Frequently Asked Questions

For over four decades, Selco Products has served a wide variety of markets on a strong yet simple foundation of personal service. Every member of our customer support team is dedicated to one goal - providing you with knowledgeable assistance, timely response to special requirements, and prompt delivery of your order.

From prototypes to volume production requirements, we have structured our service and engineering support operations to provide a virtually seamless means of meeting your changing needs. Our products range from thermal measurement and control devices to panel mounted analog and digital metering instruments to a wide range of thoughtfully engineered components. We service OEM and end-user companies with equal ease, delivering a combination of price/performance benefits and value-added features that simplify your product selection efforts and enhances your manufacturing processes.

Our customers range from the Who's Who of HVAC and telecommunications to food service, process controls, appliances and recording/instrumentation. We welcome the opportunity to help you, with a unique combination of knowledgeable and responsive people, quality products and prompt delivery. Check our site again soon! We will soon be offering a full online catalog where you will be able to browse and order all of our products.

1/2" Disc Thermostats:

Q: What is the standard differential (hysteresis or T) of the 1/2" Disc Thermostat?

A: 30°F (17°C)

Q: Are tighter or wider differentials available?

A: Yes, 15°F to 100°F (8°C-56°C)

Q: What is the tolerance on opening and reset?

A: Tolerances are as follows:

50°F to 249°F (10°C to 120°C)
OA	Open	+/- 5.4°F	3°C
	Close	+/- 10.8°F	6°C
CA	Open	+/- 10.8°F	6°C
	Close	+/- 7.2°F	4°C

250°F to 320°F (121°C to 160°C)
OA	Open	+/- 7.2°F	4°C
	Close	+/- 10.8°F	6°C
CA	Open	+/- 10.8°F	6°C
	Close	+/- 7.2°F	4°C

Q: Are 1/2" Discs available in a one shot (one shot meaning that it actuates once and cannot be reset)?

A: Yes

Q: Can the thermostat withstand vibration?

A: Yes, standard test is 2mm amplitude with a vibration frequency of 1,000 C.P.M. (Cycles per minute) applied in the x, y, and z direction for duration of 20 minutes.

Q: Can the thermostats withstand DC voltages?

A: Yes, tested by manufacturing only the following ratings apply:

12 VDC 10 Amps	30,000+ cycles
24 VDC 7.5 Amps	30,000+ cycles
48 VDC 4.5 Amps	30,000+ cycles

Q: Are the OA and CA thermostats submersible?

A: No, however Selco has the ability to over mold thermostats so that they are moisture resistant.

Q: How do I know if I need gold contacts?

A: If your amperage is .250 Amps (250 mA) or less. Gold contacts prevent premature failure due to oxidation of the contacts at low amperage levels. Oxidation forms an insulation layer on the contact and low current does not arc enough to burn off the oxidation.

Q: At what rate of temperature rise will these devices remain accurate?

A: Devices are tested at 1.8°F (1°C) per Minute but can see a rate of temperature rise as fast as 10°F and remain accurate.

Q: Will the thermostat fail open or closed?

A: There is a 90% probability that the thermostat will fail open.

Q: What is the Mean Time Between Failure (MTBF)?

A: On a case study we estimated approximately 132,000 hours of operation.

Bulb & Capillary Thermostats:

Q. What Capillary length is available?

A. Standard is 36 inches (915 mm).

Customs can range from:
In Copper - 18 inches to 8 feet (457 mm to 2438mm)
In Stainless Steel - 18 inches to 4.6 feet (457 mm to 1420mm)

Q. How many inches of capillary should I immerse in the media?

A. Recommended is 2 inches (50 mm).

If less than or more than 2 inches may vary from actual calibrated set point. Manufacturing calibrates at 2 inches immersed.

Q. What type of media is used in testing bulb and capillary thermostats?

A. 90°C (194°F) and lower the media is water.
91°C to 400°C (196°F to 752°F) the media is a salt bath.

Q. What is the rate of temperature rise while testing bulb and capillaries?

A. 1°C to 1.5°C (2°F to 3°F) per Minute.

Q. At what rate of heat increase is the bulb and capillary most accurate?

A. 4°C (7°F) per minute.

The faster rate of temperature rise the less accurate the thermostat will be (another term for this would be Thermal Delay or Thermal Lag).

Q. What is the differential (also referred to hysteresis) available on bulb and capillaries?

A. Closest is 2°C (3°F to 4°F) on lower temperatures and 9°C (16°F) on high temperatures.

Widest – Varies on temperature setting
On 4-40°C (40-104°F) Max. Diff. Is 4-5°C (7-9°F)
On 30-90°C (85-195°F) Max. Diff. Is 9-12°C (16-21°F)
On 50-300°C (120-572°F) Max. Diff. Is 25-30°C (45-54°F)

Q. Is the Stainless Steel the used on Stainless Steel Bulb and Capillary 304?

A. Yes, it is 304 stainless steel.

Q. Does the bulb and capillary lose accuracy with longer capillary lengths?

A. No

Control Knobs:

Q. Should I use a collet knob, push-on knob, or a set screw knob on my application?

A. The type of shaft you are using and your application will determine which type of knob is best for you.

Collet knobs are only recommended for a smooth, round shaft (no splines and no flat on the shaft). Collets are a good choice when a secure fit is important. A tool must be used to install or remove collet knobs.

