The Aqua-Hot FAQ 10 (http://www.aqua-hot.com/esource/ecom/esource/default/FAQs.aspx
) says to leave the diesel burner ON while driving to ensure the boiler water temperature is high enough to keep the coach warm.
The closed engine pre-heat system will circulate water through the boiler while the engine is running. The Aqua-Hot is in effect acting a like a 2nd engine radiator during this time as this is the same engine coolant water being circulated through the engine radiator. The engine heated water typically runs in the region of 180 to 215 degrees and is used to heat the Aqua-Hot boiler water. The Diesel Burner thermostat in the Aqua-Hot boiler typically operates in the range of 158 to 190 degrees. If the Aqua-Hot boiler is kept hot enough by the engine pre-heat water, then the Aqua-Hot boiler thermostat will not light off the diesel burner. If, do to Aqua-Hot system loads (ie outside temps real low), the engine pre-heat water is not able to keep the boiler temp up high enough, the Aqua-Hot boiler thermostat will light off the diesel burner in order to provide the extra heat needed to bring the boiler temp back into it's operating range. So, the Aqua-Hot boiler switch can be ON but it will not light the diesel burner if the engine pre-heat water keeps the boiler at operating range.
The floor registers and associated pumps are controlled by seperate Thermostats. Coach installations that have dual Duo-Therm A/Cs typically use a 4 or 5 button CCC unit. The Aqua-Hot heat exchangers are also controlled by the Duo Therm CCC system. For a 2 zone Duo Therm system, when set for furnace, the thermostat in the main CCC unit controls temps in the front half of the rig and a thermostat associated with the rear AC unit controls temps in the rear of the coach. Each AC unit sends a control signal to the Aqua-Hot (reffered to as zones on Aqua-Hot) as needed based on the seperate theromostat settings (zone set points of Duo-Therm CCC). These are just 12VDC On/Off signals. When the zone control signal is ON, the associated Aqua-Hot zone pump starts circulating water for the zone and the zone heat exchanger fan is turned ON.
While I used a Duo-Therm system to explain heat exchanger operation, there is no reason seperate thermostats (Front, Rear, storage Bays, bathroom, etc.) cannot be used to control Aqua-Hot zones. Aqua-hot simply needs some form of zone control thermostat to control heat exchanger operation.
Aqua-Hot (formally Hydro-Hot) Operators, Installation, Service, and Parts manuals are located here: Aqua-Hot Heating Systems Inc.
Just remember the heat exchangers distributed around the coach are feed from closed loop systems like an old radiator system in a house. The fan in each heat exchanger and the associated water circulating pump used to move water in the zone system is controlled by a standard room thermostat.
The boiler can be heated by the diesel burner, and electric element (shore power or generator), or engine preheat water. Both diesel burner and electric element are controled by a boiler thermostat. Engine pre-heat water is what ever temp the engine radiator water is at.