Reheat Sequence; Reheat Sequence - Nailor 37S Manual

Reheat Sequence
The EZvav controllers can control three types of reheat installations.
• Modulating reheat
• Staged reheat
• Floating reheat
All reheat is controlled by either the Heating loop or the Discharge Air Temp Limiting (DAT) PID loop. Loops are described in the
topic PID control loops on page 36.
• If Discharge Air Temp Limiting is enabled, reheat is controlled by the DAT PID loop.
• If DAT control is not enabled, reheat is controlled by the Heating loop.
In the following descriptions, the loop controlling reheat is referred to as the Reheat loop.
Modulating reheat
If the controller is configured for modulating reheat, it controls an analog reheat unit with 0-10 volts DC at the analog reheat
output. On a call for reheat, the reheat output is modulated over the span of the Reheat loop. If the Reheat loop is less than 10%,
the reheat output remains at zero. The reheat is set to zero if the Cooling loop is active.
See the topic Modulating reheat on page 31 for an application drawing.
Figure 8-4 Modulating reheat operation
HTG %
100
10
0
Staged reheat
If the controller is configured for staged reheat, it can control up to three stages of reheat through binary triac outputs. The reheat
outputs are commanded On when the Reheat loop rises above the On threshold and Off when the loop drops below the Off
threshold. Thresholds are described in the following chart, Staged reheat thresholds on page 39.
See the topic Staged reheat on page 30 for an application drawing.
Table 8–1 Staged reheat thresholds
Heating Stage
On threshold
Stage 1
Stage 2
Stage 3
Date: 10-2016 Supersedes: 7-2016
Nailor reserves the right to change any information concerning product or specification without notice or obligation.
Installation and Operation Manual
HTG SPAN
-2F HTG SP
Output State
Off threshold
35% 15%
65% 45%
95% 75%
EZvav Digital Controls
●
Room temp increase
Page 39 of 48
IOM-EZVAVINST