New (to me) Table Saw blowing fuses!

[ColytonJohn]

It took a long search but I've finally replaced my life-expired Clarke CTS10 DIY table saw with a chunk of cast iron, induction motor and belt drive; I bought a Wadkin Tradesmen RT25.

I'd discounted anything with a brush motor, aluminium or sheet-steel tops and none of the modern Chinese saws gave me the confidence they'd last as well as old Wadkins are reputed to and this one simply oozes quality (in a heavy, industrial-metal kind of way).

Surprisingly it doesn't have a great depth of cut but I'll just have to manage with my band saw on those occasions I need more. It has a blade guard but the riving knife it mounts on is missing although I ought to be able to make one easily enough.

What is confounding me, however, is that it persists in blowing fuses on start up! The motor (a Rockwell) is plated at 8.8 amps at 240v, came fitted with a 13 amp plug and the seller assured me it worked well (couldn't actually test it due to no power in the barn it was stored in) but it should be OK.

I'm assuming the start-up current is the issue and, while I can wire in a dedicated 16a supply to my workshop, should I really have to? Everything spins smoothly so I don't think mechanical resistance in the drive-train bearings are at fault so I'm at a loss to understand this. Any thoughts?

Cheers,
John

 

[Racers]

Have you tried taking the belts off and seeing if it runs, a long extension lead might reduce the amount of current drawn as a test but not a long term solution.

Pete

 

[Yetty]

Congrats on the Wadkin! Here's my understanding.

Yes, 3hp motors can run through 13A plugs & fuse, without blowing, if the circuit is strong enough. If it worked before at other property using the 13A plug, then it sounds like your circuit doesn't provide enough voltage to the motor at start-up. A lower voltage can cause induction motors to take more current 'to compensate', thus the fuse blowing, it's an induction motor thing... Possible causes of the lower voltage at motor during start-up, are either, resistance in your circuit, or simply the supply to the property is lower than at the other property.

Before getting a 16A plug/socket etc., there's a couple of things you can do that might make it work okay. Get rid of unnecessary circuit resistance: avoid using extension leads, keep flex length from machine to plug as short, use 2.5mm2 flex (though this makes wiring some plugs challenging!), plug in as close to the head of the circuit as possible. Worked for me using my 3HP machines.

 

[ColytonJohn]

Thanks folks, that was useful

I ran an extension cable out to the saw, removed the belts and it started fine with repeated stop-starts all good.
I then reperformed the tests with the belts replaced and, again, all was well.

As the feed to the saw is via an old spur I'll run a dedicated new cable from the 16a box in shed 1 to the adjoining shed where the saw is. I could make this a 16a supply but now don't think it'll be necessary.

Cheers,
John

 

[Lons]

I originally ran my 3 hp SIP from a 3 pin plug and it was ok but the plug got pretty warm, different plugs made no difference so put in a short 16anp supply via a "C" mcb breaker to a plug in blue socket I had surplus from old caravan days. More recently swapped to this: http://www.ebay.co.uk/itm/16A-3-PIN...582110?hash=item3f333d1a5e:g:fIgAAOSwgkRVUMaW as I prefer a switched socket.
The whole system just feels safer.
Bob

 

[ColytonJohn]

Thanks Bob, I'll do just that and put in a 16a socket. If I'm going to the trouble of running a new cable there really isn't any reason not to as I won't be removing the existing 13a spur.

Cheers,
John