Electric Issues - Help

[Glossopguy]

Hi Guys

Ive recently moved to a new house
The workshop is powered from a fused spur from the house plug ring main

Im killing motors or at least Switches

Ive gone through 3 switches on 3 different machines

1) old 12 "bench Saw - here the switch was closed loop feedback switch from the Motor - the switch was not replaceable as it was old anyway
2) Band Saw happily used for some 20 years no problem simple switch died in 6 months of relocating
3) Brand NEW Evolution Rage 10" bench Saw switch died in 6 Months - warranty replacement

AND NOW .... 4)!!! My lathe motor is starting to play up... much in the same way as the others. Power to the motor but wont spin unless assisted. Slowing down on high load. and then not even "locking on " the start button
This has a simple 2 wires in 2 wires out switch

This is more than a coincidence Surely ?
Mains Power supply (AVO) 251 V AC
Fuse Resistance 7.8 ohms


Any suggestions from you Sparkies out there >

 

[Woody2Shoes]

"...The workshop is powered from a fused spur from the house plug ring main..."

This doesn't sound great - I'd be wondering if the earthing is up to scratch as well. I think it would be worth getting the whole thing looked at by someone who knows what they're doing.

You may get a reading of 251V on no load, but there will be resistive (and reactive) effects (in the wiring and the appliance) that may cause problems when current is drawn.

 

[porker]

(Not a sparkie but an Electrical Engineer)

It sounds like your supply to your workshop may not be up to it. You don't say how far the run is from the house to the workshop and it would be worth reading the voltage on load to see what sort of voltage drop you are getting. Not quite sure what you mean by fuse resistance as no fuse should read that high. Are you measuring loop impedance? Sounds to me with the limited info that you have too much of a voltage drop to your workshop probably due to an inadequate supply cable etc. Also as @Woody2Shoes states you probably need to check out the earthing arrangement in case the fault current isn't enough to trip the breaker in case of a fault.

 

[Glossopguy]

hi Woody

the cable run to the workshop is about 3 meters armoured wire underground.

I forgot to mention that the house is a new build less than 3 years old

Any voltage drop must be from the load of the respective machines since I only use one at a time
I doubt that 3 (now going on 4 ) motors are all causing the same level of voltage drop ?

Since Im at the limit of my electrical capability - who should I contact to attempt to sort this out

 

[Rorton]

See if you can find a recommend local electrician , unless its still covered in any 'warranty' you get with the house (never had a new build, so no idea how long you have to go back to the people you bought it from with problems)

 

[Woody2Shoes]

A local electrician with an Niceic ticket:
https://www.niceic.com/householder/find-a-contractorOr similar eg ChoosingAnElectrician

 

[woodwind]

What size is the armoured cable? Surely 3m of 2.5 wouldn't cause problems.

 

[porker]

Given its a new build and the run is so short it shouldn't be a problem. I'd envisaged an old bit of 2.5mm T&E running 100ft down the garden but this isn't the case. Difficult without seeing the installation but could be as simple as a loose connection in the fixed wiring. No load would indicate good voltage but on load be unable to draw enough power. The lathe not being able to hold in the contactor for example. A spark with an MFT would be able to check the supply very quickly.

Could you run a temporary extension from another circuit to the lathe and see if the problem still exists? This could show whether that circuit is the culprit.

 

[Spectric]

The workshop is powered from a fused spur from the house plug ring main

This was never designed to supply more than a basic light and maybe a few sockets. I would suggest your issue could be volt drop but can only be confirmed by test and inspection, with reduced voltage you will try and draw more amperage. Your total run will not be three metres, you have to include the impedance of the ring main as well. What you need is a proper supply run from your dizzy board using a cable sized to match your required loads, then tested and signed off by a competant sparky.

 

[Richard_C]

Running a cable from the house to one machine as a one-time test seems sensible.

