Lochinvar 45000, 260000 service manual Outdoor Air Reset Option, Additional Temperature Controls

5Electrical connections

Outdoor Air Reset Option

For boilers ordered with the Outdoor Air Reset option, there is an additional control (FIG. 5-5). There are three setting knobs for Shutdown, Outdoor Air Max., and Ratio. There is also a switch to turn the outdoor air shutdown feature On or Off. An O.A. Sensor is also included.

(c)2002 L.C.		55			CN1				CN2			CN3
													OJ1
CN7		50	60
	D4		65	O.A. SENSOR								CN4	C10
CN8					ON ENABLE
	45
		VR3			SW1
		40	70		DISABLE
	W1			O.A. SHUTDOWN								CN5	OJ2
		SHUTDOWN
									R6	R4	C7
		55				1.0							C9
					0.9							CN6
		50	60			1.1
				0.8		1.2
	45		65	0.7			1.3					J4
										W3
		VR1		0.6		VR2	1.4					R8
					0.5
		40	70			1.5
CN1									W1	W2
		O.A. MAX.			RATIO
													CN9
	160				10 11
		200		9						10
140				8		12
							R15	R16	5			15
				7		13
			220
120				6		14
				5	VR2	15		(F-)0		VR3		20
		240
	OFF		DIFFERENTIAL						HIGH-FIRE
	SETPOINT			TST2314					OFFSET

Figure 5-5_Optional Outdoor Air Reset Control

Shutdown

The Shutdown knob specifies the outdoor air lockout temperature at which the control would prevent the unit from operating.

Outdoor Air Max (O.A. Max)

The O.A. Max knob allows a reset up to the maximum outdoor air temperature specified by this knob setting. When the outdoor air temperature is above the specified setting, the unit will not function in the O.A. Reset Mode, but will continue to run at the selected set point temperature.

Note that the set point knob will now indicate the “minimum” boiler temperature. Target temperature is determined by the ratio and outdoor air temperature below the O.A. Max setting.

Ratio

The Ratio knob allows control over the reset ratio to be used during Outdoor Air Reset. The allowable ratios are as low as 0.5:1 or as high as 1.5:1.

Selecting the 0.5:1 ratio will increase the set point 0.5° for every 1.0° drop in outdoor air temperature up to the maximum set point temperature.

Selecting the 1.5:1 ratio will increase the set point 1.5° for every 1.0° drop in outdoor air temperature up to the maximum set point temperature.

38

Installation & Service Manual

If the outdoor design and boiler design temperatures are known, the Ratio setting can be calculated using the following formula:

Ratio = (boiler design temperature - operator set point)

(O.A. Max. setting - outdoor design temperature)

Note that the reset set point cannot exceed the maximum set point of the boiler thermostat.

These settings are illustrated graphically in FIG. 5-6.

Figure 5-6_Outdoor Air Control Example Chart

Outdoor Air Shutdown Enable/Disable Switch

The Outdoor Air Shutdown Enable/Disable switch turns the outdoor air shutdown feature On and Off. Disabling the Outdoor Air Shutdown feature allows the unit to operate regardless of the outdoor air temperature. This is needed for indirect domestic hot water systems for example.

Additional Temperature Controls

High Water Temperature Limit Control

The appliance is supplied with a fixed setting, auto-reset high water temperature limit control. The setting of this control limits maximum discharge water temperature. If water temperature exceeds the setting, the limit will break the control circuit and shut down the appliance. The limit control will only be reset after the water temperature has cooled well below the setting of the limit. The auto-reset high water temperature limit control is mounted in the outlet side of the front header.