Protecting The Unit From Frost - RHOSS TCAEBY 269 Mode D'emploi

EN

Protecting the unit from frost

IMPORTANT!
If the mains switch is opened, it cuts off the electricity supply to the storage tank
plate exchanger heater, the antifreeze heater of the storage tank and the pump
(RA, RDR, RAE, RAR, RAS, RIS accessories) and the compressor crankcase
heater. The switch should only be disconnected for cleaning, maintenance or
repair of the machine.
When the unit is running, the control board protects the heat-exchanger
from freezing by tripping the antifreeze alarm which stops the machine
point value.
IMPORTANT!
When the unit is out of service, drain all the water from the circuit.
If the draining operation is felt to be too much trouble, ethylene glycol
may be mixed with the water in suitable proportions in order to guarantee
protection from freezing.
The use of ethylene glycol is recommended if you do not wish to drain
the water from the hydraulic system during the winter stoppage, or if
the unit has to supply chilled water at temperatures lower than 5°C
The addition of glycol changes the physical properties of the water
and consequently the performance of the unit. The proper percentage
of glycol to be added to the system can be obtained from the most
demanding functioning conditions from those shown below.
Table "H" shows the multipliers which allow the changes in perfor-
mance of the units to be determined in proportion to the required per-
centage of ethylene glycol.
Use of anti-freeze solutions with the BT accessory
The table provides the percentage of ethylene/propylene glycol to be used in units with the BT accessory, according to the temperature of the chilled
water produced. Use the RHOSS
Evaporator glycol water outlet temperature
From -7,1°C a -8°C
From -6,1°C to -7°C
From -5,1°C to -6°C
From -4,1°C to -5°C
From -3,1°C to -4°C
From -2,1°C to -3°C
From -1,1°C to -2°C
From -0,1°C to -1°C
From 0,9°C a 0°C
From 1,9°C to 1°C
From 2,9°C a 2°C
From 3,9°C to 3°C
From 4,9°C to 4°C
Section II :: Installation and maintenance
Software for unit performance.
Minimum % glycol in weight
33
32
30
28
26
24
22
20
20
18
15
12
10
68
The multipliers refer to the following conditions: condenser inlet air
temperature 35°C; chilled water temperature 7°C; temperature diffe-
rential at evaporator 5°C.
as their variations are negligible.
The resistance of the water side primary and secondary heat exchan-
ger (RA-RDR accessory), the storage tank (RAS-RIS accessory) and
the electric pump unit (RAE-RAR accessory), prevents undesired ef-
fects due to freezing during the operating breaks in winter (provided
the unit remains powered).
Table "H"
Design air
temperature 2 0
in °C
% glycol in
10 15
weight
Freezing tem-
-5 -7
perature °C
fc G 1.025 1.039 1.054 1.072 1.093 1.116 1.140
fc pw 1.085 1.128 1.191 1.255 1.319 1.383 1.468
fc QF 0.975 0.967 0.963 0.956 0.948 0.944 0.937
fc P 0.993 0.991 0.990 0.988 0.986 0.983 0.981
fc G
fc pw Correction factor of the pressure drops in the evaporator
fc QF Cooling capacity correction factor
fc P Correction factor for the total absorbed electrical current
Minimum % glycol in weight
-3 -6 -10 -15 -20
20 25 30 35 40
-10 -13 -16 -20 -25
34
33
32
30
28
26
24
22
20
18
15
12
10