# Thermostats



## Alexio (Nov 27, 2016)

One of the most frequently asked questions that seems to come up is ; Do i need a thermostat for my tortoise enclosure? 
Providing correct temperatures throughout the tortoise enclosure is vital to a young (or old) tortoises health. It is important to remember that each tortoise species hails from a different place on the earth, and each of those places can have vastly different temperatures and humidity. For this reason it is necessary that you reference your specific tortoises care sheet for the correct temperature requirements that it needs. 
Once you are aware of the specific requirements for your tortoise it is important to have a habitat that is set up for success. 
This picture is crude but helps to illustrate the problem with conventional tortoise tables. 




For the following example lets say we are trying to achieve a basking temperature of 95f and an ambient temperature of at least 80f. Lets also assume the temperature in the room is 70f where the enclosure is located. 
As you can see in the open topped enclosure the temperature directly under the lamp is 95f . However as you move away from the heat source the warm air rises up and out of the table leaving the temperature away from the light 70f (which is the temperature of the room) and undesirable. To fix this problem we add a roof to seal in the heat and humidity. In this second picture you can see a sealed enclosure in the same room at 70f. 




The temperature directly under the light is still 95f but instead of the heat rising and escaping it reradiates from the roof and the walls. This helps to retain the heat inside and raises the ambient temperature of the enclosure. This is where the use of thermostats comes in. If your enclosure is large or the area where the enclosure is located has a much lower temperature it may become necessary to use supplemental non-lighting heat. This is also the case during the nighttime where tortoises need to be kept warm but also need to be kept in the dark. 

The following is a list of things that you CAN use a thermostat to control. 

Incandescent bulbs 
Ceramic heat emitters (CHE)
Radiant heat panels (RHP)


The following is a list of things you CANNOT use a thermostat to control. 
Compact fluorescent lights (CFL)
Fluorescent lights
"Strip" UVB lights
Any ballasted light
Any Mercury Vapor Bulb (MVB)
If you are unsure or in doubt about the type of element you are trying to control it is much safer to ask than assume. Its important when using electrical appliances to be aware of the voltage and wattage of your inputs and outputs. Its also important to note the wattage of any power strips or extension cords. 

There are two main types of thermostats. The first one is referred to as an "on/off" thermostat. It works like its name states in the "on" position or in the "off" position. A probe senses the temperature in the enclosure and if the temperature is below the preset amount then the thermostat turns the heating element on. The element will continue to remain on until the probe senses that the the temperature has risen above the preset amount. Then the element turns off, until the probe senses the temperature has fallen below the preset limit, then it turns back on and so on and so on. 

The second type of thermostat is a bit more advanced its called a "Pulse Proportional" thermostat. 
The pulse proportional thermostat also works by utilizing a probe , but as opposed to the "on/off" thermostat which can only be on or off the pulse proportional thermostat has the ability to monitor and vary the amount of voltage going to the heating element. This works by adjusting the set point to the desired temperature. The probe monitors the temperature and slightly increases or decreases the amount of power to the heating element to keep it at the exact specified temperature. If the enclosure gets warmer the probe detects the temperature increase and puts out slightly less energy to cause the temperature to decline again. Conversely if the enclosure gets too cool the probe will detect and raise the temperature of the heating element trying to remain at the exact set temperature. 


The first thermostat I'm going to go over is the cheapest and most readily available , its also not designed for reptiles and can be found at your local hardware store. 
The Lamp Dimmer




The lamp dimmer works by reducing the amount of inline voltage to the heating element. Using the slider you can increase or decrease the amount of heat or light output from the attached element. I find it to be most successfully used with a ceramic heat emitter(CHE). A ceramic heat emitter on full power can exceed surface temperatures of 500f. This can be unsafe if left on for long periods of time with no regulation too close to the tortoise. Using the lamp dimmer you can turn down the CHE to lower temperatures to reduce the risk of burns. 
The downsides of the lamp dimmer is that since it was not designed to be used with animals it does not have any safety features and will remain at the level set by the slider. Any increase or decrease in temperature in the enclosure will not be compensated for. I like to use the lamp dimmer in conjunction with an "on/off" thermostat to lower the total output of a device to make it safer then have it turn on and off to reach the desired temperature in the enclosure while ensuring that the heating element is not getting too hot. 


The Zilla Temperature Controller 




This is widely used because its cheap and effective. The only downside is the accuracy has to be independently verified because it has all analog controls. You set the dial to the required temperature and place the probe in the coolest part of the enclosure . The thermostat turns on the heating element and when it senses the temperature has been achieved it turns off the heating element. I like to hang a probed thermometer next to the thermostat probe to make sure the probe is turning the heat on and off at the right temperature. 

Vivarium Electronics
http://www.vivariumelectronics.com/Products.html





They have several models for sale and they range greatly in both price and features. 
The lower end models like the VE-100(pictured) are a more advanced "on/off" type of thermostat. You can see in the picture above the SP(set point) is 83f. This is an amount you are able to set inside the thermostat. On the line below it tells you what the actual probe is reading so in this case also 83f. Your probes temperature should closely match your set point. You can set hysteresis value as well. This is the temperature differential that is required for the element to turn on. For example if you had a set point at 85f but a hysteresis of 3 the heating element will turn on at 82f and turn off at 85f. I like how this particular thermostat displays the numbers of the probe as well as what the temperature is set to. This thermostat also features a night drop capability as well as an alarm and automatic shutoff in the event of excessively high temperatures. The higher end Vivarium Electronics thermostats like the VE-300 are pulse proportional models and work by increasing or decreasing slightly the amount of heat the element is producing, and holding the probe at a constant temperature. 

The Herpstat 
http://www.spyderrobotics.com/index.php?main_page=index&cPath=1





Pictured is the Herpstat intro by Spyder Robotics. It is the base model they sell. All of the Herpstats you can buy are pulse proportional. For this reason I recommend them for use in incubators or with animals with very sensitive temperature requirements. The base models can only control one probed temperature but the deluxe models have multiple probes that can be used in different tortoise enclosures to independently control the temperature. Or you could control specific zones in a very large enclosure, depending on what your needs are. The Herpstat also features various safety features such as an alarm that goes off if the temperature gets too high. 

Its important to always be aware of the wattages if you are connecting multiple heating elements via the use of extension cords into one thermostat. Even meeting the exact requirements is not recommended as it would be preferable if your thermostat was rated for a higher wattage than your heating element. For example in a large enclosure you may need to use two 150w ceramic heat emitters. This would be roughly 300 w of combined power. Most 3 plug non grounded extension cords can handle up to 1625 watts(always read the tag) so this would be okay for your 300 w CHE. You would want to use a thermostat that could handle a maximum of 350 to 400 watts giving you some wiggle room to avoid damage to your heating elements or thermostat.


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