Technical data

19
Heat exchangers
Brazed plate heat exchanger (evaporator)
Protection devices - freeze-up prevention thermostat
The evaporator is protected against freeze-up. The protection is
provided by a sensor installed in the unit in the PRO-DIALOG
version and by a thermostat in the electromechanical version.
Evaporator maintenance
Check that:
• the insulating foam is intact and securely in place.
• the cooler heaters are operating, secure and correctly
positioned.
• the water-side connections are clean and show no sign of
leakage.
Cleaning
In some applications, heat exchanger fouling can be very high,
for example when using extremely hard water. The heat exchan-
ger can be cleaned by circulating a cleaning solution. Use a tank
with a weak acid solution, 5% phosphoric acid or, if the heat
exchanger is frequently cleaned, 5% oxalic acid. Pump the clean-
ing solution through the heat exchanger. For optimum cleaning,
the cleaning solution flow rate should be 1.5 times that of the
normal circulation rate, and the direction of flow should be
opposite to that of normal circulation. Afterwards rinse with
large amounts of fresh water, in order to remove all the acid,
before starting up the system again. Clean at regular intervals.
Cleaning in place
HEAT
EXCHANGER
WEAK ACID
SOLUTION
Soldering instructions
All brazed plate heat exchangers are vacuum brazed with
copper. This means that the plate heat exchanger temperatures
must never exceed 800°C under normal soldering conditions
(no vacuum), because the copper solder would change its state
and the result would be internal or external leakage at the
connections.
The soldering process
1. We recommend to protect and cool the heat exchanger by
using a wet cloth around the connection to reduce the heat
transferred to the heat exchanger during soldering.
2. Oxidation within the connection pipes is not allowed in
refrigeration installations. It is recommended to avoid this
by circulating nitrogen through the pipe/plate heat
exchanger during the soldering procedure. (The nitrogen
flow could be between 0.1 and 0.3 l/s, depending on the
size of the pipe).
3. Start with cleaning the joints to be soldered. Clean the
inside of the connection on the plate heat exchanger and
the outside of the pipe. Degrease the connections properly
with some kind of solvent (e.g. Trichlorethylene).
4. Centre the pipe in the connection.
5. Initial cooling is achieved by keeping nitrogen flowing
through the heat exchanger and by the wet cloth. The final
cooling could be done with water.
Recommendation:
The minimum silver content of the compound is 45%.
Condenser coil
We recommend, that finned coils are inspected regularly to
check the degree of fouling. This depends on the environment
where the unit is installed, and will be worse in urban and
industrial installations and near trees that shed their leaves.
For coil cleaning proceed as follows:
• Remove fibres and dust collected on the condenser face
with a soft brush (or vacuum cleaner).
• Clean the coil with the appropriate cleaning agents.
We recommend TOTALINE products for coil cleaning:
Part No. P902 DT 05EE: traditional cleaning method
Part No. P902 CL 05EE: cleaning and degreasing.
These products have a neutral pH value, do not contain
phosphates, are not harmful to the human body, and can be
disposed of through the public drainage system.
Depending on the degree of fouling both products can be used
diluted or undiluted.
For normal maintenance routines we recommend using 1 kg of
the concentrated product, diluted to 10%, to treat a coil surface
of 2 m
2
. This process can either be carried out with a
TOTALINE applicator gun (part No. TE01 WA 4000EE) or
using a high-pressure spray gun in the low-pressure position.
With pressurised cleaning methods care should be taken not to
damage the coil fins. The spraying of the coil must be done:
- in the direction of the fins
- in the opposite direction of the air flow direction
- with a large diffuser (25-30°)
- at a distance of 300 mm.
The two cleaning products can be used for any of the following
coil finishes: Cu/Cu, Cu/Al, Cu/Al with Polual, Blygold and/or
Heresite protection.
It is not necessary to rinse the coil, as the products used are pH
neutral. To ensure that the coil is perfectly clean, we recommend
rinsing with a low water flow rate. The pH value of the water
used should be between 7 and 8.
WARNING: Never use pressurized water without a large
diffusor. Concentrated and/or rotating water jets are strictly
forbidden.
Correct and frequent cleaning (approximately every three
months) will prevent 2/3 of the corrosion problems.