The sole in the head is teak grating. Under that is a stainless steel pan, cut to shape and used as a sump. There is a drain hole at the low end of the sump. A hose with a small electric pump is attached to the drain hole and discharges the shower water over the side through a very small hole in the topsides.

You don't want your dirty shower water to end up in the bilge.

[Scott Rosen]

We also have a cold hand-held shower in one of the cockpit lockers. We use that for rinsing off after swimming or the beach. I use it for washing my hair over the side, and I'll shower in the cockpit if no one is looking.

[ 04-04-2003, 11:25 AM: Message edited by: Scott Rosen ]

[Matt J.]

You guys'r YOTTIES! ;) imagine that said with a comic accent ala the late Chris Farley. smile.gif

ACtually, if Jenny sees this, I can hear her now asking for one... :rolleyes:

Thanks, guys. I didn't even think of adding a pan, with drain hose to pumpout.
-Matt

[Alan D. Hyde]

Scott,I don't have a complete answer to your problem, but it may help quite a bit if you can improve the insulation around (and particularly above) your hot water tank...

Alan

[imported_Daniel]

Scott, how about something like this? Zodi Hot Camp Shower (http://www.cabelas.com/cabelas/en/templates/purchase/products-found.jhtml?reposting=true&foundSku=true&_requestid=29370)

Simply put a couple of quick connects on to your existing lines. One off of the main cold to feed this unit and another from the unit into the cold feed for the hot water tank. I would recommend a check valve on the main feed line to the HWT before the secondary unit ties in. I realize this a propane unit, but with this set up, you could have the heater outside doing its thing while in use, when not using it, simply disconnect the lines and stow it away. Seems to me to be a lot less grief. Let me know if you want a schematic, you may need a small expansion tank on the HWT if you choose this route.

[imported_Conrad]

Here's the best solution- battery powered pump and propane for hot water. Looks like a winner, from a reputable company.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2409624274&category=6763

[Phil Young]

Wow, what a lot of brain power going into this!! I like the idea of a cooler thermostat. I'd guess you've got plenty of heat, but no flow happening, so the heat doesn't reach the hot water tank. Take the thermostat out, see how it goes. Zero cost. If that works, get a cooler thermostat. Small cost. I didn't notice what your hot water storage capacity is, other than that your boat is small, and the amount of hot water even smaller. Can you set it up so that you can drain the tank, then boil a couple of kettles of water and pour them in? Decidedly low tech.
Phil

[Dan McCosh]

One more thought. Any chance that the water heater is plumbed on the output side of the heat exchanger? In other words, is the raw-water section cooling off the engine coolant before it gets to the water heater? This would keep the water heater cool until the heat exchanger heats up from the engine running at full power. Putting the heater ahead of the intercooler would put it first in line for the heat. Just a thought.

[Scott Rosen]

Dan, the hotwater heater is plumbed on the input side of the heat exchanger. So it's attached at the hottest point.

I'm going to put in a hotter thermostat and see what happens. It will take longer to open, but when it does, the water circulating into the hotwater heater will be hotter. I don't think the problem will be solved by a cooler thermostat, because then the water going into the hotwater heater won't be hot enough.

It's a cheap solution, if it works, so I'm going to give it a try. If it doesn't work, it cost me very little, and then it's back to the drawing board.

[mhoffman]

Scott-
the hotter thermostat won't change anything except raise the operating temperture above what's designed for your engine by reducing the mass flow rate of coolant through your engine; its a basic heat balance problem.

Combustion engines are really pretty inefficient- like maybe 30 percent at best (carneau efficiency)- 30 percent of the energy of the fuel is converted to mechanical energy. The remainder is loss to friction and heat- your trying to capture that loss. The bulk of that heat is designed to go out in your exhaust. The internal cooling water system is to prevent material failure of the metal components due to their inability to transfer their heat absorbed from the combustion process.
At no-load, your fuel consumption rate should give you a rough idea of how much heat you could possibly capture. I'm guessing, but at idle, with no load, your fuel consumption rate is next to nothing, which is why your water heating capacity at no-load is next to nothing. I forget what the heat output in BTU/Gal of diesel is, but if you compare that to you usage rate in gallons per hour, you'll see you are not generating that much heat.
If you can come up with a way to load your engine- mechanically- you will produce more hot water. How about an auxillary pump circulating water in you tank and the head loss through the system will also heat the water, or maybe a belt driven alternator from a junk yard which supplies only an electric hot water heater?
Or, you can try to capture the heat going out in you exhaust- the problem there being that the heat transfer capability of a gas (exhaust), is much lower than that of a liquid or solid. Maybe some cooling coils around your exhaust plenum in series with your heater? It would get you up to temperature faster, and as long as your system can unload the heat once the thermostat opens, it should work.
Just my three cents. I fully understand the importance of keeping the spouse happy though- I took my boat out for the first time last weekend- after two years of construction- got the wife in it after verifying no leakage. Started to open it up a bit (its a runabout with a 350) and at about 20% throttle she wanted to go back to the dock. Would not get back in until I agreed to keep it slow until she got used to it. No fun driving around by myself... :rolleyes:
Matt

[TomRobb]

Perhaps you could arrange to have your spouse overhear some babe ask you for a fast ride in the boat. Her attitude might then change :D
Nevermind... too underhanded :rolleyes:

[mhoffman]

Tom-
Christmas two years ago we were at her parents house. For our presents, they gave both of us some cash to buy whatever we wanted. Wife wanted to take hers and mine and apply the funds to her entertainment center fund; I wanted to use mine for the boat engine fund. Wanting to discuss the matter further, she offered that it would be vastly more useful to have an entertainment center to finish off the living room and make the space more user friendly for when we have company over. I countered that I would be perfectly happy motoring around the river with "some bikini clad vixen on skis" behind my boat while she is inside watching TV. I think it was just after New Year's when she spoke to me again...
I was trying to be funny at the time- I guess you have to know your audience.... :rolleyes:
Matt

[Alan D. Hyde]

Matt--- :D :D :D

Alan