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vtsailguy 05-25-2013 03:33 PM

Diameter of Diesel Water Exhaust Pipe
 
Wonder if someone can help me here....

I am connecting up a hot water heater. The current tubing from the diesel for the water exhaust is 3/4". I have a bunch of 1/2" tube lying around to run to the heater's exchanger.

Does it matter to the engine to step down to a smaller size tube, or is it important to keep to the 3/4" (i.e. have to by more tubing).

sailvayu 05-25-2013 04:36 PM

Re: Diameter of Diesel Water Exhaust Pipe
 
I would stick to the 3/4" to reduce back pressure on your pump. you are adding a longer line with more connection this will add some resistance in and of itself. That said you should be using the coolant side of your engine water not the raw water. Most water heaters are not designed to have raw or salt water in them. It works but you will be replacing the heater every 4-5 years if you do.

deniseO30 05-25-2013 07:02 PM

Re: Diameter of Diesel Water Exhaust Pipe
 
Actually.. I believe most WHs are 1/2" heat exchanger connections. the "loop" from the engine would be circulation of coolant rather then actually pumping. My boat, the lines are 7/8 ID and reduced to 1/2" and it works too well!

BarryL 05-25-2013 09:23 PM

Re: Diameter of Diesel Water Exhaust Pipe
 
Hello,

I'm confused. Is your engine fresh water cooled (has coolant) or raw / sea water cooled? If it is raw water cooled I don't know if it will get got enough to heat the water tank. Also, if your boat is in salt water i don't believe the water heater is designed for salt water.

If the engine is fresh water cooled then the water heater gets connected to the engine coolant, not the sea water / raw water pump. The connection should be:
engine block water OUTPUT to water heater input, water heater output to engine heat exchanger input, engine heat exchanger output to engine block input.

Good luck,
Barry


Quote:

Originally Posted by vtsailguy (Post 1035459)
Wonder if someone can help me here....

I am connecting up a hot water heater. The current tubing from the diesel for the water exhaust is 3/4". I have a bunch of 1/2" tube lying around to run to the heater's exchanger.

Does it matter to the engine to step down to a smaller size tube, or is it important to keep to the 3/4" (i.e. have to by more tubing).


Stu Jackson 05-26-2013 11:42 AM

Re: Diameter of Diesel Water Exhaust Pipe
 
What's the connection size at the heater? That's the size I'd use, and only make it smaller to connect at the engine. For freshwater cooled (i.e., heat exchanger) engines, the take off for the heaters is usually at/below the thermostat and back to the freshwater coolant pump, and NOT on one of the lines to the HX.

vtsailguy 05-26-2013 12:44 PM

Re: Diameter of Diesel Water Exhaust Pipe
 
Quote:

Originally Posted by BarryL (Post 1035552)
I'm confused.

Me too :)

Thanks to all these posts guys, it wasn't occurring to me that the hose I was seeing IS the closed loop for coolent. It's not raw water cooled.

So it sounds like I can just tap into that loop and run to the exchanger on the water heater., with no real issue with 1/2".....

Faster 05-26-2013 02:52 PM

Re: Diameter of Diesel Water Exhaust Pipe
 
As Stu indicated there's a 'standard' tie-in point for HW heater circuits. It would be wise to find out manufacturer's recommendations - you want the loop to be 'driven' not flow neutral.

Stu Jackson 05-26-2013 08:32 PM

Re: Diameter of Diesel Water Exhaust Pipe
 
What engine do you have? Might help us to help you.

vtsailguy 05-27-2013 10:03 AM

Re: Diameter of Diesel Water Exhaust Pipe
 
:)

Volvo Penta MD2030 29hp


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