On Saturday, July 1, 2017 at 11:45:40 AM UTC-5, rbowman wrote:
On 07/01/2017 07:13 AM, Uncle Monster wrote:
On Saturday, July 1, 2017 at 6:09:00 AM UTC-5, Sherlock.Homes wrote:
Seems to be 120vac from red to ground and 120vac from black to ground but no
voltage between red and black, which should be 240vac. Reading was taken at
the external dissconnect. What might cause this?

Thanks,
S

One leg is dead and you're reading voltage through the crankcase heater.. make sure the disconnect is off before checking the voltage.

The central crankcase heater?


On a split system, there is a crankcase heater that's hooked across the 240 vac line at the contactor and is always energized. If one leg of the 240 volt supply is disconnected for some reason such as a defective breaker, a loose or burned off connection anywhere past the breaker, a high impedance meter will read 120 vac to ground/neutral from each side because one leg is feeding through the crankcase heater which is nothing more than a big resistor. A crankcase heater is either a cartridge in a well in the crankcase or a strap that resembles a big hose clamp with a flexible heating element that wraps around the base of the compressor. To go off on a tangent, some systems supply a low current to the motor windings to keep the compressor warm but you don't run across them very often. ヽ(ヅ)ノ

https://en.wikipedia.org/wiki/Crankcase_heater

https://highperformancehvac.com/cran...s-compressors/

[8~{} Uncle Cranked Monster