Table 2 — Light Commercial Thermidistat (LCT) Operating Sequence and System Response
UNOCCUPIED
| COOLING | ER Comp |
| ER Fans |
|
| RT Comp 1 |
| RT Comp 2 |
| RT Fans |
| RT Heat |
Indoor Temperature Above 2nd Stage |
|
|
|
|
|
|
|
|
|
|
|
| |
Set Point |
|
|
|
|
|
|
|
|
|
|
|
| |
| Humidity Low & OAT Low | On |
| On (cyc.) |
|
| On w/o MM |
| Off |
| On (cyc.) |
| Off |
|
|
|
|
|
| ||||||||
| Humidity Low & OAT High | Off |
| Off |
|
| On w/o MM |
| w/o MM |
| On (cyc.) |
| Off |
| Humidity High & OAT Low | Off |
| Off |
|
| On w MM |
| On w MM |
| On (cyc.) |
| Off |
| Humidity High & OAT High | Off |
| Off |
|
| On w MM |
| On w MM |
| On (cyc.) |
| Off |
Indoor Temperature Between 1st and |
|
|
|
|
|
|
|
|
|
|
|
| |
2nd Stage Set Points |
|
|
|
|
|
|
|
|
|
|
|
| |
| Humidity Low & OAT Low | Off |
| On (cyc.) |
|
| Off |
| Off |
| On (cyc.) |
| Off |
|
|
|
|
|
| ||||||||
| Humidity Low & OAT High | Off |
| Off |
|
| On w/o MM |
| Off |
| On (cyc.) |
| Off |
| Humidity High & OAT Low | Off |
| Off |
|
| On w MM |
| Off |
| On (cyc.) |
| Off |
| Humidity High & OAT High | Off |
| Off |
|
| On w MM |
| Off |
| On (cyc.) |
| Off |
Indoor Temperature Below 1st Stage | Off |
| Off |
|
| Off |
| Off |
| Off |
| Off | |
Set Point |
|
|
|
|
|
| |||||||
|
|
|
|
|
|
|
|
|
|
|
| ||
NOTE: OAT < 55° all compression off* |
|
|
|
|
|
|
|
|
|
|
|
| |
| HEATING | ER Comp. |
| ER Fans |
|
| RT Comps. |
| RT Fans |
| RT Heat |
|
|
Indoor Temperature Above 1st Set | Off |
| Off |
|
| Off |
| Off |
| Off |
|
| |
Point |
|
|
|
|
|
|
| ||||||
|
|
|
|
|
|
|
|
|
|
|
| ||
Indoor Temperature Between 1st and | Off |
| Off |
|
| Off |
| On (cyc.) |
| On, 50% |
|
| |
2nd Stage Set Points |
|
|
|
|
|
|
| ||||||
|
|
|
|
|
|
|
|
|
|
|
| ||
Indoor Temperature Below 2nd Stage | Off |
| Off |
|
| Off |
| On (cyc.) |
| On, 100% |
|
| |
Set Point |
|
|
|
|
|
|
| ||||||
|
|
|
|
|
|
|
|
|
|
|
| ||
|
|
|
| OCCUPIED |
|
|
|
|
|
|
|
|
|
| COOLING | ER Comp |
| ER Fans |
|
| RT Comp 1 |
| RT Comp 2 |
| RT Fan |
| RT Heat |
Indoor Temperature Above 2nd Stage |
|
|
|
|
|
|
|
|
|
|
|
| |
Set Point |
|
|
|
|
|
|
|
|
|
|
|
| |
| Humidity Low & OAT Low | On |
| On |
|
| On w/o MM |
| On w/o MM |
| On |
| Off |
|
|
|
|
|
| ||||||||
| Humidity Low & OAT High | On |
| On |
|
| On w/o MM |
| On w/o MM |
| On |
| Off |
| Humidity High & OAT Low | On |
| On |
|
| On w MM |
| On w MM |
| On |
| Off |
| Humidity High & OAT High | On |
| On |
|
| On w MM |
| On w MM |
| On |
| Off |
Indoor Temperature Between 1st and |
|
|
|
|
|
|
|
|
|
|
|
| |
2nd Stage Set Points |
|
|
|
|
|
|
|
|
|
|
|
| |
| Humidity Low & OAT Low | Off |
| On |
|
| Off |
| Off |
| On |
| Off |
|
|
|
|
|
| ||||||||
| Humidity Low & OAT High | On |
| On |
|
| On w/o MM |
| Off |
| On |
| Off |
| Humidity High & OAT Low | On |
| On |
|
| On w MM |
| Off |
| On |
| Off |
| Humidity High & OAT High | On |
| On |
|
| On w MM |
| Off |
| On |
| Off |
Indoor Temperature Below 1st Stage |
|
|
|
|
|
|
|
|
|
|
|
| |
Set Point |
|
|
|
|
|
|
|
|
|
|
|
| |
| Humidity Low | Off |
| On |
|
| Off |
| Off |
| On |
| Off |
|
|
|
|
|
| ||||||||
| Humidity High | On |
| On |
|
| Off |
| Off |
| On |
| Off |
NOTE: OAT < 55° all compression off* |
|
|
|
|
|
|
|
|
|
|
|
| |
| HEATING | ER Comp |
| ER Fans |
|
| RT Comps |
| RT Fans |
| RT Heat |
|
|
Indoor Temperature Above 1st Stage | Off |
| On |
|
| Off |
| On |
| Off |
|
| |
Set Point |
|
|
|
|
|
|
| ||||||
|
|
|
|
|
|
|
|
|
|
|
| ||
Indoor Temperature Between 1st and |
|
|
|
|
|
|
|
|
|
|
|
| |
2nd Stage Set Points |
|
|
|
|
|
|
|
|
|
|
|
| |
| OAT >Set Pt | On |
| On |
|
| Off |
| On |
| Off |
|
|
|
|
|
|
|
|
| |||||||
| OAT <Set Pt | On |
| On |
|
| Off |
| On |
| On, 50% |
|
|
Indoor Temperature Below 2nd Stage |
|
|
|
|
|
|
|
|
|
|
|
| |
Set Point |
|
|
|
|
|
|
|
|
|
|
|
| |
| OAT >Set Pt | On |
| On |
|
| Off |
| On |
| On, 50% |
|
|
|
|
|
|
|
|
| |||||||
| OAT <Set Pt | On |
| On |
|
| Off |
| On |
| On, 100% |
|
|
| LEGEND |
|
|
|
|
|
|
|
|
|
|
|
|
Comp — Compressor |
|
|
|
|
|
|
|
|
|
|
|
| |
ER | — Energy Recovery section |
|
|
|
|
|
|
|
|
|
|
|
|
MM— MoistureMi$er™ Dehumidification Device OAT —
RT — Rooftop Unit Set Pt — Set Point
*Unless unit compressor has been rewired as described in Step 11 (page 29).
37
