What is the effect of taking an amp reading across a valve coil?

What is the effect of taking an amp reading across a valve coil?

• A. measure the current accurately
• B. blow the fuse
• C. ruin the heat anticipator
• D. cause the regulator to shut off

Answer: (C)

Measuring current by placing an ammeter across a valve coil is incorrect because an ammeter must be wired in series with the load. Putting a meter across the coil creates a parallel, very low-resistance path that effectively short-circuits the coil. In this control circuit, that abnormal current path can drive excess current through the thermostat’s heat anticipator circuit (a small resistor that is heated to bias the thermostat). The extra or misdistributed current can cause the anticipator to overheat and fail, i.e., be ruined. The other options don’t describe this direct risk to the heat anticipator; the reading would not be a true measure of coil current, and while abnormal faults can cause other issues, the immediate consequence in this setup is damage to the heat anticipator.

Measuring current by placing an ammeter across a valve coil is incorrect because an ammeter must be wired in series with the load. Putting a meter across the coil creates a parallel, very low-resistance path that effectively short-circuits the coil. In this control circuit, that abnormal current path can drive excess current through the thermostat’s heat anticipator circuit (a small resistor that is heated to bias the thermostat). The extra or misdistributed current can cause the anticipator to overheat and fail, i.e., be ruined. The other options don’t describe this direct risk to the heat anticipator; the reading would not be a true measure of coil current, and while abnormal faults can cause other issues, the immediate consequence in this setup is damage to the heat anticipator.