On Tuesday, April 8, 2014 5:33:59 PM UTC-4, wrote:
I was called today to assist the burner repair guy with an electrical problem in one of the apartment houses I work in. He wasn't able to get correct voltages at one of the zone valves.



I heat my home entirely with wood, so first let me say that what I know about heating systems could fit into a very small vessel. But I offered my assistance as an electronics technician.



There was a bank of 24 volt transformers, each feeding two apartment's zone valves. And two of these apartments had no heat. He told me that the transformer was a 40 volt unit, he went on to say that it was good, and attempted to demonstrate this by measuring across each secondary terminal and ground. When doing this he measured 40 volts from each secondary screw to building ground. I had to look twice at this to believe it. There was indeed from each screw to ground 40 volts!



So my next best guess was that perhaps it is a 40 volt unit and with a center tap to case ground. So half expecting to see 80 volts across the secondary I read 0 volts. However I did confirm the rating on the label. It was a 24 volt non tapped transformer and an ohm meter check between each secondary terminal and ground showed infinity. And interestingly the same check across the two secondary terminals showed 1 ohm.



We replaced the transformer with a new 24 volt unit and restored the heat in the two apartments. I asked for the transformer. I may have a chance to autopsy it after the guy shows it to his boss. Whether I'll notice anything would remain to be seen.



This problem seems to defy all logic. Does anyone have any thoughts as to what could be going on here? Lenny

I forgot to mention, yes we did use a digital meter to look at this. I thought about bringing my 260 in to look at it and probably should have just to make sure I wasn't looking at noise. I will check it with a low impedance meter when I get it back. Lenny