inspection of existing fusible switchboard

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malachi constant

Senior Member
Location
Minneapolis
Consulting engineer here. We have school district that we do a lot of design work for. They have requested that we include in our documents (for their larger projects) inspection of existing switchboards that are reused. What is reasonable to ask for? I was thinking infrared scan under load (preferably when AC is running), and mechanical testing / visual inspection / lubrication of all moving parts. (Moving parts = disconnect switches.) Any thoughts?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I think anything beyond a visual inspection and verification of mechanical operation is going to get more into refurbishment than inspection.

there might be some national standards that could help you out, but from what I have seen of them they are so generic they are all but useless for anything practical.
 

zog

Senior Member
Location
Charlotte, NC
Consulting engineer here. We have school district that we do a lot of design work for. They have requested that we include in our documents (for their larger projects) inspection of existing switchboards that are reused. What is reasonable to ask for? I was thinking infrared scan under load (preferably when AC is running), and mechanical testing / visual inspection / lubrication of all moving parts. (Moving parts = disconnect switches.) Any thoughts?

Testing of all OCPD's for sure, insulation resitance, etc... all depends on what type of equipment you are refering to. And be careful with the lubrication, you can easily do more harm than good if you use spray lubricants or mix greases that are non compatible.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Testing of all OCPD's for sure, insulation resitance, etc... all depends on what type of equipment you are refering to. And be careful with the lubrication, you can easily do more harm than good if you use spray lubricants or mix greases that are non compatible.

the OP said that it was a fusible switchboard. How would one go about testing the fuses?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Consulting engineer here. We have school district that we do a lot of design work for. They have requested that we include in our documents (for their larger projects) inspection of existing switchboards that are reused. What is reasonable to ask for? I was thinking infrared scan under load (preferably when AC is running), and mechanical testing / visual inspection / lubrication of all moving parts. (Moving parts = disconnect switches.) Any thoughts?

If you have 'bolted pressure switches' (e.g. fusible switches over 800A) and large electronic trip breakers, you should just plan on an actual service/refurbishment requirement rather than a simple inspection/lubrication. If these switches have not been maintained every 3-5 years, their odds of 'getting stuck' are better than 50-50.

I am currently working on a municipal project with 17 facilities, the inspection found that 13 of them need to be replaced primarily due to lack of regular service and secondarily due to age.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
If you have 'bolted pressure switches' (e.g. fusible switches over 800A) and large electronic trip breakers, you should just plan on an actual service/refurbishment requirement rather than a simple inspection/lubrication. If these switches have not been maintained every 3-5 years, their odds of 'getting stuck' are better than 50-50.

by "getting stuck" what do you mean? will the switches not open at all?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
by "getting stuck" what do you mean? will the switches not open at all?
Yes, a common failure mode is that one or more 'blades' do not open fully. It is also not uncommon to have blades fail to close completely.

I often hear people say 'we don't even try to operate that switch any more, because the last time we tried it took us hours to get it opened'.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
is this common with all brands?

what causes it? just poor design?

In my experience over the years, yes, pretty common. Any time someone wants me to operate an old bolted pressure switch that has not been maintained I give all the warnings of what this can lead to. I even had one shear off the handle shaft while cocking it.
 
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jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
is this common with all brands?

what causes it? just poor design?

Common to all brands.

Too many moving parts under high pressure. effectively the grease gets squeezed out causing binding. Problem is usually rare in switches which are operated yearly.
 

malachi constant

Senior Member
Location
Minneapolis
Missed that in the title, still test them with DLRO and compare to manufactures values

Great stuff here, thanks everyone. Here's what I'm hearing (for my application):
* Bolted pressure switches, if not regularly maintained, have a 50-50 chance of getting stuck.
* Hence, an argument for not testing unmaintained switches: If there was ever an overcurrent event the fuses would go, and the BPS-being-stuck issue would become known at that time. Why force the replacement of half the switches when there is something like a 95% likelihood none of the district's BPS's will ever need opened? Being proactive (so the argument goes) is unnecessary and costly, so be passive and provide clear warning labels that state switches have not been maintained and may not open.
* I presume the argument FOR testing them would be if you have bad switches, you should be proactive and find them before someone gets hurt. Tell the Owner if he proceeds this way to budget replacing half his switches.
* If you do test: Call out for visual inspection and confirmation of mechanical operation. Test (contacts?) using DLRO and compare to manufacturer's values. Don't lube anything as mixing/misapplying the wrong lubricants could cause more harm than good.
* I assume that testing for standard fusible switches (non-BPS) should be same as for BPS.

