hot water from inverter

[jlp0217]

Your diagram in post 57 shows the wh return going to the engine heat exchanger. If accurate, it would explain you engine not getting to temperature. The bypass is supposed to bypass the heat exchanger. Doesn't explain the wh not getting hot. I think only badly corroded heat exchanger would explains that.

 

[Hayden Watson]

Your diagram in post 57 shows the wh return going to the engine heat exchanger. If accurate, it would explain you engine not getting to temperature. The bypass is supposed to bypass the heat exchanger. Doesn't explain the wh not getting hot. I think only badly corroded heat exchanger would explains that.

The water heater is inserted into the thermostat bypass hose fittings. It comes out at the thermostat housing and returns to the water pump.

As is evident in this post I have two related mysteries.

1. The heat transfer in the WH exchanger is much lower than what Kuuma says it should be. I am going to contact Kuuma engineering again to get the spec on the heat exchanger. I heard from another source that the heat exchanger is not a single solid pipe. It is actually a double walled pipe so that if there is a leak in either wall the leak will be to the bilge so that you do not have the possibility of getting antifreeze into the drinking water. I will investigate what the medium of transfer is in this system.

2. The engine will not come up to thermostat temperature. The heat exchanger is the standard 3"ø that was installed on later models. It should provide plenty of cooling but the thermostat should still control the temp because very little coolant should pass through it until the T-stat opens. As I stated before, I have bench tested all 3 T-stats and they open and close at the proper temp of 160º as marked by the 72C on their flange.
My setup is the standard factory for a MkII C30 with an M25XP. When I start from cold, my infrared thermometer shows the water jacket heating up just as fast as the T-stat housing so it seems that somehow the T-stat is being bypassed. I am intending to temporarily remove the WH hoses and reinstall the bypass hose to see if that is the cause. After that, I am going to remove the T-stat and place a couple of layers of duct tape in place of the stat and see if I can force the temperature up to 160. If it still won't heat up then the coolant must be finding a different path to the heat exchanger.

 

[Claude L.-Auger]

Hayden,

In your point 1, if you had a leak of coolant into the bilge, your coolant level in the engine would go down and in a fairly short time you would have an overheat situation.

In your point 2, I would not use duck-tape to block the flow to the T-Stat. If it gets loose then it's going in the engine ! Perhaps you can fabricate a thin piece of sheet metal. But before you do that, after you have removed and bypassed the WH hose, if you still do not get the engine to operating temp, you could partially and carefully close the engine intake valve, reducing the intake flow until you get the engine temp up. We use to do that on a raw water cooled racing boat years ago when going to different lakes where temperature water was colder. If indeed that helps then you'll need to figure out why it stays cold. Perhaps as you said a T-stat bypass. Is the 25X diagram posted here exactly as per your engine ?

 

[jibes138]

Hayden, In your point 1, if you had a leak of coolant into the bilge, your coolant level in the engine would go down and in a fairly short time you would have an overheat situation. In your point 2, I would not use duck-tape to block the flow to the T-Stat. If it gets loose then it's going in the engine ! Perhaps you can fabricate a thin piece of sheet metal. But before you do that, after you have removed and bypassed the WH hose, if you still do not get the engine to operating temp, you could partially and carefully close the engine intake valve, reducing the intake flow until you get the engine temp up. We use to do that on a raw water cooled racing boat years ago when going to different lakes where temperature water was colder. If indeed that helps then you'll need to figure out why it stays cold. Perhaps as you said a T-stat bypass. Is the 25X diagram posted here exactly as per your engine ?

if the thermostat is never opening and the hot water heater is getting coolant from the thermostat outflow then logic suggests close to zero flow to the water heater. Solve the engine temp issue first.

 

[Hayden Watson]

... First is that the temp control valve is something that I've not seen on other heaters..usually the domestic water is what is bypassed and not the engine coolant. This way, the water tank is at high temp and because the domestic water is tempered, the hot water behaves as if it had a larger tank.. have you removed the coolant side valve and are feeding coolant directly to the little stub instead of using the riser hose from the bypass?

Sorry for the late response. I missed a group of these posts. I agree with your assessment of the CTV. it is much better to let the tank heat to thermostat temperature and use a fresh water tempering value to bring the tap water down to safe levels and this is what I suggested to my friend down the dock. I removed the CTV last year and am plumbed strait to the WH exchanger.

... ask Kumma if the space between the double wall exchanger tubes is supposed to be filled with a fluid to let the heat from the inside tube wall get to the outside tube wall. If they were using a heat exchange medium between the tube walls, and forgot to fill this one, that might act as a heat block and limit heat exchange between coolant and domestic water.. another heat exchange block: ...

