Northern Heatpump RT-SE* Installation & Operating Instructions Manual - page 47
09/17/2010 1
HC112
HELPS – EZGEO Controller
All functions and definitions will apply to all NHP models, see appropriate model or type. Use Installation
Manual to determine which part of this Helps document applies.
This Electro Industries’ exclusive controller provides several installer and user-friendly functions for Geo heat
pump applications. It will be helpful to grasp the EZGEO concept prior to studying the mode configuration
charts and sequence of events.
First, this is a list of features/functions which are an integral part of this EZGEO system.
Geo source, forced air – EZGEO is standard on all Electro Industries’ models.
Geo source, split – EZGEO is standard on all Electro Industries’ models.
Room thermostat – conventional or commonly called 4-wire stat required.
Application mode selection – 4-position dial switch allows installer to select the mode that fits the
hardware/usage configuration.
Outdoor temperature sensing (OT) – determines compressor staging, auxiliary electric (when
applicable) and/or switchover to gas.
Two-stage compressor (Copeland) – sequenced by outdoor temperature (OT) and SOT timeout, see
function charts – Figures 1, 2, 3, 4.
Forced air supply temperature sensing (ST) – used for the “dead compressor” alarm and controls
compressors if ST is too high – zone dampers, accidental gas furnace, full load to high, etc. – where
AUX electric is installed (mode B only) this regulates AUX EL module based upon heating needs and
comfort.
Alarms or fault notification – front panel yellow EL LED pulses at two different rates.
o
After compressor control board (ICM) has sequenced through three retries.
o
Dead compressor, plenum temperature is less than set point (factory default 85° F).
Interface and control associated with utility control receivers (LMC or blues).
Standby (SB) – forced function by LMC, front panel switch, optional remote switch, E-GAS, alarm, or
stat override timer (SOT). Also, for modes B, C, D when OT is below SW OVER set point.
Dual fuel – gas furnace with split models (RT-SE Series), mode D.
o
This is also possible with other Geo units (two blower) but special consideration needs to be
addressed for ducting, airflow arrangements, both blowers, etc. (modes B and C).
Mode dial switch – installer must determine application/configuration and set up as required.
Mode
Switch
Mode SW
OVER
Configuration
A Geo
only N/A
No AUX EL, no gas, no auto SB, but load control can interrupt
compressor for cooling (not heating)
Geo/AUX EL
0
AUX EL (with compressor supplement or emergency), utility
load control, etc.
B
Geo/AUX EL/gas
Value
AUX EL, gas, auto SB, utility load control, etc. AUX EL is
compressor supplement above SW OVER value, below SW
OVER point gas has priority.
C
Geo/gas
Value
No AUX EL, gas furnace, auto SB, utility load control
D
Split/gas
Value
No AUX EL, gas furnace, auto SB, utility load control
SW OVER dial switch – if the OT sensor temperature is below this set point (at R to W start) the action shown
on the appropriate Figures 2, 3, 4 mode sequence chart takes place. Remains to end of stat cycle. Notice –
mode B has two conditions, correct position of SW OVER is very important.
If configured with AUX EL only (no gas), must set to 0 position.
If no gas is connected or operational and SW OVER is set in a non-0 position, cold air only could result
because the stat W cannot be satisfied without a heating source.