Dometic DX Remote & Self-Contained A/C, Installation And Operation Manual

Page: 12 / 40

12
v
English L-2086 Installation
Warning
PR3X and PR8X pump relays are certified ignition
protected. However, pump relays with electromechanical
relays or contactors (such as 3-phase pump relays) are
not ignition protected and must never be installed in
spaces containing gasoline engines, tanks, LPG/CPG
cylinders, regulators, valves or fuel line fittings. Failure to
comply may result in injury or death.
Voltage and Triggers
PR3X and PR8X pump relays are identical in operation. When
the first A/C unit turns on, the pump relay will turn on the sea-
water pump, and the pump will stay on until the last A/C unit
shuts down.
The PR3X can operate up to 3 A/C units, and the PR8X can
operate up to 8 A/C units. Both can operate 115V and 230V
pumps.
Triggers are used in the pump relays to isolate the signals from
each A/C unit. Some pump relays come with pre-installed trig-
gers, or you can buy triggers separately. Triggers come in 115V
and 230V, and must match the control voltage of the A/C unit.
Both 115V and 230V triggers can be used in a single pump
relay if the system requires it.
The trigger is simply a relay that closes when the A/C unit turns
on. Because each trigger is isolated, the polarity of the signals
from the A/C units does not matter.
Electrical Connections
Warning
Make sure all power is off before opening any
electrical box.
The following guidelines apply to both self-contained and
remote condensing unit systems:
• Failure to properly ground and bond the system will void
warranty.
• All electrical connections should be made within the
electrical junction boxes supplied with the units. Most units
have terminal strips that are labeled or have color-coded
wiring. Open terminal strips (such as supplied with switch
assemblies) require that the included terminal strip covers
be installed over the strip and switch back after installation
is complete.
• Wiring diagrams are included in the back of this manual and
under the cover of the electrical boxes on all units. Contact
Dometic Corporation if you are not sure if you have the
correct diagrams.
• Each air conditioning unit requires it’s own dedicated circuit
breaker, of the appropriate size. See the table below for
suggested circuit breaker and wire sizing.
• If there is only one a/c unit, the seawater pump does not re-
quire a separate breaker, but make sure the breaker is sized
for the combined load of the unit and the pump. If multiple
a/c units are supplied by a single pump, then a pump relay
will be needed, and will require it’s own circuit breaker.
• All units must be grounded to minimize the potential hazard
of electrical shock and personal injury.
• All metallic fittings in the seawater system that are isolated
from the a/c unit or pump by rubber hose should be bonded
per ABYC standards E-8 and E-9.
• On larger F-type condensing units a fuse can be added to
protect the fan and control wires.
Note
Always follow ABYC guidelines or local codes when selecting
breakers and wire sizes.
Three Phase Power
Some larger compressors and pumps have 3 phase motors
that will run forwards or backwards depending on the wire
connections. Reciprocating (piston type) compressors can run
either way without any problem, but scroll compressors and
centrifugal pumps are direction sensitive and must be wired
so the motors run the correct direction. If running backwards,
Scroll compressors will usually make loud, unusual noises and
will not perform properly.