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Author Topic: How do I size heat exchanger to preheat engine?  (Read 940 times)
belfert
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« on: August 28, 2006, 12:39:16 PM »

Since I am putting in a hydronic heating system, I figure I should add a heat exchanger to preheat the engine.

My Series 60 used to have a Webasto to heat the engine that is long gone.  I am thinking I should use the heater hose that used to go to the Webasto for the heat exchanger.  The problem is that the heater hose to the Webasto is 1 1/2" hose.

Will I restrict the coolant flow too much if I use a heat exchanger with 1" NPT ports?

Brian Elfert
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H3Jim
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1995 Prevost H3-41, series 60, B500 Allison




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« Reply #1 on: August 28, 2006, 09:29:20 PM »

Brian, mine came with a 41k btu Espar heater.  The heater hose from teh bus engine was 1 1/2" like yours, then it was stopped down to 3/4 inch inlet and outlet for the Espar, then back up to a 1" for eth rest of the heating run.  When I added the heat eschanger that I bought from Dick wright, it had /has 3/4 " inlet and outlet, so I just cut the heater out and replaced it with the heat exchanger.  I ahve not finished my system yet, but after extensive talks with both Dick and  David Haynes   800-685-4298 x127, I think it will be ok with proper flows.

The flow needs to be high enough that the delta T (the difference in temperature between the inlet and oultlet of the heater) is -- darn it I'm having a senior moment, but I think its less than 10 degrees.  A call to David can confirm the correct delta max.  If the delta is too high, then the heater will cycle on and off too rapidly and not function effectively.  The flow required for a 41k btu heater is well within the flow abilities of  3/4 inch pipe.

The way the coolant pipes are set up, you are not restriciting the coolant flow in the engine, so that is not a worry.
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Jim Stewart
El Cajon, Ca.  (San Diego area)

Travel is more than the seeing of sights, it is a change that goes on, deep  and permanent, in the ideas of living.
Paso One
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« Reply #2 on: August 29, 2006, 07:22:45 AM »

Hi Brian my Webasto 2010  45,000 Btu unit has 3/4 inch outlets and I have one loop that feeds 5/8 hose.  Paul
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68 5303 Fishbowl 40' x 102"
6V71  V730 4:10
belfert
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« Reply #3 on: August 29, 2006, 08:45:26 AM »

Hi Brian my Webasto 2010  45,000 Btu unit has 3/4 inch outlets and I have one loop that feeds 5/8 hose.  Paul

My bus had a 80,000 BTU Webasto originally and that may be the reason for the 1 1/2" feed to the Webasto.  I want to be sure that if use a plate exchanger with 1" fittings that I won't be restricting coolant flow too much.  I believe the coolant line to the Webasto went first to the passenger/driver heat so I suppose it isn't an important line.  Everything except the driver's heat and defrost is longer gone.

I think I'll be okay.

Brian Elfert
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David Anderson
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« Reply #4 on: August 30, 2006, 06:32:46 PM »

Brian,

I too have the DB2010 setup with a 40k heat exchanger.  I hung the exchanger close to the engine and run a 3/4" fitting and line out of a pipe plug just below the t-stat on my 6v92 and continue through the heat exchanger and loop around to the back side of the water pump on the engine.

It takes about 20 minutes to heat the block in 20 degree weather.   The webasto came with a book that had diagrams of inlets/outlets for all makes of engines.  The 60 series should be included. 

If you use a webasto make sure they tell you about adjusting the damper for high altitude operations.  I found out the hard way at Wolf Creek ski resort.  You will make lots of carbon black if not adjusted and it won't heat your coach.

David
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