Water Analytics AquaMetrix AM-2250 Installation And Operation Manual
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152250-series Operating Manual rev 2.03.7 Relays (AM-2250 and AM-2251)3.7.1 Wiring relaysThe AM-2250 and AM-2251 contains three dry contact relays. For a resistive load they are rated 10A @120/240 VAC or 8A @ 30 VDC. For an inductive load they are rated 5A @ 120/240 VAC or 4A @30 VDC.Though these relays will work in most process control applications, we advise, for safety reasons, to usethem as switches, i.e. low power DC relays that activate a second set of AC-powered relays separate fromthe controller.Figure 3-12 Wiring connections to the three relays. All relays are powered by internal jumpers between the ac power andterminals 21 and 22.3.7.2 SnubberWhen a relay is used to control an inductive device (relay coil, solenoid, transformer, small motor, etc.),the energy stored in the device will subject the relay contacts to a high voltage when the relay opens.When the switch contacts open, the contact gap is initially small. Arcing across this contact gap can occurimmediately after the switch opens. This can happen in resistive as well as inductive loads, but inductiveloads generate a higher voltage and causes increased arcing. Increased arcing decreases relay life. Arcsuppression requires the use of an RC suppression network, called a snubber.Each relay of AM-2250 and AM-2251 is connected to a snubber. Despite the fact that snubber prolongsrelay life they have one disadvantage – they leak a small amount of AC current. If there is a low powerLED or voltage meter connected between the COM and NO (or NC) terminals there will always be someAC voltage across them. If your application requires having only an LED use the alternative wiring shownin Figure 3-13 below.Figure 3-13 Alternative wiring for low power equipment (LED) only |
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