Mashmate/2400w Element Blowing Inline 10a Fuse

[Daniel.lear]

I would also agree with a 10 AMP breaker being the No 1 issue. Hopefully the wires used in the box are at least 2.5mm SQ, and they will handle 20 AMPS of current. Fuses are there to prevent fires, not electrocution, safety switches help prevent electrocutions. If you have resistance issues, then fitting a bigger fuse could result in fire. Are any of the wire ends soldered? Solder and 240V is a dangerous mix!

This is the back of a male socket, see how the copper is burnt/corroded and and heat damage to the neutral.
This was a person using a 2400W element with a 10 AMP extension lead.
See this picture of what a soldered wire end can do for your setup;

Why is the soldered end dangerous??

Leary

 

[roger mellie]

Why is the soldered end dangerous??

Leary

I dont think they are Leary - loose terminals are dangerous - Soldered ends need tightening and wriggling and re-tightening to make sure they arent loose - but you are right - they arent dangerous.

RM

 

[Carbonator]

I dont think they are Leary - you are right - they arent dangerous.

So your telling me a "desk jocky" uni degree home brewer constructing an in-line 3600W kettle controller going to Tandy and buying a soldering iron and 20 grams of solder is going to do a better job, after adding a resistive lead and tin mix around copper wire, is going to have a better (less resistive) connection than the same person tightening the screw that bights into twisted plain copper wire strands (for a perfect interface)?

I've had this arguement before, being in favour if solder, untill I saw that mess I had to fix for someone else on their kettle. The guy was wondering why his new BigW extension leads were melting during every use!

 

[roger mellie]

So your telling me a "desk jocky" uni degree home brewer constructing an in-line 3600W kettle controller going to Tandy and buying a soldering iron and 20 grams of solder is going to do a better job, after adding a resistive lead and tin mix around copper wire, is going to have a better (less resistive) connection than the same person tightening the screw that bights into twisted plain copper wire strands (for a perfect interface)?

I've had this arguement before, being in favour if solder, untill I saw that mess I had to fix for someone else on their kettle. The guy was wondering why his new BigW extension leads were melting during every use!

Not at all - but the Solder isnt the reason of the hot joint - the termination is.

Basically - in fact - completely - the whole thing about electrical terminations is cross sectional area - the more the better. The tighter and more secure the joint - the better. If you can manufacture your termination with solder to provide maximum connectivity with the type of connection - you wont have a problem.

Put it this way Carbonator - you can have exactly the same results with bare stranded copper terminations as you can with Solder joints - if you dont do it right.

RM

 

[Rob C]

Im not sure what you guys do for a living, But if your not qualified to do so dont give out information regarding electrical work. I have seen some stupid things done from second hand information and people do get hurt.

And yes i am qualified to comment.


Cheers
Rob

 

[LethalCorpse]

As much as it pains me to admit it, carbonator is right - to a point. When you tin the ends of a copper cable, the solder has a film of flux, oxides and other crap on the surface. It also, despite being soft and malleable, doesn't give under the screw enough to give the same flush connection that stranded copper does. Add to that the fact that solder is actually a pretty poor conductor (certainly as compared with copper), and you've got the potential for some dodgy joints.

Roger is also correct, though. If you did the soldered connection up tightly it would perform more or less as well as the bare end. A loose connection, along with the corrosion that forms on the surfaces, will end up causing a resistive join, and hence heat.

None of this has anything to do with the topic, though. You won't cause fuses to blow with weak connections.

And Carbonator, if you make that kind of reference to uni degree desk jockeys again, with your track record for completely ignorant comments on electrical circuits, I will make it my business to hand you your arse in every single thread you post. You're out of your depth, swim for the shore.

 

[MartinS]

I would be betting that your voltage is dropping sufficiently below 240 to put the line current over 10 Amps.

If you have a multimeter - measure the voltage before and after you turn your URN on - if you are dropping below 240Volts (you almost certainly will be) then the current will be > 10 Amps given a fixed resistive load. Depending how much over you are will dictate the time to blow a 10A fuse.

Why is this such a common misconception? I thought if people knew only one thing about electricity, it was Ohm's law, yet this pearler keeps coming up.

Ohm's Law: I = V / R. The resistance is constant in an electric element, so if you decrease the voltage, you decrease the current.

 

[MartinS]

Im not sure what you guys do for a living, But if your not qualified to do so dont give out information regarding electrical work. I have seen some stupid things done from second hand information and people do get hurt.

And yes i am qualified to comment.

