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RT, Druckschalter

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39 Artikel

FAQ

What is the neutral band (or neutral zone)?
- Antwort The neutral band is common to a special series of RT switches, which have two set points, a high point and a lower point. The range in between these two switching points is called the neutral band. For instance, you may wish to have both a high pressure alarm as well as a low pressure alarm on a pressure vessel, in which case the ideal switch would be a type with a neutral band.
In my application there are pulsations. Which pressure switch should I choose?
- Antwort When there are pulsations we recommend to use our diaphragm versions together with a damping coil, which is available as an accessory.
Is it possible to use Danfoss pressure switches when the medium is sea water?
- Antwort Yes, but we recommend using only our diaphragm versions: KPS 43-45-47, CAS 143-145-147, MBC 5000/5100 with diaphragm type of sensor.
What is the maximum/minimum pressure/temperature at which Danfoss switches can be set?
- Antwort 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?
- Antwort 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).
Is it possible to use Danfoss pressure switches when the medium is oxygen?
- Antwort As it is not possible for Danfoss to guarantee a bellow element that is free of oil, we advise customers not to use oxygen together with Danfoss pressure switches. In principle, our pressure switches will work well with oxygen if the parts in contact with the medium are totally free of oil. If there is oil, there will be an explosion risk.
What does it mean that an RT switch has an IP66 grade?
- Antwort IP is a classification of enclosure grades. It contains 2 digits. The first digit indicates the degree of enclosure against foreign bodies and the second one indicates the degree of water tightness. IP66 means that a wire of 1 mm diameter and dust cannot enter, and that the enclosure will withstand water jets from all directions, 100 l/min.
Are the pressure switches KP, KPI and KPS suitable for liquid media?
- Antwort KPI and KPS switches are recommended for liquid media. KP can be used with liquid media when a direct pressure connection of 6 mm or higher are used.
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?
- Antwort Scale values are indicative only and for accurate settings a pressure gauge (for pressure switches) or a thermometer (for temperature switches) must be used.
Which types of pressure switches have Pressure Equipment Directive (PED) approval?
- Antwort All BCP pressure switches have the PED approval, and the RT pressure swiches for steam plant with the measuring range 0-25 bar are also appoved.
I am looking for the on/off switch with the highest possible IP protection, what options do I have?
- Antwort KPS and CAS pressure and temperature switches has the highest IP protection - IP67.
Which on/off pressure switch has the highest vibration resistance?
- Antwort The MBC pressure switch has the highest vibration resistance, with maximum permissible vibration level of 20g.
How does the manual reset work in relation to on/off switches?
- Antwort After cut out operation, the unit (pressure or temperature switch) will not cut in until the reset button is manually activated.
For the RT pressure switches, what do the letters A, W, B and S in the type designation mean?
- Antwort A: Units suitable for the medium ammonia W: Units for control purposes B: Safety units with external reset S: Safety units with internal reset
Does Danfoss offer special pressure switches suitable for steam boiler applications?
- Antwort BCP and RT pressure switches are available with safety PED approval.
Does Danfoss offer special pressure switches suitable for sea water as medium?
- Antwort Yes, KPS 43, 45 or 47 diaphragm versions are suitable for sea water as medium.
What does SPDT stands for?
- Antwort Single Pole Double Throw refers to the type of the contact system.
What is the most common contact system type used in Danfoss switches?
- Antwort The SPDT (Single Pole Double Throw) contact system is the most used.
Which is the best choice among pressure switches for marine applications with high pulsating media?
- Antwort Pressure switches with a diaphragm type of sensor (types MBC, KPS, CAS) are the most capable for systems where high pulsations occur. When such pulsations are present, a damping device or pulse snubber should be considered.
What would be the best pressure switch choice for applications requiring high repeatability, accuracy and adjustable differential?
- Antwort 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?
- Antwort Gold plated contacts are particulary suitable for low voltage contol systems.
Do you have a pressure switch for steam applications, PED approved?
- Antwort You should order the new BCP switch with TÜV approval or the the RT TÜV versions, constructed especially for boiler applications.
What kind of pressure switch can I choose for a water pump?
- Antwort Our CS and KP/KPI are commonly used in this application, depending on other specifications that you have. Be aware that the pressure connection for the KP must be min. 6 mm.
Where I can find technical information regarding on/off switches?
- Antwort In our internet catalogue you can see all relevant product data, as well as download literature and approvals for the specific products.
Do I need an external power supply for RT switches?
- Antwort No, our RT range of temperature and pressure switches operate without external power supply. The switching force comes from the bellows. It works with an SPDT switch over contact.
Do you offer pressure switches in stainless steel?
- Antwort Yes, such a design is possible for the KP and KPI types. Please contact Danfoss to specify your needs.
Is a bellows-type pressure switch better than a diaphragm-operated one?
- Antwort It depends on your need. Diaphragm versions (if units are of the similar size) are more resistant to pressure pulsation and fluid hammering. They are also better for media with particles or sediments. However, usually diaphragm versions have higher differential and lower repeatability.
Do we have device for measurement of liquid level of a open tank?
- Antwort A very good solution is RT 113, equiped with external pipe for liquid level up to 3 m, while differential could me measured from 10 to 50 cm.
Can I use RT or other pressure switches in steam applications?
- Antwort Depending on the temperature you have to use a steam trap in order to create a natural sealing with the water in the system. Normally you can use RT up to 80 °C. and BCP up to 120 °C.
I am looking for a simple pressure switch to start up my 3-phase compressor - which one should I take?
- Antwort We recommend the CS series which is available in IP43 and IP55 versions, and which has 3-pole contacts.
Can you confirm that Danfoss does not use "deca-BDE" for pressure switches?
- Antwort Our products (including pressure switches) are covered by RoHS Directive and meet its requirements. This directive bans using some hazardous substances, e.g. PBDE (polybrominated diphenyl ethers) and PBB (polybrominated biphenyls). PBDE and PBB were used as flame retardants in plastic parts. There is no PBDE in our products.
Does Danfoss have a product for controlling the vacuum in a vacuum pump?
- Antwort Yes, the RT 121 pressure switch should be perfect for your need.
Do you have pressure switches with "GOST" approvals for the Russian market?
- Antwort No longer. We had in the past, but since CE marked units are now accepted, GOST is no longer required.
Is it possible to recognize if a RT has "double" bellows installed, from just looking at it from outside?
- Antwort Yes, there is one feature that enables you to recognize that the RT has double bellows; a nut (key 32 mm) on the pressure connection.
Do Danfoss pressure switches feature UL, CSA and ETL certificates?
- Antwort Our KP switch is made especially for the North American boiler market. This product range has special versions with UL and can be enclosed in IP55 cover. Our BCP and RT switches do not have UL/CSA or ETL approvals.
How can I monitor when I have to change the element of my filter?
- Antwort Please use our differential pressure switch; take the inlet and outlet pressure of the filter. When the element is saturated the pressure will increase and the switch will turn on, warning you.
Is it possible to buy just the contacts for the RT switches?
- Antwort Yes, please see our internet product catalogue for options in spare parts & accessories.
Which switches should I use for seawater - or other media with particles or depositions?
- Antwort 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?
- Antwort 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)