Wednesday, January 29, 2014

A Wired In Surge Protector Also Protects From Low Voltage


We had turned on the Dometic heat pump as it was quite cool. A few minutes after the compressor had come on, the Progressive Industries EMS-HW30C surge suppressor (hard wired in the coach) tripped shutting off all AC power. The EMS showed a low voltage code on the LED display after I reset it. It trips when the incoming voltage goes below 104VAC. I thought this was interesting as it was showing 110VAC coming from the campground power pedestal. Without the Dometic running the coach was drawing only 2-amps AC (probably the converter).  I then turned the Dometic back on and when the compressor started amperage rose to 17 (which is normal)  @ 110VAC.  Then shortly thereafter the voltage began to slowly drop with amperage staying the same. I shut the Dometic off at 106 VAC and the camp voltage went back up to 110VAC. I thought this was somewhat strange so I took my multi-meter to the camp pedestal measuring voltage there as the compressor came back on. Same falling voltage results there.
I then reported the incident to the camp office. They quickly responded with a technician. He found that the 30-amp breaker was old & weathered and the socked was corroded  so he replaced both.  The voltage was a bit higher at that time (115VAC) so I turned the Dometic back on and again watched the line voltage fall about 3-VAC. At this point all was within proper range and there were no other problems.

I assume (I know the old saying about this word) that this is normal as I did the same testing inside my shop (very adequate 121-VAC power supply w/8-ga wire to the 30-amp RV socket) and watched the same 3-voltage drop when the compressor was running.  I submit this for other owners to be aware of campground voltages and how their varying can occur and the problems that result. The PI Electrical Management System saved me lots of $$$$$ in repair or replacement of the compressor. It's LED status display on the kitchen cabinet face makes it easy to monitor at a glance. I had wired it into the output of the transfer switch so it would monitor all AC power (shore or generator) at all times. That is the only way it should be done.  
Mike C

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