Hot water heating system

Aug 12, 2009
38
Beneteau 423 Beverly, MA
Hi
I have a Beneteau 423. Hoping to get some help. I replace the hot water tank last year and since then I cannot get hot water. The system works as expected under shore power but not when heated from the engine. It's a purely mechanical system via the heat exchanger so I cannot really see what could go wrong. I've checked for an air bubble, flow valve, nothing seems wrong. It was suggested that the there is a thermal couple on the heat exchanger that may not be opening but looking at the schematics it looks purely mechanical as well. I measure the heat of the engine and it does run cool but the hot water did work quite well before. Is there some thermal couple on the engine that controls the flow hot water heater or something similar? -- Just trying to figure out could be wrong. No a lot of options.
 
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Jan 7, 2011
4,723
Oday 322 East Chicago, IN
Seems odd that it worked before you replaced the WH, but not now.

Did you do the work or someone else?

My first thought would be air in the coolant line between the engine and the WH. But you said you checked that...how?

Are there any valves between the engine and WH? I have one on my coolant line that imth8k is there to keep me from losing all of the AF if I have remove the WH. If so, is it open?

Do you have bypass valves on the water lines (so you can isolate the WH when winterizing your water system? I have 3 valves that I have to turn to isolate my WH. One spring I turned 2 of the 3 (in error). Could not get hot water...finally replaced the electric limiter thing on my WH...and STILL NO HOT WATER. Then, while crawling around in the lazzarette where the WH is, I notice the 3rd valve.... opened it and what do you know...I had hot water. Old temp limiter switch was probably Ok.

Those are the only things I can think of.

Good luck.

Greg
 
Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
Hi
I have a Beneteau 423. Hoping to get some help. I replace the hot water tank last year and since then I cannot get hot water. The system works as expected under shore power but not when heated from the engine. It's a purely mechanical system via the heat exchanger so I cannot really see what could go wrong. I've checked for an air bubble, flow valve, nothing seems wrong. It was suggested that the there is a thermal couple on the heat exchanger that may not be opening but looking at the schematics it looks purely mechanical as well. I measure the heat of the engine and it does run cool but the hot water did work quite well before. Is there some thermal couple on the engine that controls the flow hot water heater or something similar? -- Just trying to figure out could be wrong. No a lot of options.
I just installed a new hot water heater and added a mixing valve to control the hot water out to my sinks and shower. So please give us more details about your heater name and a drawing by hand what you have connected and where on the heater.
In the meantime, while your getting stuff to post here, I will try to add value here.
1. You stated your engine does not get hot! How hot? If it's less then 100 deg. while running then you have a problem with your Thermostat is stuck open or its the wrong temp size.
2. The engine heat exchanger only cools the engine when the thermostat is in the open condition calling for cooling of the engine which causes the fluid to circulate threw out the engine including, your hot water tank.
3. Your engine has a circulation pump that causes fluid to flow to the hot water tank and then back. However, if your hose is hooked up wrong you may be met with a "check-valve", not allowing proper circulation flow! reverse lines at hot-water tank and test.
So there is some idea's to work with till you get us more information. Hope this helps! Capt. Rob
 
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Jim26m

.
Apr 3, 2019
579
Macgregor 26M Mobile AL
All good points above.
I would just add; describe the relative elevations of the engine, water heater, and hoses. Are there high points in the hose lines going to/from the heater? Is the heater mounted above the engine? Is there a bleed valve or valves at high points to allow trapped air to be purged?
If there are no closed valves or connection errors, trapped air is a likely issue. As seems to be a concern of other posts, some system configurations are inherently hard to bleed. Further details of your bleeding process would be helpful.
 

RoyS

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Jun 3, 2012
1,739
Hunter 33 Steamboat Wharf, Hull, MA
Engine block near cylinders should be too hot to hold your hand against at about 160 F. Start there.
 
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NYSail

.
Jan 6, 2006
3,048
Beneteau 423 Mt. Sinai, NY
If he has this in the original configuration, the engine is above the hw heater by 3+/- feet with a clean run from the engine down. As long as he removed thermostat housing and filled one hose, he would eventually see antifreeze come out of return hose..... No more air! My engine (I have same boat / Yanmar engine) has a bleed fitting on one of the hoses.

Greg
 
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Jim26m

.
Apr 3, 2019
579
Macgregor 26M Mobile AL
If he has this in the original configuration, the engine is above the hw heater by 3+/- feet with a clean run from the engine down. As long as he removed thermostat housing and filled one hose, he would eventually see antifreeze come out of return hose..... No more air! My engine (I have same boat / Yanmar engine) has a bleed fitting on one of the hoses.

Greg
Thanks for that! Seems to virtually eliminate air binding as the problem.
 

NYSail

.
Jan 6, 2006
3,048
Beneteau 423 Mt. Sinai, NY
Just a thought.... I remember I purchased a hw heater for last boat (Raritan) and over the water fittings on tanks there were plastic inserts (not caps) guarding from anything getting into tank prior to installation..... Leave those on and no hot coolant getting to tank!
 
