This specific part is engineered for horizontal mounting

technicians should typically calibrate the outlet pressure to 10

as it compromises the factory-sealed terminals and can lead to voltage loss or improper spark timing

and PFG series

Johnson Controls T-4000-3139 Plastic Cover This specific part is engineeredThe Johnson Controls T 4000 3139 is a professional grade horizontal pneumatic thermostat cover designed specifically for the T 4000 Series room thermostats. Engineered for demanding commercial environments, this white plastic cover provides a clean, uniform look for horizontal mounted controllers where a blank faceplate cover is required. As a genuine Johnson Controls replacement part, it ensures a precise fit for single or dual element sensing units