My neighbour keeps a freezer in his garage, it failed so he bought a new one. New one didn't work, so he asked me what I thought. Plugged extension through kitchen window, ahhh, magic. Now he's got 2 freezers.

Electrician found a continuity problem on the negative side.

 

[Davey44]

In respect of your lathe, is it possible that the capacitor is faulty. The symptoms seem remarkably similar to one of my machines prior to fitting a new unit.

 

[xy mosian]

Hi all.
There seem to be enough suggestions for sorting this problem out, and I am not able to offer anything worthwhile any way.
However some seem to suggest that voltage drop along the feed might be the issue. Could someone please explain to me how this could cause problems with the motors, with a drop of less than say 30V or so. I can see that a drop could trigger an NVR switch, but in general terms how much of a drop causes the NVR to trip out?
xy

 

[Stevekane]

When he says a fused spur are we assumeing that this is just that, taken off a ring main, but does he mean that his armoured cable is connected to a spare way on his consumer unit, much more likely I would have thought?

 

[woodwind]

Maybe plug a kettle in and measure the voltage would be a fair indicator of the robustness of the wiring, I know it is not the same as a motor due to power factors, but the motors the OP is running don't sound very big.

 

[Dangermouse 2nd]

you need to put the supply to the workshop on a seperate trip, rated at 16 amps if thats possible with your supply. You need to get a qualified electrician in and sort it ASAP !

 

[Woody2Shoes]

Hi all.
There seem to be enough suggestions for sorting this problem out, and I am not able to offer anything worthwhile any way.
However some seem to suggest that voltage drop along the feed might be the issue. Could someone please explain to me how this could cause problems with the motors, with a drop of less than say 30V or so. I can see that a drop could trigger an NVR switch, but in general terms how much of a drop causes the NVR to trip out?
xy

I think the main problem with voltage drop is with induction motors (likely to be the lathe motor in this case, perhaps). When run undervoltage they tend to overheat. Of course, voltage drop implies heat loss in the wiring too - which could cause trouble.

 

[xy mosian]

I think the main problem with voltage drop is with induction motors (likely to be the lathe motor in this case, perhaps). When run undervoltage they tend to overheat. Of course, voltage drop implies heat loss in the wiring too - which could cause trouble.

Thank you Woody.
I was not aware of the overheating when induction motors run on low voltage.
I continue to learn, hopefully. The definitate problem, if ever found, will be interesting.
This sounds like one of those problems which is sorted by 'doing the job properly', at which point the intial cause is irrelevant.
Thanks again.
xy

 

[Dee J]

I've seen plenty of outbuildings (garages etc) on new builds supplied by a fused spur on a downstairs ring circuit. It's a bit of a minimal way of doing things, but generally enough to run a light and an odd power tool. Troublesome in that damp in the outside wiring trips out à significant proportion of the house.

 

[OldWood]

In my ignorance of the niceties of wiring, but being a graduate electronics engineer of course I knew all about electricty (!!!!), so some 40 years ago I wired my garage/workshop with at least a 30m run from my house CU with a buried 2.5mm cable.

There's a local CU with RCD and suitable trips. I appreciate this is seriously not ideal as far as voltage drop in concerned, but I am detailing this as I have a 3kw motor on my bench circular saw and the lights don't even dip when it starts.

I'm telling this to show that the transient motor start up current doesn't really have much impact even on such a long run.

Like omeone else here, I am puzzled by 'Fuse resistance' - if this is real resistance then an induction motor start up current surge peak of say 30 amps would kill the mains voltage totally.

This sounds to me like 'new-houseitis' in that either the ring hasn't been tested properly - incomplete ring, or there is an improper connection within one of the ring sockets or the spur itself.

I worked for a while with my brother - a qualified electrician - and one thing he was insistent on was that the cables in a ring circuit are twisted together in sockets to improve the joint. Recently he was talking about the wiring in a new build where many of the work force were from the EU and the quality of the wiring was way below that undertaken by British trained electricains.
Rob