I fully agree with you that if it has a double wall there must be an exchange medium. If it is an air gap then it would act as and insulator. I am in the process of doing this but it is hard to get through the industrial road blocks to get a real engineering option. I just talked with the Kuuma tech support and she said it is just a tube, but she also said that is it a double walled tube with nothing in-between. both can't be true. They took my name and number with a promise of a return call from someone in the engineering department.

...There may be a bubble trapped in the coolant tube which would very much limit the coolant contact with the walls of the exchanger tube yet allow a small flow through that would be enough to heat air in the Red Dot. If the coolant standpipe from the temp control valve remnants is still there, that could do that.. ?? dunno..
This is a strange one ..

I do not think that I can have a bubble in the exchanger because the exchanger pipe is horizontal and it is not at a low point. the exit line runs horizontal with a slight incline to the RedDot. I also purged the line with a drill mounted pump with a pretty high flow rate until no bubble came out of the discharge line. The mystery continues. I is looking like there must be some problem with the heat exchanger as that is where the heat flow stops. One thing that I just remembered is that my engine heat exchanger got plugged up several years ago and caused the engine to over heat. I first noticed the low engine temps after having the HX rebuilt. I wonder if it is possible that the exchange medium in the WH exchanger has a low melting point and it turned to liquid and ran out leaving just air behind. that would defiantly cause what I am seeing.

 

[Stu Jackson]

I do not think that I can have a bubble in the exchanger because the exchanger pipe is horizontal and it is not at a low point. the exit line runs horizontal with a slight incline to the RedDot. I also purged the line with a drill mounted pump with a pretty high flow rate until no bubble came out of the discharge line. The mystery continues. I is looking like there must be some problem with the heat exchanger as that is where the heat flow stops. One thing that I just remembered is that my engine heat exchanger got plugged up several years ago and caused the engine to over heat. I first noticed the low engine temps after having the HX rebuilt. I wonder if it is possible that the exchange medium in the WH exchanger has a low melting point and it turned to liquid and ran out leaving just air behind. that would defiantly cause what I am seeing.

Hayden,

I agree that you don't have an air bubble. Why? 'Cuz if you did you would be overheating in a heartbeat. It is simply the NATURE of the coolant system on these engines. That's why we repeatedly post on How to Burp Your Engine.

Your conjecture about the HX sounds backwards to me. If there was something wrong with it, it would reduce, not increase, the heat exchange and you wouldn't have your low operating temperature.

We don't know if you've had the time to do this yet, but I'll go back to what many of us have suggested to you all along, and is simple:

Put the 3/8" bypass line back and see what happens to your engine temperature first. Let us know what happens.

Good luck.

 

[Hayden Watson]

Darn it Hayden, no offense but I can't help myself after reading the 60+ posts of this thread. You were a diesel mechanic. Diesels are supposed to run hot ! 140 is way low. Universal 25MX specs call for operating temp from 165 to 195°

None taken. I very well know that 140 is WAY TOO COLD!. For the first got the boat 17 years ago it ran at the correct temp. It gradually got hotter over time until on one cruise it over heated and I found that the heat exchanger was plugged. i ran a coat hanger down as many tubes as I could and got it working enough to finish the trip. after getting it rebuilt, i have always run cold. it looks like my first thermostat was a carful "tuned" blockage.

1) Disconnect in and out coolant hoses to WH and Red Dot, and bypass with short hose from engine outlet to inlet. Run engine under load and make sure to get to "normal" operating temp for your engine. If not reaching 165 find out why and correct the problem.[/COLOR][/FONT]

2) Once satisfied, connect WH but not Red Dot. Run engine under load again long enough to bring engine temp to normal and heat water (my Yanmar takes +/- 30 mn with same Force 10 as yours). Check water temp. If still cold, problem with tank. TCV ? I was advised by Force 10 to bypass it 5 years ago and WH has performed perfectly since. Seem to recall you addressed this issue earlier on this thread. If problem with tank, you might need to replace.

3) If satisfied, reconnect Red Dot and check again. If water temp drops, then suspect Red Dot. Getting air to comfort zone from 140° coolant is much easier than get water to 120 or 130° from same 140° coolant. Hoses may be too long ! Does your neighbor have the same length ?

If all else fails, replicate exactly your neighbor system (if same boat) or make an offer on Stu's boat ! Good luck and keep us posted please.

