Understanding heating systems

View previous topic View next topic Go down

Understanding heating systems

Post  Admin on Fri Apr 20, 2012 11:39 am

Many different types of heater are available, and some are more suitable than others for providing essential heat for captive reptiles. There are a number of considerations to bear in mind when selecting heaters; suitability, cost , economy of operation, and not least, safety. The most common types of heater used in reptile installations may be classified as follows:

Infra-red dull emitters (ceramic heaters)
These are a useful heat source for large terraria. They are available in a wide range of powers from 60 watts to 250 watts and are easy to install. Most are shaped rather like spot lamps but instead of being constructed from glass are made from an opaque ceramic material. They get extremely hot in operation so must be installed and positioned with great care using the special heat-proof (usually ceramic) holders provided.Cables too must be of the heat resisting variety. They are an excellent source of basking heat for tortoises. A note of caution should, however, be sounded. Due to their intensity, these heaters are not safe for juveniles, or indeed for any animal, if it falls on its back directly under the emitter. Death from overheating is a real possibility and can occur surprisingly quickly. The author is aware of young tortoises dying within a few minutes of inversion under a ceramic heater. They must also be positioned well out-of-reach of the animals as severe burns are caused almost instantly on contact. I have found some species, particularly box turtles, forest hingeback tortoises, and some Asiatic semi-terrestrial turtles, to respond badly to high intensity dull emitters unless ambient humidity is carefully maintained at adequate levels. In general, for such species, I would not consider using ceramic dull emitters without an accompanying warm-air humidifer. For more on humidifiers, see the links below.

Ceramic heaters are extremely long-lived, and although more expensive to purchase initially, they will ultimately prove less costly than incandescent lamps which require constant replacement. I have some ceramic dull emitters in daily use which are now over 12 years of age and still performing as good as new.

It is important to note that while ceramic heaters are certainly useful basking aids, they emit NO UV-B and their output is restricted to infra-red heate ONLY. This is their major drawback. Of course, for species that do not bask, such as rainforest tortoises, this is not so relevant. UV-B and visble-spectrum lighting can also be used in combination with ceramic heaters to provide a properly balanced environment. They are particularly well-suited to use alongside UV-B emitting fluorescent tubes.

Heat or Hot Rocks
This type of heater is promoted as 'ideal' for vivarium inhabitants, although our experience is quite the opposite. There are numerous cases of animals badly burning themselves on the imitation-rocks with a built-in heating element. It is suggested that they be avoided.

Combined light and heat sources

Please see separate article on 'Understanding Reptile Lighting Systems' for a full discussion of combined light/heat sources, including UV-B emitting light/heat sources.

These are cylindrical heaters usually rated at 60 watts per 300 mm and are available in many different lengths from 300 mm to 2 m (approximately 1ft to 6ft). They are usually sold for cupboard heating, window demisting or for industrial drying applications. For small vivaria the 600 mm and 900 mm versions are best, larger units will require the 1.5 m or 2 m versions which are rated at 300 W and 360 W respectively. Thermo-tubes are extremely versatile and highly reliable. They may be used individually or in multiples for background heating of large reptile enclosures.Heat pads
Heat-pads are sometimes recommended as a universal solution to the problems of heating reptile cages. This view is not shared by the author who has encountered many behavioural problems linked to their use with tortoises. Heat pads provide very little direct radiant heat and can also seriously impair thermoregulatory behaviour in many species. They should not be relied upon as the sole heat source as they do not encourage natural basking. Some species are also prone to overheating if heat-pads are used. Heat pads can be used effectively in incubators, however, and waterproof types are also very useful for the base heating of shallow aquatic turtle aquariums. Their other uses are somewhat limited with most tortoise species and they are definitely not recommended as the principal daytime source of heating for hatchlings. Heat pads are also well suited to base-heating box turtles and other semiaquatic species, particularly those requiring a high humidity environment and minimal temperature fluctuations, i.e. many equatorial species. We have also found heat pads to be very useful for heating sick tortoises overnight, especially those with respiratory diseases or those on antibiotic therapy where body temperature needs to be maintained within close tolerances in order for drugs to attain maximum effectiveness.

