DLRO question

[electricalperson]

can anyone tell me when and why we would need to use a DLRO?

 

[mdshunk]

can anyone tell me when and why we would need to use a DLRO?

I don't know when or why you'd need one, but I'll tell you when I use mine.

It is handy to evaluate the condition of existing equipment with mechanical electrical connections, and to evaluate the condition of salvaged equipment that is being relocated.

The low resistance ohm meter is basically a super-sensitive ohm meter, that will check to see if you have a "perfect" path for electrons, in layman's terms. It checks that all the connections are proper and tight.

I use mine to check from side to side on busway connections, where sections of busway have been relocated. I use mine to check from line to load on sidearm disconnects. I use mine to evaluate the condition of large contactor and motor starter contacts, by using the DLRO from line to load (coil pulled in, obviously). These checks are done on de-energized equipment.

At Brian John's suggestion, I even bought a very long calibrated set of leads to check receptacles in a home, to find the intermittent "open". Put one lead in the receptacle where the home run hits, then use the other lead to probe each receptacle in the chain until you find the one with the high resistance.

After everyone gets on board and buys meggers and starts to use them, then I'll start preaching DLRO's.

 

[electricalperson]

thank you. too bad they are so expensive

 

[mdshunk]

thank you. too bad they are so expensive

Check eBay. I'm not sure if you're an employee or a contractor, but the tip about using it to find an intermittant open in backstabbed receptacles is a real time saver. It turns a several hour job into a 5 minute job, literally. I'm sure it has even more uses I havn't even thought about yet. You ought to be able to pick one up second hand for a few K.

edit... I just checked eBay. There's a few on there right now for just a few hundred bucks.

 

[dereckbc]

I have one and they are used for two primary things in my experience.

I use them to check battery terminal and battery inter-cell connections. We require 15 micro-ohms or less in the Telco industry.

The other application I have used them or at least seen them used is to check contactor resistance in very large POCO switches used in sub-station yards.

There is not really a whole lot of need for them in electrical contracting unless you specialize in industial or Telecom sectors.

 

[mdshunk]

There is not really a whole lot of need for them in electrical contracting unless you specialize in industial or Telecom sectors.

True. You really don't need gadgets, but after you get used to using them and get spoiled, you can't figure out how to live without them.