This is my plan of attach exactly (except for the part about Stu's boat.) No offence Stu but I have been working to get Papillon just the way I like her and intent to keep her as long as I can sail.

 

[Stu Jackson]

This is my plan of attack exactly (except for the part about Stu's boat.) No offense Stu but I have been working to get Papillon just the way I like her and intent to keep her as long as I can sail.

Whew! I was worried about that for the past few days. Now that you've cleared that up, I think I'll go sailing for a few days.

Sounds we both have "keepers." :dance::dance::dance:

 

[Hayden Watson]

Watson -

Attached is a link to the manual from your engine manufacturer. It addresses water heater installation at page 25. This is a better explanation than the water heater manufacturer has so far offered. The point is that if any part of the heat circuit - not just the heater itself - is above the reservoir then a secondary expansion tank is mandatory. The purpose is pretty obvious.

I hope no part of your system is above the coolant source, but if so we cannot conclude siphon theory will save the day. All things considered trapped air explains all the symptoms you describe.

Charles

http://www.westerbeke.com/operator's manual/200494_m320a_thru_m35b_operator_man.pdf

Erwin - I prefer to go my by first name, Hayden.

As i stated in post #63, all points in the WH circuit are at least 10" below the point where the hoses leave the engine. My connection is exactly as shown on page 25 of the manual. Thanks for the link. That will come in handy.

The water heater is at a low point in the circuit (the outlet hose runs uphill from the WH to avoid an obstruction). The fact that there is significant heat output from the RedDot in series eliminates the bubble issue.

 

[mitiempo]

I would remove both the water heater and the bus heater from the cooling circuit. Then make sure the engine gets up to it's proper operating temperature (160 - 190) before proceeding. If it does add the other 2 items one at a time, checking for proper temp as you do.

If one item in a system is not working properly it shouldn't be hard to diagnose. When you have what is likely multiple issues with things not working it can be a nightmare to find the fix.

 

[Hayden Watson]

Whew! I was worried about that for the past few days. Now that you've cleared that up, I think I'll go sailing for a few days.

Sounds we both have "keepers." :dance::dance::dance:

I can't testify to yours but Papillon is defiantly a "keeper".

In the past few years we have been doing the "second life" maintenance. I now have all new running and standing rigging, the full "Mine Sail buff job" and by wife made me the most beautiful spinnaker in Puget Sound. Besides she is paid for so I can put my payments into upgrades.

It will be a while before I can strip the system back to the bypass and start over because I need to leave in a few days to go see my brand new grand daughter but will post the results when they I get them done.

 

[kloudie1]

You are heading in the right direction, Hayden.. My comment on the bubble in the tank exchanger is based on a few problems that I have had on industrial exchangers that had a minimal up-slope from inlet to outlet. It happens that a long bubble can form and cause the wetted area inside tube to be only half or less wet by the circulating fluid. This alone can very much limit the heat going into the water side. The bubble is sometimes very hard to get out, but it sounds like you've purged it well .. The Red Dot is not a really good gauge because it doesn't take very much heat to heat air.... Thinking again out loud, it seems like you may have a stuck open thermostat.. The thermostat being closed gives you the most pressure to drive the coolant through the bypass..as it opens, the pressure drive decreases, the flow rate slows, and the heat transfer really goes down... BUT, if that were the only problem, all the heat would be going into the water before the Red Dot.. and that isn't what you are seeing.. The large drop across the Red Dot kinda means that your flow is a little low (again it does not take much heat to heat air).. After you remove the thermostat and verify that it is OK and not hanging open (and causing cold running and low drive pressure to the water tank) replace the thermostat.. then plug the return opening at the water pump (it will suck air if left open).. Open the return hose and let the engine pump force the cold coolant out of the return hose until no bubbles.. Unplug the return at the water pump, and re-attach.. I think your plan of attack may accomplish most of that . Again, Good Luck, hayden.

 

[Hayden Watson]

I have had two conversations with one of the Kuuma engineers and have some more info on the construction of the WH exchanger. It is a double wall pipe but there is nothing between them. What they do is run one pipe through another with the outer pipe at the correct length of the exchanger. The outer pipe has a flare on each end to allow it to be welded to the tank. The inner pipe is just small enough to fit inside the outer with minimal space. These two pipes are then bent around a mandrel to the "U" shape and the outer pipe is welded to the tank. All of the water heaters they have ever built are constructed this way.

This gives the following
1. No welds on the antifreeze pipe to reduce the change of weld pitting corrosion.
2. Double wall thickness to decrease the chance of rupture.
3. If a leak does form, the fluid will not cross contaminate but will drain out into the bilge giving notice of failure without the possibility of antifreeze poisoning.

