Appendix 3. Installation - Sensors; Warnings - Danfoss EIM 336 Manual

Manual
Appendix 3
Installation sensors
S2 sensor positioning in the suction line
The position of the S2 sensor is crucial for an optimal control of the
liquid injection.
The main purpose is to measure temperature of the superheated
gas leaving the evaporator. In addition to this, the S2 sensor plays
an important role detecting fast changes of superheat. Suction
pressure is on the whole stable where as the leaving gas condition
is depending on the temporary mixture of gas, liquid refrigerant
and oil.
The sensor is also there to react quickly on liquid passing the
evaporator, to avoid damage of the compressor.
S2 sensor placed 2/3 up a riser after an oil trap is where conditions
are at their optimum i.e. good mixture of gas, oil and liquid
droplets provided this is not more than 0.5 m from the evaporator.
If a horizontal pipe is the only option, the S2 sensor must be
placed close to the outlet of the evaporator.
Pressure transmitter (P pressure) is less critical but must be close
e
to the actual suction pressure right after the evaporator.
If the measured value is 1-2 K lower than the actual value of P
right after the evaporator, it may cause the evaporator to flood.
This is the case when the pressure transmitter is located in the
machine room away from the evaporator. A measure higher value
will suffer the evaporator of liquid.

Warnings:

ƒ Accidental damage, poor installation, or site conditions, can
give rise to malfunctions of the control system, and ultimately
lead to a plant breakdown.
ƒ Every possible safeguard is incorporated into our products to
prevent this. However, a wrong installation, for example, could
still present problems. Electronic controls are no substitute for
normal, good engineering practice.
© Danfoss A/S (AC-MCI / sw), 2014-11
Superheat Controller EIM 336
e
EIM 336
DKRCC.PS.RQ0.B7.02 /520H8832
Choice of S2 sensor type
Surface sensor S2
Pt1000 Ω - Type AKS21, AKS 11 or AKS10.
Suction pipe of copper or on thin (≤ 3mm) steel pipe.
Pocket sensor S2
Pt1000 Ω Type AKS21W.
Suction pipe of steel ≥ 3mm
Remember to put on heat conducting paste and
insulate the sensor.
AKS 21W
S2 sensor fixing on the suction pipe:
When the S2 sensor is fixed to surface of the suction pipe, the
angle of the sensor position will depend on the diameter of the
pipe as given in the following diagram:
ƒ Danfoss will not be responsible for any goods, or plant compo-
nents, damaged as a result of the above defects. It is the
installer's responsibility to check the installation thoroughly,
and to fit the necessary safety devices.
ƒ Particular attention is drawn to the need for a "force closing"
signal to controllers in the event of compressor stoppage, and
to the requirement for suction line accumulators.
Heat compound
17