Last week we discussed how a heating element could be quickly field tested in an electric boiler or electric heater. What you needed to know though was the expected ohms to compare to the actual ohm reading. If you do not have that expected ohm value you can still determine if a heating element has failed.
Fortunately, for a trained service person checking the function of a heating element for electrical continuity can be done in just a few steps with a minimum amount of equipment. An untrained service person may jeopardize their safety and should not attempt doing electrical service.
Trained qualified service people may examine the boiler by first Turning OFF the electrical supply to the boiler at the service panel and at the boiler.
Open the wiring access panel on the boiler with a key. Use a probe or multimeter to test voltage on the incoming wiring. Check the voltage from all power leads to ground. If the reading on your meter is anything other than zero, stop immediately. Check the breakers in the service panel. If the breakers are off and the meter is still getting a nonzero reading, repair the problem before performing any other testing, service or repair. Once the power is assured to be cut to the boiler see if any elements look failed at their flange wiring connections. Assuming you are not able to see any failed element(s) by looking at them locate the heating element contactors. The photo shows four typical contactors.
In this discussion you are not sure what the element ohms should read on your meter so select an ohm reading of 100 or 200.
See photo. At a contactor touch one meter probe to wire 1 and the other to wire 2. The three wires on that contactor normally lead to one element. Be sure you are touching the connections on the underside wires of the contactor. Note the meter reading. Move the red probe to the 3rd wire at that contactor. Note the meter reading. They should be similar. If they are this element is likely good. However a reading difference of over 20% or a zero (infinity reading) indicates a bad or failing element. Reimers can get you replacements fast for voltages up to 600 for 1 and 3 phase boilers.
Do the same meter check on all the contactors. Do write down meter readings and compare afterward. In this situation if you see one or more elements are far different in meter readings from the majority, replace the minority elements.
TIP: The highest elements in the boiler shell are more prone to damage should a low water problem occur. Under abnormal conditions they could run dry and overheat often melting their rods inside the boiler. Proper maintained boilers do not run low on water without safely shutting off the elements.