Compressor blowing fuses
Turbo Mini Forums

What size breaker is tripping at the fuse board? I.e 16A? 30A?

Shouldnt make any difference, the hose outlet to tools and the safety valve(yellow in pic) are on the same ports anyhow as they come from the tank, as long as you didnt move the small tube between the non return and the switch, it is this that unloads the larger tube when the switch operates/or is operated by the red knob on top. Even so this is only to allow the motor to start turning, they are still regarded as a high starting torque application as opposed to a low starting torque say a circular saw for example.



I will have a metophorical tenner on a popped capacitor, if memory serves run capacitors are connected across L-N, I will stand corrected though

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

None-Its the appliance plug fuse

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Oh... That's strange, the 13A cartridge fuse can't take the load? Well it sounds like a fault with the appliance then. If it is manufactured with a 13A fuse then it should be sufficient for the compressor.

Maybe check the flex itself for any damage, could have a minor short somewhere if damaged?
By the sounds of it I bet my bottom dollar you can eliminate the electrical supply up to the plug.

Is it under warranty?

Yes, wiring is good and the lead to the unit isn't damaged.

From memory the cap does go between post and neg.

Not sure on warranty as I bought it second hand. going to check with seally tonight.

Yes, forgot that, the capacitor could be faulty. Depends on the notor as to whether there is a start capacitor or a run capacitor or both. A start capacitor will usualy have a start relay to drop out the start capacitor and start winding.

From what you describe it does sound like an'overload' conditiob caused by a stalled motor. Check wikipedia for bs1363 and scroll down to the section on fuses where it states the time and capacity ratings for the fuses to blow and youll see that an overload of 100% wont blow the fuse for anywhere up to 5 minutes!

Edited by Sprocket on 8th Feb, 2013.

Tried it with the feed to the one way valve disconnected. lasted maybe two seconds then popped the fuse.

This is the cap and it's spunky bit. I think it's just glue to hold it in the case.



I tested it as you said and it's discharged - showing 0 volts and the negative symbol stopped flashing.

I now don't have anything left in my garage with a 13amp fuse...

Nail time!

If something is worth doing, it's worth doing half of.

Bet there's shit loads of fuses in the house lol, have you disconnected the capacitor ?

Edited by oli79 on 8th Feb, 2013.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

It's got crimped terminals on it and I'm a bit CBA at the moment....

What type of circuit are you running in your garage? Is it a ring or a radial? Do you have a fuse box in your garage?

I was just doing a bit of googling as I'm interested in the problem myself.
It would seem this is a common fault with air compressors and other appliances that require a high surge of power on start up, motors etc..
The fact that it's blowing the fuse in the plug and not the mcb or rewireable fuse or whatever you have at your main fuse board suggests you need a few extra amps scope at the compressor.

May be a bit of overkill but you could run a new circuit from your main fuse board, say from a 20A mcb and position one of these just above your compressor:

http://www.tlc-direct.co.uk/Main_Index/Plu...k_Up/index.html

Then take off the plug and refit with a blue 3 pin socket. The compressor would then be protected by a 16A RCBO. The one in the picture has two outlets so if you could find one with just one outlet it'd probably be quite cheap?

Just an idea? Also, I read that using the compressor with an extension lead causes problems, if you are plug it directly into a socket and see what happens.

The garage is fed from a C rated breaker in the cellar. Big chunky cable runs out to the garage supplying a lighting ring and a socket ring. Not using an extension lead.

I would be surprised if it was the supply to the garage/socket that was at fault. I had problems with the spot welder popping the breaker when I had a B rated breaker on that circuit, it's been fine even with the mig pulling 120+ amps.

Adding an extra circuit is a bit of a pain as the box is full.

Edited by apbellamy on 8th Feb, 2013.

Ya I can understand that... If you could get a higher rated Bs1362 fuse I'd say that would sort it but they only go up to 13A.

Maybe it's just down to a poor design?

I reckon something has broken in it. It worked fine when I first tried it.

As a qualified Electrician please allow me to clear this up before someone does something potentially dangerous from missinformation.

