20/80F 2-SPDT 10' 2f DIF A28 Series Two-Stage Temperature Control With NEMA 1 Enclosure 20/80F 2-SPD
A28 Series Two-Stage Temperature Controls With NEMA 1 Enclosure
These two-stage controls are designed to cover a broad range of general purpose operating temperature control applications in the refrigeration, air conditioning and heating fields. Two SPDT switches permit independent control circuits. Each switch may be wired for “open high” or “close high” action, as required, providing automatic changeover on heating-cooling or similar requirements. Models are available with close differential on each switch. A jumper across the “common” terminals is supplied as a standard feature. Models are available for fixed or adjustable between stage differential.
All Series A28 temperature controls are designed for use only as operating controls. Where an operating control failure would result in personal injury and/or loss of property, it is the responsibility of the installer to add devices (safety, limit controls) or systems (alarm, supervisory systems) that protect against, or warn of, control failure.
On a temperature increase to the dial setting, the circuit between R and Y of the low stage switch (RYL) closes. Simultaneously the circuit between R and B (RBL) opens. On a further increase in temperature the high stage switch operates and closes RYH while simultaneously opening RBH. The reverse sequencing takes place on a temperature fall.
Follow equipment manufacturer’s instructions if provided. If instructions are not provided, proceed as follows:
Controls are normally mounted to a surface through holes in back of case.
! CAUTION: On rough mounting surfaces use the top two mounting holes only. When these controls are mounted on an uneven surface using screws in all four holes, the case can be twisted enough to affect the control’s calibration and operation.
For closed tank applications without well assembly, Part FTG 13A-600R packing nut assembly may be supplied. Place parts over support tube section of the element, placing bulb into tank (be sure tank is drained so liquid level is below tank opening). Tighten the 1/2 in. NPT adapter. Screw packing nut into adapter with the retaining washers and
packing in place as shown. To install models supplied with a bulb well, first install the bulb well into the tank opening. Remove bushing from the bulb well and slide the bushing over capillary. Place the bulb and bushing into the well. Push bulb into position in bottom of the well. Tighten set screw in end of the adapter to hold bulb in position.
! CAUTION: Do not dent or deform the sensing bulb of this control. A dent or deformation will change the calibration and cause the control to cycle at a temperature lower than the dial setting. When the bulb mounting clip is used to mount the bulb near the refrigerant tubing, be sure the sheet metal screw does not pierce the tubing.