Water-based Indoor Climate Systems, 2007
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GUIDELINES
GUIDELINES
GUIDELINES
Test methods for water based climate systems
Test standards are needed to be able to compare products from different suppliers. It is only then that product data will be of equal value, comparable and unambiguous.
The standards that have been applicable in Europe are the Nordtest method NT VVS 078 "Ceiling Cooling Systems" and in recent years also the V-method V-publication 1996:1 (mainly in Sweden). At the same time in Germany a DIN standard has been drawn up for flat cool ceilings, which is also used for passive chilled beams (chilled beams without supply air).
Nordtest and V-publication
The Nordtest and V-method are very similar. The V-method is a slightly revised version of the Nordtest method and was produced by the Swedish Testing and Research Institute and the then Ventilation, Climate and Environment Association (now Svensk Ventilation) together with some suppliers from Sweden and Finland. The main difference between the two methods is at which water flow the products should be tested. In the Nordtest method the water flow is fixed and related to the pipe diameter in the heat exchanger, i.e. all products are tested with the same water flow irrespective of the cooling capacity.
The purpose of the V-method was to allow products to be tested using an operating instance that reflected true conditions and it was then chosen to steer towards the water flow that gives a temperature difference of two degrees through the heat exchanger. This means that if two products have a different cooling capacity, then they should be tested at different water flows.
The test room consists of two rooms, as in Figure 44, where heat is delivered to the inner test chamber indirectly via the floor and walls. The heating balances the supplied cooling capacity during the measurement sequence on the test object so that the test chamber’s temperature is constant.
DIN 4715
In the German DIN 4715 the test room is somewhat different, Figure 45. Here the test chamber consists of an insulated room. Inside the test chamber the test object’s cooling capacity is balanced with the help of "dummies" (human simulators) that emit heat directly in the room.
EN-standards
As chilled beams are now starting to be used in other parts of Europe, a few years ago work was started to produce common European test standards. Since 1996 Swegon has been an active part in this joint European effort and currently there are three proposals, which in a few years will lead to the finalised standards for flat cool ceilings and passive and active chilled beams (without and with supply air).
To consider
Which of the standards is preferable is more a philosophic question. There are advantages and disadvantages with all standards. Yet sometimes the clarity of the presentation of product data can suffer due to a standard, as quite frequently the standard deviates from the practice employed with installations in different countries.
Note that the test methods in question do not necessarily correspond with the operating instances that may come into question when designing a climate system. The most common error is that the cooling water system is not designed for a two degrees temperature difference on the cooling water, but usually with three or sometimes four degrees. If the supplier’s data is based on a test standard with a two degree temperature difference, then this data cannot be used without recalculating it to the appropriate water flow.
In Swegon documentation all capacity data is based on a fixed water flow to make it possible to easily correct the preferred water flow. These correction curves are always available in connection to respective product data.
For reasons of simplicity the Swegon calculation software ProPipe and BeamSelect is recommended for products with water cooling. This automatically corrects the cooling capacities to the preferred water flow.
