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Old 03-04-2016, 06:11 PM   #1
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Tapping the cooling system for a heater

Has anyone done this off a Cummins 6BTA? Simple?
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Old 03-04-2016, 06:49 PM   #2
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Yes, it's very simple and does quite a good job. I teed off the exhaust manifold and returned to the water pump inlet.

Ted
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Old 03-04-2016, 06:51 PM   #3
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What you want is often called a bus heater. Heatercraft, among others makes the exchanger/blower unit. You use the same engine taps that supply coolant to your boat's hot water heater, if installed. You typically plumb the water heater first and then the coolant flow goes to the bus heater and then back to the engine.


There are some hydraulic tricks about elevation and venting that need to be observed.


You also need to know that heat will stop fairly soon after you shut the engine down.


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Old 03-04-2016, 07:53 PM   #4
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If your boat has a diesel heat system, you can use the engine heat loop and a heat exchanger to heat/run the heating system while underway. But it would only matter if you have an existing heating system.
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Old 03-04-2016, 10:26 PM   #5
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We run the Wabasto underway. Much much quieter than the bus heater fan in the salon. When the Wabasto is running while underway I only realize it's on when I step outside to the aft cockpit.
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Old 03-05-2016, 07:26 AM   #6
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"You use the same engine taps that supply coolant to your boat's hot water heater, if installed. You typically plumb the water heater first and then the coolant flow goes to the bus heater and then back to the engine."

Too many domestic HW heaters attempt to regulate the HW temperature by using a thermostat that blocks the coolant flow.

The heater in series will have almost no water flow after the HW is warm

You can remove this thermostat , or use a parallel setup for HW and boat heat .

Either way an ANTI SCALD valve in the fresh water system is advised , esp if kids or old folks are aboard.
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Old 03-05-2016, 08:00 AM   #7
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Interesting. I haven't encountered a thermostat controlling coolant flow to a domestic HW tank, but would remove it too if I did encounter one.

And I very much encourage a mixing valve as well. 180F water will burn you very quickly, and that's your hot water's temp when heated from the engine. I have also encountered fresh water plumbing devices that are only rated to 150F or some other value well below 180F. Running those devices so far out of spec is asking for failures. Whale quick connect fittings are a good example. They are only rated to 150F which is normally more than enough, except when the water is heated to engine temp....
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Old 03-05-2016, 08:35 AM   #8
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Has anyone done this off a Cummins 6BTA? Simple?

There are two simple taps on the starboard side of the engine. The supply is on top the return is lower behind the alternator and just forward of the oil filter. Which must be removed to access the fitting. Click image for larger version

Name:	ImageUploadedByTrawler Forum1457184799.726687.jpg
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ID:	49538Click image for larger version

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Old 03-05-2016, 10:01 AM   #9
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We run the Wabasto underway. Much much quieter than the bus heater fan in the salon. When the Wabasto is running while underway I only realize it's on when I step outside to the aft cockpit.
My buddy's Red Dot bus heater was quite noisy. Our Heatercraft is so quiet we can barely hear it, and does a great job keeping our cabin warm and dry.
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Old 03-05-2016, 11:54 AM   #10
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There are two simple taps on the starboard side of the engine. The supply is on top the return is lower behind the alternator and just forward of the oil filter. Which must be removed to access the fitting. Attachment 49538Attachment 49539

Do you know the size and type of fittings that were used?
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Old 03-05-2016, 10:15 PM   #11
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Tapping the cooling system for a heater

They are nothing special. Normal NPT thread. But you will have to look on your engine to see if they are 1/2" or 3/4". Mine are 3/4".
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Old 03-06-2016, 07:15 AM   #12
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"And I very much encourage a mixing valve as well"

If a mixing valve runs out of cold water it will pass Hot water that can scald.

An anti-scalding valve will shut the Hot off in the same condition.

Your choice....same instal time.
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Old 03-06-2016, 07:31 AM   #13
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I'm not 100% up on the nomenclature, but when I bought a "tempering valve" years ago for my house, it just passed a set amount of cold water, regardless of the relative temperature of hot and cold:


I ended up ripping it out and replacing it with a "thermostatic mixing valve":


I think the latter is what FF is referring to.

The tempering valve can only statically adjust the amount of cold water by turning the dial on the top. And even that didn't offer enough range for the wide swings of both the incoming cold water (seasonal) and the domestic hot water (from the boiler.)

I suspect it's the same in a boat, so I put in a proper termostatic mixing valve.

In my case, it wasn't so much about scalding - most people are smart enough not to hold their hands under steaming hot water that long - but to get a more even temperature and extend the time between having to power the water heater.
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Old 03-06-2016, 07:31 AM   #14
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Quote:
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My buddy's Red Dot bus heater was quite noisy. Our Heatercraft is so quiet we can barely hear it, and does a great job keeping our cabin warm and dry.
Also what makes a difference is fan speed and distance/turns to vent if any ducting is used. Usually remoted diesel heaters are quiet compared to surface mounted bus heaters.

Apples to apples as they say....
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Old 03-06-2016, 06:47 PM   #15
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Not sure why I would need a mixing valve as this is for a heater, not the water heater. I do have a Wabasto heater, just trying to cut down on the use of fuel and harness some of the heat off one of the engines.
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Old 03-06-2016, 07:45 PM   #16
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I have 3 Heatercraft units with a small pump to push the coolant around the 100'+ of hose that makes up the heating loop in my 45' boat. Dose a nice job down to around 32 degrees while the engine is burning 2 GPH. When I get some time, I will do a thread on my engine coolant heat system.

Ted
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Old 03-06-2016, 07:48 PM   #17
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Interesting...my run from the engine to heater will be less than 10' so i shouldn't need a pump. I don't have one on the other side with the water heater.
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Old 03-06-2016, 09:59 PM   #18
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One problem you may run into is that the heater system may cool the engine system more than normal. The thermostat bypass is designed to keep the coolant at a minimum temp and still circulate coolant to avoid hotspots, and with cold water into the heat xchanger it may be at the minimum. Add in another cooling source, at idle, and your engine may be running very cold. Newer electronic engines especially dont deal well with this.
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Old 03-07-2016, 02:10 AM   #19
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Great points. As with everything, there is always a trade off. I suppose you just have to be aware of how you are operating the engines and switch to the Wabasto heater if operating conditions warrant.
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Old 03-07-2016, 05:51 AM   #20
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Install petcocks at the engine where you connect so you can shut it off if you need to or if you don't need the heat.
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