Pneumatic Retrofits

Pneumatic controls can still be found in some buildings. In this scenario, water control valves have pneumatic actuators that are controlled by a pneumatic thermostat in the room. There is a separate electric switch that controls fan speeds. For this type of retrofit there are two options:

Keep all the controls at line-voltage

Migrate all the system to 24VAC.

In most cases, option 1 is the simplest since valves and fan selector switches are usually close to each other. If this is the case, the voltage adapter (FCA-47) is required to control the fan speeds. For controlling the pneumatic water valves, a 3-way electro pneumatic (EP) valve is needed for each valve needing control. The 3-way EP valve will be installed in the pneumatic tubing feeding each water valve. The 3-way EP valve will be connected in the same way as the fail position of the water valve. For example, in colder climates, the heating valve will fail open. The 3-way EP valve can then be connected using the normally open (NO) port to the pneumatic tubing feeding the water valve. The 3-way EP valve opening signal voltage needs to match the line voltage of the fan coil.

Option 2 is a better solution when the water valves and fan speed selectors are not relatively close or where valve location is not easily accessible in the room. In this case, the 3-way EP’s are selected to use 24VAC as the driving voltage and for controlling the fan speeds, you will need to add a 24VAC relay per fan speed. A new 24VAC transformer needs to be installed as well, which could complicate the install and increase costs of the retrofit.