Dometic Mini Bar RH423 wierd electical problem?

[Mark Watson]

I am after a bit of advice on a strange problem. I am an electrical engineer and have been asked by a friend of a friend to have a look at a strange problem that has been plaguing a small hotel. They have motion sensor lights on the stairwell going up through the main part of the hotel and have been experiencing the lights turning on randomly during the night. The sensors are all perfectly OK and set to accept only large object moving, this has all been tested out and found to be all working well. So, first ruling out ghosts, with the help of the owner I went through the system and isolated each of the circuits and devices on the circuit and tested each items individually - anyway, to cut a long story short, it turns out the the a several of the mini bar fridges are the culprits. It seems that occasionally when they cut in and out they trigger the lights on the landing to come on. I have tried surge protectors and even put suppressors in to try to solve the problem, but nothing seems to work. Also tried contacting Dometic who were singularly unhelpful. Not an easy problem to solve or to observe due to its random nature, but i was just wondering whether anyone else has experienced similar problems and been able to solve it?

[Yuri B.]

Hello Mark
If the sensors are all of one make, maybe the problem with this particular model?

[SeanB]

Probably surges and spikes fed back via the mains. If the hotel is wired for 3 phase operation try moving the light circuit to another phase, or do a dedicated power feed just for them from the main breaker board ( this will also allow you to put in place a link to feed in emergency power to power the lights only as well).

If this does not help, and they are sensitive to mains noise ( common on these kind of sensors) then you will have to put an isolating transformer on the feed to them, and provide a separate clean supply just to power them. If the cabling to the lights runs in the same conduits you probably will have to replace it with a shielded version, and run it separately in the ceiling space from light to light, to reduce noise on the line