There are NO Suburban AC or heat Pump units for RV's. You have Suburban furnaces. If you have Heat Pumps, Tiffin installed RVP (Coleman) AC and Heat Pump units. NO, Tiffin did not install any type heat Strip in the roof top HP units. Here is the quick parameter of HOW RVP Heat Pumps operate on Tiffin. The HP's will work until the outside temp goes below 35 degrees give or take a few degrees. If below 35 degrees outside ambient, ONLY the furnace will come on even in HP mode(Electric Heat which means Heat Pump, NOT electric coils).
RVP units have a 5 degree separation between the set temp and the inside actual temp. IF, the set temp is MORE than 5 degrees from the inside temp, even in HP mode, the Furnace will come on as well as the HP until the set temp is within the 5 degrees and then the furnace kicks off and the HP continues the HEAT until you reach the set temp.
Example. The RV interior is 55 degrees. You set the HP to 70 degrees. BOTH the HP and the Furnace will come on and start to heat up the RV. Once the interior gets to 65 degrees, the furnace stops and the Roof HP continues until the 70 degree temp is met. Then the HP will shut off and when it gets below 70 degrees the roof top HP will then come on and reheat without the furnace. IF the interior of the RV is 66 degrees and the set temp is 70, ONLY the HP will come on and will heat the RV that 4 degrees and then shut off. Doug