Strebel S-WG 100, Installation, Operating And Maintenance Manual, Page: 35 / 125

E09.012.246 Manual S-WG
36
8 THE S-WG WATER HEATER
8.1 Water quality
In direct water heating appliances the water flows directly through the heat exchanger of the
water heater. Because all the time fresh water, containing dissolved minerals, is heated, sca-
ling may occur. To prevent this, water quality must meet a number of standards.
The values are the following:
Water temperature max. = 70°C
Maximum allowed water hardness is 205 PPM or 205 mg/L CaCO
3
(= 11.5°dH)
TDS (total dissolved solids) may not exceed 450 PPM
Water hardness and TDS together may not exceed 450 PPM
The pH value of the water may not be under 6.5 and not above 7.5 (measured cold)
If water hardness is too high a water softening system is necessary.
If TDS alone or the combined value is higher than the abovementioned, the water should be
heated by means of an indirect water heating appliance.
Minimum water hardness = 80 PPM or 80 mg/L CaCO
3
Minimum TDS = 100 PPM
Water that’s under these minimum values normally has a pH value which is aggressive and
corrosive.
NEVER install a direct heated water system in an area where water quality does
not comply with abovementioned values.
If the water hardness is too high, a water treatment installation should be installed reducing the water hardness
within acceptable level.
8.2 Frost protection
The water heater has a built-in frost protection, that is automatically activating the pump when the water heater
return (water) temperature drops below 5°C (programmable). When the water heater return temperature drops
below 3°C (programmable), the burner is also ignited. The pump and/or burner will shut down as soon as the
return temperature has reached 10°C (programmable). The abovementioned temperatures are related to the
temperatures measured by the RETURN sensor of the water heater. This frost protection function will not fire up
the water heater in case
of a “general blocking” of the burner demand.
NOTICE: - This frost protection function is only protecting the water heater and not the whole sanitary
system.
- This frost protection function is only useable provided that water circulation through the system is
possible - if not, the water heater goes in a lock-out.
- Because it concerns a programmable setting, a water heater damaged by frost is not covered un-
der warranty.
8.3 Legionella program
To avoid contamination
of the water with Legionnaires’ disease, a special anti-Legionella program is present in
the software of the water heater control, the settings of which are freely programmable.
NB! This option is default turned ‘OFF’, the responsibility for a Legionella-free installation lies with the end-user.
See § 11.1.2 on page 90 for an extensive explanation of how to use this option.