Final Hot Water Heater With Twc; 2�3 Heat Pump Restrictions; Time Restrictions; Return Temperature - Danfoss DHP-R 7Ua User Manual

2�2�6 Final hot water heater with TWC
The TWC (Tap Water Control) module monitors and controls an electrical hot
water heater to ensure that the water at the tap points is the right temperature.
The module controls the electrical heater and measures temperatures on both
the outgoing water and the re-circulated water. If either of these temperatures
falls outside the set limits alarms are generated.
When the heater starts and stops is decided by high and low limits on both the
outgoing and re-circulated water. The upper limit for outgoing temperature
has the highest priority to avoid burn hazards. Different start delays are used
for the outgoing and return temperature limits.
A special legionella function is designed to ensure that all legionella bacteria
in the final heater are killed. A week schedule defines when to start a legio-
nella heat run. When started the heater will be on until the water reaches the
legionella stop temp. The week schedule is not activated in the factory default
setting, but can be set to run once a week if heater seldom reaches high tem-
peratures in normal operation.
2�3 Heat pump restrictions
2�3�1 Time restrictions
The heat pump has two time conditions that must be met if it is to be allowed
to start. One states that when stopped it must be standing still for at least five
minutes before it can start again. The other states that any two starts must be
at least 20 minutes apart. This time limit can be changed using the setting Min
start interval.
The display on the pump shows whether it is blocked by a time condition, and
how many seconds are left until it is allowed to start again.
2�3�2 return temperature
If the temperature on the pump return reaches a threshold, an alarm is gene-
rated and the pump stops. This alarm is inactivated when the pump is making
hot water, and the alarm does not prevent the pump from making hot water.
The default setting for the threshold is 48 °C.
2�3�3 Brine flow guard / pressure guard
In each heat pump there is a setting that tells whether the brine flow is moni-
tored by an external flow guard or pressure guard. If a flow guard is activated
there is an alarm with an adjustable delay that stops the pump on error.
If the pressure guard is selected a choice can be made whether the alarm
should stop the pump or not.
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