A push-on knob can only be used on a splined shaft or a D shaft. A push-on knob is a good choice when cost savings is an important factor. Push-on knobs are held on by an interference fit, which means that they can be installed and removed relatively easily.

A set screw knob is recommended for either a round shaft or a D shaft. A set screw knob is a good choice when you are using a D shaft, and you want a secure fit. Set screws are not recommended for splined shafts. A tool must be used to install or remove set screw knobs.

Q. What materials are Selco knobs made of?

A. Nylon – The majority of the collet knobs and push-on knobs are made of nylon 6, with a matte finish. This material is stable in the temperature range of –20 degrees C to +70 degrees C.

Thermoplastic Elastomer – The Soft Touch knobs have bodies that are made of thermoplastic elastomer, which has a soft, textured velvet touch. The pointers on the soft touch knobs are made of a hard polypropylene.

ABS – Many of the set screw knobs are made of ABS.

Aluminum – The remaining set screw knobs are made of aluminum.

Thermoplastic – Some of the appliance knobs are made of thermoplastic and withstand temperatures up to +70° C.

Thermosetting – The remaining appliance knobs are made of thermosetting material and withstand temperatures up to +220°C.

Q. What is your minimum order for knobs?

A. Selco has a $50.00 minimum order. In addition to the $50.00 minimum, certain knobs will have a minimum order quantity. While Selco does stock many different varieties of knobs, we are not able to stock every variety. The knobs that we do not stock usually have a minimum of either 500 or 1,000 pieces.

Q. What is your lead-time for knobs?

A. Many knobs can be shipped immediately from stock. Other knobs are made to order. For knobs that are made to order, the lead time can be anywhere from 3 weeks to 8 weeks. Please call Selco to get an accurate lead time for the specific part number that interests you.

Applications:

Professional Audio Equipment
Laboratory Equipment
Medical & Dental Equipment
Industrial Equipment
Lighting
Ovens
Food Equipment
Musical Instruments

Digital Panel Meters:

Q. What type of accuracy?

A. Selco/Asahi DPMs offers 0.1% to 0.3% accuracy ±1 digit, depending on the model.

Q. How many digits are available?

A. The more digits the higher the resolution.

4 digits have more resolution than 3 ½ digits. Example, the outside temperature is 19.99º F, 3 ½ digits is more than enough for outside temperatures, but probably not enough for the surface temperature of aluminum used in the production of commercial airplanes. 19.999ºF may be more adequate.

Q. What type of display do you offer?

A. Either of the following:
LED, Light Emitting Diode
LCD, Liquid Crystal Display

LCD’s use little power to operate and are the first choice for digital displays on battery power.

Q. What Range input signals are available?

A. DPM’s monitored a variety of input variables directly or monitors sensors, which step down the signal to a manageable level.

Asahi manufactures meters for AC/DC signal monitoring as well as temperature and other process variables. You can monitor a variety of signals.

Generally, it is advisable to select the input range closest to but not less than the input being monitored.

For example, with a signal of 80 Volts, you would need a 200 Voltmeter, because a 20-volt meter could not handle the high voltage signal. A 750 volt meter would not be necessary; the 200 volt meter could handle the load and provide one order magnitude better resolution.

Q. What type of operating power for the meter is required?

A. Selco/Asahi offers meters with all of the below operating power requirements.
110 (VAC domestic)
220 (VAC off shore)
9-32 (VDC battery or reduction)
Loop (Best to eliminate noise)
Many Power supply options are available. The most common are 110/220 VAC and 9-32 VDC. Loop powered meters derive power from the 4-20mA loops they are monitoring, requiring only a small voltage drop. Loop powered systems are ideal for noisy electrical situations, as the system is closed from external power lines running to it.

Q. Do you have meters that can be used in a wash down environment?

A. Selco/Asahi offers meters that are IP66, NEMA 4 splash proof. In addition, Selco/Asahi offers covers front covers for 1/8 DIN sizes that are rated IP66, NEMA 4.

Q. Will your meters fit into my current enclosure cutout?

A. Selco/Asahi offers 1/8, 1/32, and 3/64 DIN Size meters
By moving to the DIN Standard of measurement, it has become easier to measure a panel space and fit a meter. The most common is the 1/8 DIN, which takes up 96mm x 48mm
or (3.78” x 1.89”) and requires 92mm x 45mm cutout or (3.622” x 1.77”).

Q. Do your meters offer any type of output?

A. Selco/Asahi meters are available with Analog, Digital, Excitation or BCD output.

Analog output signals such as 4-20mA or 0-10 V are usually sent to chart recorders or other simple recording devices. As the display increases in value, the analog output increases in value also. For example, 0-100% displays with a 4-20mA output would have a 20mA when the display indicates 100%. The output would be 4mA when the display is 0%. Digital outputs are for communication between the controller and a host computer or a printer.

BCD outputs, RS232, RS422, and RS485 are examples of digital outputs.
Excitation outputs are available in most DC indicators and controllers, allowing you to power DC external transmitters. This eliminates the need for expensive DC power sources for 2-wire transmitters and active transducers.

Relay Outputs, relays are coupled with set points programmed in the controller. The meter takes on control functions when relays are added to the alarm set points. Generally, when a set point for the signal input is exceeded, a relay will be triggered. The relay can be used to turn on or off a light, a process or an alarm indicator.