Fuses, Breakers, Amps, Max Load... Crossy!

[Mudcrab]

good points muddy.

65m does seem a little to worry about. So just UV relays? the unit is measuring +-10%. These are extra factors that can be looked into, but logically the control fuse is blowing, and within each control ciruit is just the monitoring equipment, UV relays, and the coil to the contactor. So why is just 1 phase blowing, and indeed the same fuse, whereas the other 2 are not affected?

If the UPS is 65m away aswell then that would be worrying. The whole thing needs to be looked at, and after 4 bottles of chardonay

Dunno...would need to physically check the installation. Something is amiss as the fuse should be able to handle such a light load. Maybe there is a wiring cock-up and is introducing an intermittent fault somewhere...random thoughts......maybe whatever is switching is causing a phase to neutral/earth fault and blowing the fuse (only on the one phase)under certain conditions. I'd look at the relays that the UV's control and check for correct connections. (I've assumed the relays in the pic are controlled by the UV's). Edited April 13, 2013 by Mudcrab

[Forkinhades]

^ thats along my line of thinking, good job

and I am thinking crossed connection on an output, or faulty relay, or faulty monitoring

Edited April 13, 2013 by Forkinhades

[Mudcrab]

If you would open it up to the "general sparky populace" it would surely be more entertaining, and possibly even more informative. Even very skilled professionals can sometimes gain something from an apprentices enquiring mind.

When we stop learning...its time to give the game away.

Changes happen so fast in the electrical/instrument/control field. What I do today has little resemblance to what I trained on. I don't want to sound bad but where I work the last really major change in the mechanical field was moving from reciprocating stem engines to steam turbines. That was in the 60's (yeah I know...but the sugar industry is subject to many market forces and can be really tight with money when times are bad. They aren't at the moment and we a investing heavily). Ok grudgingly acknowledge the advances to mechanical seals.

Conversely the electrical/instrument/control field has gone from relay logic to full on digital devices that can give and receive a tremendous amount of information. The "smart" overloads these days are a sight to behold. Sitting on my bum in my office I can see why a motor has tripped (loss of phase, phase imbalance, earth fault etc etc etc)know the time taken for auto reset and make a decision to reset it remotely if it makes sense. I can make changes to the control scheme, tuning and modify logic if necessary also. All this allows me to keep my electricians out of harms way...opening a motor starter cubicle to reset an overload (yes we had a bloke plated a few years ago doing that). The days of using a jumper to bypass a fault are rapidly becoming a thing of the past. Current signature analysis, thermal imaging...the list goes on. I love my job.

[Naam]

good points muddy.

65m does seem a little to worry about. So just UV relays? the unit is measuring +-10%. These are extra factors that can be looked into, but logically the control fuse is blowing, and within each control ciruit is just the monitoring equipment, UV relays, and the coil to the contactor. So why is just 1 phase blowing, and indeed the same fuse, whereas the other 2 are not affected?

If the UPS is 65m away aswell then that would be worrying. The whole thing needs to be looked at, and after 4 bottles of chardonay

you had already some Chardonnay Forky? i will type now very slowly for the benefit of all not so fast readers and concentrate on facts, not assumptions.

-within a period of 5½ years a (one) fuse was blowing

-this fuse was wrongly labelled by a technical apprentice

-the apprentice does not recall whether the equivalent MCB tripped

-wife of apprentice claims "this little grey switch was off too" (pointing to MCB)

-wife's claim seems to be valid because this was the only time when all aircons were running full blast for an extended period of 14 hours.

reason: preparing house for announced power cut lasting 12 hours the next day.

-supporting evidence for afore-mentioned assumption is that one phase was clearly overloaded by a three-ton aircon unit i use in my pool area and which never ran before with 6 other units supplied by the same phase.

corrections:

-the UPS is not 65m away from the "phase cutting unit"

-the apprentice had to walk one way 65 paces from my PC to check delinquent being questioned

-one UPS (inverter cum batteries) is located 0.5 meters from the delinquent

-a second UPS is located 20 meters from the delinquent

-a third UPS is located 15 meters from the delinquent

of topic corrections:

-Chardonnay would be served only to guests which are not welcome

-distinguished guests like Sparky Devils and Brainy Experts deserve better!

caveat:

-my two vicious fighting dogs, trained in various oriental and occidental martial arts, will be on stand-by duty when we all meet monday april 22nd. they will hunt down without mercy any participant probing with a variety of instruments whether electrical outlet #391 is installed according to and matching 100% British Sparky Code BS 6423 (bullshit?) "Code of practice for maintenance of electrical switchgear and controlgear for voltages up to and including 1 kV"

Edited April 14, 2013 by Naam

[Forkinhades]

^ haha

[Mudcrab]

It sounds like the fault happens when indeed the voltage drop by 10% and the control circuit kicks in, could be a lose wire, wrong connection, or faulty device sensor or relay.

