Lochinvar 90, 500 service manual Maximum SET Point Determination, Locating Temperature Control

5Electrical connections (continued)

Locating Temperature Control NOTICE

Remove the control panel door on the front of the unit in order to locate and access the temperature control.

Installation & Service Manual

Anytime that OJ1 is the only jumper cut, a new overlay is required under the Set Point knob on the temperature controller because the scale has changed to a maximum of 190°F.

Temperature Control Settings

Remove the control panel door on the front of the unit unless your unit is specified as a boiler only with an outdoor air reset option. If your unit is a boiler only with an outdoor air reset option, there are additional controls for this option. They are explained under Outdoor Air Reset Option, page 37.

The three setting knobs on the temperature control are for Set point, Differential, and High-Fire Offset (see FIG. 5-4).

Figure 5-4_Temperature Control

Maximum Set Point Determination

The maximum set point for the control is factory set. Boilers can be set to 240°F max., water heaters are set to 190°F max., and specialty state and local codes to 200°F.

These maximum set points are established by cutting the OJ1 and OJ2 jumpers located on the right side of the temperature controller. The maximum set point is determined as shown below in Table 5C.

TABLE - 5C

MAXIMUM SET POINT DETERMINATION

OJ1	OJ2	MAX.
		SET POINT
Connected	Connected	240°F
Cut	Connected	190°F
Connected	Cut	200°F
Cut	Cut	160°F

Anytime the OJ2 jumper is cut (with or without OJ1), a new overlay is required under the Set Point knob on the temperature controller because the scale has changed to a maximum of 200°F.

Set Point

The Set Point knob specifies the target inlet (or system sensor, if used) water temperature in degrees, Fahrenheit. After the water temperature reaches the set point, the temperature control shuts off the burners.

Differential

The Differential specifies the number of degrees below the set point that the control will allow the water temperature to drop before it brings the unit back on again.

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 at full rate while Low-Fire operates the burners at approximately one-half rate.

The High-Fire Offset 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 the High-Fire stage until the set point is reached and the temperature control shuts the unit off.

If the High Fire Offset knob is set to 0 or 1, the delay will be 10 seconds; if set to 2 or above the delay will be 120 seconds.

Boiler Application

Standard boiler units are equipped with one inlet water temperature sensor. An optional sensor is also provided for use as a remote system sensor. Boilers with the outdoor air reset option also have an outside air temperature sensor.

Water Heater Application

Water heater units are shipped with an inlet water temperature sensor and a multi-purpose temperature sensor to be used as a tank sensor. The inlet water temperature sensor is factory installed on all water heaters.

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