As a rough guide 1 HP is 750 watts or 0.75 Kw, therefore a 3hp motor is approx 2.25 Kw, you will see them labelled as 2.2 or 2.3. That is the largest motor that can be run from a domestic 3 pin plug top. Look in your machine mart catalogue, all the 230v compressors stop at 3hp, the only industrial unit they have that is larger has 2 motors at 3hp each and it even states the nature supply that is needed, above this they are all three phase. This is not an accident, its because all these machines will come with a normal 3 pin plug on to be used from a normal domestic outlet.

Now if you look through the motor section you will see they do sell one cheeky 4 HP single phase motor, the fact is there are larger single phase motors out there 4/5 HP and beyond and the reason is simple-they are designed for small commercial premises or anywhere they need a larger motor but do not have the luxury of a 3 phase power supply. In any case any motor or machine fitted with a single phase motor larger than 3HP WOULD need a dedicated supply with a suitable breaker and suitable cable right up to the motor, and it would quite clearly state this if it was a new machine.

A common mistake is centred around the circuit breakers as I have stated with b types and c types. As stated motors smaller that 3hp can knock out 16A or 20A breakers on start up due to the inrush current, commonly people then overate the supply to say a 32A to solve the problem-in essence its doing the same thing as putting a 16A c type in.

As Sprocket has pointed out, a plug top fuse does not actually blow at 13amps, in fact all protective devices ie circuit breakers actually operate at higher levels than the current stated but thats a whole other subject.

In Andys case it is simply the fact the plug top fuse is operating first because the supply breaker will be larger. A 16Amp industrial plug and dedicated 16 amp supply as has been suggested is a wank idea because

1. It will be taking much more than 16Amps to knock the 13amp plug fuse out for the reason stated above, so the breaker would just trip in the same manner.

2.That is an appliance that has come from the manufacturer designed to go on a 3 pin plug/13 fuse and the supply cable to the uniut will be sized accordingly, as stated even a 16amp breaker will potentially in low fault conditions take much more than 16amps so you start to reach the stage where there is a fire risk as the cable is now underated for the new supply you have given it, sprockets said this already.

Large motors should not be run on long extention leads because it causes a large voltage drop, this means the motor pulls more current and if run for a while it burns the motor out, thats why manufacturers say this. Essentially an extention lead is a radial circuit that anyone can add into a circuit, long radials in mains power circuits dont exist because voltage drop is accounted for in the design of that circuit(or at least it should be-but thats a whole other story too1)

Finally I have had 2 of these compressors one after the other on plug tops, both run for many hours, shot blasting, to the point of destruction, and on a 16 amp radial b type breaker-never an issue.

Edited by oli79 on 8th Feb, 2013.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Schrödinger's cat - so which one am I ???

Well put oli.

Maybe my idea was 'wank'... However, not dangerous.

Ok Bud Wank is probably not the best term and it was in no way designed to offend, but dangerous it is, unless the motor cable was already designed/changed in order to be sufficiently rated for a larger 16 Amp supply then under a low fault condition it could cause a fire, its the whole reason we have bs7671.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

My understanding was that the 16A breaker would trip long before the flex would overheat and burn if the compressor pulled too much current under a fault condition.

No offence taken, after being on this site for a few months I've learned that this is no place for someone who may be a bit sensitive....

Look were getting way o/t and there are reams and reams of ac theory and waffle that can be thrown in here, hence why it took me 3 years at college.

Sprockets said this on many occasions, the breaker/fuse is there to protect the cable downsteam of it. Circuit design starts at the load and works backwards to the supply, what we are doing here is changing something in the middle and ignoring what is downstream that may be affected

The cable fitted to the machine is designed to be protected by a 13amp fuse as per its design and will be rated to be able to operate this device under any fault condition,

because manf's make things screwed down to the last penny it is unlikley that it may be rated to operate a 16a device, the only way to confirm that is to get the size of the cable and check in a regs book.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Anyhow to lighten things here is an image of what it will run like when repaired

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Well it wouldn't be a good thread unless we went off topic...

Is that picture after I've wired it lol?

Oh dear, what have I started. I never though Oli had a serious side to him...