You have 3 control circuits, 1 is bad for whatever reason. Look at the 2 good ones!! The items positions should be relative, but you will need to check that.

for one incident in five years i don't do anything because i'm not qualified to do the check and i don't know where to find a qualified electrician.

replacing the fuse and the melted holder takes 3 minutes. i have spare fuses as well as spare holders.

but the question is still whether i can replace these fuses with MCBs because i would save 2 minutes 59 seconds of work by flipping the tripped MCB if it happens again.

now tell me something interesting how my two 3-phase gadgets come into the picture although i have plans to replace the motors with single phase units.

Another comment from a technically incompetent person whose advice will be ignored if not ridiculed based on past experience in this particular thread (by one particular person I should add).

If you do change the 3 phase drives to single phase be sure that you understand the purpose of the neutral conductor in each system.

Be prepared for some extensive rewiring as it is likely your current drives do not have a neutral in their present location.

Keep a fire extinguisher handy near the box you show in the pic, unless you have the incoming supply rewired also. The neutral conductor might be a bit light on capacity after the 3 to single phase conversion has been done. But you already knew that didn't you?

@forkie....please be sure to let us all know the outcome of your investigation....thanks mate.

[Forkinhades]

^ as Naam said with the threat on his dogs, I will NOT be doing any investigations, well certainly not with any instruments.

This is a very simple system, and very easy for me to get my head around, you have one control circuit that is faulty, witch has in effect 3 switches incorporated, the fault lies there, as that is why the control fuse is blowing. If you had a fault on a lighting circuit would you go looking at some sockets!

Not sure who you are calling techinaclly imcompetent here, and certainly no need to change any drives?? It is a simple domestic TP+N supply, and no change any other configurations at all.

Edited April 14, 2013 by Forkinhades

[Mudcrab]

^ as Naam said with the threat on his dogs, I will NOT be doing any investigations, well certainly not with any instruments.

This is a very simple system, and very easy for me to get my head around, you have one control circuit that is faulty, witch has in effect 3 switches incorporated, the fault lies there, as that is why the control fuse is blowing. If you had a fault on a lighting circuit would you go looking at some sockets!

Not sure who you are calling techinaclly imcompetent here, and certainly no need to change any drives?? It is a simple domestic TP+N supply, and no change any other configurations at all.

Not having a go at you at all (from your postings you seem very competent indeed) , just being facetious as I expect a reply from the OP accusing me of incompetence. He said he was going to change the 3 phase drives to single phase sometime in the future. This has a great bearing on the size of the neutral installed. 19 aircons, pumps etc going to single phase could be a serious increase in the single phase load....and so the neutral size. Hence the fire extinguisher comment.

[Mudcrab]

^ as Naam said with the threat on his dogs, I will NOT be doing any investigations, well certainly not with any instruments.

This is a very simple system, and very easy for me to get my head around, you have one control circuit that is faulty, witch has in effect 3 switches incorporated, the fault lies there, as that is why the control fuse is blowing. If you had a fault on a lighting circuit would you go looking at some sockets!

Not sure who you are calling techinaclly imcompetent here, and certainly no need to change any drives?? It is a simple domestic TP+N supply, and no change any other configurations at all.

Investigation is simply a term I use, call it anything you want, its no real issue. But please do let us all know what you find. We may all learn something from this.

[Forkinhades]

OK, I think the OP has got the answer he wanted, that is indeed why I am having breakfast, and a glass of some luxurious wine.

I dont really expect to find anything, as the system in most is working.

[Naam]

It sounds like the fault happens when indeed the voltage drop by 10% and the control circuit kicks in, could be a lose wire, wrong connection, or faulty device sensor or relay.

You have 3 control circuits, 1 is bad for whatever reason. Look at the 2 good ones!! The items positions should be relative, but you will need to check that.

for one incident in five years i don't do anything because i'm not qualified to do the check and i don't know where to find a qualified electrician.

replacing the fuse and the melted holder takes 3 minutes. i have spare fuses as well as spare holders.

but the question is still whether i can replace these fuses with MCBs because i would save 2 minutes 59 seconds of work by flipping the tripped MCB if it happens again.

now tell me something interesting how my two 3-phase gadgets come into the picture although i have plans to replace the motors with single phase units.