I'd love to see these "How do I screw around with 240V" style threads banned. 99% of people responding have no idea what they're talking about, and worse: don't know it. The people asking the questions are never going to listen to the other 1% (professionals in related fields, but unlicensed) who are trying to explain that the information is wrong, and they need an electrician. Licensed electricians are never going to post answers online for obvious reasons.

It's only a matter of time before someone gets this shit wrong.

 

[bill_gill85]

:icon_offtopic:

Whilst the cons of soldering 240V mains is being brought up, I recall either reading or being told that soft solder (60/40 Tin/Lead, rosin core... whatever) can "cold flow" under pressure, making it dangerous to use tinned wires in terminal blocks for 240 V wiring, as the termination loosens over time. Also, with what limited supvervised work I have done, bootlace ferrules were used on all wires going into terminal blocks (including 800V 3 Phase). Is this standard practice for all wiring or only specialised cases? This becomes impractical for most DIYers that don't do this stuff all the time as the correct crimp tools are not cheap & the cheap ones are well... cheap.

 

[Carbonator]

I recall either reading or being told that soft solder (60/40 Tin/Lead, rosin core... whatever) can "cold flow" under pressure, making it dangerous to use tinned wires in terminal blocks for 240 V wiring, as the termination loosens over time.

This my point. DIYers think they get a great termination by soldering copper wire strands, then they get a nice tight fit in a screw termination. Problem is the wires mostly do get a bit of manipulation in the equipment, thus fractionally loosening the termination because the solder is so soft.

There is nothing like a nice tight fit of a screw bighting firmly into tightly twisted shiny Hard Drawn copper wire strands, without severing any, to ensure a robust termination to prevent resistance.

bootlace ferrules were used on all wires going into terminal blocks (including 800V 3 Phase). Is this standard practice for all wiring or only specialised cases?

There is a physical reason for crimp terminals with the Ferrules. There is a chance of stranded wires being manipulated after the termination is made in relation to the properties of copper being a soft metal. When copper is bent, it becomes harder and fractures occur in the strands, therefore, there is a need to move the bending point of a stranded copper wire away from the clamped termination point to avoid fracturing at the clamped point, as it is already under great stress from the clamp in the termination. Using crimp terminations assists in providing a termination to an Aus Standard.

 

[reVoxAHB]

I want to take a moment to thank everyone for such impassioned and thorough replies.

I will absolutely have another sparkie around, preferably one with an association to AHB/brewing community (the thread a few weeks ago asking for a compile of AHB tradesmen sounds real handy atm), and reg offered to pop around, pending milage. Happy to cover petrol mate, and shoot you my finest.

And I'm bummed the sparkie I had around, didn't take care of me (or worse). Screwtop's likely hit the head on the nail where he pegged him as being a contracted installer (or sorts!?) as our regular electrician was in hospital with health issues (who we rang, and put us onto the bloke who came out).

I have taken comments on board to rectify the obvious things I should have done from day 1 like glands, securing the terminal blocks and so on. And before I mess with fuses, etc. I'll have a sparkie advise.

Thank you again all, for your time and direction.

reVox

 

[reg]

Revox

I have shot you a PM and will more than likely head to Yarraville on Sat morning to G&G for some yeast so will take that long trip over the westgate to your place from Yarraville. :lol:

I will call Friday to reconfirm.

:icon_cheers: Reg

 

[schooey]

Why is this such a common misconception? I thought if people knew only one thing about electricity, it was Ohm's law, yet this pearler keeps coming up.

Ohm's Law: I = V / R. The resistance is constant in an electric element, so if you decrease the voltage, you decrease the current.

Maybe I'm wrong, but I think Roger was meaning that the suplly voltage maybe lower at the OP's place than the standard used 240V. Which is very much the case at my place, stick a multimeter in the wall at my house and you only get 231V

Maybe I'm wrong here too, but you've quoted the Ohm's Law formula for resistance. I always thought the formula for current drawn was I=P/V

Therefore at my place it would be I= 2400/231 = 10.39 A

 

[Jono_w]

Maybe I'm wrong, but I think Roger was meaning that the suplly voltage maybe lower at the OP's place than the standard used 240V. Which is very much the case at my place, stick a multimeter in the wall at my house and you only get 231V

Maybe I'm wrong here too, but you've quoted the Ohm's Law formula for resistance. I always thought the formula for current drawn was I=P/V

Therefore at my place it would be I= 2400/231 = 10.39 A

schooey

A resistive element that has a rated output of 2400W @ 240V .
The resistance of 24ohms is the constant not its energy(watt) output.

Current of element without measuring it = Rated watts / rated voltage

I=P/V

2400 / 240 = 10amps

-now resistance of element

R = V / I

240 / 10 = 24ohm

-Now you have the constant resistance you cant try different voltages to get your current

I = V / R

231 / 24 = 9.6 amps

Hope this helps
jonathon.

