Planer keeps burning through fuses.

[Mike G]

You'll remember the saga of my planer thicknesser from a few months ago. Well, all is not quite well. I ended up simply re-wiring the lead from the NVR switch into the junction box on the motor, and replacing the capacitor.

Three times since then the planer has died after a second or two of pressing the on-button, and each time it has been the fuse in the plug. Why would a plug fuse blow instead of the workshop trips tripping? This place was properly wired by an electrician 5 or 6 years ago, so the trips are absolutely as they should be..........so what is going on that might lead to a fuse blowing?

 

[Raymedullary]

I have an Electra Beckum 260. It will only run off of a 16amp supply. I at first tried it via 13 amp but too blew the plug fuse. Its all to do with the amount of current that they draw on start up. A 16 amp spur away from the board solved the problem.
I should add that I am not an electrician but I have a friend who is qualified for domestic.

 

[Mike G]

It's worked perfectly well for 5 years without doing this. It's only since the recent electrical work that this has started happening.

Ray.......don't hit the submit button again! :lol:

 

[Trevanion]

You've got a little Inca planer, haven't you? It should be fine running from a regular 13A socket as that's what it was designed for, a lot of people will try and make 16A (blue plug) machines run from 13A socket and that's usually the problem of fuses going pop.

Is the machine totally mechanically sound? No bearings on their way out or moving parts under power that haven't been lubricated in donkey's years causing the machine to start slowly and overload? Too much tension on the drive belt?

 

[Mike G]

I slightly damaged the pulley on the motor when taking it out last time, so it vibrates a bit more than it did. It doesn't start with quite the oomph that it used to.

 

[Raymedullary]

Ye I am surprised it did work on 13amps, these machines have a reputation for requiring (or being very borderline) 16amp supply. Over to a spark now...

 

[Mike G]

As Trevanian says, it's a Startright Inca, and it was designed for 13amps.

 

[DaveL]

Ok so you fitted a new cable between the switch and the motor, I know you were going to make it a bit longer, but not by much, does the new cable have thicker wires in it?
It could be that the old cable was limiting the in rush current to just less than the fuse blowing and the new cable is not, you don't need much to take it over the edge.
Also it's a bit colder, so the start current will be higher.
The other thing is did just the pulley chip or has the shaft/bearing had a little damage?

It could be all three of these stacking up against you!

 

[Trevanion]

Ah, Autowest switch! I had a similar problem with my planer that had an Autowest switch that wouldn't start properly with everything tightened off, once I replaced the switchgear it was fine and fired up perfectly every time.

Not saying that is 100% the problem but it was in my case.

 

[Mike G]

Ok so you fitted a new cable between the switch and the motor, I know you were going to make it a bit longer, but not by much, does the new cable have thicker wires in it?

It's the same sized cable, Dave.

The other thing is did just the pulley chip or has the shaft/bearing had a little damage?

I think the pulley just bent slightly. It has a slight wobble now. Of course, it's not impossible that there was some bearing damage, but I doubt it.......although I guess a wobbly pulley will lead to bearing damage in due course anyway. I can feel myself arriving at a conclusion thanks to a nudge or two here: it's time to order a new pulley, and get the mechanics running absolutely smoothly again.

 

[Mike G]

Ah, Autowest switch! .......

Is it? There's no sign that any other switch has ever been on the machine, so I assume that it's the original.

 

[Trevanion]

Is it? There's no sign that any other switch has ever been on the machine, so I assume that it's the original.

My Multico NS had an Autowest switch when I bought it, it had always been wired directly into the circuit when the last owner had it from new and when I went and put a plug on it and ran it from an ample supply it simply would not fire up right with the belt tensioned properly. I went through everything, bearings, capacitor, cables, and eventually swapped out the switch which solved the issue.

As I said, it may not be the issue here but it's worth checking.

 

[sunnybob]

With the power supply COMPLETELY disconnected :shock:, try turning the thing by hand.
If you bent the shaft rather than the pulley the motor will be very stiff to turn. Rotate it several times to check properly.
If there is a stiff section then the extra power inrush needed to get past it is whats causing the fuse to blow.

The other likely cause is you have not tightened all the cable terminals securely. A loose wire (especially a neutral) will cause a spark to jump, overloading the fuse.

 

[Mike G]

Thanks Bob, I'll go through that tomorrow.

 

[RogerS]

Replace your 13 Amp plug. Over time, the internal fuse holder connections can develop a slight resistance, which then creates heat, which then melts the fuse connections.

