I am modeling a building in eQUEST that uses hot water coils to meet the heating load. The water is heated using electric heat pumps as well as propane boilers. Most of the time in the year the heating system is electric heat pumps, but when the outside air temperature drops very low (and the COP of the heat pump drops) the electric heat pumps shut down and boilers come online. My problem is using both of these systems as the sources of heat for the water coils. Can anyone suggest a method to do that in eQUEST?