Heating engineer
20
3
system are fundamental to ensure reliability over
time of the mechanical components, in particular
the circulation pumps.
Figure 3.3
Pump/Roma valve assembly on AY appliances
A Roma valve
B
Air vent (internal circuit)
C
Air vent (system)
D Flexible hose
E
Circulator
F
Return pipe
G Delivery pipe
A
G
E
F
B
C
D
3.2.5
Pump antifreeze and anti-lock function
Heating antifreeze function
If the outlet water temperature detected by the
water temperature probe inside the boiler falls
below the antifreeze activation value (default 12
°C, settable via parameter P81), the control board
starts the water pump and the ignition of the burn-
er at minimum power.
When the outlet water temperature reaches 30 ºC
or the inlet water temperature reaches 20 °C (anti-
freeze temperature OFF) the control board will turn
off the burner.
Electrical and gas continuity
The antifreeze function is only effective if the power
and gas supplies are assured. Otherwise, antifreeze
fluid in the system water might be required.
Pump anti-lock function
In order to prevent the circulation pump from lock-
ing, the boiler is equipped with an anti-lock func-
tion which, every 24 hours of inactivity, operates
the circulation pump for 30 seconds.
Electrical continuity
The pump anti-lock function is only effective if the
power supply is guaranteed.
3.2.6
Antifreeze liquid
Precautions with glycol
The manufacturer disclaims any liability for any
damage caused by improper glycol use.
Always check product suitability and its expiry
date with the glycol supplier. Periodically check the
product's preservation state.
Do not use car-grade antifreeze liquid (without
inhibitors), nor zinc-coated piping and fittings (in-
compatible with glycol).
Glycol modifies the physical properties of water
(density, viscosity, specific heat...). Size the piping,
circulation pump and thermal generators accord-
ingly.
With automatic system water filling, a periodic
check of the glycol content is required.
In the presence of glycol
In the presence of glycol it is necessary to warn the
TAC before the first start-up and to set parameter
P52 correctly.
When producing DHW by DHW buffer tank, use
propylene glycol only.
3.2.6.1
Type of antifreeze glycol
Inhibited type glycol is recommended to prevent oxida-
tion phenomena.
3.2.6.2
Glycol effects
The Table 3.1
p. 20 shows, indicatively, the effects of us-
ing a glycol depending on its %.
Table 3.1
Technical data for filling the hydraulic circuit
Glycol %
Water-glycol mixture freezing
temperature
Percentage of increase in pressure
drops
Loss of efficiency of unit
10
-3 °C
-
-
15
-5 °C
6,0%
0,5%
20
-8 °C
8,0%
1,0%
25
-12 °C
10,0%
2,0%
30
-15 °C
12,0%
2,5%
35
-20 °C
14,0%
3,0%
40
-25 °C
16,0%
4,0%
