Westinghouse DA-50 trip unit - old 1

[wbd]

Hello,
I am working in a facility that has some older vintage electrical equipment and I am trying to figure out a trip unit on a Westinghouse DA-50 1600A breaker. Does any one have any information on these? What are or how to find the settings? It has not been maintained and I need to build a case for replacement but want to understand what I have first.
Thank you

 

[DTR2011]

Those are old Dash Pot trip units. This LTPU settings are listed on the bottom of the device (you can see the 1600A setting. You need to verify that there is still dash pot oil in there, and it's the correct viscosity. This is what provides the delay for the LTPU. I would consider retrofitting the trip unit to something modern. There are many NETA companies that can perform the retrofit.

 

[DRWeig]

I don't know if it's what you're looking for, but see attached.

If you're looking to convert to a modern trip unit, put this phrase in Google exactly as I've typed it:

westinghouse "da-50" "trip unit"

You'll get lots of hits for folks selling retrofit trip units.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[dpc]

Contact Easton-Cutler Hammer. They can provide information on these old trip units. They were unreliable when new and are worse now. They need to be replaced.

 

[wbd]

Thank you all for the replies. I understand on the long time pick up but where is the Instantaneous setting or is it fixed based on breaker size?

 

[unclebob]

Hmmm, me wants to look at a 8000A frame DA breaker!

 

[Zogzog]

DA-50 was built with series trip units as DTR2011 described, the INST trip is part of that series trip unit, it has a coil which magnetically pulls a contact in when the field strength overcomes the spring resistance. That part is usually reliable, it is the oil dashpots that usually give problems.

Lots of options for upgrades, I have about 150 DA-50's in stock with many different upgraded trip units from older amptectors to modern AC PRO's. There are also 3 upgrade kits we install on these to ammend performance issues over the years.

A refirbished and retrofitted replacement is your least painfull option, there are modern retrofills available for these but retrofills lead to more possible failures from the cradles they install as well as very rare and unique parts of repairs are needed in the future.

 

[waross]

Printed in U.S.A. (Rep 11-52)
Does this mean that the 11th reprinting of the manual was in 1952?
Agree with dpc on the dashpots. You may consider cleaning and re-oiling the dashpots immediately. The oil viscosity is part of the calibration. I would use transformer oil if you are setting for fairly quick action and W30 (single viscosity, not 10W-30) motor oil if you are setting for a long delay.
Instant trip settings are 100%, 125% 150%, 175% and 200%.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Nice link, Dave.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

By the way, the old Dash Pot oil is now considered a hazardous substance under the new rules of RoHS. You might be able to use that as part of your upgrade justification. Of course you heard here that you can replace it with modern less hazardous transformer oil, but the purse string powers don't necessarily need to hear the entire story. Sometimes just the mention of "hazmat" will put enough scare in them to open the checkbook....

"Will work for (the memory of) salami"

 

[DRWeig]

Good thoughts jraef -- and I'll toss in the word "liability." That's worked for me in the past.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[wbd]

Waross - where are the markings for the instantaneous to tell what it is set at? I am sure a replacement is in the near future but for now I just want to know what is there.

 

[Zogzog]

If I recall they are not marked or adjustable, they are factory set at 15x the breaker rating +/- 10%.

 

[DTR2011]

If you can get a bus outage (fixed breaker) and need the information, you can have the breaker tested via primary injection to determine the Inst PU.

 

[rhatcher]

I haven't seen that type of breaker in a long time and, even at that time, they were considered very obsolete. For waross, "rep. 11-52" means that the manual was reprinted during November 1952. I believe this type of breaker was superceded by the DB-50 sometime during the 1960's.

The picture says a lot. The oily substance seen on the left and center dashpots is the dashpot oil used for inverse time delay. Under overcurrent conditions, these trips will operate with little or no time delay. That is assuming that they operate at all. In many cases, after years of inactivity the series trip mechanism will become frozen by lack of lubrication and/or rust.

The same can be true for the breaker mechanism itself. In many cases, the mechanism on an old breaker like this will be frozen shut from rust, corrosion, and lack of lubrication. Try pushing the "open" button on one and see what happens. If you are lucky and the breaker does open, it may not latch closed again.

I would not recommend trying to rebuild the dashpots. Their operation is based on the use of springs to determine pickup and dashpot oil to provide the delay. Potential problems include weak springs, improper oil viscosity, and worn or damaged dashpot seals. If you were to attempt a rebuild, it would be necessary to setup the breaker on a high current test set to perform the calibration and testing.

I agree with zogzog's suggestion that replacing the breakers with rebuilt units featuring updated trip units is an option but, as he pointed out, maintaining the units in reliable condition will be problematic.

Another concern is interrupting ability. If the line side transformer (or incoming utility service) has been replaced since the 1950's, then it would be necessary to be certain that the available short circuit current does not exceed the breaker rating of (if memory serves me correctly) 50,000 amps. Keep in mind that this rating is for a "new" breaker. Weakening of the opening springs over time can reduce the short circuit interrupting capacity. Of course, if the incoming transformer has not been replaced since the 1950's then that is another big problem of its' own.

This brings to mind another question, is the rest of your distribution system just as old??

Finally, although most electrical types do not care about this; the phase barriers between the dashpots as well as the arc chutes are made of asbestos. Usually the environmental types go nuts when they find out about this.

 

[waross]

I later realized that rep. 11-52 probably meant "reprinted Nov. 52". Thanks for confirming.
Re the environmental types; They probably would not appreciate a label;
"Caution do not inhale this circuit breaker!"
It is a good flag to get the environmental department to push for replacement.

Bill
--------------------
"Why not the best?"
Jimmy Carter