20/80F 2-SPDT 10' 2f DIF A28 Series Two-Stage Temperature Control With NEMA 1 Enclosure 20/80F 2-SPD
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A28 Series Two-Stage Temperature
Controls With NEMA 1 Enclosure
Replaces Part Numbers:
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
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