Power Exhaust Power Exhaust steveski (Mechanical) (OP) 23 Oct 04 11:53 What are the basic issues to consider when deciding whether an HVAC unit will require "Power Exhaust"?Example: New HVAC unit with outside air economizer & demand-control ventilation serving a high-school cafeteria.Thank you. RE: Power Exhaust lcleveland (Mechanical) 23 Oct 04 22:35 power exh is one way to control building pressurization. how do you intend to control the static pressure of the building during economizer and during normal run with fresh air make-up? is the return ducted or plenum?ducted returns should have return fan. you may also want to consider an exhaust fan with integral energy recovery . in short many factors are to be considered when designing a system , check your local codes for air turn over requirements in a cafeteria they can differ from other spaces. power exhaust is critical to achieve needed air turn over with the most economical sized unit. RE: Power Exhaust 8RLJ (Computer) 12 Jun 05 17:31 I currently have a White-Rodgers Heat Pump Thermostat 1F58-910 that I am replacing with a Totaline P474-1050 and need help with the wiring.The White-Rodgers is using 5 wires as follows:F-GreenV-Red also jumped to VRY-WhiteM-YellowR-OrangeThe Totaline has the follwing terminals:GY1W1,O,BRCY2W2Can someone help me match the wiring between the two thermostats?thanks... RE: Power Exhaust cme (Mechanical) 13 Jun 05 19:59 Is this DX or CHW?I would look into and AAON unit with enthalpy wheel if it is DX. They have a power relief fan. You can get all kinds of options, hot gas reheat and return air bypass.Barometric relief only works for retail strip malls where there is no neturn ductwork.