User Guide

6
Solenoid coils are classified by their insulating materials with regard to
coil-temperature rise. The maximum permissible temperature that can be
tolerated is limited by the type of insulation and materials used in the
construction of the coil assembly.
Introduction
There are three classes of insulation commonly used for refrigeration coils. These
are referred to as Class F, H and N. The temperature limitations of these classes
are set by various standards associations (UL, CSA, etc.) and are as follows:
Temperature limitations
of insulation classes
Regardless of which class insulation is used, the surface of the coil can become
too hot to be safely touched by hand, even though the temperature is within
the design limits of the insulation system. For this reason, solenoid coils should
be located to avoid accidental human contact.
Safety warning: Hot coils
Other factors that affect solenoid-coil temperature include voltage, ambient
fluid temperature and frequency. These are depicted in the following diagrams.
Other temperature factors
Figure 4 shows the effect of voltage on solenoid-coil temperature.Effect of voltage
Temperature ratings
Temperature
Effect of Voltage
Figure 4
110% rated voltage
Time
Rated voltage
85% rated voltage
Class Maximum temperature rise
°F °C
F 171 95
H 207 115
N 243 135
Table 1