That doesn' sound correct. It is not how my Aqua Hot works. If I turn my diesel burner switch on then the boiler fires up and maintains boiler temp regardless of what the thermostats are set at. Turning the thermostat on and setting the thermostat to furnace mode turns on the circulating pumps. Raising the temps on the thermostat then turns on the fans to blow hot air. My thermostats do not control the diesel boiler only the fans and circulating pumps. With the circulating pumps running then when the fans come on I get hot air right away.
"Gunner" USN Retired, Airdale
2004 Monaco Signature 44' Conquest. Detroit 60