Engine preheat hose to the boiler

[RainbowrvGreg]

The Aquahot in my last bus was early setup and the ah dealer did not understand how it was setup. we had a bit of a discussion about two system coolant loops where he claimed the AH used the coolant from the engine and engine 12 gal contents as the reservoir. I was not able to convince him that the systems were separate and unique.

On my prior bus 94pt Bluebird set up there is a transfer heat ex changer in a wheel well where the detroit coolant loop was not part of the AH coolant loop heat system. the two closed systems meet at a Transfer heat exchanger . the 94 was a Wabasto burner more or less and the motoraid waterheater and interior registers was part of that system detached from the detroit . I think it is necessary to differentiate the term heat exchanger and Transfer heat exchanger because the interior radiators and bay radiators are called heat exchangers in the AH manuals . The aquahot system in my lxi and your bus is likely a 431-12 . AH has manuals online
http://www.aquahot.com/files/owners_manu...l05-02.pdf
The install instructions show engine coolant being introduced as a separate loop but I do not see an actual plumbing depictions other than inlet and outlet. since it does not say that engine coolant is necessary and the expansion tank is included with the other three zones I would say there are two coolant paths and loops to the ah burner. check out notes page 19.
http://www.aquahot.com/files/installatio...l03-96.pdf
BUT
this does not mean that Bluebird did not tie the engine coolant look to the two plastic expansion tank loops and introduce a Transfer Heat exchanger some place under the frame rails ? I guess coolant color difference may be a tall tell sign if you have different detroit coolant color.
If you are close to this junk yard, you may get a good insight on the methods employed.
https://rvexteriorbodypanels.visonerv.co...704/s56.pl
I found no documentation of the plumbing of the detroit to the front chassis heat system or connection to the AH sorry I will have a look if I get around to dropping the LP tank as planned

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I plan to make up a loop for the inlet and exit of the Detroit coolant lines you found for use if I find an issue while traveling. the damage to your system may be the result of someone confused with the plumbing employed and there being a dead end in the Detroit loop to the front chassis heat. Or a switch in the pump control wires that start the engine preheat pump there is a warning in the engine preheat Wanderlodge owners manual that I can vaguely remember . One other thing that comes to mind with the AH engine heat pump is: if they use a Transfer heat ex changerer there will need to be another pump to flow fluids from and to the detroit and it may or may not loop to the chassis heat?