10 Standard Motor Protection
Conventional inherent internal line break motor protection is provided with models ZH15K4E to ZH45K4E.
11 Low
Ambient
Cut-Out
A low ambient cut-out may be required for systems using air as a heat source.
12 Pressure
Controls
A high pressure cut-out may be required according to individual national regulations and is strongly recommended
with three-phase compressors due to their capabilities of pumping to high pressures once the discharge is obstructed.
There is an internal pressure relief valve in the ZH 15 K4E...ZH 45 K4E.models, which opens at a differential pressure
of 28 bar ±3 bar between high and low pressure sides. For the low-pressure side a minimum working pressure setting
of 0.3 bar is recommended.
13 Shut-Off
A check valve in the discharge connection of the compressor prevents the compressor from running backwards for
more than one second or two. This momentary reversal of direction of the scrolls has no effect on compressor
durability and is entirely normal. Additionally there is a dynamic discharge valve mounted on the fixed Scroll, which
effectively eliminates reverse rotation.
14 Starting
During the very brief start-up, a short metallic sound is audible, resulting from initial contacting of the spirals and is
normal. Due to the design of the Copeland Scroll, the internal compression components always start unloaded even if
system pressures are not balanced. In addition, since internal compressor pressures are always balanced at startup,
low-voltage starting characteristics are excellent for Copeland Scroll compressors.
15 Deep-Vacuum
Operation
The danger of pulling deep vacuums is avoided due to an internal low vacuum protection which prevents the scrolls
pumping (unloads) when the pressure ratio exceeds approximately 20:1. In order to avoid nuisance trips, it is
recommended to set the low-pressure control as described in Section 12 above.
16 Brief Power Interruptions
With single-phase Copeland Scroll compressors brief power interruptions of less than 1/2 second may result in
powered reverse rotation. This occurs as a result of the high-pressure discharge gas expanding backwards through
the scrolls at power interruption, causing the scroll to orbit in the reverse direction. When power is reapplied while
reverse rotation is occurring, the compressor may continue to run in the reverse direction for several minutes until the
compressor’s internal protector trips. This has no effect on durability. When the protector resets the compressor will
start and run normally.
To avoid the loss of heating resulting from powered reverse rotation Copeland strongly encourages the use of an
electronic control which can sense brief power interruptions and will lock the compressor out of operation for five
minutes. This control could be incorporated with the other system controls (such as defrost or thermostat), or be a
stand-alone control. Functional specifications for this control are the following:
Timer opens: 1 electrical cycle (0,02 sec at 50-Hz operation) after power is removed and closes: 5 minutes (± 20 %)
delayed whether power is restored or not. No such device is required on three-phase models.
C6.2.9/0203-1004/E 6
