Danfoss RT 280A, RT 281A Data sheet

Data sheet

Liquid Level Alarms, Safety Control, Liquid Level Regulator
RT 280A, RT 281A

RT 280A and RT 281A are primarily used as liquid
level alarms and safety switches to prevent too
high a liquid level in liquid separators.

Secondarily, RT 280A and RT 281A can be used
as liquid level regulators where a liquid level
dierential of up to ±40 mm can be permitted.

When used as safety switches, RT 280A and RT
281A ensure that the max. permissible refrigerant
level in ooded evaporators, pump tanks or
liquid separators is not exceeded.

As liquid level regulators, RT 280A and RT 281A
maintain a constant average refrigerant level
in ooded evaporators, pump tanks or liquid
separators.

Features

Approvals

• Waterproof versions, enclosure IP66

• Single pole changeover switch (SPDT) suitable
for AC / DC loads

CE-approved according to
EN 60947-4, -1 EN 60947-5, -1

• Interchangeable contact system

Meets the requirements of VDE 0660 (VDE:
Verband Deutscher Elektrotechniker)

© Danfoss | DCS (jmn) |2016.07

DKRCC.PD.GF0.A4.02 | 520H11306 | 1

Data sheet | Liquid Level Alarms, Safety Control, Liquid Level Regulator, types RT280A, RT281A

Technical data

Refrigerants

R717 (NH3), R22 and R502
"For other refrigerants, please contact Danfoss."

R12 -50 – 10 °C

Operating ranges for RT 280A

R22 and R717 (NH

) -50 – 0 °C

3

R502 -65 – -5 °C

Operating ranges for RT 281A R22 and R717 (NH

) -30 – 20 °C

3

Ambient temperature -50 – 70 °C

Switch Single pole changeover switch (SPDT), code no. 017- 4030 66

AC1: 10 A, 400 V

Alternating current

AC3: 4 A, 400 V

1

)

Contact load

AC15: 3 A, 400 V

Direct current DC13: 12 W, 220 V

Weight 2.0 kg

Enclosure IP66 to IEC 529.

Pressure connection G

3

⁄8 A with ø 6.5 / ø 10 mm weld nipple

Max. working pressure PB = 22 bar

Max. test pressure Pe = 25 bar

Materials

Ordering

Adsorption charge

Thermostatic element

3 m capillary tube

Max. permissible bulb temperature: 80 °C

Bulb with electric heater

1)

Max. short-time AC3 current: 28 A

10 W heater for 24 V DC or AC The heater must be constantly
energised whilst the system is in operation. 1.5 m connection cable.

Liquid level dierential
With a steady liquid level and a liquid level
variation rate of max. 15 mm/min, the dierential
will be approx. 10 mm on a rise in level and
approx. 20 mm on a fall in level. In unfavourable
operating conditions, dierentials of approx.
20 mm on a rise in level and approx. 60 mm on a
fall in level must be expected.

Gaskets are non-asbestos.

RT 280A code no. 017D004066
RT 281A code no. 017D004666

© Danfoss | DCS (jmn) |2016.07

DKRCC.PD.GF0.A4.02 | 520H11306 | 2

Data sheet | Liquid Level Alarms, Safety Control, Liquid Level Regulator, types RT280A, RT281A

Design / Function

3. Pressure connection

4. Bellows element

5. Setting disc

9. Scale

10. Loop terminal

11. Pg 13.5 screwed cable
entry

12. Spring

14. Terminals

15. Spindle

16. Switch (17-4030)

17. Upper guide bush

18. Contact arm

20. Lower guide bush

38. Earth terminal

RT 280A and RT 281A units are based on RT 260A.
The lower element is thermal and has an
electrically heated bulb.
As stated, the units are primarily for use as liquid
level alarms and safety switches. In designing the
units, emphasis was placed on the failsafe function
In the event of a defect in the thermal element,
the compressor is stopped and liquid injection
cut o. Restart is only possible after the defect
has been rectied.

Note:

If the evaporating temperature, and with it the
reference pressure, is higher than the max.
regulation range temperature, the unit will react
as though the liquid level in the liquid container
was too high.

This also applies in the case of loss of charge, for
example if the capillary tube or heating element
in the bulb is damaged, or if current to the
heating element falls.
The element heating or cooling signal is
compared to the reference pressure and then

.

converted to an electric on / o impulse.
The regulating principle is based on the heat
conduction dierence between the liquid and
vapour phases of the refrigerant.

© Danfoss | DCS (jmn) |2016.07

DKRCC.PD.GF0.A4.02 | 520H11306 | 3

Dimensions [mm] and
weights [kg]

Net weight 2.0 kg

© Danfoss | DCS (jmn) | 2016.07

DKRCC.PD.GF0.A4.02 | 520H11306 | 4