Digitrip RMs 310

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wyreman

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
Two year old 800Amp 480/277v main has opened randomly now twice.
Facility is very lightly loaded at the time [weekend night].
Normally has much more HVAC and pools loads when occupied.

Opening main sends fire alarm notifier to director of operations and cops.

Director sees no reason main should be off and resets. Just fine.
Next day same thing, but he calls me before reseting.

I went with him that night in my PPE and we opened it up and looked for arcing/discolor, measured temperature and voltage. Couldn't clamp amps on the buswork but I only clamped less than 50 amp of load mostly pool pumps.

Engineer's dials show
ST: pickup is at max which is 8
ST: time is min = INST
GF: pickup min 1
GF: time min INST

We have had problems with these new breakers giving nuisance tripping.
We have another 1200AMP 12Kv cabinet that really likes the loads to come back in a certain order.

I would love to be there quickly after cb opens to see if the thermal delay calls it an overload or a faulty load that just pulls the main before the subbreaker.

Question is why only intermittently? Faulty motor comes only sporadically?
There is a tester [and a qualified test person] who can plug in and read the digitrips report.

In the short term, and I don't want to take the fire responsibility for this, isn't the theory that you can "crank up" the dial on the main and this way the fault [if there is on] will show on the sub breakers?


Any insides?

Digitrip RMS 310
 
1. Have you tested the CB?
2. Have you looked at all panels down stream for tripped CB's, in particular parking lot lighting.
3. Have you asked for a coordination study (I know there isn't one), Good item to push for.
4. Can you install a monitor phase, neutral and ground current.
5. "Cranking up" is often completed, is it recommended, NO, if something should go wrong you are liable.
6. Have you measured current on the neutral ground bond?

It is possible the device is defective, but I'd bet on the low setting.
 
1. CB testing will likely be done if nuisance continues. We just exercised it, obviously, and so far it has held.
2. Downstream panels show no opens so far that I saw. All prkng lots were well lit.
3. Co-ordination? this is a new $20M building. There might be one.
4. Donuts can be ordered if nuisance continues. I did it before just for usage data.
5. Liable, no thanks! It doesn't nuisance me! Is the theory correct tho?
6> Great idea!! thank you:)
 
wyreman said:
3. Co-ordination? this is a new $20M building. There might be one.
Click to expand...

The only way to determine that is to review the construction specs and plans. Manufacturers typically ship devices set at the lowest (AKA - most sensitive) settings for product liability issues.
 
ST: pickup is at max which is 8

ST: pickup is at max which is 8

funny thing, there are four dials:

Engineer's dials show
ST: pickup is at max which is 8
ST: time is min = INST
GF: pickup min 1
GF: time min INST

I wonder why all the ST pickups in that room are set on what appears to be the max. Is that the default?
 
wyreman said:
Two year old 800Amp 480/277v main has opened randomly now twice.
Facility is very lightly loaded at the time [weekend night].
Normally has much more HVAC and pools loads when occupied.
Click to expand...

How much more?

wyreman said:
I would love to be there quickly after cb opens to see if the thermal delay calls it an overload or a faulty load that just pulls the main before the subbreaker.

Question is why only intermittently? Faulty motor comes only sporadically?
Click to expand...

Digitrips require >20% loading for the CT's to power the trip unit, so likely your internal battery is dead and you will not have an indication of the type of trip that is occuring.
wyreman said:
There is a tester [and a qualified test person] who can plug in and read the digitrips report.
Click to expand...
Knowing what type of trip you are getting would be good to know.

wyreman said:
Any insides?
Click to expand...

At <20% loading digitrips are very sporadic, if you have a 3 wire system a phase imbalance can cause false GF trips. We see this often. Is this 3 or 4 wire?
 
real quick i have to run
it tripped again last night.

i had taken the photo voltaics out of the equation and it held for a day.
closed in the cb and knife switch and it tripped within two hours
but that was at 5pm and it opened at 7:11pm

reset last night and left the pvs out of it and so far it has held [12 hours and back in use]
only one 20a cb was open in all the panels and that was just for convenience outlets.

I read that the green light should blink either at one seconds or stay green - only two choices- depending if you were +/- >20% of what "I" is

by the way, what is 'I" set at... sounds like I for amps but is it the 800 or some other calculated number

so the green light has various blinks as far as we can judge.
brought loads on and off and got some differnet signal : no light; around one second flash; 1-1-1-3 kind of flash, dimmer lights; etc. is this normal? didn;t read that in the book.

3-4 wire? 12kv / 480/277 xfmr is 40 feet away, commericial use ... i would assume 4 wire

phase imbalance: we have emon dmons everywhere but they are only showing me a four hourdata in the history. I am trying to get the updates down to the second for the next week or so till this is resolved...

how often is the battery to be changed?

thanks
 
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wyreman said:
I read that the green light should blink either at one seconds or stay green - only two choices- depending if you were +/- >20% of what "I" is

by the way, what is 'I" set at... sounds like I for amps but is it the 800 or some other calculated number
Click to expand...

