We have Hydro Hot. It should take no more than 10 minutes it should be blowing warm air. For Hydro Hot service use this link:
http://www.aquahot.com/Service-Help/Service-Locations.aspx
another good resource is: www.rvhydronicheaterrepair.com (Roger Berke) he lives in California but has lots of info on his site.
If the fans aren't blowing you need new fans inside the vents.
If the air is not warm, some of your brass check valves may be sticking from lack of use. Tap with a screw driver. Remove cover from Hydro Hot and follow hoses until you see the valves.
You can also look at the lights outside to see if there are any warning lights on the unit like low coolant.