Custom Thermoelectric - Peltier

TEC FAQ

Q. How do I determine which TEC or TEC Assembly I need?
A. Please see the Selecting a TEC or TEC Assembly guide.

Q. What does the term Qc mean?
A. Qc is the amount of heat a TEC is absorbing at its cold face.

Q. What does the term Qcmax mean?
A. Qcmax is the maximum amount of heat a TEC can absorb at its cold face and pump over to its hot face. Please also see the "Terms & Definitions" section of the TE Encyclopedia.

Q. What does the term Imax mean?
A. Imax is the maximum input amperage that can be given to a particular TEC. Powering a TEC at Imax will also achieve Qmax when delta T is zero. Going beyond Imax will cause decreased TEC performance and eventual damage. It is recommended to not exceed Imax.

Q. What does the term dTmaxor delta Tmax mean?
A. DTmax is the maximum difference in temperature that can be created (by a TEC) between the cold side and hot side faces of that TEC.

Q. What does the term Vmax mean?
A.

Q. Can I epoxy over the lead wire solder joints to strengthen and protect the lead wire connections?
A. Sometimes, customers feel that the solder joint that connects the lead wire to the TEC needs to be reinforced with either epoxy or RTV silicone. There is nothing wrong with this concept although care must be taken not to use too much epoxy that would create a significant heat path from the hot plate to the cold plate.

Q. What does the term Tmax mean?
A. Tmax is the maximum temperature that a TEC can experience without damage. Temperatures above this limit will cause damage. It does not matter whether the TEC is creating (a powered TEC) the temperature or simply exposed to it.

Q. What is the difference between a TEC and a TEG?
A. A TEC is a ThermoElectric Cooler. DC power is supplied to a TEC so that it pumps heat from its cold face to its hot face. A TEC is also known as a Peltier device since it utilizes the Peltier effect. A TEG is a ThermoElectric Generator that generates electrical energy when one side of the device is heated and the other side cooled. A TEG is also known as a Seebeck device since it utilizes the Seebeck effect. Most TECs can be used as TEGs, although some are better suited for power generation than others.

Q. What is the recommended input power for a TEC?
A. The most commonly recommended input power for a TEC is 60% to 80% of the Imax for that TEC. Input power of greater than 80% of Imax usually results in minimal increases in both heat pumping and Delta T while significantly increasing both power consumption and waste heat generated. Input power of lower than 60% (of Imax) is also common to create a more efficient system (input power versus heat pumping created).

Q. What is a Multistage or Cascade TEC?
A. A multistage or Cascade TEC looks as if two or more TECs have been stacked on top of each other. In fact they are specifically manufactured with "middle" ceramics that are designed to handle circuit both above and below it. The purpose of "stacking" TECs is to achieve larger Delta Ts. Whereas a single stage TEC can reach 63-68C in delta T, a 2 stage can achieve 83-90C in delta T, a 3 stage can achieve 90-110C delta T and so on. Multistage TECs do not increase heat pumping ability, they only increase delta T.

Q. Can I make my own Multisatge TEC by stacking single stage TECs on top of each other?
A.

Q. What is Thermal Cycling?
A. Thermal Cycling is where a TEC is powered to heat or cool by having the input power polarity constantly reversed. For example, a TEC is powered so that it cools an object, then the DC polarity is reversed so that it heats the object, then the cycle continues to repeat back and forth.

Q. Is Thermal Cycling damaging to TECs?
A. Thermal cycling is one of the worst things that can be done to a TEC. Nevertheless, it is sometimes unavoidable. A TEC in a typical static powered application can last 5 to 10 years and even more. Worst case cycling applications can reduce that to 6 to 18 months and even less. The severity of the thermal cycling plays a large role in shortening the TEC's useful life. The severity factors are;

  1. The temperature extremes. For example, a range of 30C to 70C is lot better than -20C to 150C 
  2. The rate of temperature change. For example, a rate of change of 1C/sec is less damaging than 4C/sec 
  3. The amount (or lack) of dwell time between polarity reversals. For example, making instant changes from heating to cooling (or vice versa) is much more damaging than waiting 30 seconds or several minutes between. 
  4. The number of cycles. For example, 5 cycles per day is much less damaging than 20 cycles per hour. 
  5. The physical dimension and length to width ratio of the pellets. Larger/wider pellets are more able to withstand cycling than smaller/skinnier pellets. This is caused by the crystal boundaries (which are weak) within a pellet. Large pellets have less crystal boundaries that span from one pellet edge to another.

