Electric Boilers & DHWT's - couple questions

Apprentice_3

Hey folks, a quick troubleshoting question for y'all...
What is the correct procedure for testing an element OR a thermostat in a DHWT to determine if it needs replacement?
I understand that a reading of Ohms must be taken....should this reading be done through water or with the tank drained? And what reading (how many Ohms) indicates an "good" or "bad" element or thermostat? And last but not least....can the same procedure be used for the elements & thermostats/aquastats in an electric boiler? Or is there s slightly differnt way to go about it?
Pretty basic questions I know....but in my 3 years of working for a mechanical contractor I've been installing exclusively, and so have my colleagues, so I'm trying to teach myself the troubleshooting side of things.

singh

Addam

Shut power off, and then with ohms tester check element at each screw. Water does not need to be drained. It really depends on the type of element, but a typical residential water heater will read around 12.7 for a good element, I will change if reading is 9.0 or so. And obvious 0 is a broken element.
Thermostats need replacing when the reset button keeps trippin' when tank heats up. If it trips once, I'll usually replace to avoid a call back, rather than resetting.

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Apprentice_3

Thanks DS, Does the same hold true for the elements in an electric hydronic boiler? Different Ohm reading perhaps?

singh

yes same for electric boiler

but may be higher reading, typical boiler have 7000kw elements each so they be in the 14.0 ohms reading, best to check with manufacturer though.

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Apprentice_3

Thank you! I'll bother you for one more if you don't mind...Ohms reading for Tankless Electric water heater elements???
Thanks again.