It is the rating plug size. What size rating plug does it have?

wyreman said:
so the green light has various blinks as far as we can judge.
brought loads on and off and got some differnet signal : no light; around one second flash; 1-1-1-3 kind of flash, dimmer lights; etc. is this normal? didn;t read that in the book.
Click to expand...
Should blink every second, this is a self test of the circuit that only occurs when load is >20%.

wyreman said:
3-4 wire? 12kv / 480/277 xfmr is 40 feet away, commericial use ... i would assume 4 wire
Click to expand...
If it is 4 wire you should have a nuetral CT, so unbalanced loads would not affect it. Could be lots of issues, was a GF test performed as part of the commisioning process? Do you have that report?

Don't assume the 4 wire, this is the key here.

wyreman said:
phase imbalance: we have emon dmons everywhere but they are only showing me a four hourdata in the history. I am trying to get the updates down to the second for the next week or so till this is resolved...
Click to expand...

I suggest you hire a testing company.

wyreman said:
how often is the battery to be changed?

thanks
Click to expand...
With loads<20%? Maybe a week.
 
there is no battery in the digitrip rms 310

there is no battery in the digitrip rms 310

zog said:
Digitrips require >20% loading for the CT's to power the trip unit, so likely your internal battery is dead and you will not have an indication of the type of trip that is occuring.
Knowing what type of trip you are getting would be good to know.



At <20% loading digitrips are very sporadic, if you have a 3 wire system a phase imbalance can cause false GF trips. We see this often. Is this 3 or 4 wire?

Originally Posted by wyreman
how often is the battery to be changed?

thanks
With loads<20%? Maybe a week.
Click to expand...

There is no battery in the digitrip rms 310 according to the manual.
 
meggr

meggr

Found the study and it pointed to a certain subfeed cb which was supposed to have been replaced. Half that un is old wire to baseball prkng lt. Got. Our old megger on it from 1932 or so and ... git a newer small battery one on it with really short numbers. Hard to believe, or calibrate.
I heard the fluke 1653 is great tool $1500!
Any tool suggestiojs?
 
vacuum tube tv repairman

vacuum tube tv repairman

well my boss is a real old school fixer and he is trying to cobb together some resistors to give the refrence megaohm value. He was a vacuum tube tv repairman in his yout:) . He is actually pretty amazing in mine estimation...

My values were all pretty short
2011-02-14_15-18-59_356.jpg

here the green scale is ohms with zero [short] on the left and 100 ohm [resist] to the right.
l

on the other hand, the 500v and 1000v scales are reversed with
a lot of resistance = meter to the left
lots of flow = meter to the right

All measured the same phase to ground and I did not do phase to phase.
I couldn't believe the meter because everything works and the meter is saying pretty much dead short. We only had nuisance tripping every couple weeks. The whole thing is shut down now,has been shut down for the last week or so.

Eaton is supposed to come out and finish the co-ordination and give the recommended breaker and values, but I have to get a reliable megger on this and maybe it is time to buy one... i would prefer a calibrate-able, newer mode


anyway the panel in question has some new wire to a manhole and then some old wire from the manhole to the ... puddle it is in

XHHW-2 is a much better insulation than THHW for wet locations. I have seen several failures of THHW in underground conduits, which around here, are water filled. Plus XHHW-2 is 90 C rated for wet locations and THHN in a wet location is not.
Click to expand...
2011-02-14_14-15-49_88.jpg
 
There is a high probability that main beaker cannot be coordinated with those branch breakers, particularly in the GF region.
 
the baseball guys are going to really want their scoreboard back when the rain clears here after president's day and all...:confused:

any good suggestions for new megger purchase?
ebay?
 
wyreman said:
the baseball guys are going to really want their scoreboard back when the rain clears here after president's day and all...:confused:

any good suggestions for new megger purchase?
ebay?
Click to expand...

This question gets asked here all the time, it all depends on what you use. I prefer the Megger MIT 510's, getting a 1020 this weekend. It does not sound like you do much testing so a entry level model would be just fine.
 
I have never seen the ST set for max which in this case is 6400 amps, but the fact the GF pickup is still set at the factory 1 (800) amps leads me to believe any ground fault in a down stream panel will trip this main, as Brian pointed out in post 2, I don't think a proper coordination study was done.
 
coordination done but doesn't include the gf

coordination done but doesn't include the gf

So the results of the coordinations study are just that the main at the remote panel should be smaller 100 instead of 200A.
Since there is no GF protection on any of the remote panels, in this case, it is not relevant.

The intermittent gf is coming from a wire run with three vaults. One of the vaults has plenty of splicing in it and is full of water. When we pump it out and hang the splices out to dry, the megger goes from 0.1 to 10Mohms, at 1000v meg.
So I get to cut out all the splices, megger the wires coming and going, and then redo the splices "better"

It is already done with kearnys & weather tape.
It's nominal 208v.
I'd really prefer some pre-insulated connectors or connectors with snap on boot.
Any recommended methods/products for direct burial 500mcm available now locally...
thanks

http://www.greaves-usa.com/pdf/USA & UPP Color Sheet.pdf
http://www.aplussupply.com/nsipolaris/gelsplice.htm
 
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