Brown University Application Notes
Brown University 2570 Thermostat Application Notes
1. Background
This application note applies to the use of 2570 thermostats as survival heaters on the EBEX astrophysical experiment. Since EBEX is a balloon-borne experiment which will be flying at low temperatures (typical range: 0 to -40 Celsius), various electronic components need to be maintained above some failure temperature, typically around -25 C. Normal heat control on EBEX is typically accomplished through the use of a negative feedback loop in which a software-controlled relay (typically a solid-state relay) opens or closes as necessary to maintain a particular temperature. The purpose of the thermostats is to act as a backup heater control in the case of the failure of the computerized temperature control system. The thermostats are set to close if the temperature drops below -20 C, allowing current to flow to the ohmic heater attached to the instrument body. We chose the 2570 thermostats because they function in the desired temperature range and can be made with the setpoints we need.
2. Schematic
The computer system contains an on-board DAQ which measures the temperature by reading out
the voltage across the 10k resistor in series with the AD590 thermometer, which is attached
to the instrument body. When the temperature drops below a programmable setpoint, the
computer closes the solid-state relay, heating the instrument through the 50 Ohm resistor.
The relay is turned off again once the temperature of the instrument body rises above a
second programmable setpoint, which is typically 10 to 15 degrees higher than the turn-on
point. During this time, the 2570 thermostat should be open, as the software setpoint is
higher than the 2570 setpoint. In the case of failure of the control computer, the solid
state relay will be open and the temperature is expected to drop below the 2570 setpoint,
causing the thermostat to close and supply current to the 50 Ohm resistor.
Back to Top
Solar Radiant Heating System – Over Heating Protection
In solar radiant heating systems, thermal energy is usually stored in a large well insulated hot water storage tank. Depending on the system requirements these tanks can be as large as 800 gallons. Some tanks that are used for domestic hot water may require an approved pressure vessel, others like drain back systems are at atmospheric pressure.
The heat required for radiant home heating can be very large thus requiring a large store of high temperature water. Unfortunately during the summer months when heating is not required and the solar energy is at its strongest, unsafe tank temperatures will require a safety mechanism for diverting the heat to some form of heat dump. This can be a pool, spa or ground source heat dump.
A snap which can be used to turn on a small circulating pump (1/25 hp), or activate a three port valve that will divert the heat to a heat dump. The temperature requirements will vary depending on the type of storage tank and type of heat dump mechanism required.
101A: For atmospheric (non-pressurized) tanks that use container water proof
liners:
ON temperature of 165
degrees F, and OFF temperature of 150 degrees F
101B: For pressure vessel type storage:
ON temperature of 180
degrees F, and OFF temperature of 165 degrees F
Operating currents are under 2 amps for 120v AC and under 4 amps for 12 volt DC
Back to Top
Carlisle Finch Application Notes
General use: Defrost Heaters and High Intensity Search Lights
Switch Details: Part # 2570
AC 120V 10 Amps
Hermetic seal
Min close temperature is 32° F and max open temperature is 43° F.
General Description from Customer:
Please send a sample of the #2570 sealed defrost thermostat that has a minimum close temp
of 32° F and a maximum open temp of 43° F. The close temperature of 32° F is more
important than the open temperature but I would like the thermostat to have as little
differential as possible. We’ll mount it on a flat plate and slots as shown in
the picture below would be fine. Note that your request page is attached to this
email. http://www.carlislefinch.com/marine/
Back to Top
Heat Exchanger Application Notes
Overview: regulating temperature by activating a heat exchanger in passively heated home.
Technical Details: Thermostat activates 120V 60W Taco 007 pump to circulate water when temperature exceeds120° F, and deactivates when temperature drops below 70° F.
General Description from Customer:
I am building a custom fireplace in a meditation room that will be built of compressed straw bale wall construction with a super insulated roof. The room will be 100% passively solar heated except for the very rare times when the sun does not shine for 2 or more consecutive days in Southern Colorado, or temperatures drop below -20° F for extended periods. During those times, the fireplace will be used to provide additional heating. Due to the basic inefficiency of fireplaces vs. wood stoves, I am installing a copper coil heat exchanger in the top of the fireplace which will connect with closed loop in floor radiant heat tubing buried approximately 2” in the poured adobe floor. The switch will activate a 120V 60W taco 007 pump to circulate the water to the floor loop when the tubing above the fire reaches approx 120° F and will deactivate the pump when the temperature of the coil is approximately 70° F. It may cycle a couple of times in the beginning because the water initially returning from the floor loop will be approx. 60°, but as heat is transferred to the adobe mass, the returning water will quickly warm up to above the open set point and then there will be constant operation until the fire burns low and the coil cools to below 70° F.
General use: To keep a security camera dry and cool in the presence of hot, moist conditions.
Switch: 2570 Series Sealed Thermostats
P/N 2570F016–047 – Fan (close on rise), close at 90° F ± 5° F,
open at 80° F ± 5° F with 8.5” red 18 AWG lead
P/N 250L337–1689 – Heater (open on rise), opens at 80° F 5 ± 5°
F, close at 68° F ± 5° F with 17.5” brown 18 AWG
Back to Top
NC State Correctional Facility Application Notes
General Description from Customer:
For use at the North Carolina State Correctional Facility.
The facility has multiple units of Bosch cameras installed on the exterior of the building. These units are installed with heating and fan systems to maintain the camera temperature in the operating range.
Both the heating unit and the fan unit use a 24VAC supply from the thermostat. A
couple of different mounting styles are used for the different units. The 2570 sealed
thermostat works well in this application as it can handle the moisture and the outdoor
environment well.
Back to Top
