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Danfoss District Energy
VI.GP.N2.02
DKDHR
Instructions Water
Heaters
14.1 Maintenance of gasketed heat exchanger, Akva Lux II GW
Never open the plate heat exchanger until the unit has cooled below
40° C (105° F)
Never open a plate heat exchanger, which is under pressure from
any source.
Never open a plate heat exchanger with piping to the follower or
connector grids.
Deacidfication of gasketed heat exchanger (cleaning without
opening the heat exchanger , i.e. cleaning in place)
Close the shut-off valves to the water heater and drain the heat
exchanger as much as possible.
Disassemble all connected pipes as well as the controller from the
heat exchanger and if necessary release it from the mounting plate.
Cleaning in place is accomplished by circulating a suitable cleaning
solution* through the secondary side (the domestic hot water side)
of the heat exchanger, as shown to the right.
Cleaning in place works best in the reverse direction of normal flow.
The cleaning solution must be circulated at sufficient velocity to
flush out the product and be able to dissolve the fouling/calification
on the plates. Great care must be taken to select a proper cleaning
solution that does not damage plates or gaskets.
Example of cleaning:
1. Drain product residues, cooling and heating media.
2. Rinse with cold or lukewarm water.
3. Circulate warm cleaning fluid solution.
4. Rinse with warm water or warm water with softener added.
5. Rinse with cold or lukewarm water.
In simple cases cleaning can also be effected without circulation,
but by pouring a cleaning fluid solution into the system.
After some time of standing, flush the solution with clean water.
Insufficient cleaning is most often due to:
• Insufficient circulation rate.
• Insufficient cleaning time or temperature.
• Insufficient concentration of the cleaning agent.
• Excessive periods of operation.
*Cleaning agents
Mineral lime scale deposits are removed with nitric acid (HNO3) -
max. concentration 0,5% - max. temperature 65°C (150 °F). 0.5% con-
centration corresponds to 0,58 litre 62% HNO3 per 100 litres water.
Note!
Excess nitric acid can seriously damage NBR gaskets and other
types of rubber gaskets.
Several alternatives to nitric acid can be used e.g. phosphoric acid
up to 5% and 85 °C.
Note!
Do not use clorine-containing agents such as hydrochloric
acid (HCl).
