The required operating pressure for your propane heater is purely dependent on the LP or NG or the model or configuration number of your portable propane heater. The heater can usually be operated at different pressure irrespective of the fact how much fuel is used so it is highly recommended to gather all the required information of the pressure according to the heater you preferred for. Generally, if the LP gas and the inlet pressure which have a burner on it having a maximum length of 13.5 inches is regarded as one of the best pressure ratings to be used in a heater.