Reheat for DAB Terminal Profile

| Overview

The 75F BMS on the software side reviews the system at regular intervals. And with customer satisfaction and occupant comfort at the forefront of the vision, continues to upgrade and enhance features.

A provision to include Reheat capability in the DAB terminal profile is introduced as part of that process.

With this in place, the overcooling of certain zones during a DAB system profile operation can be avoided. 

| Configuration

In the configuration space, a new field "Use Reheat" is introduced to provision the reheat capability.

"Not installed" is the default value.

| Staged Reheat Control

A DAB terminal profile is already provided with options to control two dampers, with the Analog 1 and 2 of the SmartNode.

Since Analog 2 is mapped to Damper type 2 by default.

Only the relay options of the SmartNode are made available for the staged reheat control as below.

The user can use this option for a staged reheat control, in the terminal.

| Modulating Reheat Control

The "Use Reheat" option also is capable to provision a modulating Reheat control.

For setting up a modulating reheat control

• Remap the damper type2 from Analog 2 types to Smart Damper as below, In the configuration space.

With the above action, the Analog 2 of the SmartNode is made free and is therefore made available for the modulating Reheat control as below.

• Map any of the Analog 2 types to the reheat control.

You can either configure an electric reheat or a water reheat.

| Additional Parameter

With the reheat mapped to Analog 2 or relays, an additional configuration parameter for the Minimum Reheat Damper Position is introduced. The "Minimum Reheat Damper position" ensures that a minimum amount of air always flows to the zone while the reheat loop is running as insufficient air during reheating might damage the unit.

| Operation

A PI loop that uses the value of Heating Desired Temperature - the Reheat Offset (Tuner value) with the current temperature to produce loop outputs is introduced.

When:

Current Temperature < Heating Desired Temperature - Reheat Offset (Tuner Value)

The resultant loop output is a positive one that is scaled for the Analog out 2 or Relay mapped modulating or staged reheat.

It should be noted that when the reheat loop is activated the loop output will scale the analog 2 as mentioned above mapped to the modulating or stage reheat, but the min reheat damper position is not dependent on the same and shall remain at the default value of 40% until changed from the configuration by the user.

When:

Current Temperature > Heating Desired Temperature - Reheat Offset (Tuner Value)

There will be no reheat loop output, and this means the zone requires no further reheat. 

During this, the zone is conditioned as per the DAB profile logic.