 

[Cabinetman]

Just a thought, you might have bought a packet of fuses that just weren’t quite rated properly, try a better make, but I agree with what Rogers said, try an MK plug, and it might also be worth checking the wall socket, I had the electricians in checked my system over completely last week and it’s amazing how some of the wires come loose over time, brand-new system fitted eight years ago. I was really surprised just how tight the electrician was tightening the connections. Ian

 

[Mike G]

Thanks guys. I'll have a look at that today.

I'm still puzzled as to why a fuse would blow as distinct from a trip tripping. I thought trips were way more sensitive than fuses, and should go at the first sign of strain on the system.

 

[RogerS]

Thanks guys. I'll have a look at that today.

I'm still puzzled as to why a fuse would blow as distinct from a trip tripping. I thought trips were way more sensitive than fuses, and should go at the first sign of strain on the system.

You're making the assumption, Mike, that it is over-current making the fuse blow. If I am right then it is heat being generated by a bad connection in the fuse holder part of the plug that is causing the connection inside the fuse to fail. Not over-current.

 

[Pete Maddex]

Mike have you tried running it through a long mains lead, it could be the old cable had enough resistance to limit the current to below what the fuse could carry, If it works o/k on a long mains lead then a 16A socket will be required.

Pete

 

[Mike G]

I replaced the lead, Pete, and it made no difference. My first assumption when I couldn't detect power through the lead was that the cable had broken somewhere, so I just put a new one in. Of course, my first assumption should have been that the fuse had blown.

 

[RogerS]

Mike have you tried running it through a long mains lead, it could be the old cable had enough resistance to limit the current to below what the fuse could carry, If it works o/k on a long mains lead then a 16A socket will be required.

Pete

But it was working perfectly fine, Pete, on the existing set-up. So something within that has changed.

 

[DaveL]

Thanks guys. I'll have a look at that today.

I'm still puzzled as to why a fuse would blow as distinct from a trip tripping. I thought trips were way more sensitive than fuses, and should go at the first sign of strain on the system.

Mike,
I would think your sockets are wired as a ring circuit, that will a have trip rated at ~30 amps which is what the ring of cable can support. The fuse in the plug is rated to protect the lead connected to it, so the trip only pops on a massive overload on a small overload the fuse goes first.

 

[novocaine]

what fuse are you putting in the plug?
doesn't really matter just wondering.

you've got a short in the cable somewhere that's only showing on start up current, most likely a rub between 2 insulation layers but it could also be corrosion on the live (might be in the switch but more likely to be in the new cable).

change it. not like it takes or costs much and rules it out (don't change it for another bit of the same cable).

this is quite a useful cheat sheet for cable size to fuse size.

Appliance Rating Cable Size
<3A 0.5 sq mm or greater (3 amp fuse)
<6A 0.75 sq mm or greater (5 amp fuse)
<10A 1.0 sq mm or greater (0.75 is allowed if <2m cord) (13amp fuse)
<13A 1.25 sq mm or greater (13 amp fuse)

 

[Mike G]

It's happened with 2 cables now, so it isn't likely to be the cable.

 

[novocaine]

It's happened with 2 cables now, so it isn't likely to be the cable.

well that answers that then doesn't it. the fuse only protects against resistance appliance. the only other bit you've touched is the wiring between the switch and the motor. so I wonder where the issue is. out of interest, did you make sure to put the capacitor in the correct way round?

you say it doesn't start with the same uumph it used to, that's normally because the capacitor is fecked, but that's a new cap so the next question is correctly installed really. is there a pair of capacitors on the circuit? one start one run? is the start cap disconnected from the circuit once running, normally through a relay or switch on the motor?

got to say, there are far to many variables to answer anything more, you need a sparky to stick his pointy thingy in your dark holes and let you know what went wrong (by your own admission, electricals aren't your strong point).

 

[RogerS]

Mike,,,when you say replaced the cables...did that inclkude a different plug on the end? If so then ignore my theory!....You may have already

 

[Mike G]

No, I used the same plug. I'll be swapping it in the next hour or two.

 

[9fingers]

No, I used the same plug. I'll be swapping it in the next hour or two.

I only vaguely recall these details of the original problem
1) A new capacitor did not instantly fix the problem
2) We did not resolve whether or not the motor has a centrifugal starter switch
3) There was another wiring issue.
Possible Problems giving the symptoms:-
a) If in error you have rewired such that you are now running on the starter winding and starting with the run winding.
b) The centrifugal switch is sticking shut from time to time.

Good Luck

Bob

 

[Guineafowl21]

Do you have a link to the original thread? We might be able to spot what’s gone wrong. For example, if you fitted too large a capacitor, more inrush current will result.

