20
Instructions for installation and use
TD & S substations
DKDHR
VI.GP.U2.02
Danfoss District Energy
18. Operation and maintenance
Operation and maintenance
The caretaker/owner must perform visual checking and reading of
the district heating meter at short, regular intervals. (The meter is
not a part of the delivery from Danfoss).
Service procedures must only be performed by trained, authorised
personnel.
NB! Excessive consumption for whatever reason is not covered by
the Danfoss warranty.
Service
The substation should be checked regularly by authorised person-
nel. Any necessary maintenance must be performed in accordance
with the instructions in this manual and other sets of instructions.
During service the dirt strainers are to be cleaned (
pos. 8
– including
the filter (
F
) on the controller, see the photo to the right), all pipe
connections must be tightened and the safety valve (
pos. 5
) must
be function tested by turning the lever.
Rinsing / Return rinsing
To clean the plate heat exchanger, rinse it by running clean water through
the exchanger at high speed and in the opposite direction to the normal
flow. This will remove any dirt deposits that may have built up in the
exchanger. If rinsing with clean water is not sufficient, the exchanger
can also be cleaned by circulating a cleaning agent approved by Danfoss
(e.g. Kaloxi cleaning fluid) through the exchanger. Kaloxi cleaning fluid is
environmentally friendly and can be disposed off through the standard
sewer system. After use of a cleaning fluid, the plate heat exchanger must
be rinsed thoroughly with clean water.
Acid cleaning of brazed plate heat exhanger
In principle, we do not recommend using acid cleaning of the plate
heat exchanger. Deposits of limescale may build up in plate heat ex-
changers for domestic hot water on account of the large temperature
fluctuations, and because aerated water is used on the secondary
side. If it becomes necessary to clean the exchanger with acid, this
can be done as shown in the figure to the right. Brazed plate heat
exchangers can withstand rinsing with a dilute acid solution – e.g.
5% formic acid.
Measures after maintenance work
After maintenance work and before commissioning:
•
Tighten all pipe connections
•
Replace insulation covers on heat exchangers and other
insulated equipment
•
Wipe down the substation and clean up any fluid spills
•
Clear all tools, materials and other equipment from the work area
•
Switch on the energy supply and check for leakage
•
Vent the system
•
Carry out any necessary adjustments again.
•
Check that pressure and temperature are at normal levels.
Cooling / Reading the return temperature
Cooling – i.e. the difference between the supply and return tempera-
ture of the district heating water – has a significant effect on overall
energy economy. Therefore, it is important to focus on the supply
and return temperature in the heating system. The difference should
typically be 30–35°C. Please note that a low district heating return
temperature is directly related to the return temperature from the
heating circuit and the return temperature of the circulation water.
It is therefore important to focus on these return temperatures.
Cooling from the water heater alone:
During tapping, the level of cooling will typically be 30–35°C. When
hot water is not being tapped, it is completely normal for the return
temperature from the water heater to rise slightly. In this situation,
the district heating meter will register very modest consumption as
the volume of water is very small.
On water heaters with recirculation, the calorie meter registers the
heat loss in the circulation pipe.
