Burnham RSA manual L7224 / L7248 Controller Operating Sequence, Trouble Shooting Guide

Table 5: L7224 / L7248 Controller

Operating Sequence

Action	System Response
Thermostat	Circulator starts when water temperature is
calls for heat.	above Low Limit setting (if applicable). Boiler
	temperature is checked. Burner starts when
	water temperature is below High Limit setting.
Boiler exceeds	Burner is turned off. Burner restarts when the
the High Limit.	water temperature drops below the High Limit
	setting minus the Differential.
Thermostat is	Circulator and burner turn off.
satisfied.
Error condition	If an error condition is detected, all outputs ex-
1-5.	cept ZC are shut down. Burner is off. Control
	continues to function and restarts when error is
	corrected.
	During the error check sequence, the system
	checks for drift in the sensor and corrosion in
	the connections.
Error	EnviraCOM communication is not available.
condition 6.
Error	The control has reset the High Limit, Low Limit
condition 7.	and Differential setting to a default setting and
	will continue to run at those settings.
	Performance of the system will be degraded.
Error	If the error condition is detected, all outputs
condition 8.	except ZC are shut down. Burner is off. Control
	continues to function and restarts when all
	three user keys have been pressed longer than
	60 seconds.

Differential. The L7248 models have High Limit Differential presets of 15°F (8°C). The L7224 models have High Limit Differential presets of 10°F (6°C).

Table 6: Trouble Shooting Guide

9.LOW LIMIT AND CIRCULATOR CONTROLLER

On a temperature rise, with the adjustable Differential at the default setting of 10°F (6°C), the burner circuit breaks and the circulator circuit makes (assuming no call for heat is present) at the Low Limit setpoint. On a temperature drop of 10°F (6°C) below the Low Limit setpoint, the burner circuit makes and the circulator circuit breaks. See Figure 24.

Figure 24: Setpoints and Differentials

System Condition	Diagnostic Condition	Check		Action
Boiler is cold, house is	Display is OFF.	120 Vac System power.	Turn system power on.
cold.
	Display is ON.	24 Vac T-T	No 24 V; replace control.
		24 V present; disconnect thermostat,	Boiler starts, check wiring and thermostat.
		short T-T.
		120 Vac at B1-B2	•	If no, replace control.
			•	If yes, check burner and wiring.
		Refer to Err on display.	-----
Boiler is hot, house is	Display is ON.	120 Vac at C1-C2	•	120 Vac at C1-C2, check wiring
cold.				to pump.
			•	Wiring OK, is pump running?
			•	If not, replace the pump.
			•	If pump is running, check for
				trapped air or closed zone valves
		Boiler below the Low Limit tempera-
		ture, wait for boiler to go above Low	-----
		Limit temperature.
		Boiler above LL? If yes, check for	•	If no 120 Vac , replace control.
			•	If yes, check zone relays, circulators
		120 Vac between ZC and L2.
				and wiring.

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