Home TechTime January 2017 HVAC Controls
TechTime is a Neptronic publication aiming to inform you on the best ways to deal with common issues highlighted by our technical support team. Each edition features three new topics and will be posted on neptronic.com.

Ramp It Up
VAV Ramps and Controller Possiblities

The following article explains the various VAV ramps available on our products. Not all controllers come with the same options. Refer to the Specification and Installation Instructions of each controller for appropriate information.

The first section concerns motor ramps, which are the type of action taken by the damper actuator of the VAV box. The second section covers the duct reheat, baseboard and sub-cool sequence of operation. The third section shows the possibilities and limitations of each controller able to control a VAV box.

Motor Ramps

Cooling Only - The central system can only deliver cool air to the VAV box. All the heat will come from the reheat and baseboard.

Heating Only - The central system can only deliver hot air to the VAV box.

Cooling & Heating (Changeover) - The central system can deliver cool and hot air to the VAV box. A changeover sensor/switch is required.

CH1 - The central system can only deliver cool air to the VAV box. When there is a demand for heat, the controller uses the maximum and minimum heating airflow setpoints and activates reheat. This ramp is only supported by the EVCB series.

Note that the EVCB series controllers can also be configured as CAV (Constant Air Volume).

Cooling and Heating Ramps

Reheat refers to the heating device located after the VAV box. It can either be a water coil or it can be electric. Signals vary based on the type of heater. The supported signals are:

Note that the cooling ramps can be in the same format as the heating ramps, except for pulse signals (heating only).

Baseboard refers to the heating devices located on the exterior walls of a building. They are used to maintain temperature for external zones and are great to cut the cold drafts generated by the windows in winter time. Baseboards can be supplied by hot water or they can be electric. The signals supported are the same as the reheat (except for stages).

Note that the reheat and baseboards can be activated at the same time or offset from one another. Some prefer setting the baseboards as a first stage and other prefer the reheat as the first stage.

Sub-cool refers to the cooling devices located after the VAV box. In terminal unit applications, these are water coils, but DX coils are possible. We do not have many requests for this type of control, but it is available. The supported signals are:

- On/Off or 1 Stage (water and DX)

- 2 Stages (DX only)

- 3 Stages (DX only)

- 4 Stages (DX only)

- Modulating 0-10Vdc & 2-10Vdc which includes 0-20mA & 4-20mA with a 500Ω resistance (water only)

- Floating (water only)

Possible configurations based on the controller model for single duct applications

Controller models are identified on the top of the page.

Application drawing shows the possible configurations and required input/output(s).

The controller at the bottom of the page represents the input/outpoint point count and configurations supported.