As far as recommended maintenance - assuming the BPS's are fairly new (or are old and pass their initial tests) the Owner should plan on exercising them on a biannual basis? What about fused disconnects - every five years? Is visual/mechanical operation acceptable for biannual testing or is DLRO recommended as well?

Keep in mind this is NOT manufacturing, health care, etc. This is an "install-it-and-forget-it" K-12 switchboard that sits relatively undisturbed for 50 years before it is replaced. It is not worked on live and is minimally touched. So adjust your recommendations accordingly.

Thanks!!
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Hence, an argument for not testing unmaintained switches: If there was ever an overcurrent event the fuses would go, and the BPS-being-stuck issue would become known at that time. Why force the replacement of half the switches when there is something like a 95% likelihood none of the district's BPS's will ever need opened? Being proactive (so the argument goes) is unnecessary and costly, so be passive and provide clear warning labels that state switches have not been maintained and may not open.

Protective Devices must be maintained. NFPA70E, and OSHA, require protective devices to be maintained in working condition.
I am sure the school district maintains its fire protection system doesn't it?

Relying on the fuses to do their job is bad engineering.
Say that for some reason 1 fuse decides to blow, the system is now single phasing, but the power cannot be turned off because the switch doesn't work. How will any 3-phase equipment respond to this?

Say that you are making modifications to the school (e.g. adding CIC panels), don't you need to turn off the main power? What is the contractor going to do if the switch doesn't work (can you say Change Order)?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
There are contractors who do this kind of PM for a living. Not exactly the kind of thing I would have your average EC doing.

I think Zog is part of some organization that certifies ECs to do this kind of work. maybe just put in the spec that the work has to be done by someone certified by whatever organization that is to whatever national standards apply.
 

malachi constant

Senior Member
Location
Minneapolis
Good point Jim. I'm a little sheepish I didn't think of that first.

Zog - regarding Peterson's "average EC" comment - do you have a recommended certification I can require?

Anyone have thoughts on testing non-BPS fusible disconnects? Same recommendations as mentioned above? (I should add "infrared testing under load" to the list.)

Thanks all!
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Protective Devices must be maintained. NFPA70E, and OSHA, require protective devices to be maintained in working condition.
I am sure the school district maintains its fire protection system doesn't it?

Relying on the fuses to do their job is bad engineering.
Say that for some reason 1 fuse decides to blow, the system is now single phasing, but the power cannot be turned off because the switch doesn't work. How will any 3-phase equipment respond to this?

Say that you are making modifications to the school (e.g. adding CIC panels), don't you need to turn off the main power? What is the contractor going to do if the switch doesn't work (can you say Change Order)?

I would add another reason. Suppose that switch has GFP and a ground fault occurs. One would want the switch to function correctly.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Good point Jim. I'm a little sheepish I didn't think of that first.

Zog - regarding Peterson's "average EC" comment - do you have a recommended certification I can require?

Anyone have thoughts on testing non-BPS fusible disconnects? Same recommendations as mentioned above? (I should add "infrared testing under load" to the list.)

Thanks all!

do these switchboards have incident energy posted? can't open up the door unless you know what the incident energy is. can't do the IR w/o opening the door.
 

zog

Senior Member
Location
Charlotte, NC
Good point Jim. I'm a little sheepish I didn't think of that first.

Zog - regarding Peterson's "average EC" comment - do you have a recommended certification I can require?

Anyone have thoughts on testing non-BPS fusible disconnects? Same recommendations as mentioned above? (I should add "infrared testing under load" to the list.)

Thanks all!

A BPS needs to be tested and maintained, work to be left to people that specialize in this sort of thing. Only a massive failure would require replacement, these are simple to repair if there are problems but make sure you find the right people for that type of work.

NETA is an orgization that certifies companies (And more importantly develops testing standards for ANSI) and thier techs for this type of work, that dosent always mean they are good at everything, nor does it mean a testing company that is not NETA is not qualified to do this type of work. There are specific requirements that stop some very good companies from becoming NETA certified. I used to be NETA level 4 certified (Highest there is) but now I work for a non NETA company that has 10 times the abilities of my last company, I still know the same stuff I did before.... you get my point.

On the other hand NETA companies do mostly testing, and while they may offer reapir services of equipment like this it is not what they do best.

Here is a good company in the twin cities that happens to be NEAT certified, I know the owner (Bruce), good guy/company.

DYMAX
4751 Mustang Circle
St. Paul, MN 55112
Phone: (763) 717-3150
 
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