Another comment from a technically incompetent person whose advice will be ignored if not ridiculed based on past experience in this particular thread (by one particular person I should add).

If you do change the 3 phase drives to single phase be sure that you understand the purpose of the neutral conductor in each system.

Be prepared for some extensive rewiring as it is likely your current drives do not have a neutral in their present location.

Keep a fire extinguisher handy near the box you show in the pic, unless you have the incoming supply rewired also. The neutral conductor might be a bit light on capacity after the 3 to single phase conversion has been done. But you already knew that didn't you?

@forkie....please be sure to let us all know the outcome of your investigation....thanks mate.

yada yada yakety-yak

what part of "plans to replace the motors with single phase units" is it you don't understand and needs an explanation from an incompetent person?

of course the single phase units, which will replace the threephase units, will be powered with a single phase each and not with methane derived from my dogs' farts.

you don't seem to know the difference between "replacement and conversion"?

will you understand if i translate these two expressions into French, Spanish, Italian, Schwyzer Dütsch or perhaps Arabic?

ok, ok! i'll be patient... here's what i am planning to do. i will carefully switch off power supply to the first threephase unit while my wife and her maids stand by with fire extinguishers. then i will select appropriate tools in order to remove carefully that dangerous threephase unit. switching off the breaker might require special tools and years of experience in British electrical codes but i will do it just with my bare hands.

once i have selected the tools i will sweat and say

"vhat and vhy ze hell should i sveat in ziss heat vhen zere are people on my payroll who kan do ze tchob vizzout me sveating?"

zen i vill kall my vife's driver who is also my maintenantz entchineer and tell him "please replace zat zreefase unit vizz ze vonefase unit vhich vee prokured last veek from zat factori in BangCock vhich supplied ze fans originally and make shure zat ze neutral conductor is not too lite on kapazity vhen yew remoof ze zreefase viring and konnect ze singlefase viring. kareful! you hear? take a skale and veigh ze kapazity before you do zomezing foolish like burning ze building down! if you are not ekstremely kareful we have to kall ze elecktrick kompanie to kompletely revire ze hole building!"

"after zat do ze same vizz ze sekond unit and vhen you have finisched tcheck vhezzer all systems have ekzellent go too mutt, report to ze TeeVee room and vake me up bekause i vill be napping zere."

[Naam]

^ as Naam said with the threat on his dogs, I will NOT be doing any investigations, well certainly not with any instruments.

This is a very simple system, and very easy for me to get my head around, you have one control circuit that is faulty, witch has in effect 3 switches incorporated, the fault lies there, as that is why the control fuse is blowing. If you had a fault on a lighting circuit would you go looking at some sockets!

Not sure who you are calling techinaclly imcompetent here, and certainly no need to change any drives?? It is a simple domestic TP+N supply, and no change any other configurations at all.

LO AND BEHOLD! LISTEN YE SPARKY...

the fuse is not blowing, the fuse was blowing... and that only once... several rainy seasons ago.

Forky, you are of course allowed to "get your head around" based on the condition that you hold a glass of Port in one hand and put your other hand in whatever pocket is most convenient. the focus of our meeting is to have besides some fun a hopefully interesting technical discussion (on apprentice level, that goes without saying) concentrating on inverters, crystal clean sine waves with smooth repetitive oscillations, potential problems with battery chargers and battery maintenance which is also of big interest to the other attending TV-member.

do you agree or yes?

[Forkinhades]

Indeed sir, I believe you are happy, was you not following my off beat tact? Well I must apologise, and indeed look forward to our meet. As indeed your OP has been answered, maybe some were unaware of that, just my tangent on affairs.

[Naam]

this topic seems to be squeezed out. i have to think of something new to generate interest, excitement and last not least revenue for George. but it should have either a technical or a financial (and last not least Thai) relevance to attract learned eggsburts and avoid topics to be closed.

unfortunately all topics which came into mind have some flaws and i discarded already

-Does your Thai Wife / Girlfriend / Partner / Mother-in-Law Comply With European Money Laundering Legislation?

-Do You Find Chewed Chewing Gum Remnants On A Burned Fuse In Your Breaker Box Disgusting? if yes, tell us how disgusting on a scale 1-10 (10 = extremely disgusting).

-If You Had A Choice Selecting Offered Drinks. Would You Prefer A Bottle Of Warm Stale Ale Without Any Foam On Top Over A Glass of 35 Year Old Portwine? if yes, state why. if no, state why not.

