District cooling is  an energy-efficient way to deliver cooling based on delivering chilled water to the end-users such as residential or commercial properties. Besides being extremely energy-efficient, district cooling does not require much space and compared to a mechanical air condition system, there are only a few moving parts, making it very robust and easy to maintain. Within district cooling, the end-user is typically billed based on measurements made using a cooling meter installed on the pipe with chilled water.

Figure 1: Temperature sensor used on a cooling meter application

Cooling meters have a special challenge regarding condensation. When hot air with relatively high humidity comes into contact with a cold surface, the air is cooled down and the moisture in the hot air forms condensation on the cold surface. As shown in the above figure, the condensation is typically able to intrude any electronics  in contact with the pipes with chilled water. This may eventually lead to short circuits or corrosion problems which have a detrimental influence on the performance of a cooling meter and ultimately reduce the lifetime of the cooling meter. This is very different from what happens on a heat meter/thermal meter where the pipes are hotter than the surroundings as shown in the above figure to the right and therefore, condensation does not occur on heat meters.

Historically, the use of heat meters has been more widespread than the use of cooling meters. Therefore, many cooling meters on the market, popularly known as BTU meters, are actually meters that were originally only designed for heat meter applications and therefore not for the special requirements of  cooling meters regarding condensation. This can have a very significant influence on the lifetime of the meter when applied within district cooling. At Kamstrup, we have more than 15 years of experience from installing our cooling meters in hot and humid environments like the Middle East. Our latest generation of cooling meters has therefore been designed to have a high immunity against intrusion of water when operating in hot and humid environments.

The degree of protection of a product against intrusion of water and dust can be determined using the product’s Ingress Protection code or IP code. The IP code consists of two digits, e.g. IP68. The first digit can be between 0 and 6, where 0 is no protection against dust and 6 is a dust-tight product. The second digit can be between 0 and 8, where 0 is no protection of ingress of water and 8 means that ingress of water in large quantities causing harmful effects is not possible, even when the enclosure of the product is continuously immersed in water as specified by the manufacturer. For all Kamstrup products, the IP code is determined as part of the type testing process required prior to approval. The IP code of a specific product can thus always be found on the MID or Danish cooling approval of the product, which is issued by an independent public authority.

Kamstrup ULTRAFLOW® 44 is a flow sensor specifically developed for cooling meters. It contains a unique solution in which the electronics are moved away from the pipe with chilled water where condensation occurs and are instead placed on the cable. Thereby, it is avoided to have DC voltage close to the condensation and this stops the intrusion of salts into the electronics. Kamstrup ULTRAFLOW® 44  has an IP68 approval and its robustness can be seen by the fact that it can be used in underground applications where the flow sensor is completely submerged for up to 2 months. Kamstrup ULTRAFLOW® 44 has the same great accuracy and long-term stability as all other Kamstrup ULTRAFLOW® products, but is also available in a special version with documented accuracy of ± 0.5 % at nominal flow qp.