 

[eamonnfoley]

I would be betting that your voltage is dropping sufficiently below 240 to put the line current over 10 Amps.

If you have a multimeter - measure the voltage before and after you turn your URN on - if you are dropping below 240Volts (you almost certainly will be) then the current will be > 10 Amps given a fixed resistive load. Depending how much over you are will dictate the time to blow a 10A fuse.

I would be putting a bigger fuse in - 16A.

I would also be checking that your shed is on an RCD supply. Much more important than short circuit protection.

RM

Agree here. Your fuse should be rated comfortably above your rated load, as its real purpose is to blow on fault conditions (short circuits) where the current will significantly higher than 16A - so 10A is too low. I agree with 16A.

Also one of your comments it about a 10A rated extension cord is alarming. Using a 16A fuse together with this is dangerous. i.e. you might burn out the cord as it may not be protected.

Actually I think wiring up equipment of this power rating is a bit dangerous for somebody who is not a licensed electrician.

 

[schooey]

Edit: Sorry just re-read all the above posts. thanks for the lesson..

 

[eamonnfoley]

schooey

A resistive element that has a rated output of 2400W @ 240V .
The resistance of 24ohms is the constant not its energy(watt) output.

Current of element without measuring it = Rated watts / rated voltage

I=P/V

2400 / 240 = 10amps

-now resistance of element

R = V / I

240 / 10 = 24ohm

-Now you have the constant resistance you cant try different voltages to get your current

I = V / R

231 / 24 = 9.6 amps

Hope this helps
jonathon.

Correct - and you will find that devices and equipment have a range of voltage tolerances. If V gets too low, the equipment may not work/cut out. Being a simple resistive element here, it will probably just not heat up as much.

Your utility company is obligated to supply you a certain voltage range (e.g. 240V +/- 5% depending on state), so voltage problems at home should be referred to them. 231V (as mentioned in the thread) is usually considered an acceptable voltage.

 

[LethalCorpse]

Guys, please stop guessing at this stuff.You're muddying the waters.

The power rating of an element (eg 2400W) is only correct for a given voltage. The element is basically a fixed resistance (it varies slightly with heat, but for our purposes we can call it fixed). Consider an element which has a resistance of about 24Ohms. When you connect this element to 240V, it will draw 10A (I=V/R). This amounts to 2400W (P=VI), so it's quite valid to label and sell that as a 2400W element. But if you then connect that element to 220V, it will only draw 9.17A, or 2016.67W. If you connect it to 250V, it will draw 10.42A, or 2604.17W.

Now what if you determine your power labelling at 230V, since that is after all the actual standard voltage? A 2400W element would then be 22.04ohms, and draw 10.43A. Now imagine you've got 10% tolerance on your manufacturing process, so the element could be as low as 19.84ohms. Let's say an element rolls off your line with a resistance when hot of 21ohms. You then sell this to a customer in part of Australia where the mains voltage is normally 245V. That element will draw 11.67A, more than enough to blow a 10A fuse in fairly short order.

I hope this clears up much of the confusion, but I should specifically address some of the incorrect comments in the last few posts. Schooey, as Jonathon said, you're assuming a 2400W element always draws 2400W regardless of the input voltage. It doesn't.

Roger, you've buggered your calculation. A 10ohm element on 231V will draw 23.1A, or 5336W.

foles, you've missed the point of what the fuses are for. The fuse in the equipment should ensure that it can't draw more than 10A, which is the rating of the outlets and plugs before it. Almost all domestic 10A outlets will be protected by 16A fuses, because the manufacturer of the equipment is supposed to ensure that it doesn't exceed 10A. The problem here is that we've got a 10A rated system trying to deliver a little over 10A. The fix is not to remove the fuse, or use a bigger fuse. The fix is either to install higher rated outlets and interconnects (and hence fuse), or a lower rated element.

 

[eamonnfoley]

2.) I was using a 15A cord/plug from HLT element to MM/control plug. He thought the 15A cable may have been "pulling too much" and could be causing a fuse-blow issue. I removed the 15A cable over the weekend, replacing with common 10A extension cord. I blew 2 fuses on Sat's brew day (didn't resolve).

Is this really advice from an licensed electrican? The "pulling" comes from the connected load, i.e. element. The cable should always be rated higher than the protective device (i.e. fuse) and the load. Otherwise you risk burning your house down.

 

[schooey]

Schooey, as Jonathon said, you're assuming a 2400W element always draws 2400W regardless of the input voltage. It doesn't.

Yep.. got it from johnathon's post, dude... but thanks for your reassurance