Enertech EAV060 - Sequence of Operation

Enertech Global 
EAV - EME/EMD Rev. A Models
Installaon and Operaons Manual


The system is o and waing for a call.

The load pump runs at maximum speed and the EEV (Electronic
Expansion Valve) opens completely to equalize the system and
prepare for the compressor to start. The diverng valve and
reversing valve move into posion accordingly.
The reversing valve is energized only in cooling.
The diverng valve is energized only in hot water heang. This
state runs for one minute to allow temperatures and pressures
to equalize and provide relevant sensor informaon.

This step is primarily a vericaon of condions.
If the pressures have not equalized, the system will not connue
to the running phase. Also, the system will verify that the load
temperature does not exceed the required target temperature
(see the next secon “Variable Speed Control”).

The EEV moves to the starng posion and the compressor
starts at the minimum speed (1650 RPM).
Run
The compressor modulates speed according to the required
load. The EEV modulates as needed to maintain 8°F superheat.
The pump modulates to maintain ΔT across the heat exchangers.
See the next secon, “Variable Speed Control”, for more
informaon.

Aer all calls have been sased, the compressor ramps down
gradually to zero RPM.

The pump maintains its current speed for one minute as it slowly
ramps down to turn o.
 Zone controls must allow post purge aer a call to allow
the internal load pump to stop.

The an-short cycle mer prevents the compressor from running
for three minutes aer the unit has been shut down. All calls will
be held unl the ASC mer has expired. The three minute ASC is
in addion to the pump start and stop duraons to provide an
industry standard ve minute an-shortcycle of the compressor.

• The compressor ramps down to minimum speed (1650
RPM) for 45 seconds. The pump will slow down as
compressor capacity ramps down.
• The reversing valve is energized or de-energized if switching
from heang to cooling or cooling to heang. If the system
is switching from heang to hot water or hot water to
heang, the reversing valve does not change.
• The zone valves in the Indoor Module switch from the
hydronic load to the domesc hot water tank or the zone
valves switch from DHW to hydronic heang/cooling.
• Aer the valves have transioned, the system resumes to
its normal running mode where the pump, compressor,
and EEV modulate accordingly. Note that when switching
from DHW to cooling or cooling to DHW, the valves will not
switch to hydronic load or DHW tank if the leaving load
temperature is not within 20°F of the target temperature.
This approach eliminates hot water going to a fan coil in
cooling mode or chilled water going to the DHW tank.
When the higher priority call is sased, and there is sll a call
holding, the system will transion back to the original call in the
same manner. The compressor is able to connue running and
thus no ASC delay is experienced.

The use of the variable speed compressor and pump includes
advanced control algorithms to match the load demand of the
space. The control described here takes place during the “Run”
poron in the system sequence of operaon described in the
previous secon.

Control of the compressor is based on the target outlet
temperature of the system. The system monitors the current
load out temperature and compares to the target temperature.
Using the control algorithm, the system seeks to maintain the
exact target outlet temperature. Outlet temperature above or
below the target temperature causes the compressor to throle
faster or slower as needed. In radiant oor heang, with an
outdoor thermistor, the outdoor reset dictates the targeted load
temperature. In cooling and hot water, the stac menu sengs
control the target temperature.
This control allows the system to react to changing condions.
As zone valves open and close, the compressor speed is adjusted
to meet the current demand.
In some small load situaons, such as very small radiant zones,
the system may not be able to run slow enough to avoid thermal
runaway. To accommodate this situaon, the compressor can
shut down when the load outlet temperature over/under shoots
its target by 4°F. During this me, the pump will connue to
circulate and the ASC mer is started.
The compressor will be cycled on again when the ASC mer
expires AND the outlet temperature has dropped below the
target temperature. All priories are sll obeyed during this
me. If the call becomes sased the system will shut down
normally.
 It is recommended to size zones in order to avoid this
cycling condion. It is preferred to avoid compressor cycling and
improve eciency.

When the pump is in “auto” mode, it controls to maintain ΔT
(Default 5°F) across the heat exchangers. To do so, load entering
and leaving temperatures are connually monitored. A sensed
ΔT above the 5°F setpoint will cause the pump to run faster.
Below the setpoint causes the pump to run slower – down to the
set minimum speed.
: If, aer setup, the EME/EMD detects the minimum ow
rate allows less than 5.0 GPM, it will aempt to increase the
minimum ow percentage unl 5.0 GPM is achieved. This will
overwrite the previous minimum seng.
