Baths and Thermoregulator FAQs


Q: How long does it take to heat the bath water to the correct temperature?

A: The thermal energy required to heat water = (mass of water in kg) x (specific heat capacity of water in J/kg°C) x (temperature rise in °C)

For example, how long will it take a 1kW heater to heat 12 litres of water from 17.5°C to 80°C?

Energy (J) = 12kg x 4180 J/kg°C x (80-17.5°C) = 3135000 W·s
3135000/1000W = 3135 seconds
3135/60 = 52.25 minutes

This assumes no heat loss. Because some heat will be lost to the environment it will take a little longer than this.

Q: What type of water do you recommend for the bath?

A: We recommend distilled or deionised water with neutral pH. However, ultra pure deionised or RO water with a resistivity >1Mohm should not be used, as this can leach the iron from the stainless steel and lead to corrosion. If necessary, add a little tap water to the pure water in the bath. Hard tap water should also be avoided as this can cause build up of scale inside the bath and on the heating elements of the thermoregulator. Other salts in tap water such as chlorides and sodium ions can also lead to pitting and corrosion.

A: It is possible that small spots may be visible in the bath which resemble rust spots. In most cases these will be small ferrous particles on the surface of the bath which have oxidised causing the appearance of rust. These can usually be cleaned away using a standard stainless steel cleaner and a plastic scourer.

Q: I want to maintain the temperature of my bath close to ambient; what is the simplest way of doing this?

Q: What maintenance do you recommend for my bath?

Q: What is the difference between a Dip Cooler and Flow Cooler?

A: For water-filled baths it is recommended that the bath is drained, cleaned and re-filled on a weekly basis to avoid build up of salts and contamination. Regularly adding fresh water will replenish the oxygen which helps maintain the protective chromium oxide layer on the stainless steel. This is especially important if the water is stationary or has been boiled.

Baths that are used for biological applications and heated to physiological temperatures can become breeding grounds for algae, fungi and harmful bacteria. Regular heating to >60°C for 30 minutes can be used to thermally disinfect the bath before cleaning. If this is not possible, then a chemical biocide may be used. Check that the agent is suitable for use with stainless steel. Do not use bleach (sodium hypochlorite) or other chlorine based solutions as a disinfectant.

Make sure the bath contains sufficient liquid to cover the heating element to avoid running the bath dry. Turn the bath off overnight and when not in use. If a bath is not to be used for some time, it should be emptied, cleaned and kept dry.

Q: How should I clean my water bath?

A: In general baths should be cleaned with a mild household or laboratory detergent using a sponge or soft cloth. Scouring powders, steel wool or other abrasive pads should not be used. Scale build up can be removed using a mild household descaler and soft brush; follow the manufacturer's instructions for correct use. Rinse thoroughly after cleaning and dry the bath.

A: The dip cooler has a coil filled with refrigerant which sits in the bath next to the thermoregulator, through a hole in the bridge piece. With a flow cooler, the liquid in the bath itself is circulated by the thermoregulator through the cooler, which has a reservoir inside. The liquid is cooled inside the unit and passed back to the bath. Neither of these units have their own temperature control; this is provided by the thermoregulator which, at the same time, heats the liquid in the bath to maintain the set temperature. When working at low temperatures always use a bath liquid suitable for the lowest temperature at which the unit is capable of achieving. The dip cooler is often the most flexible option as it can easily be removed if the bath is required for higher temperatures.

Q: Is it possible to continuously record and control the temperature of the bath fluid?

Q: I can see small spots in the bath which look like rust. Is it corroding?

A: If the system needs to be maintained close to ambient temperatures then a simple cooling coil (part code FCC01) attached to a cold water supply may be sufficient. The cooling coil is suitable for use in smaller baths where the temperature needs to be maintained between 5°C above the cooling water supply temperature to ambient + 5°C. For larger baths and for sub-ambient conditions, a refrigeration system will be required.

A: The TU-20 models can be used with our TechneWorks software which can be downloaded from our website or ordered on a CD to be supplied with the unit. The software allows various temperatures to be set remotely and sent via RS-232 to the TU-20 controller which controls the bath temperature.