Crown Boiler TWZ Series, Installation Instructions Manual

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41
TABLE 14.0 - DIAGNOSTIC CONDITIONS
Condition Possible Cause
Burner will not fire See Flow Chart 1, page 42
Burner will not shut down See Flow Chart 2, page 43
Temperature display exceeds
high limit setting
Under normal operation, boiler temperature will continue to rise after the control shuts off
the burner. This condition, known as “thermal stacking”, results from hot boiler surfaces
continuing to release heat into the boiler water.
No or insufficient domestic hot
water
For boilers equipped with a tankless coil, make sure the low limit setting on the control is
set properly. NOTE: If the low limit setting is dialed fully counterclockwise, it will shut
off the low temperature maintenance feature and will function as a cold start control. If
installed with an indirect water heater, check that the Zone/Indirect Switch is set in the
Indirect (I) position. Verify that the end switch in the relay box controlling the indirect water
heater is connected to the ZC-ZR terminals. This will ensure that the domestic water calls
are prioritized.
Low water light (Red LED) is on
or blinking
WARNING : A low water condition is a serious and potentially
dangerous condition. Do not attempt to add water to a hot boiler.
Allow the boiler to fully cool before adding water.
When the LOW WATER light is on, this indicates that the control is not detecting water
in the boiler. When the LOW WATER light is blinking, this indicates that the control has
been programmed to provide low water lock-out protection and is currently locked out (see
Manual Reset Low Water Cut-Off). Pressing the TEST/SETTINGS button after the low
water condition is resolved will reset the lock-out condition.
1. If the light is on and the heating system is filled with water, pull the sensor out of the well
and inspect it. Make sure that the metal clip is protruding enough to come in contact with
the inside of the well tube. Check that the well does not have excessive build-up of heat
transfer grease that may interfere with the clip contacting the well.
2. Remove well and examine for excessive residue build-up. Clean and re-install.
Boiler will not maintain
low limit temperature
Check for overlapping high temperature setting. If the high limit setting is set below the low
limit setting, the control will default to the high limit setting and the corresponding high
limit differential setting.
House will not get or stay warm
1. Check for air-bound radiators.
2. Check thermostat settings including heat anticipator settings (common on non-digital
thermostats).
3. Check the Economy setting. The Economy feature, much like outdoor reset controls,
lowers average boiler temperature and can slow or, in some cases, prevent the house from
coming up to temperature. Move to a lower setting (see “Setting the Economy Feature”).
Circulator contacts
C1 and C2 not energized on call
for heat
Check to see that boiler water is at or above 125°F. On a call for heat, the control will
not permit the circulator to operate if the boiler water temperature is below 125°F (see
“Circulator Hold Off”).
All LED lights and temp display
are blinking
If the LED lights and the temp display are blinking alternately, this indicates the control has
sensed a boiler temperature of 250°F. When this occurs, the control pulses the burner relay
and then shuts down and locks-out the burner. The system should be analyzed to determine
the cause of the overheating condition. Check that the sensor is inserted all the way into
the well so it can accurately sense the temperature of the boiler water. Check the load on
the burner contacts: If the load exceeds the 7.4 Amp rating, the contacts may have welded.
Correct the overloading condition and replace the control before reenergizing the system.
If the load on the contacts is below the rating, check system wiring and operation as well
as the control’s high limit setting. If the cause of the overheating is found and the system is
deemed safe, the control can be reset by removing power from the control and then repow -
ering while simultaneously pressing the Test/Settings button on the top of the control. If the
cause of the overheating condition is not determined, the control should be replaced.