This damper is normally closed but will open fully during cold outdoor weather when the no.1 paper machine is down and not providing heat for the economizer. The recirculation damper is operated by a pneumatic operator controlled by a separate air temperature controller and an outside thermostat.
An electric heater heats the recirculated air before it is supplied back to the building. This heater will be used when the No.1 Machine is down and the outside air temperature is below 13 degrees centigrade. The heater is also controlled by the above mentioned air temperature controller.                                    next page