Radiant Heat Panels

This type of heater is really a development of a heat pad. They typically radiate much more heat however, and come in higher wattage ratings. Instead of being used on the floor of a vivarium, they are designed for use on the ceiling or back wall. Much the same comments apply as to heat pads: they are potentially useful as sources of background heat for tropical, non-basking species, and most models (check carefully before purchase!) are well suited to use in high humidity environments. Their reliability is excellent. They should be controlled using a high accuracy electronic thermostat. They are not suitable as a sole source of heat for most savahhah or desert species, however. For these, we recommend a 'pont source' of combined light-heat-UV-B (see lighting article)

All electrical fixtures and fittings pose a potentially serious hazard. The risk of fire is particularly acute. Tortoises are especially strong and destructive, so ensure that any and all heating elements are absolutely impossible to damage or knock over. Bolt everything down firmly. Use fuses and circuit-breakers of the correct rating, and install effective smoke detector alarms. Ensure that all cables are of a professional standard, and under no circumstances risk 'temporary' set-ups. Be constantly aware that tortoises and heaters represent a very dangerous combination.

Heating for large installations
Individual vivarium accommodation is the preferred method for small collections, but where many animals are to be accommodated it is both costly and inefficient. The Tortoise Trust's own collection, for example, relied for many years upon individual electrical vivarium heaters: the energy usage (and wastage) proved to be very considerable. A move to new premises presented the opportunity to design everything from the ground up, with energy conservation and efficiency high on the agenda.
The solution ultimately arrived at involved highly insulated main buildings, with polycarbonate twin-wall roofing for maximum natural light transmission and minimum heat-loss. A first building comprising 90 sq. m. (800 sq. ft) included both a humid tropical zone (for Red-foot, Hinge-back and similar tortoises) and an arid semi-desert zone (intended primarily for G. sulcata, G. pardalis and G. elegans). A second building with 70 sq. m. (625 sq. ft). floor area was then designed to provide additional accommodation for tropical semiaquatic turtles such as Geoemyda, Rhinoclemmys, Cyclemys and Heosemys species. Roofs were angled at 50* to allow for maximum solar gain (at our latitude of 52*N, the optimum angle will vary according to location) and black plastic water containers were placed against a rear wall to provide a heat store. Additional thermal mass was provided by constructing the internal tortoise enclosures from concrete blocks. These were painted dark brown to increase solar heat absorption during the day - at night they act as an impromptu storage radiator, drastically reducing overnight heating costs. For further design hints on such buildings, organic gardening and permaculture manuals are a good source of advice.

The main heating for our buildings is provided by a combination of under floor hot-water piping and a number of central heating radiators. These are both efficient and economical. The main boiler is oil-fired. This system has proved extremely cost-effective to install, and the running costs are less than 25% of those incurred with our previous electric heating system.
The under floor heating 'pads' were constructed by excavating a 20 cm deep pit and filling this firstly with 15-cm-thick insulation material and then overlaying this with cement containing embedded plastic hot-water heating pipes. This method has proved extremely effective and is greatly appreciated by all tortoises. Some pens were also equipped with wall-mounted central heating radiators. To improve basking possibilities, these were fitted at just above floor-level and a mound of earth positioned just in front of each radiator. The slope facing the radiator is self-selected by tortoises wishing to take advantage of the heat for basking.
The role that insulation can play in reducing heating costs and improving thermal stability should not be underestimated. Our own tropical house was lined with 40 mm thick aluminium foil-lined insulation sheets on all external walls and ceilings. This alone reduced heat losses by 40%. The floors of the tortoise sleeping quarters were also insulated from ground losses by 80 mm thick insulation sheets which reduced overnight heat pad losses to almost zero. Insulation sheet is a very useful material, easy to install, and in conjunction with polycarbonate twin-wall it offers many design possibilities for energy efficient reptile maintenance. With ingenuity, these materials can be employed in most vivarium and terrarium installations to great effect.