Because they are tight fitting to each other and bent as an assembly, there is significant surface contact so not transfer medium is needed.

The engineer is as stumped as I am se to why the outlet temp is only 3º less then the inlet given the 80º difference between the fresh water and antifreeze.

He is doing further research and I will post any updates.

The mystery continues.

Hayden

 

[kloudie1]

Great that they talked to you.. I didn't figure they had stuff in there, but again, I have worked with a bunch of industrial ones that did .. and didn't. Have a safe trip, Hayden.. Congrats on the grandcritter..

 

[mitiempo]

The engineer is as stumped as I am see to why the outlet temp is only 3º less than the inlet given the 80º difference between the fresh water and antifreeze.


Hayden

If the coolant is hot enough the only other answer is flow rate. Has to be one or the other.

 

[Hayden Watson]

If the coolant is hot enough the only other answer is flow rate. Has to be one or the other.

Exactly. That was why he was stumped. there are three variables in the simplified model. the difference in temp fresh to AF, the amount of heat transferred through the pipe wall to the fresh water and the velocity of antifreeze.

in my case one there is almost no change in the fresh or AF so scratch that one off. That leaves the heat transferred across the pipe wall and the velocity of the AF. to increase the drop in AF temp you can either decrease the flow of AF or increase the thermal conductivity of the pipe.

I see a 3º drop across the WH and a 30º drop across the RedDot. they both use the same flow of fluid so the only conclusion left is that the WH only has 10% of the thermal conductance of the RedDot. It seems to leave me with a problem with the WH exchanger. I don't see how that is possible. it acts like there is a plastic liner inside the exchanger. I plan to use my descaling liquid inside the exchanger to see if it improves anything.

Hayden

 

[mitiempo]

The Red Dot is causing a very large drop in fluid temperature. To me this indicates a very low flow. If the flow was substantial the drop in temp would be much less.

But as I posted before the original (engine) temperature is too low as well.

 

[jibes138]

The Red Dot is causing a very large drop in fluid temperature. To me this indicates a very low flow. If the flow was substantial the drop in temp would be much less. But as I posted before the original (engine) temperature is too low as well.

flow is a huge factor in a water heater. Try getting water up to temp with the engine idling at anchor. It takes forever. Then take the boat out and motor around for fifteen minutes, the water will be scalding hot. You need to validate flow through the circuit by yanking the hose after the red dot and see what is happening. Speculation won't solve this, time for some action.

 

[Charles Erwin]

Erwin - I prefer to go my by first name, Hayden.

As i stated in post #63, all points in the WH circuit are at least 10" below the point where the hoses leave the engine. My connection is exactly as shown on page 25 of the manual. Thanks for the link. That will come in handy.

The water heater is at a low point in the circuit (the outlet hose runs uphill from the WH to avoid an obstruction). The fact that there is significant heat output from the RedDot in series eliminates the bubble issue.

A thousand apologies concerning your name - and I promise not make the same mistake twice.

As to the link to the manual, yes access to entire manual may prove handy to have. For example - your putting the water heater in the by- pass circuit is quite correct on a Universal whereas that is verboten on other manufacturer motor cooling designs. This is because in the Universal the by-pass circuit is still open even if the main circuit is active - ie thermostat open. I confess surprise on that one.

However to the detail of that low mount diagram - your hookup may not be exactly the same. N.B. the petcock at the heater return line even in a low mount case. That is - even if the water tank is lower - Universal still advises a petcock at the heater thus to eliminate any possibility of persistent air pocket (albeit one not amounting to an air lock. ) Might try it. Putting one in is simple, cheap, and there is no downside.

Incidentally, I imagine if you take the space heater out of the calculus your motor operating temp will rise. This is - of course - a separate and parallel issue to creating hot water at the water heater.

Charles Erwin

 

[Hayden Watson]

The Red Dot is causing a very large drop in fluid temperature. To me this indicates a very low flow. If the flow was substantial the drop in temp would be much less.

But as I posted before the original (engine) temperature is too low as well.

The most significant conclusion about the drop in coolant temp across the RedDot is that it is removing heat from the coolant while the WH exchanger is not. The water to water transfer should be much more efficient than the water to air transfer in the RedDot. If the flow is low as you state, then the WH should drop the temp even more. As it is, the WH drops the temp about 10% of what the RedDot does.

Remember, the flow is the same in both and 3º cooler in the RedDot.