Bedienungsanleitung Steuerung S4_2006_09_25-neu.doc
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© wodtke GmbH Tübingen. All rights reserved. Subject to change without notice.
Month of issue xx/2007
Art. No. 950 281
7.3 Internal control functions “H.M” and “TW OFF”
These functions have already been described in detail in sections 0 and 0 in the Chapter on
Operation. They are summarised here again in brief since they are also used for monitoring
operating safety and are significantly influenced by external parameters. These are control
functions, not actual errors, since they are the way the appliance responds to external
influences / operating parameters.
Control function /
message
Cause
Desired
value
How to correct error
H.M =
Internal Modulation; see
also Chapter 0
This is a control function
rather than an error.
The temperature limits for the
exchanger, TW, or flue gas fan (TR)
have been exceeded, and the appliance
powers down to minimal load until the
limit values are met again. This is a
control function (not an error), which can
be activated, for ex. by excessive flow
temperature (too little heat transfer via
water) or use of pellets with excessive
calorific value (average output above
nominal thermal output) or high ambient
temperatures.
TR
max
< 200
°C with 6 K
hysteresis (all
models) and
for Waterplus
models
additionally
TW < 75 °C
with 6 K
hysteresis
A soon as functional values
have dropped to desired
range, allowing for hysteresis,
appliance will automatically
jump from “H.M” modulation to
preset output level. Thus, TR
must have dropped to
≤
194
°C. TW must have dropped to
≤
69 °C.
TW OFF =
Appliance shutdown due
to excessive temperature
in heat exchanger (see
also 0) Only in Waterplus
models!
“TW OFF” and “G OFF”
blink alternately for
duration of fan after-run.
Measuring point: internal
boiler sensor (heat
exchanger) FKY.
This is a control function
rather than an error.
Control function or external error.
Temperature in heat exchanger (TW)
above desired value.
Appliance switches from fan after-run “G
OFF” to “TW OFF”.
The cause is almost always external, not
due to the appliance, since TW only
triggers when heat generated by the
appliance is not transmitted. This can
happen, for ex., when the heat demand
of a single-storey heating system without
storage drops to zero. TW OFF then
serves as a control function.
TW < 85 °C
11 K
hysteresis
Appliance restarts
automatically as soon as TW
has dropped to
≤
74 °C.
If “TW OFF” occurs frequently,
check the domestic water
system.
7.4 Burn-back protection
Burn-back protection is provided by a number of mechanisms, some of which are protected by
registered design or patent rights. All wodtke appliances are equipped with a unique fivefold
protection against burn-back into the fuel hopper, consisting of pellet chute cooling, wodtke air
flow sensor technology, temperature cutoff (STB) and a temperature sensor in the chute. This
goes far beyond even the most stringent legal requirements.
7.5 wodtke air flow sensor technology
Located in the central suction pipe is an air flow sensor which measures the current air flow
velocity in the suction pipe, compares it with the set desired values and automatically corrects
deviations by increasing or decreasing the speed of the flue gas fan. In this way the appliance
automatically adjusts itself, within its range of control, to changes in chimney draught, internal
resistance (for ex. soiling of flueways or burner pot) and varying air suction resistance and is
provided with an optimal air flow at all times.