-Are You Aware How Easy It Is To Reduce Your "Leccy" Bill? note: "Leccy" is the correct British expression for breakfast as is "Brekkie" for electricity bill. or is it perhaps the other way round? please answer without googling!

[Forkinhades]

Ah Naam wants to keep this alive, ok I will oblige with that,

1. Yes of course

2. Yes 10

3. Yes, you really want an answer as to why?

4. No, please enlighten - other way round, without googling

edit : inserted want

Edited April 15, 2013 by Forkinhades

[jbrain]

Ah Naam wants to keep this alive, ok I will oblige with that,

1. Yes of course

2. Yes 10

3. Yes, you really want an answer as to why?

4. No, please enlighten - other way round, without googling

edit : inserted want

3. Yes, you really want an answer as to why?

Can't wait for the answer. Please post it

[Forkinhades]

35 year port will always win against stale ale

[jbrain]

35 year port will always win against stale ale

That's a fact, but I read your answer as.

- If You Had A Choice Selecting Offered Drinks. Would You Prefer A Bottle Of Warm Stale Ale Without Any Foam On Top Over A Glass of 35 Year Old Portwine? if yes, state why. if no, state why not.

Your answer : Yes

[Forkinhades]

must of had too much warm stale ale last night.

[Naam]

35 year port will always win against stale ale

i underestimated the Brits! now i wonder why these intelligent people lost an empire. could it be because they still play a silly game like creak-eat (or whatever it is called) which might end as a draw even if they play for three consecutive days?

[Forkinhades]

test match 5 days, yes that game is definetly pants

there we go another digression

[Forkinhades]

Personally I prefer a nice game of wiff waff after an evening meal, followed by some nice coburns, which has silent letters in, so I have chosen to miss them out.

[Naam]

test match 5 days, yes that game is definetly pants

there we go another digression

let's assume you meet my wife, a highly unlikely event because she is a night owl and goes much later to bed than i get up. anyway, should that highly unlikely event occur, please refrain from making any derogatory remarks on that game. reason: she is a big fan of creak-eat and tries to explain to me the complicated rules since something like 35 years

[jbrain]

test match 5 days, yes that game is definetly pants

there we go another digression

let's assume you meet my wife, a highly unlikely event because she is a night owl and goes much later to bed than i get up. anyway, should that highly unlikely event occur, please refrain from making any derogatory remarks on that game. reason: she is a big fan of creak-eat and tries to explain to me the complicated rules since something like 35 years

Naam, it's not that she try's to avoid you for some reason, is it ?

Edited April 15, 2013 by jbrain

[Naam]

test match 5 days, yes that game is definetly pants

there we go another digression

let's assume you meet my wife, a highly unlikely event because she is a night owl and goes much later to bed than i get up. anyway, should that highly unlikely event occur, please refrain from making any derogatory remarks on that game. reason: she is a big fan of creak-eat and tries to explain to me the complicated rules since something like 35 years

Naam, it's not that she try's to avoid you for some reason, is it ?

you mean she told you?

[wayned]

All of thi because of a blown fuse!

[Forkinhades]

so 40A MCBs are OK? if yes, what about their "behaviour"? in Germany we have

three different ones, called something like "fast", "moderate" and "lazy". i think it

indicates how many initial amps an MCB can take for a short time before tripping.

Ah now songkran is over time for some more debate

^Just to expand on this

You do indeed have 3 different types of MCB's, namely 'B' 'C' and 'D' types, basically you can change the letter for a number, so B=5, C=10, and D=20, with it it so far?

So lets say you have 32A MCB. You can now multiply this by the said values, eg B=5, so 32 x 5( B )= 160A, 32 x 10©= 320A, and of course 32 x 20(D) =640A

What this means is how much over current these MCBs can handle over a short period of time.

This also also applies to HRC fuses, but typically they have ratings of between 4-7

So when your 30A HRC blew, you did actually have a fault current of 30 x 4 = 120A (weakest possibility).

So at some point down the line, you did in fact have a short, as there is no way that the control (monitoring fuses) would generate that kind of current. At most that circuit would be 300W

Edited April 20, 2013 by Forkinhades

[Crossy]

Indeed Forky, and I would expect to see something a bit black in the area of said short.

I'm sure you would have said if you'd seen anything untoward during your visual inspection.

[Forkinhades]

Naam has previously said that the fuse holder melted

[Forkinhades]

^ Would also like to say that an ingress of water is highly unlikely to generate such fault currents.