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#24120 - 04/04/03 07:38 PM Lim's  
Weekend  Offline
Junior Member
Joined: Mar 2003
Posts: 3
I'm an electrician in a hospital that wants to remove rather than replace or repair Lim's. Personally I think it's a mistake but they are not required except in designated "wet locations". Since the panels are not grounded (obviously )and the breakers are 2 pole it would mean installing new panels or fewer panels of larger capacity. Any thoughts?

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#24121 - 04/04/03 09:23 PM Re: Lim's  
Roger  Offline
Joined: May 2002
Posts: 1,716
How old is this installation? All modern Isolation installations use brown, orange, and yellow. This would mean that all the circuits would have to be rewired .

What is the primary voltage to the transformers? This could mean alot of work if new feeders have to be routed to your new panels. In any case, in the very least you would have to pull a second ungrounded conductor or a neutral, (what ever the case may be) even if the existing conduit could be used.

If these are going to serve patient care areas, you will have to retest the grounding system in these rooms.

These are just some of the things I see might be problems.

In reality, if these Iso systems are not needed or required by any local or state amendment, I can see doing away with them. For these to be in service you have to do the yearly testing and problem solving periodically or as you said repairing.


[This message has been edited by Roger (edited 04-04-2003).]

#24122 - 04/05/03 03:48 AM Re: Lim's  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,217
SI,New Zealand
(What a cool name!)We all look forward to these!!
Welcome to ECN, mate.
BTW, what is a LIM?

Let's face it, these days if you're not young, you're old - Red Green grin

#24123 - 04/05/03 04:46 AM Re: Lim's  
Roger  Offline
Joined: May 2002
Posts: 1,716
Trumpy, LIM stands for "line isolation monitor". these are used to monitor the leakage and overall impedance of each line (usualy 5ma alarm level) of our health care isolation systems.


#24124 - 04/05/03 04:50 PM Re: Lim's  
Weekend  Offline
Junior Member
Joined: Mar 2003
Posts: 3
Lim's are 5-20 years old. Newest might be color coded. Yeah, brown,orange and yellow don't work on 120v..
Primary voltage on most if not all is 120 volts. Management(!) is under the impression that we can simply remove the monitors and ground the secondary. Then again that's why they are management they would be dangerous with tools. I see removing the isolation panel, transformer and monitor (all in an enclosure) at each location and rewiring that location if the raceway can handle it. If not we run new conduit. Since they are not required the NFPA and my local inspector had no problem with me removing the monitors. But it seems that anything less than rewiring would be subject to violation of UL. Not a good thing. Isolation transformers are built and installed for a specific purpose and I'm thinking any deviation is wrong if not illegal somewherer down the road. Yup, it's my license and butt I'm looking out for besides proper electrical work.
All input welcome.

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