Q. What can be done to minimize damage from Thermal Cycling?
A. To minimize the damage from thermal cycling, try to do the following;

  1. Minimize the temperature range extremes if at all possible 
  2. Minimize the speed of the temperature ramp rate. If you need 2 C/second, don’t allow it to be 3 or 4 C/second. 
  3. Allow the maximum possible dwell time between polarity reversals. In other words, if you have been heating, stop power, wait, and then reverse polarity to cool. The longer the dwell time the better. 
  4. Make sure the assembly allows for thermal expansion and contraction. Use springs or Belleville washers. See TEC mounting guide. 
  5. Use higher Imax TECs than needed and operate them at a lower power input point. For example, you calculate you need 50 watts of cooling/heating, choose a 200+ watt device and operate it at 20-50% of maximum power input. Higher amperage (Imax) TECs are more cycle resistant than lower amperage TECs. Higher Imax TECs have larger and shorter pellets which makes them more able to withstand the cycling. (see Severity factor 5 above) 
  6. As a last step for TECs larger than 30x30mm, Have us section one face of the TEC to minimize thermal expansion stresses. Usually dividing the face in to 4 sections will suffice.

Q. Can I power a TEC without it being mounted to a heat sink?
A. A TEC should never be powered without the hot side connected or mounted to some metallic object to absorb the heat. Typically, this metallic object is a heat sink or water block, but for testing purposes, a metal table, chunk of aluminum, copper, or even steel may be used for a short period of time such as a few minutes or less.

Q. Why does the TEC need to have a heat sink or other metallic object on the hot side?
A. The TEC pumps heat from its cold face to the hot face, therefore, heat is being dumped out of the hot side and must be removed in order for the TEC to continue to work. If no heat sink or metalic object is there to absorb the heat, then the TEC will stop cooling and can even be damaged as it begins to overheat.

Q. How do I tell which is the hot and cold sides of a TEC?
A.

Q. How cold can a TEC get?
A.

Q. Can a TEC be used to heat as well as cool?
A. Yes, simply by reversing the DC polarity, a TEC can be made to heat. The TEC does not have to be physically flipped over to do this.

Q. What is the maximum temperature a TEC can heat to?
A. For a standard single stage TEC, the maximum temperature it can generate is about 120 Celsius. It can go higher, depending on application, ambient temperatures, and the rest of the assembly, but care should be taken to avoid damage to the TEC if the maximum temp is exceeded.

Q. How much heat can a TEC produce?
A. The amount of heat produced at the hot side is the sum of the input power and the heat pumped (Qc). Using the two charts (graphs) from the spec sheet, look up the Qc for the input amperage you are giving the TEC and add it to the input power (input amps times input volts). For example, let's say you decide to give a certain TEC 12 volts at 5 amps. This is 60 watts (5 x 12) of input power. Now, looking at the left hand chart ( Qc vs. Amps), you find that the TEC will have a Qc of 85 watts with an input of 5 amps and an expected delta T of 20 degrees. So, the total heat dumped at the hot face is 60 + 85 = 145 watts of heat. All input power given to a TEC always comes out as heat.

Q. How strong is a TEC?
A.

Q. Can a TEC be submerged in a liquid?
A.

Q. How efficient is a TEC?
A.

Q. What is the most efficient operating point of a TEC?
A.

Q. Can you supply me a TEC without either one of or without both ceramic plates?
A.

Q. What material is used in your TECs and TEGs?
A. Our TECs and TEGs use a semiconductor material called Bismuth Telluride (BiTe). More specifically, we use an alloy of Bismuth (Bi), Tellurium (Te), Selenium (Se), and Antimony (Sb) along with some dopants to make both a "P" and an "N" doped material.