Do breakers get weak over time? - Page 1
Forum section: electronics / general

author: XOIIO
author_rank: Super Contributor
timestamp: April 04, 2016, 02:43:27 am
content: So, I hooked up my new server to update the bios and check some settings, thankfully it didn't go down until after I was done that, but suddenly the entire server rack lost power, and this happened once before but without the new server in.The breaker on the power bar tripped, and this is a 15 amp breaker. After it cooled down and I was able to reset it, I measured the current draw, and the rack with new server was only drawing a max of 7 amps, it's usually around 5.It seems to me that the breaker has gotten pretty weak, I'm just wondering if that is in fact a thing, or if I should look for some other cause, though I can't think of anything.This is a second hand power bar, so it may have been tripped many times before, maybe causing the mechanism to become more sensitive?It's a larger version of the one in the pictures below. Looking for a replacement breaker now, hopefully, though doubtfully, the local electronics shop will have something compatible. edit: They do! I'm going to pick up two of them to replace both of the old ones if this is the case.I also have to manage to get the darn thing out lol. edit2: oh man these things, unlike most panel mount ratchet things, are an absolute pleasure to remove.

author: Thilo78
author_rank: Regular Contributor
timestamp: April 04, 2016, 05:19:39 am
content: Yes, Miniature Circuit-Breakers (MCBs) do age.I'm not sure about the processes behind that, but I found that after some time they start to produce erroneous trips, leaving you in the dark.After some more time they don't even latch anymore. (Which is a good thing rather than not tripping instead)Looking at the MCB in your pics, I'd expect it to be gone.I've found, that for domestic and industrial installation with 24/7 operation and a considerate number of trips MCBs last for 25 to 30 years. Less if they are used as a mains Switch.Then they have to be replaced.Luckily, the units after ~1980 have very similar form factors. So they just swap out quite easily.Thus I think you should exchange it with a new one.When selecting the MCB you have to consider the inrush current. If you have SMPS it will be quite high and requires a C-type MCB with the proper rating.(Learnings from the recent server racks I installed. B-type tripped every time. So we went for C16 instead)

author: XOIIO
author_rank: Super Contributor
timestamp: April 04, 2016, 05:35:35 am
content: Alright, the one I pulled apart has 8723 stamped on it, it might be a date code but I don't know.If it is it's ridiculously old and still in great shape so I kind of doubt it. The replacement they have locally is an exact match, so not sure on the inrush current rating, but I can fire the servers up one by one as I start them up.

author: Richard Head
author_rank: Frequent Contributor
timestamp: April 04, 2016, 06:43:46 am
content: Also check for poor connections on the breaker and associated wiring. At high currents the heat generated at a poor connection causes the breaker to trip at a much lower current. This assumes the breaker is a thermal-magnetic type. Hydraulic magnetic breakers don't have this thermal issue.

author: XOIIO
author_rank: Super Contributor
timestamp: April 04, 2016, 06:45:22 am
content: Quote from: Richard Head on April 04, 2016, 06:43:46 amYeah, it needed a minute or two before I could reset it, so it must be a thermal type.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 04, 2016, 07:46:01 am
content: Quote from: Thilo78 on April 04, 2016, 05:19:39 amSo do big ones---they just take longer!

author: Kjelt
author_rank: Super Contributor
timestamp: April 04, 2016, 07:53:01 am
content: Adding to what is said, my experience is that if a breaker has had a few tripping incidents the contacts also wear out due to the arcing.So after some time you might have a higher ohmage over the contacts which also adds to heat and also had a breaker that was making arcing noise.After about 10-15 events I preventively replace them in critical applications (24/7 home applications).

author: tautech
author_rank: Super Contributor
timestamp: April 04, 2016, 08:13:10 am
content: Quote from: vk6zgo on April 04, 2016, 07:46:01 amAll the sparkies here call them MCB's;MainsCircuit BreakersQuote from: Kjelt on April 04, 2016, 07:53:01 am+1Not uncommon for MCB's performance to degrade after numerous trip events, a sparkie mate regularly replaces MCB's that have past the "best before" life .....even quite new ones.

author: Thilo78
author_rank: Regular Contributor
timestamp: April 04, 2016, 10:48:42 am
content: Quote from: vk6zgo on April 04, 2016, 07:46:01 amThat's why the big ones -air circuit-breakers and moulded-case circuit-breakers alike- come with a rather elaborate maintenance instruction.MCCBs (160 up to approx. 1000 A) are usually replaced after a certain number of operations; ACBs (1000 up to 7000 A) have to be cleaned, regreased and their contact pieces (which might have burnt away after 5000-10000 operations) replaced.

author: XOIIO
author_rank: Super Contributor
timestamp: April 04, 2016, 11:13:30 am
content: Tested it again, turns out all the servers draw 8 amps powered up, though it was for a shorter time I think, not sure. Going to replace it anyways to eliminate it. (If I can manage to get the bigger bar open).

author: XOIIO
author_rank: Super Contributor
timestamp: April 05, 2016, 03:09:17 am
content: Alright so just replaced the one in the server rack, I couldn't pry the case open easily like the old one so I basically had to rip the breaker apart with some pliers, then bend the end of the case to get to the wires. It's in a bit worse shape than it started but seems good so far. The old breaker smelt burnt as I was ripping it's insides out like a small animal in the plains of africa.I'll have to try it out with the other server running for a decent amount of time but I'm thinking it should be problem solved. The new breakers have 1514 stamped on them in the same place, so I'm wondering if maybe it is a date code. I think the bars themselves are from 99-ish if the sticker had a proper date code on it.

author: calexanian
author_rank: Super Contributor
timestamp: April 05, 2016, 03:48:41 am
content: The miniature types typically just work on expansion of typically nichrome type elements and they can change in dynamics over the years. I would switch it out for a new one. They are still fairly common.