Question for the Electrical Engineers!

[Peter]

I'm not sure about the gauge sizes, but 8mm is not that big at all. About $3 a meter.

10 metres of 50mm2 cable costs around £86.

Hence why I was asking the question!

 

[Peter]

If I did downsize the cable to something like Al suggested, 4 gauge (21.2mm2?), would downsizing the fuse to match also prevent the wiring catching fire in the event of something going wrong with the unit.

I have run it a lot on a 70 amp fuse, although I don't know how accurate those fuse ratings are, it seems likely that it wouldn't pop with a 71 amp current, maybe more and variable between individual fuses. I have seen a 13amp fuse completely melt a plug and socket on a domestic 240v circuit, so I don't imagine the fuse is too reliable.

 

[Al Smith]

You'd about have to fuse it at 150 if that's the load .Don't forget the load rating on wire is greater in free air than it would be in a conduit .

 

[Al Smith]

It's been a long time since I looked up the wire ampacities in free air so I googled it .Free air for number 4 is 125-140 amps depending on the type insulation .If you're worried about it go to number 2 .

Seems to me the battery cables on a normal automotive circuit are either 4 or 2 .

 

[SoonerFan]

One more question for the experts. My ceiling fan was making a small clicking noise. I could sleep through it but it drove my wife crazy! I won't list the long list of things I tried but here is what seems to have fixed it... Flipped the switch to run it in reverse for a few minutes. Flipped it back the other way. Quiet as a mouse. It's not making any noise at all now.

If running it in reverse fixed it, why???

 

[Cobleskill]

My guess is there was a piece of something in there rubbing. When you put it in reverse it cleared it. Just a guess.

 

[NeTree]

That would be my guess.

 

[woodworkingboy]

Rubbing some grease or oil, can't remember which, through the bearing dust cover quieted down my shop ceiling fan. Could also be that running in reverse dislodged some grease into the bearing.

 

[NeTree]

I've had bugs get caught in motors.

 

[Peter]

One more, or maybe two more!

Fitting an isolator switch and a fuse, should they be on the + or - side?

 

[NeTree]

+

 

[Al Smith]

Most ceiling fans have "oil lite " bushings which is just brass with encapsualed oil in the metal .They dry out and get noisey .If they get too noisey give them a squirt of WD-40 which shuts them up for a while .

Also you just cannot imagine the stuff that gets caught in fans of all types .Clings to the blades or squirerel cage then rattles and drives you nuts until you find it .Exhaust fans in resterants are the worst .If half the people ever saw those fans they'd never eat out again ,yuck .

 

[MasterBlaster]

At Micky Dees, we have our exhaust vents cleaned twice a year. One of us has to babysit the fellow while he works all night. I wouldn't want his job.

 

[NeTree]

Sounds like a good fire prevention plan.

 

[Cobleskill]

I bet there is one heck of a build up after 6 months. They use a high pressure washer and suit up?

 

[MasterBlaster]

Oh hell yea, that and a bunch more. I've had to do it once, but I didn't pay much attention to him. Kinda like a chimney sweep on steroids!

 

[woodworkingboy]

One of those unpleasant get it over quick jobs, but it takes all night. Hope it pays well.