 

[9fingers]

Do you have a link to the original thread? We might be able to spot what’s gone wrong. For example, if you fitted too large a capacitor, more inrush current will result.

The original capacitor was an AC electrolytic, no longer available so was replaced with a modern one which could likely have a lower inductance but I've not had this sort of problem in many years of working with motors

original thread here viewtopic.php?f=23&t=4816

Bob

 

[Mike G]

Just a quick update......I've replaced the plug, and it isn't working at all (brand new plug, brand new fuse). I'll test in a minute whether any power is getting as far as the switch, but the switch certainly isn't even trying to hold itself in.

-

As an aside, since this planer started misbehaving I have been able to start the woodburner so much easier, and without using paper or a fire-lighter. Shavings from a hand plane set as a bed in the bottom of the burner are just brilliant for starting a fire.

 

[9fingers]

Just a quick update......I've replaced the plug, and it isn't working at all (brand new plug, brand new fuse). I'll test in a minute whether any power is getting as far as the switch, but the switch certainly isn't even trying to hold itself in.

-

As an aside, since this planer started misbehaving I have been able to start the woodburner so much easier, and without using paper or a fire-lighter. Shavings from a hand plane set as a bed in the bottom of the burner are just brilliant for starting a fire.

I would suspect dodgy mains cable Mike.

Bob

 

[sunnybob]

Assuming you have wired the NVR correctly, the fact it isnt holding in at all means there is no power getting to it.
You really need to obtain a multitester and learn basic circuit testing.

I have discovered several mains leads in my time that appear perfect but have a break inside. With a multitester diagnosing that kind of fault takes only seconds.
Of course, you could try plugging something else into the same socket to prove or disprove the household wiring. :eusa-whistle:

 

[Mike G]

Well other things work perfectly well in the socket. That maybe doesn't tell us very much because the planer works well enough when it works. It was fine yesterday, until it wasn't.

 

[9fingers]

Well other things work perfectly well in the socket. That maybe doesn't tell us very much because the planer works well enough when it works. It was fine yesterday, until it wasn't.

My strong suggestion would be to disconnect the motor L and N from the output of the NVR. Then get the NVR working reliably.
i.e. Connect the supply, press the start, get a click.
press the stop get another click
press start, get click, switch off at socket, get another click etc
Connect the supply, press the start, get a click. wiggle, push, pull cable shaking all about make sure there is no click off or any fuse blowing.
Only when your are 100% confident with the NVR action and the mains cable, reconnect the motor and then if you get fuse blowing you can be certarin the problem lies down stream.

Bob

 

[Mike G]

OK, I'll do it Bob, but that's a pain as the terminals are really difficult to get at. It makes sense, though.

 

[Mike G]

I've re-wired everything between the consumer unit and the input side of the NVR switch. This comprises a junction box, the socket, the (new) plug, and the NVR switch itself. The planer now works......which isn't to say the problem is solved. It's worked quite a lot over the last month or two, and then gone through fuses like they were toffee. I don't know what the team think, but I suspect we might have had 2 faults, and that re-wiring has solved at least one of them.

 

[9fingers]

Whilst you might now have a working planer, I strongly suspect that you might have not fixed the problem and certainly not learned anything in the process.

I can't (at the moment ) think of a mechanism in changing the wiring between the CU and the wall socket that could have stopped the downstream fuse in the plug blowing.
You could have had a faulty lead from the plug to the NVR which would have been exposed by following my method above but due to your method we will never know.

Lets hope you continue to make shavings without blowing fuses from now on.

Bob

 

[Mike G]

Sorry, Bob, I should have made clear.......I did do precisely what you suggested, and "get the NVR working" is covered by the rewiring I've just done. Nothing worked when I simply disconnected everything upstream of the NVR, nor when I replaced the plug and the lead, again. That left the supply to the socket as the fault (ie, the 2nd fault which was preventing the NVR working, not necessarily the first fault which was the burning out of fuses). This was confirmed by my drill failing to work when plugged into the socket. So, I can be pretty certain that the socket fault is now cured, and I can guess that this was merely coincidental to the fuse-blowing fault.

So I am currently at this position, and awaiting the next blown fuse:

........Only when your are 100% confident with the NVR action and the mains cable, reconnect the motor and then if you get fuse blowing you can be certarin the problem lies down stream.

Bob

As to not learning anything...yeah, well I already knew I hate effing electrics, so you're right, I've learnt nothing.

 

[9fingers]

OK fair enough. Apologies.
Bob