Help With Line Isolation Monitors (LIM)

[luke.stickney]

Help With Line Isolation Monitors (LIM)

I currently have about 40 Line Isolation Monitors (LIM) installed in one of my customers facility and I am hoping that someone here can help with some troubleshooting questions that I have.

Here's the deal:
It looks like about 10 years ago almost all of the original LIM's were updated to electronic LIM's, leaving eight that were still fuse driven. I am not quite sure why they would update all but eight but they did.

Here's the problem:
The hospital has recently bought some new equipment that they are using in the operating rooms. This new equipment is now setting off the isolation alarms in the rooms were the old LIM's are still installed. The new equipment is not affecting the rooms were the LIM's have been updated to the electronic monitors.

Even though I suspect that these old monitors are simply to sensitive for the new equipment, I am a bit apprehensive to make a recommendation for a replacement without knowing if this is the exact problem.

Is there any way to test these monitors other then the recommended monthly "test button"? According to the "test button" everything is fine.

It seems like everywhere I turn people just scratch their heads. Even the sales rep. for SQD didn't have any answers except to replace them.

I am going to spend some more time this weekend trying to pin point the problem in more detail and will post my findings.

Any help would be great.

Luke


Forum Monitors:
I know that this really isn't really a NEC issue, but I wasn't sure were the best place was to post this topic. Feel free to move the post to a better topic.

 

[roger]

Re: Help With Line Isolation Monitors (LIM)

Re: Help With Line Isolation Monitors (LIM)

Luke, it sounds as though the old units are set at a lower level, maybe even 2ma.

The calibrated iso testers are quite expensive.

For quick testing that is reasonably accurate, I use an old adjustable greenlee GFCI tester.

Any push button type GFCI tester will alarm the unit, but it won't give you any idea of what level the trip occured at.

You can check out a newer muti level model HERE

Roger

 

[luke.stickney]

Re: Help With Line Isolation Monitors (LIM)

Re: Help With Line Isolation Monitors (LIM)

Thanks for the help with this Roger. I can't belive I didn't think of a GFCI tester! I guess sometimes when it's right in front of your nose you can't always see it clearly.

I found a great article on the internet that gives a lot of good info on LIM's.

http://www.iaei.org/magazine/02_f/johnston.htm

Thanks again.

Luke