Controlling the temperature in your Vivarium is critical to the well-being and longevity of your animals. Many of the setups used in a home setting use a heat mat or lamp to raise the temperature. Maintaining the temperature to a high accuracy requires  a) that it be constantly monitored and  b) that the method of controlling the heat source has minimal hysteresis (the temperature difference between the switch on and switch off points)

​There a few ways to achieve this:
On-Off thermostats as the name suggests switch on the heater until the set temperature is reached and then switch off. As the temperature falls they at some point switch on again. The temperature Is measured constantly via a trailing lead sensor.
​Dimming thermostats don't turn off the heat source but instead vary the power to them. They too have a trailing lead sensor.
Pulsing thermostats constantly switch the heat source on and off at a very fast rate and mimic the smoother control the dimming type has over the on-off type. But they can't be used with heater lamps as they burn out very quickly. Again temperature is monitored constantly with a trailing lead sensor.

​Prices vary considerably but is generally the case that the Dimming and Pulsing types are more expensive than the On-Off type.

​For our PD-018 product we have settled on the On-Off method of control as that suits most home-based setups. We've designed a product whose hysteresis is very low; the temperature will not drop more than 1C below the setpoint on the dial before the heater is switched on again. The dial is tamperproof so that children can't fiddle with it and the control box is small so that it can be hidden from view. More details can be found on our Products page and you can buy them on eBay.
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If you have a commercially run kitchen then invariably you'll have one or more extraction hoods. The fan used to pull air through the hood will have a speed control to adjust the amount of airflow.

​Usually mounted somewhere where they wont be tampered with these generally have an on/off switch and dial to adjust the speed.

​The speed control is the weak point in the system, if it fails you lose your extraction and have to shut down your kitchen. You can of course get an electrician to temporarily wire the fan to run at full speed until you can get a new speed controller fitted.

​So reliable speed controllers are a must and the fan manufacturers own versions are usually the best. But they're expensive because despite being a critical component the manufacturers know they represent a small proportion of the overall cost of the installation.

​Aftermarket speed controllers need not be less reliable than the original equipment but they can be a lot cheaper. Our UF-019 and UF-020 controllers are designed and made in Britain, are drop-in replacements for the leading brand and are shipped with simple to follow instructions. Details can be found on our Products page and they are permanently on sale via eBay.
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 Maintaining a constant temperature in your greenhouse/growroom is not as easy as you may think. Even in the British climate you may have to consider a means of cooling as well as heating it.

​Active cooling is usually dealt with by drawing cooler air in with a fan, exhausting the hotter air to the outside.
​Passive cooling may involve opening the top vents manually or with temperature controlled opening devices.

​Here we discuss heating and temperature control - which methods should you choose?
You can heat using electrical devices, paraffin-based heaters or gas-based heaters, the choice depends on two things:
1. do you have or can you provide a local electricity supply?
​2. what accuracy of temperature control do you want?

​Paraffin heaters generally have no means of maintaining a constant temperature, they are either on or off. Yes you can adjust the heat output but you'd have do this every time the good old British weather affects the temperature in your greenhouse; adjusting for daytime and again for night time. They do smell a bit too.
​Gas heaters are often more sophisticated. They come with a built-in thermostat which regulates the flow of gas and thus the heat output, controlling the greenhouse temperature to within 3 degrees of your setting. Often quite bulky due to the gas bottle being stored internally they take up a fair amount of space but if you have no electricity supply available they're a better bet than the paraffin type.
Electric heaters tend to come in three forms: there's the tube type, usually fixed to a wall or the floor near the base of the greenhouse, the fan heater type which can be placed anywhere its trailing cord will allow and finally the heat-mat or heat-tape types which are used for very localised heating under seed trays. All are available with thermostatic temperature control, just like the heating in your house. This method of heating offers the widest choice of products and with the exception of the fan heater is fully waterproof so you don't have to worry about watering near them. Again, if you choose a model with a built-in thermostat it will control the greenhouse temperature to within 3 degrees of your setting.

​Accurate temperature control will only be achieved if you install methods for cooling and heating. Even then the thermostats which are integral to the heater, or indeed the independent mechanical ones both measure locally; you can't put the thermostat where your most sensitive planting is. For electric heaters this can be remedied using an separate thermostat with a trailing sensor cable; you can place this anywhere in the greenhouse and the thermostat will switch your heater on and off as necessary.

More choices now, there are two types of trailing sensor thermostat!!
​Capillary types rely on the pressure of air contained within a thin tube to vary according to temperature; they control to within 3 degrees of the setting on the dial. This means that if it switches off your heater at 20C the temperature will fall to 17C before the heater switches back on again.
​Electronic types use a sensor at the end of a trailing cable which relays the temperature back to the switch box. These vary from make to make but the best ones switch on just 1C below the switch off point. This differential is called 'hysteresis'.
​Both types are available with waterproof switch boxes.

So in summary, you should consider methods for heating and cooling. For heating, if you have no power source nearby we'd recommend a gas heater. If you have power then use a waterproof electric heater with a separate thermostat. Finally, if you want minimal temperature fluctuation choose an electronic thermostat.

​We make no apologies now for introducing you to our electronic thermostat the PD-012, you'll find details on our Products page. They are available from 1st September every year via eBay.
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