Danfoss KDC 65-200 Data sheet
Data Sheet
Pressure control valve
Type KDC 65-200
Ecient control of excessive discharge pressure
The KDC valve is a pressure control valve . The
valve controls the discharge pressure of the
compressor to ensure fast build-up of pressure
and lubrication pressure. The valve also acts as
a check valve in the discharge line of the
compressor.
The KDC valve is force-controlled so that when
pressure in the oil separator becomes 2 bar (29
psi) higher than the suction pressure, the
spring is compressed and the valve opens. In
lowpressure units (boosters), the spring
requires a dierential pressure of 0.5 bar (7 psi)
for the valve to open.
Features
• Applicable to HCFC, HFC, R717(Ammonia)
and R744 (CO2).
• Each valve type is clearly marked with type,
size and performance range
• Angle valves with weld connections
• Fast build-up of oil pressure in oil separator
during start-up.
• High closing force on the cone during
standstill, even without dierential pressure
across the valve
• Very low pressure drop because of spring
force
• Low part-load without risk of valve chattering
• Stainless steel bolts
• Housing and bonnet material is in low
temperature steel according to requirements
of the Pressure Equipment Directive and
other international classication authorities
• Pressure range: 40 bar (580 psig)
• Temperature range: -50 °C / +150 °C (-58 °F /
+302 °F)
• Classication: DNV, CRN, BV, EAC etc. To get
an updated list of certication on the
products please contact your local Danfoss
Sales Company.
AI225686433549en-001001
Pressure control valve, type KDC 65-200
Functions
The KDC valve opens in a 3 step sequence. The sequence of steps depends on the start-up situation (see Figure 1:
KDC valve).
Step 1
The valve is always closed by a minimum dierential pressure of 1.5 to 2.0 bar (0.3 to 0.5 bar in a booster system).
Step 1 will occur when the compressor is stopped and the discharge pressure has equalized to the top of the valve
through the suction side of the compressor.
pc – p1 < 2 bar (0.5 bar for booster) and pc > p
2
Step 2
Step 2 will occur as soon as the condensing pressure becomes higher than the pressure in the oil separator, and
when the dierential pressure between suction side and condensing pressure is bigger than the spring force.
pc – p1 > 2 bar (0.5 bar for booster) and pc > p
2
When the compressor starts the valve will either be in step 1 or step 2 position, depending on the pressure
dierence between the oil separator and the condensing pressure.
Start up situation 1
Condensing pressure is lower than oil separator pressure.
Start up will occur from step 1 position and go to step 3 as soon as a dierential pressure between suction side and
oil separator that can overcome the spring force is present.
Start up situation 2
Condensing pressure is higher than oil separator pressure but the dierential pressure is lower than the spring force.
Start up will occur from step 1 and go to step 2 when dierential pressure between suction side and condensing
pressure is bigger than the spring force. When oil separator pressure comes close to the condensing pressure the
valve will start opening and the small spring will open the valve completely. The valve will then be in step 3 position.
Start up situation 3
Condensing pressure is higher than oil separator pressure + spring force pressure. Start up will occur from step 2
position.
When oil separator pressure comes close to the condensing pressure the valve will start opening and the small
spring will open the valve completely. The valve will then be in step 3 position.
When the compressor stops, the valve will be in step 3 position and as soon as the condensing pressure has
equalized to the suction side the spring force will close the valve. The valve will be in step 1 position until enough
dierential pressure between condensing pressure and oil separator/suction side pressure occurs for the valve to
enter into step 2 position.
NOTE:
The KDC valve cannot be used on compressor units where the non-return valve is placed between compressor and
oil separator instead of on the suction side of the compressor. The reason for this is that the KDC valve needs to have
the pilot pipe connected to a point on the compressor unit, where the pressure is low during running and high
during standstill.
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Step 1 Step 2 Step 3
System with KDC valve
System without KDC valve
Time
Pressure difference (p₂ -p₁)
Pressure control valve, type KDC 65-200
Figure 1: KDC valve
Figure 2: Time and Pressure dierence graph
© Danfoss | Climate Solutions | 2021.02 AI225686433549en-001001 | 3
KDC valve
p
c
Screw
compressor
Oil separator
p
1
p
2
Pressure control valve, type KDC 65-200
Applications
Example
Figure 3: Compressor discharge line after oil separator
© Danfoss | Climate Solutions | 2021.02 AI225686433549en-001001 | 4
Pressure control valve, type KDC 65-200
Media
Refrigerants
Applicable to HCFC, HFC, R717(Ammonia) and R744 (CO2).
For further information please see installation instruction for KDC.
New refrigerants
Danfoss products are continually evaluated for use with new refrigerants depending on market requirements.
When a refrigerant is approved for use by Danfoss, it is added to the relevant portfolio, and the R number of the
refrigerant (e.g. R513A) will be added to the technical data of the code number. Therefore, products for specic
refrigerants are best checked at store.danfoss.com/en/, or by contacting your local Danfoss representative.
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