News Article

Factory Mounted verses Field Mounted Controls

When faced with a renovation or construction of a new building one of the choices that building owners and engineers face is whether to order HVAC equipment with factory mounted or field mounted controls.  While either method may be capable of achieving the desired result, communication between the owner, engineer, equipment manufacturer and controls contractor is vital to ensuring the success of the project.  Clearly assigning responsibilities between the equipment manufacturer and the controls contractor can eliminate delays and unexpected costs to the project.

If field mounted controls are selected, it is expected that the controls contractor will provide and install all controllers and all of the sensors (I/O points) that are required to accomplish the sequence of operation and graphical display of the HVAC systems.  However, when factory mounted controls are selected the expectations are not always clear to everyone.  These expectations can be clarified by adding the following to drawings and specifications:

“If factory mounted controls are provided, the equipment manufacturer is responsible for meeting the entire sequence of operation as outlined.  In addition the equipment manufacturer is responsible for providing the data required to meet all of the points indicated in the points list for that piece of equipment.”

In addition, many sensors are shipped loose with factory mounted controls and the controls contractor is expected to install and wire these to the factory controller.  This can again be clarified by adding one of the following to each sensor or control component shown in piping and airflow diagrams:

① Installed and wired by the equipment manufacturer.

② Provided and shipped loose by equipment manufacturer.  Installed and wired by the temperature controls contractor.

③ Provided, installed and wired by the temperature controls contractor.

 

While at first glance factory mounted controls may appear to be the best option for ease of installation, the required points, complete sequence of operation and desired graphical representation for each piece of HVAC equipment must be considered.  Regardless of which method is selected, communication of requirements and assignment of expectations are keys to eliminating confusion, delays and potential cost increases to a project.

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