Who's Fault?

[RogertheBodger]

Re-called to a job today.
(Hate it when that happens)
Motor overloads tripping on a 3ph. water pressure boost pump, but intermittently, not every day.

First visit, tested everything - current draw, voltage, winding resistances, IR etc - nothing,
no trips, everything working fine, like your car when you take it into the garage 'cos its running rough and then it purrs like a kitten, the swine ( the car, not you TC)
Put it down to the pump struggling to force water round the system, because it's a big house, and turned the O/L's up a bit - see how that goes.

Anyway, today its a bit different, clamped it and the current is fluctuating from 4+ to 6+ Amps, the pitch of the motor changed at the same time, sounds like it's losing a phase so checked it from that angle. turns out one of the line connections between the contactor and the O/L unit is burned and losing contact. cleaned it up, OK now, must have been a loose connection.

The pump/motor set including the base plate, Pressure switch, enclosure with MCB, RCD, Contactor and overloads was supplied and installed by the plumbers as a pre-wired unit, all I had to do at the time was to run a supply to it.

When I explained to my customer what the problem was, he said, didn't you check all the connections were tight when you installed it? Ouch, well yes, all the connections I made were tight, but this unit was supplied by others, quality control stickers on it, so would I be expected to go through someone else's work and check it?

Nevertheless his question stung a little, feel I should have spotted it first time, spent two apprentice weeks every Manchester Wakes tightening dist. board connections on shutdown planned maintenance.

So what do you all think, should we check connections made in supplied equipment? I normally check light fittings etc. but a whole panel? not charged him yet and not sure if I should.

 

[vernam616]

Factory connections are usually "torqued", however the torque they use is rubbish, i always triple check every connection when doing a db

I was always taught that a loose connection is a dangerous one

 

[VoltzElectrical]

All panel boards and distribution boards I have fitted state that ALL connections must be checked for soundness, including manufacturers ones. I'm not pointing any fingers here, just stating what I have seen and followed. Manufacturer's instructions supersede everything else.

 

[snowhead]

The other 9999 pumps made in the same batch are purring away with no problems.

It's just one of those things.

If you'd charged the customer for commissioning the pump he'd have a valid complaint I believe.

I always check the connections in motors I fit, new or rewound, but that's only 6 connections and the terminal cover is off anyway.
Anything else it's just the cable connections on the opposite side of any terminals that I touch.

 

[RogertheBodger]

Factory connections are usually "torqued", however the torque they use is rubbish, i always triple check every connection when doing a db

I was always taught that a loose connection is a dangerous one

And you have been taught correctly, but a CU is normally something you supply and that you have to make connections to, but say you are wiring a new oven, would you check all the connections in that?

If a CU is existing then yes, it's prudent to check all connections, and any Electrician worth his salt would.

 

[Deleted member 9648]

There's usually a manufacturer gettout stating "Check all connections for tightness,including factory made connections"....that said,we've all done it mate,you cant think of everything all the time......if I had a quid for every time I've left a job feeling a bit sheepish........well it'd add up to a fair old wedge after 30+ years.

 

[MKS]

Don't beat yourself up, not worth the heartache! I like to check all connections, as I am pedantic like that. However, there are somedays where I completely miss the obvious, happens to us all

 

[VoltzElectrical]

the days of the torque screwdriver are upon us, next on the 'must buy' list. blimmin expensive though!

 

[RogertheBodger]

the days of the torque screwdriver are upon us, next on the 'must buy' list. blimmin expensive though!

OK, fair point Voltz, but really the point of my post is how far do you go in checking the workmanship of equipment that is supplied and installed by others?

 

[Deleted member 9648]

the days of the torque screwdriver are upon us, next on the 'must buy' list. blimmin expensive though!

There was a fella in CEF today showing off with his 90 quid 1000v kewtech set...........I'll hang it out a bit longer I feel......managed without one for 30 years.

 

[Knobhead]

A good few years back one plant it worked on (built in the early 60’s) had problems with motor terminal boxes burning up.
To cut a long story short I shadowed the one electrician that every shut down would go around the plant checking all motor terminals. As I watched him he would give each terminal a tweak. Over the years he’d managed to reduce the thickness of some lugs by about 50%.
Checking is one thing, but be careful.

 

[Mark_Burgess]

I dont see why you RogertheBodger should have to open up a panel and check every thing within it if you did not supply the panel. You are really only responsible up to and including the termination you make to it and have probably only quoted to do that at the time.
Was it a spade terminal that was iffy? No way should you be checking them especially as you did not supply it. You were unlucky like snowhead said, the others from that production run are probably fine.

 

[Marvo]

I don't think it's reasonable to expect the installer to check every termination in a new appliance or machine unless it comes with a planned maintenance schedule. With many items you'd need to completely dismantle it to get at some of the terminals. I would just normally check screws on the termination strip although I do often check the main neutral connections and contactors if you can get to them, mainly out of habit. With a CU it's different, all the terminations are accessible.

 

[RogertheBodger]

I dont see why you RogertheBodger should have to open up a panel and check every thing within it if you did not supply the panel. You are really only responsible up to and including the termination you make to it and have probably only quoted to do that at the time.
Was it a spade terminal that was iffy? No way should you be checking them especially as you did not supply it. You were unlucky like snowhead said, the others from that production run are probably fine.

Hi Mark - no it wasn't a spade terminal, it was one of the three copper pins that connect the O/L unit to the contactor, everything else was tight.

 

[RogertheBodger]

I don't think it's reasonable to expect the installer to check every termination in a new appliance or machine unless it comes with a planned maintenance schedule. With many items you'd need to completely dismantle it to get at some of the terminals. I would just normally check screws on the termination strip although I do often check the main neutral connections and contactors if you can get to them, mainly out of habit. With a CU it's different, all the terminations are accessible.

That's my way of thinking Marvo, in the plant room in question, in addition to the booster pump there is also a sump pump, two swimming pool pumps, heat pump, 4 A/C units, pump for the swimming pool salt, controls for the pool lighting, and in the room next door is the lift mechanism.

All of this has been wired and terminated by me, but supplied and installed by others, at the moment I don't want to suggest to the client that I am responsible for faults within this equipment, as I will then be getting the call every time there is a fault on any of the machinery.
And if I don't charge him now, I would be setting a precedent, so I couldn't charge him in the future