Ronk MTS

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chris kennedy

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
Retired electrician
I put power to a Ronk manual transfer switch (400A 3? 240V) this morning and found the contact arraignment rather unusual. They merely are pressed onto the bus with spring tension. Anyone ever install one of these? This was customer supplied.

Contact open;

Ronkopencontact.jpg


Contact closed;

Ronkclosedcontact.jpg
 
Not the big heavy plated contacts I am used to seeing in onan's auto transfer switches. Would like to see a thermal image of that with full load.

Does not look like much contact area for a 400a switch
 
massfd said:
Does not look like much contact area for a 400a switch
Click to expand...

Yeah, my thought also. Look at the top picture, you can see the marks on the bus where we closed this a couple times, and it doesn't look like the whole thing is making contact.
 
Chris,

From what I can make out in the photos, it looks like the spring is fully compressed in the closed position so that the insulated arm is actually supplying the pressure..the sure way to test would be to try to lift the contacts up while in the closed position..if they lift even a little bit then you are correct that it is only spring tension holding them down.

BTW the springs are there to help provide a fast make/break of the contacts.

As for the contact area issue, yes that is a problem as it is only making point contact at each end..that will heat up a lot under a heavy load. I guess it would be possible to dress the contacts down so they are flat and make full contact but that would most likely void the warranty.

How big are the contacts? They look to be only about 1/4 inch wide,,way too small for 400 amps IMHO.

What size service is this on? The incoming conductor looks awfully small too.
 
I have been around those things quite a bit.....they are really common around farms. Usually involved in a "center pole" distribution setup, with a pto or engine driven generator. They seem to be ok...I have yet to have to replace one, but they rarley if ever get opened or closed while under load. They are about the cheapest (cost wise) manual transfer switch that I know of.......You should be fine..;)
 
I don't see a problem with them. The ones I installed were were TPDT, UL Listed and Service Entrance rated. If you use them as the instructions say and don't switch them under load they should work just fine.
 
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