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Chapter 4
Power Cable Mat-
ing Ends
PD Pressure
Relief Valve
4 - 4 Merlin
Every five years inspect the power cable mating ends for signs of corrosion
and damage. Clean or replace as required.
Leaks
A very small leak between the pump and motor is normal. If this is a new
pump, allow it to run for 24 hours and reinspect. A continuous leak will
require pump replacement.
The pressure relief valve is used to adjust the chiller's fluid pressure.
NOTE The valve is factory preset for the most common applications and
normally requires no further adjustment. The valve is factory preset not to
exceed 80 ± 5 psi (550 ± 1 kPa).
NOTE PD pumps are capable of 110 psi maximum output pressure.
Ensure your plumbing is rated to withstand 110 psi at the highest operating
temperatures.
System back pressure is installation and application dependent. Due to
internal Merlin back pressure, the minimum pressure setting for a deadheaded
pump is 28 psi for a PD-2 pump (these settings prohibit external flow from
the Merlin).
Before adjusting the valve turn the chiller off. Locate the circular relief valve
opening on the rear of the chiller. Turn the threaded stem fully clockwise.
If the chiller is not plumbed to an application, install a loop of hose equipped
with a shut-off valve between the supply and return fittings.
Turn the chiller on. Ensure that there is back pressure on the system. Use the
pressure gauge to read the relief valve setting.
Back out the threaded stem on the relief valve counterclockwise. Continue
until the gauge indicates 80 psi (550 kPa) or the desired setting.
NOTE The relief valve may drip if the threaded stem is backed out too far.
NOTE Should the chiller start to vibrate the valve setting may be the cause.
Changing the pressure setting ±5 psi will eliminate the
vibration.
Thermo Scientific
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