Aug 12, 2009
38
Beneteau 423 Beverly, MA
Hi Thanks for your reply. There are no values between the WH and heat Exchanger. There's a by pass for winterizing and and a flow value that keep water from the HW tank from feeding up to the heat exchanger. The WH heater unit is the same as the one that came with the boat., an 11gal Seaward
 
Aug 12, 2009
38
Beneteau 423 Beverly, MA
Thanks for that! Seems to virtually eliminate air binding as the problem.
Seems odd that it worked before you replaced the WH, but not now.
I do my own work.
I've checked and ruled out the air in the line. I pulled the lines of the hose, drained them, ran them above the engine and ran coolant into the the feed. Came right out the other, drop for drop.
There are no values. I disconnect the lines for winter and splice them via a nipple and drain the HW heater.
I just find it too coincidental that it's not worked since I replaced it. Just can't see what I missed or if something else is broke.


Did you do the work or someone else?

My first thought would be air in the coolant line between the engine and the WH. But you said you checked that...how?

Are there any valves between the engine and WH? I have one on my coolant line that imth8k is there to keep me from losing all of the AF if I have remove the WH. If so, is it open?

Do you have bypass valves on the water lines (so you can isolate the WH when winterizing your water system? I have 3 valves that I have to turn to isolate my WH. One spring I turned 2 of the 3 (in error). Could not get hot water...finally replaced the electric limiter thing on my WH...and STILL NO HOT WATER. Then, while crawling around in the lazzarette where the WH is, I notice the 3rd valve.... opened it and what do you know...I had hot water. Old temp limiter switch was probably Ok.

Those are the only things I can think of.

Good luck.

Greg
 
Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
Still waiting for information on!
1. Engine Type?
a. with a heat exchanger?
b. Model of HW tank ex: mine is an F600 6Gal.
2, Take pictures of your installation starting from your engines thermostat or your water pump and NOT the raw water pump.
take pictures of the new hot water tank and connections and post, please!
3. get a bucket "Home Depo style" Remove the 2 hoses from the heater and put into the bucket pour in antifreeze to cover the hoses in the bucket. Start the engine IDLE please, view the bucket hoses you should see current moving fluid when the thermostat OPENS. IF NOT then you need to remove your thermostat it is malfunctioning. If you see the fluid moving right away in idle and engine is still cool... bad thermostat stuck open.
Your thermostat is used to maintain the engines temp when it needs to cool down the thermo OPENS when its too cool the thermo starts to close, much like your car.
Take thermostat and put into water and bring it to a boil.. you should see it open when temp or boiling water starts. Carefully with needlenose or pliers remove from boiling water and run cold water on it. You might check too that you have the right THERMOSTATE too!
 
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Jul 23, 2009
857
Beneteau 31 Oceanis Grand Lake, Oklahoma
Aren't the lines going to the water heater often the thermostat bypass? The bypass hose would always have flow, but less after the thermostat opens. Correct?
 
Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
Stargazer Hot water system.jpg
Aren't the lines going to the water heater often the thermostat bypass? The bypass hose would always have flow, but less after the thermostat opens. Correct?
On some engines YES, some engines usually have a throttle valve to adjust the flow rate. I have seen this before!
If the flow was on all the time the engine would starve for heat-up... So it should be heating up first and then when the engine is hot enough to allow aiding its engine cooling cycle. I guess you could say being up north where water temps are 40-55 deg year around, I want my engine to have proper heat-ups before adding on the options. That's why I shut OFF my raw water till The engine starts, then I open the seacock for Raw Water Flow. I installed a run-dry impeller GLOBAL to allow this. This way ill never have to see if raw-water backed up into my exhaust manifold. So I guess My Boat, My Way....LOL
 
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Aug 12, 2009
38
Beneteau 423 Beverly, MA
I do have the original configuration. bought the boat when it was 4 years old in 2008. It has a Volvo engine rather than a Yanmar. The water heater is about 2.5 below the heat exchanger.
 

Jim26m

.
Apr 3, 2019
579
Macgregor 26M Mobile AL
If it were mine, I'd get a piece of clear tubing and rig a bypass at the water heater. I'd try to prove flow through engine and hoses first. Then, I'd use a wet vac, garden hose, etc, to prove flow through the heater. If engine/hoses flow, and heater flows, you're back to a bleeding issue. I would be trying to narrow the problem some. May be as simple as a kinked hose where you can't see it. Could be styrofoam, packing caps, or any foreign object causing a blockage. Just start testing individual sections and components. You'll find it.
 
Aug 12, 2009
38
Beneteau 423 Beverly, MA
Still waiting for information on!
1. Engine Type? Volvo D2-55
a. with a heat exchanger? Yes
b. Model of HW tank ex: mine is an F600 6Gal. Seward 11ga
2, Take pictures of your installation starting from your engines thermostat or your water pump and NOT the raw water pump.
take pictures of the new hot water tank and connections and post, please!
3. get a bucket "Home Depo style" Remove the 2 hoses from the heater and put into the bucket pour in antifreeze to cover the hoses in the bucket. Start the engine IDLE please, view the bucket hoses you should see current moving fluid when the thermostat OPENS. IF NOT then you need to remove your thermostat it is malfunctioning. If you see the fluid moving right away in idle and engine is still cool... bad thermostat stuck open.
Your thermostat is used to maintain the engines temp when it needs to cool down the thermo OPENS when its too cool the thermo starts to close, much like your car.
Take thermostat and put into water and bring it to a boil.. you should see it open when temp or boiling water starts. Carefully with needlenose or pliers remove from boiling water and run cold water on it. You might check too that you have the right THERMOSTATE too!