Some weird problem with one of my showers in our house. There is a 50mV to 60mV DC voltage on the showerhead, while the pipe it connects to is properly grounded (a teflon tape appears to isolate the showerhead from the pipe). It is DC, not AC, like the house mains electrical. It is a low voltage (1/1000th of normal AC voltage at the outlets) but is enough to produce some twiching when touched. When all the breakers are off, there is still ~ 15-30mV residual voltage. When the breakers are back on, but the phone wires are disconnected in the phone interface box, there is a ~ 15mV residual DC voltage on the showerhead. When both main electrical and phone are disconnected, there is still a residual DC voltage of 15 - 30mV. There is never any AC voltage. The hot water pipe is grounded to the cold water pipe at the water heater. All voltages were measured with the negative of the voltmeter connected to earth (round prong of a 3-prong outlet). Our wireline phone has a constant humming sound which is very annoying (symptomatic of a bad ground). We actually discontinued the service due to poor audio quality. I am thinking the house has a weak grounding rod, maybe due to corrosion. A google search points to other people experiencing such problems. The recommended solution is to separate the phone interface box ground from the house AC mains ground, although I was told that codes require a common ground, which I tend to agree with, a good ground should have 0 potential on it.
After we installed out solar roof I noticed that the digital inverters 9one per panel) were rebooting often, even on sunny days. That caused spikes on their output and we were loosing about 20 percent of our power. This was not noticeable in any other way. I hacked into the inverter raw data and found error messages--AC out of spec. I requested the PUD to put a recorder on our meter and they saw the same thing. it turned out that the transformer on the pole in the alley was faulty. Bad neutral wire. they replaced that and the problem went away. it might have been that way for years.
ReplyDeleteI wonder how many other problems exist in houses like yours and ours and in the grid but go unnoticed for a long time.