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Thermostats (temperature switches), type CASFor numerous land and marine applications

CAS, Temperature switches

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FAQ (23)

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23 Item(s)

FAQ

What is the maximum/minimum pressure/temperature at which Danfoss switches can be set?
- Answer: Danfoss manufactures various pressure switches which can have a setting range of anywhere between -1 to 400 bar and temperature switches from -60 to +300°C. However, each switch will have its own regulation range as detailed within the product catalogue pages. It is always good practice to avoid choosing a product which will be switching near to the limits of its range.
What is the DIN numbering of terminals?
- Answer: Terminal numbers are always ODD for inputs & EVEN for outputs, which explains why the changeover switch in almost all pressure & temperature switches has numbers 1, 2 & 4. The live feed goes in at 1. It comes out at 2 when the pressure or temperature is low (so take this to your pump or heater as a live feed) out of 4 when the temperature or pressure is high. (You can take terminal 4 to a ''satisfied'' tell-tale lamp or to an unloading valve or cooling fan, if you wish).
How can I characterize vapour charge in the sensor of the temperature switch?
- Answer: The sensor is filled with small quantity of liquid charge (normally propylene) and its saturated vapour. Sensor must be the coldest part. Ambient temperature has no effect on working points.
How I can characterize adsorption charge in the sensor of the temperature switch?
- Answer: The sensor is partially filled with carbon particles, and the rest of the element contains superheated gas, normally CO2. Reaction is always in the sensor and working point will vary with the ambient temperature.
After installing the switch and making the setting based on scale values, the real system pressure value and scale value seem not to correspond. What is the reason?
- Answer: Scale values are indicative only and for accurate settings a pressure gauge (for pressure switches) or a thermometer (for temperature switches) must be used.
What is the time constant in relation to temperature switches?
- Answer: The time constant of a temperature switch is an expression of the rate at which it reacts to a (sudden) temperature change. In other words – temperature inertia of the sensor. Sensor temperature always lags behind the temperature of the media.
I am looking for the on/off switch with the highest possible IP protection, what options do I have?
- Answer: KPS and CAS pressure and temperature switches has the highest IP protection - IP67.
How does the manual reset work in relation to on/off switches?
- Answer: After cut out operation, the unit (pressure or temperature switch) will not cut in until the reset button is manually activated.
What does SPDT stands for?
- Answer: Single Pole Double Throw refers to the type of the contact system.
What is the most common contact system type used in Danfoss switches?
- Answer: The SPDT (Single Pole Double Throw) contact system is the most used.
What would be the best pressure switch choice for applications requiring high repeatability, accuracy and adjustable differential?
- Answer: RT switches used for regulation, monitoring and alarm purposes feature the highest repeatability and accuracy. They are also available with adjustable differential.
When is it recommended to use a gold-plated contact system?
- Answer: Gold plated contacts are particulary suitable for low voltage contol systems.
What is the key difference between KPS and CAS switches?
- Answer: KPS is equipped with a contact system, and has adjustable differential. The CAS has a microswitch and differential is fixed, meaning differential value cannot be adjusted.
How can I improve the heat transfer if I use a sensor pocket with a temperature switch?
- Answer: You can use heat conductive paste, available from Danfoss.
Where I can find technical information regarding on/off switches?
- Answer: In our internet catalogue you can see all relevant product data, as well as download literature and approvals for the specific products.
Is there any way to tell if charge is lost in a temperature switch?
- Answer: The only way is to test the temperature switch is by heating and cooling the sensor.
Do Danfoss temperature switches come with sensor pocket included?
- Answer: No, sensor pockets come in different sizes and material, and are therefore supplied seperately. Please see the Danfoss internet product catalogue for options.
How do I maximize response time of a temperature switch?
- Answer: First, the sensor should be immersed in the media with biggest possible surface. If this is not possible and a sensor pocket is needed, remember that the additional thermal inertia of the pocket will play a significant role. You can use heat conductive paste to reduce it.
What do I do if I need very quick reaction to changing temperature?
- Answer: In case of any mechanical switch with charge sensor, the reaction time will always be a considerable factor. The solution could be using a temperature sensor, which has much smaller themal inertia.
What is the response time of Danfoss temperature switches?
- Answer: There is no exact data on the time constant for temperature switches in particular - it largely depends on sensor charge, way of mounting (contact to media), temperature changing speed, ambient temperature and other factors.
Which temperature switch should I use to control the area temperature in an engine room?
- Answer: The best temperature switch for this application is the RT 4, which features a room sensor element, a range from -5 to 30 °C and easy wall-mounting.
Which switches should I use for seawater - or other media with particles or depositions?
- Answer: In case of seawater you should generally use diaphragm versions of switches: - KPS 43, 45 & 47 - CAS 143, 145 & 147 - MBC 5100 with diaphragms Seawater may contain contamination and certainly salt, both of which will likely accumulate inside the application. Not least inside the switch,, because the water inside is almost still (no flow). If salt crystallizes on the bellows surface it can easily affect its proper function. In case of diaphragms, very smooth and flexible, this problem is less visible. This will cause the depositions to be removed from its surface, and until the whole system is filled and blocked with depositions, it will work. Depositions are especially dangerous when you have a small bellows - like in MBCs. If you need to use bellows version of switches then try to choose comparatively big bellows - surfaces on which depositions are stored are comparatively far away and it would take a longer time before they affect bellows function. RT is a switch of this kind.
Where do I find production date on pressure or temperature switches?
- Answer: Look for a code similar to the below: AB - identifies factory location (in this case, Poland) 29 - first two digits tell you production week 6 - last digit tells you about production year (2006)