Product Overview

4 P20, P21 Product Bulletin
Standard Differential Options
To convert psi to kPa multiply psi by 6.895
HOW TO USE DIFFERENTIAL OPTION TABLES
Critical Setting: Ordinarily the critical setting on air conditioning limit controls (Series
P20) is the cutout setting, but factory calibration will be made to either cut-in or cutout on
original equipment manufacturers’ specifications. Tolerances on such settings are shown
in the following tables. Opposite or non-critical operating point will then depend on choice
of standard available differential options chosen from applicable table.
Example: Suppose a high pressure cutout setting of 400 psig is required. Also suppose
325 psig cut-in is desired. Differential Option CM, Fig. 10, shows nominal differential of
75 psi at 400 psig cutout setting or a nominal cut-in of 325 psig. Note, also, that at
400 psig cutout, Differential Option BM gives a nominal cut-in of 350 psig; Option DM, a
nominal cut-in of 292 psig.
Also suppose a low pressure cutout setting of 40 psig is required. If a cut-in of 65 psig is
desired, Differential Option CL, Fig. 9, should be selected to provide a nominal cut-in of
70 psig. Option DL at this setting would provide a nominal cut-in of 80 psig; Option BL a
nominal cut-in of 62 psig, not high enough to assure coil defrosting on R-22 systems.