Reconditioning Old Heating Systems; Elimination Of Air And Gas From Central Heating System; Use Of Antifreeze - Riello RTC-80 Series Installation, Operation And Service Manual

INSTALLATION
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NOTICE:
− Loss of water from the system, and the consequential need
to add water, can be caused not only by leaks from the
circuit, but also from the incorrect sizing of the expansion
vessel or precharge pressure. (If normal thermal expansion
causes pressure in the system to increase beyond the set-
ting of the safety valve, that safety valve will open contin-
uously.)
− The expansion vessel size should be corrected to prevent
unnecessary safety valve blow-off.
The heating system should not need any further topping up once
it is filled and bled of all air.
Any top-ups need to be monitored (by a meter), treated and re-
corded in the heating system's technical log. The presence of a
water softener in conjunction with an automatic filling system is
not sufficient to ensure proper performance.
If more than one boiler is installed in a large system, all boilers
must be switched on at the same time to ensure that any possible
limescale formation is uniformly distributed.

2.8.6 Reconditioning old heating systems

Frequent mistakes and necessary precautions.
If a boiler must be replaced, do not refill the entire central heating
circuit if the quality of water in it conforms to requirements.
If the quality of water fails to conform to requirements, either re-
condition the old water or separate the water circuits (water in the
boiler circuit must conform to requirements).
Conclusions
Never forget that proper water conditioning and proper heating
system design not only guarantee safety and security but also en-
sures significant savings in maintenance costs and overall thermal
efficiency.
2.8.7 Elimination of air and gas from central heating
system
When designing new heating systems, it is necessary to eliminate
the air and other gases that form in the system.
Recently added fill or top-up water loses much of its volume in
the first few days because it releases gases. With new systems you
should therefore initially check the heating water pressure on a
daily basis, and then at gradually longer intervals. Air and gas in
the water system not only causes the corrosion problems listed
above, but also reduces thermal efficiency, causing pump fail-
ure and noise and vibration throughout the heating system. Air
bubbles and gas inevitably form in heating circuits during normal
functioning, especially if the precautions listed above are not fully
respected.
In particular:
− as temperature increases, oxygen becomes less watersolu-
ble and bubbles begin to form;
− CO2 (carbon dioxide) is generated as the carbonates of cal-
cium and magnesium precipitate out;
− the chemical oxidation of the metals in the system also
generates hydrogen.
These gases must be eliminated as they are formed. The system
needs to be designed and installed so that all gases can be vented
quickly, easily, and effectively.

2.8.8 Use of antifreeze

Do not use automotive silicate-based antifreeze in the heating
system.
In areas where freezing may occur, an antifreeze may be added
to the system water as protection. Please adhere to the specifica-
tions provided by the antifreeze manufacturer.
− Use the anti-freeze manufacturer's data to determine the
anti-freeze ratio for the desired freeze protection tempera-
ture.
− Do not exceed 50% antifreeze mix ratio and do not use an-
tifreeze other than specifically made for hot water heating
systems.
− the chemical oxidation of the metals in the system also
generates hydrogen.
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