Honeywell DDCM Technical features

18	P r e s s u r e s w i t c h e s
	Mechanical pressure switches

M e c h a n i c a l p r e s s u r e s w i t c h e s

Te c h n i c a l f e a t u r e s / A d v a n t a g e s

Diecast aluminium housing

IP 54 or IP 65

version also available

Wall mounting

or directly on the pressure line

Switching element (microswitch)

Lead sealable setpoint adjustment

Setting spindle locking element

Terminal connection or plug connection to DIN 43 650 Form A

Stainless steel sensor housing

Stainless steel bellows

with internal stop

Pressure connection

G 1/2“ external

G 1/4” internal

Centring pin

26	P r e s s u r e s w i t c h e s
	Mechanical pressure switches

P r e s s u r e s w i t c h e s

G e n e r a l d e s c r i p t i o n

Operating mode

The pressure occurring in the sensor housing (1) acts on the measuring bellows (2). Changes in pressure lead to movements of the measuring bellows (2) which are transmitted via a thrust pin (4) to the connecting bridge (5). The connecting bridge is frictionlessly mounted on hardened points (6). When the pressure rises the connecting bridge (5) moves upwards and operates the microswitch (7). A counterforce is provided by the spring (8) whose pretension can be modified by the adjusting screw (9) (switching point adjustment). Turning the setting spindle (9) moves the running nut (10) and modifies the pretension of the spring (8). The screw (11) is used to calibrate the microswitch in the factory. The counter-pressure spring (12) ensures stable switching behaviour, even at low setting values.

1= Pressure connection

2= Measuring bellows

3= Sensor housing

4= Thrust pin

5= Connecting bridge

6= Pivot points

7= Microswitch or other switching elements

8= Setting spring

9= Setting spindle (switching point adjustment)

10= Running nut (switching point indicator)

11= Microswitch calibration screw (factory calibration)

12= Counter pressure spring

Pressure sensors

Apart from a few exceptions in the low-pressure range, all pressure sensors have measuring bellows, some made of copper alloy, but the majority of high-quality stainless steel. Measured on the basis of permitted values, the measuring bellows are exposed to a minimal load and perform only a small lifting movement. This results in a long service life with little switching point drift and high operating reliability. Furthermore, the stroke of the bellows is limited by an internal stop so that the forces resulting from the overpressure cannot be transmitted to the switching device. The parts of the sensor in contact with the medium are welded together without filler metals. The sensors contain no seals. Copper bellows, which are used only for low pressure ranges, are soldered to the sensor housing. The sensor housing and all parts of the sensor in contact with the medium can also be made entirely from stainless steel 1.4571 (DNS series). Precise material data can be found in the individual data sheets.

Pressure connection

The pressure connection on all pressure switches is executed in accordance with DIN 16288 (pressure gauge connection G 1/2A). If desired, the connection can also be made with a G 1/4 internal thread according to ISO 228 Part 1. Maximum screw-in depth on the G 1/4 internal thread = 9 mm.

Centring pin

In the case of connection to the G 1/2 external thread with seal in the thread (i.e. without the usual sheet gasket on the pressure gauge connection), the accompanying centring pin is not needed. Differential pressure switches have 2 pressure connections (max. and min.) each of which are connected to a G 1/4 internal thread.

P r e s s u r e s w i t c h e s	27
Mechanical pressure switches

G e n e r a l t e c h n i c a l d a t a

with microswitches of the DCM, VCM, DNM, DNS and DDC series.

The technical data of type-tested units may differ slightly.

(please refer to type sheet)
Normal version		version
Plug connection	Terminal connection

	…200	…300	…700
Switch housing	Diecast aluminium GD AI Si 12		Diecast aluminium GD AI Si 12
Pressure connection	G 1/2 external thread (pressure gauge connection) and G 1/4 internal thread
	G 1/4 internal thread for DDCM differential pressure switches

Switching function and con-	Floating changeover contact.
nection diagram	With rising pressure switching
(applies only to version with	single-pole from 3-1 to 3-2.
microswitch)

Switching capacity	8	A at 250	VAC
(applies only to version with	5	A at 250	VAC inductive
microswitch)	8	A at 24 VDC
	0.3 A at 250 VDC
	min. 10 mA, 12 VDC
Mounting position	preferably vertical
	(see technical data sheet)
Degree of protection (in vertical

Floating changeover contact. With rising pressure switching single-pole from 3-1 to 3-2.

3 A at 250 VAC

2 A at 250 VAC inductive

3 A at 24 VDC

0.03 A at 250 VDC min. 2 mA, 24 V DC

vertical

position)	IP 54; (for terminal connection …300 IP 65)	IP 65
Ex degree of protection	–	EEx de IIC T6 tested to EN
		50014/50018/50019 (CENELEC)
PTB approval Electrical connection	–	PTB 02 ATEX 1121
	Plug connection to DIN 43 650 (200 series)	Terminal connection
Cable entry	or terminal connection (300 series)
Ambient temperature	PG 11 / for terminal connection M 16 x 1.5	M 16 x 1.5
Switching point	See data sheets	–15 to +60°C

Adjustable via spindle. On switching device 300 the terminal box cover must be removed

Adjustable via spindle after the terminal box lid is removed

Switching differential

	Adjustable or not adjustable	Not adjustable
Lead seal	(see Product Summary)
Medium temperature	Only possible on plug connection housing 200
	Max. 70°C, briefly 85°C	Max. 60°C
	Higher medium temperatures are possible provided the above limits for the switching device are
Vacuum	ensured by suitable measures (e.g. siphon).
	All pressure switches can operate under vacuum. This will not damage the device.
Repetition accuracy of switch-
ing points	< 1% of the working range (for pressure ranges > 1 bar)
Vibration strength
Mechanical life	No significant deviations up to 4 g.
	With sinusoidal pressure application and room temperature, 10 x 106 switching cycles.
	The expected life depends to a very large extent on the type of pressure application, therefore this fig-
	ure can serve only as a rough estimate. With pulsating pressure or pressure impacts in hydraulic sys-
Isolation values	tems, pressure surge reduction is recommended.
	Overvoltage category III, contamination class 3, reference surge voltage 4000 V.
Oil and grease-free	Conformity to DIN VDE 0110 (01.89) is confirmed.
	The parts of all pressure switches with sensors made from steel or stainless steel are oil and grease-

free. The sensors are hermetically encapsulated. They contain no seals. (See also additional function ZF 1979 Special Packing)