Honeywell W7750A specifications Resistance Value ohms, Excel 10 Alarms

EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

1.Check the version numbers of the controller firmware, E-Vision and the E-Vision script.

2.Check the wiring to the power supply and make sure there is a good earth ground to the controller.

3.Check the occupancy and HVAC modes.

4.Compare the current actual setpoint with the actual space temperature.

5.Check the desired configuration settings.

6.Check the network wiring and type of wire used.

7.Check the Zone Manager mapping and referred points.

NOTE: If the fan shuts off periodically for no specific reason and the controller restarts the fan by itself after about 20 to 60 seconds, the cause could be a bad Air Flow switch. If the controller has a digital input assigned as a Proof of Air Flow input, try unconfiguring this digital input to see if these shutdowns continue. If not, adjust or replace the Air Flow switch to get it working.

Temperature Sensor and Setpoint Potentiometer Resistance Ranges

The T7770 or T7560A,B Wall Modules or the C7770A Air Temperature Sensor has the following specified calibration points, which are plotted in Fig. 40:

Temperature (°F)	Resistance Value (ohms)
98	11755
80	18478
70	24028
60	31525
42	52675

The T7770 Wall Module setpoint potentiometers have the following calibration points:

Temperature (°F)	Resistance Value (ohms)
85	1290
70	5500
55	9846

.

	80K
(OHMS)	70K
	60K
RESISTANCE	50K
	40K
	30K
	20K	20K OHM AT
		77oF (25oC)
	10K

30	40	50	60	70	80	90	100 110 oF
0		10		20	30		40 oC

TEMPERATURE (DEGREES)

AIR TEMPERATURE SENSOR
10K OHM SETPOINT POT	M11620
RESISTANCE VALUES

Fig. 40. Temperature sensor resistance plots.

Alarms

When an Excel 10 has an alarm condition, it reports it to the central node on the LONWORKS Bus (typically, the Excel 10 Zone Manager). See Table 12. Information contained in an alarm message is:

•Subnet Number:

LONWORKS Bus subnet that contains the Excel 10 node that has the alarm condition. Subnet 1 is on the Zone Manager side of the router; Subnet 2 is on the other side.

•Node Number:

Excel 10 node that has the alarm condition (see Network Alarm).

•Alarm Type:

Specific alarm being issued. An Excel 10 can provide

the alarm types listed in Table 12.

		Table 12. Excel 10 Alarms.
	Alarm type
Name of alarm or error bit	number	Meaning of alarm code or error bit
RETURN_TO_NORMAL	128U	Return to no alarm after being in an alarm condition. This code is added
		numerically to another alarm code to indicate that the alarm condition has
		returned to normal.
ALARM_NOTIFY_DISABLED	255U	The alarm reporting was turned off by DestManMode. No more alarms are
		reported until DestManMode turns on alarm reporting or on application restart.
NO_ALARM	0	No alarms presently detected.
INPUT_NV_FAILURE	1	One or more NV inputs have failed in receiving an update within their specified
		FAILURE_DETECT_TIME.
NODE_DISABLED	2	The control algorithm has stopped because the controller is in
		DISABLED_MODE, MANUAL or FACTORY_TEST mode. No more alarms are
		reported when the controller is in the DISABLED_MODE. Alarms continue to be
		reported if the controller is in the MANUAL or FACTORY_TEST mode.
SENSOR_FAILURE	3	One or more sensors have failed.
FROST_PROTECTION_ALARM	4	The space temperature is below the frost alarm limit 42.8°F (6°C) when the
		mode is FREEZE_PROTECT. The alarm condition remains until the temperature
		exceeds the alarm limit plus hysterisis.
INVALID_SET_POINT	5	One of the setpoints is not in the valid range.

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