Lochinvar 065, 495 Outdoor Air Reset Option, High-FireOffset, Shutdown, Outdoor Air Max O.A. Max

Installation and Service Manual

High-Fire Offset

The temperature control operates a two-stage firing system. The two stages are High-Fire and Low-Fire. High-Fire operates all burners while Low-Fire operates approximately one-half of the burners.

The High-Fire knob specifies the number of degrees below set point that the High-Fire stage shuts down. At that point, the unit will continue to operate at the Low-Fire stage until the set point is reached.

The High-Fire offset knob has settings between 0°F and 20°F. If set at 0°F, the High-Fire offset is disabled and the unit will operate at the High-Fire stage until the set point is reached and the temperature control shuts the unit off.

When the High-Fire offset knob is set to 0 or 1, the unit will light at Low Fire and operate for approximately 10 seconds before the High-Fire stage actuates. When set to 2 or above, the unit will operate at Low Fire for 2 minutes before the High Fire stage actuates.

Outdoor Air Reset Option

For boilers ordered with the Outdoor Air Reset option, there is an additional control (see Figure 36). There are three setting knobs for Shutdown, Outdoor Air Max., and Ratio. There is also a switch to turn the outdoor air sensor On or Off. An O.A. Sensor is also included.

Shutdown

The Shutdown knob specifies the outdoor air lockout temperature at which the control would prevent the unit from operating. This feature can be enabled/disabled with the O.A. Shutdown switch.

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 the 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°F for every 1.0°F 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°F for every 1.0°F drop in outdoor air temperature up to the maximum set point temperature.

See Figure 37 for an outdoor air reset chart example.

(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 36 - Optional Outdoor Air Reset Control

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