ISO 21978:2021 Heat pump water heater — Testing and rating at part load conditions and calculation of seasonal coefficient of performance for space heating.
6 Setting and part load test conditions
6.1 General
Set points for internal control equipment of the unit, i.e. thermostats, pressure switches or mixing valves, shall be set to the values as stated in the installation and operating instructions.
If several set points or a range are stated, the manufacturer shall indicate the one to be used for the tests.
6.2 Setting for capacity ratio
The capacity ratio to be tested shall be set according to the instructions of the manufacturer. The manufacturer shall provide laboratories with the necessary information on the setting of the unit for operating at the required capacity conditions upon request. The unit shall operate continuously during the part load test. The only discontinuity allowed is the defrost cycle of a unit.
For staged or variable capacity units, the setting of the compressor stage, frequency) shall he done for each part load condition. The manufacturer shall provide in the documentation information instructions on how to obtain the necessary data to set the required frequencies. To set up a system with staged or variable capacity control, skilled personnel with knowledge of control software may be required. The manufacturer or his nominated agent is allowed to attend when the system is being installed and prepared for tests.
6.3 Setting the external static pressure difference for ducted units
The volume flow and the pressure difference shall be related to standard air and with dry heat exchanger. If the air flow rate is given by the manufacturer with no atmospheric pressure. temperature and humidity conditions, it shall be considered as given for standard air conditions.
The air flow rate as stated in the installation and operating instructions shall be converted into standard air conditions. The air flow rate setting shall be made when the fan only is operating.
The rated air flow rate as stated in the installation and operating instructions shall be set and the resulting external static pressure (ESP) measured.
If the ESP is lower than 30 Pa, the air flow rate is decreased to reach this minimum value. The apparatus used for setting the ESP shall be maintained in the same position during all the tests.
lithe installation and operating instructions state that the maximum allowable duct length is for inlet and outlet together less than 2 in, the unit shall be tested with the duct length and the ESP is considered to he 0.
6.4 Setting of units with integral pumps
For units with integral water or brine pumps, the external static pressure shall he set at the same time as the temperature difference.
When the liquid pump has one or several fixed speeds, the speed of the pump shall be set in order to provide the minimum external static pressure.
In case of variable speed liquid pump, the manufacturer shall provide information to set the pump in order to reach a maximal external static pressure of 10 kPa.
Deviations from set values shall not exceed values indicated in Table 2. Variations from specified conditions shall not exceed values indicated in Table 3.ISO 21978 pdf download.