System Settings; Hot Water Production; Top-Up Function; Systems With Hot Water Heat Exchanger And Wcs - Danfoss DHP-R 7Ua User Manual

2�2�2 system settings
The master pump controller contains settings to define whether the plant uses
double jacketed hot water heaters or a heat exchanger. If the plant uses a heat
exchanger, the WCS module is needed.
2�2�3 Hot water production
The sensor Hot water start sensor measures the temperature of the water go-
ing in to the hot water heater. When this falls below a certain limit (Start limit)
a hot water pump is started to produce hot water. Hot water production has
priority over building heating, so if there is a pump already running to heat the
building it switches over to produce hot water.
If the temperature continues to drop, more heat pumps are used to produce
hot water. The setting Delta limit next hp decides how much the temperature
is allowed to drop between each heat pump start.
If the heat pumps are set to stop producing hot water at a certain tempera-
ture, they will be stopped in the same manner as they were started as the hot
water heating temperature starts to reach the Stop limit setting. However, the
default setting is that the pumps continue to produce hot water until the ope-
rating pressure switch is activated.
When a heat pump stops producing hot water it will instead produce heat for
the building, if there is a demand for heat.
2�2�4 Top-up function
Before hot water production is turned off, the Top-Up function performs a check to
see whether it can top up the hot water first. If the hot water temperature is lower
than Top up temp limit degrees over the start limit Start limit it will produce hot wa-
ter instead of stopping immediately. The Top-up function is by default inactivated.
2�2�5 systems with hot water heat exchanger and WCs
The WCS-module measures one charge temperature Wcs temperature and
controls one charger circulation pump and one valve.
If the heat pump hot gases are used for hot water production the hot gas fun-
ction should be activated. This causes the charger pump to always be on. Oth-
erwise it runs only when the heat pump is producing hot water.
When the charger pump is running the valve is controlled to keep the char-
ge temperature constant. Directly after the charge pump is started the valve
opens fully, and is kept fully open for a number of seconds defined in the set-
ting Wcs ctrl start delay.
The set point for the charger temperature is defined in the setting Wcs set-
point. The controller is a PD-controller with the controller parameters Wcs p-
area and Wcs d-factor.
12 – Danfoss