The requirements of terraria are similar to those required of incubator thermostats. Obviously this application is by no means as critical but some reliable method of controlling temperatures is certainly required. In practice, ordinary on-off air temperature thermostats of the central heating type will be found more than adequate for controlling thermo-tubes and similar background sources whilst the precision and security of electronic controllers will be found of enormous benefit where infra-red dull emitters are to be employed

Thermostats may be found in three basic types:

Mechanical on-off (bi-metal) types
Electronic on-off types
Electronic proportional types
Mechanical thermostats are typically fairly cheap, but are not as accurate or reliable as electronic types. Electronic on-off types are far more accurate and reliable. When choosing one, do make sure that the WATTAGE RATING is more than adequate to handle the power requirements of the heater to be used. The best thermostats are electronic proportional types: these are sometimes also known as 'pulse-proportional' controllers. This type of controller responds to even tiny temperature variations, and responds almost instantly. They are capable of maintaining temperatures to a fraction of a degree if required. As may be expected, however, they are the most expensive of the three designs.Some highly advanced controllers offer extra facilities, including automatic day-night changes in temperature. The model illustrated uses a photo-sensitive switch to change between pre-set daytime and a (lower) temperature setting overnight. This can be extremely useful with certain sensitive species. For suitable thermostats we recommend checking with 'serious' tropical fish/aquarium stockists.

We strongly recommend using a separate thermometer to cross-check all thermostat indications and settings. Electronic, LCD types are the easiest to use. Most come with a remote-sensing proble. These are now available very cheaply, and have many applications in animal husbandryOther considerations

It is extremely important when designing or installing any vivarium lighting or heating system to understand the biological implications for the animals concerned. Tortoises and turtles are reptiles and, as poikilotherms or exotherms, they are largely dependent upon their environment for adjustment and maintenance of body temperature. They have only a very limited ability to compensate for environmental temperatures either above or below their preferred optimum (P.O) level. Outside the P.O temperature, normal metabolic activity will be impaired and at excessively low or high temperatures death will occur.

Unfortunately these figures are not known in detail for every species of reptile but almost all reptiles have a P.O temperature range between 20 °C - 35 ºC, and with terrestrial tortoises the range is usually between 22 °C- 30 ºC. This is certainly a good starting range when dealing with a species with unknown preferences. Desert or savannah species almost always have a somewhat higher P.O temperature than those species which dwell in lush jungle or undergrowth. The latter are also inclined to display poor thermoregulatory abilities. It is extremely important to note that the critical thermal maxima of many terrestrial species is in the range 34 to 36°C. If maintained at these temperatures without the possibility of escape, death can occur very rapidly. Many accidental deaths in collections occur when tortoises become inverted beneath a heat lamp, for example. It is also important to recognise that as temperatures rise beyond about 28°C many species will show disinterest in feeding and will prepare to enter a state of aestivation.

The term 'preferred optimum' is in itself somewhat misleading and there are some indications that just because a particular temperature range may be favoured by self-selection this is not necessarily the temperature which is most conducive to long-term health or survival. For example, many tortoises will, if allowed to, bask under a heater all day. This can have quite serious metabolic side effects. So, although the 'preferred optimum' temperature should be taken as a general guide, it should not necessarily be available at all times. Temperatures in the wild are cyclic, peaking at about mid-day and falling off towards evening. By far the best guide to ideal captive maintenance conditions will be gained from a careful study of the species' natural habitat and prevailing climate. Ordinary tourist guide-books dealing with the region inhabited by the species are often a very useful source of climatic, seasonal and habitat data. The many technical publications available from geographic and meteorological authorities are also a source of valuable captive maintenance information.

© A. C. Highfield 1989-2002.

Posts : 400
Join date : 2012-04-20


Back to top Go down

View previous topic View next topic Back to top

Permissions in this forum:
You cannot reply to topics in this forum