Mashmate/2400w Element Blowing Inline 10a Fuse

[reVoxAHB]

Hi gang,

I have a relatively annoying issue where my MashMate controlled HLT is regularly blowing fuses. I blow 1 or 2 fuses each brew day at no significant point (intermittent).

I have wired the MM with inline 10A fuse, as per LethalCorpses' diagram:


I have omitted the optional master DPDT switch. My element is a 2400W bolt on, with ground. My power source is a power-point (close to brewing area by 1m) on an independent circuit rated to 16A. Nothing shares this power-point.

Pics of my control box/wiring:


Now, before I have my head ripped off, I've had a licensed electrician out to the house (who installed the power-points on independent circuit to my brewing area) who examined my wiring to LC's diagram (including the wiring to HLT) and said all looked fine. He saw no real reason or had any indication as to why I might be blowing fuses. He did, however, offer the following suggestions:

1.) Previously, my nearest power point to brewing area was 10m away where I ran a very long 10A extension cord to control box/kettle. He thought the long run might have created issues, and his installing proper power points (1m to brewing) would rectify (it didn't).

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).

3.) He suggested I could have a loose wire. I removed, respliced and rejoined all connections confirming all is tight to no avail.

Finally, I ordered a second MashMate for use with my 2000W herms in dedicated HE. Thinking it could be the MM controller, I swapped the new MM with the would be faulty MM.. placing old controller on the herms HE and new unit on HLT. Still blowing fuses only on HLT. Herms control is fine.

I don't think I've swapped transformers between the two controllers, fwiw. Could a faulty transformer be the cause? Any other red-flags present themselves? Been blowing fuses with this since day one. Always have a box of 5 replacement fuses available on brew-day. Annoying and haven't made it around to posting until now.

Thanks guys,
reVox

 

[Tony M]

Sounds like it shouldn't happen. but 240 V X 10A = 2400W so you are right on the edge. How far beyond the nominal rating does your element have to be before there are problems. 50 years ago when I was studying electrical technology, I was forever amazed how far off the nominal rating (up to 30%) actual values were with electrical components.

 

[roger mellie]

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

 

[barfridge]

When you run a fuse of exactly the same power draw as your load, you are bound to run into problems. The fuse is designed to blow when you run 2400W through it, and you are running 2400W through it

Replace with a 12 or even 15 amp fuse, and all should be good.

disclaimer: I am some random guy on the internet, I am not even qualified to tie my own shoelaces, let alone give out electrical advice. Use at your own risk, do not take internally, and if symptoms persist, RDWHAHB (in the dark)

 

[Bribie G]

Yup my 2400 urn is right at the limit, when I'm doing a boil I need to switch the garage fridge off for the duration or it trips the circuit breaker.

 

[Doogiechap]

Bloke you may have something happening like the element shorting to earth when at a certain temp. You can buy these plug in safety switches which will trip in such a scenario before blowig the fuse (and possibly saving your bacon too !)
Cheers
Doug
PS Saw RM's post and concur with his opinion on a dedicated RCD although the cheap plug in unit will give you a quick heads up one way or another

 

[LethalCorpse]

Hi gang,

I have a relatively annoying issue where my MashMate controlled HLT is regularly blowing fuses. I blow 1 or 2 fuses each brew day at no significant point (intermittent).

I have wired the MM with inline 10A fuse, as per LethalCorpses' diagram:
View attachment 26794

I have omitted the optional master DPDT switch. My element is a 2400W bolt on, with ground. My power source is a power-point (close to brewing area by 1m) on an independent circuit rated to 16A. Nothing shares this power-point.

Pics of my control box/wiring:
View attachment 26795

Now, before I have my head ripped off, I've had a licensed electrician out to the house (who installed the power-points on independent circuit to my brewing area) who examined my wiring to LC's diagram (including the wiring to HLT) and said all looked fine. He saw no real reason or had any indication as to why I might be blowing fuses. He did, however, offer the following suggestions:

1.) Previously, my nearest power point to brewing area was 10m away where I ran a very long 10A extension cord to control box/kettle. He thought the long run might have created issues, and his installing proper power points (1m to brewing) would rectify (it didn't).

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).

3.) He suggested I could have a loose wire. I removed, respliced and rejoined all connections confirming all is tight to no avail.

Finally, I ordered a second MashMate for use with my 2000W herms in dedicated HE. Thinking it could be the MM controller, I swapped the new MM with the would be faulty MM.. placing old controller on the herms HE and new unit on HLT. Still blowing fuses only on HLT. Herms control is fine.

I don't think I've swapped transformers between the two controllers, fwiw. Could a faulty transformer be the cause? Any other red-flags present themselves? Been blowing fuses with this since day one. Always have a box of 5 replacement fuses available on brew-day. Annoying and haven't made it around to posting until now.

Thanks guys,
reVox

First off, your sparky is an idiot. Don't ever trust him with your house again - he has absolutely no understanding of electricity, nor probably the difference between his arse and his elbow. Things he said that were wrong:
-Your wiring looks fine: it doesn't, and a decent sparky should have rapped you over the knuckes for it. That doesn't mean it won't work, it's just that it's very rough and not something a sparky should consider "fine". At the very least you need cable glands or cord grips to prevent the metal edges from fraying the mains cords, but I'd also screw down those terminal blocks and rewire it so everything goes in straight lines and you can see where it's going. Most importantly, this allows you to see when something's wired to the wrong place, or wires are left loose or whatever - at the moment, I can't really see that.

-The long run could be causing the blown fuses: No, it couldn't. In fact the longer the run, the less likely it would be to blow fuses. But we'll come back to that in a minute. Basically, I'm sure it makes brewing much easier to have the outlet right there, but as you found, it can't possibly make any difference to whether the fuse blows. Anyway, the run is just as long now as it was before, it's not like the power miraculously changes when it goes from being in-the-wall power to on-the-extension-cable power.

-the 15A cable may have been "pulling too much" and could be causing a fuse-blow issue: This is the particularly stupid bit. Cable doesn't draw power (at least, not unless you short the two wires together). The load draws the power. The gauge of the cable determines the maximum current you can safely draw down it without causing excessive heat in the cable. 15A cable is heavier duty than 10A cable - it has thicker conductors, which have lower resistance than thinner ones. The lower the resistance, the better, particularly if you plan to be drawing close to the rated current over a significant distance. You can put the 15A cable back on, in fact, I highly recommend doing so.

The only thing he said which was actually worthwhile was that you might have a loose connection. He probably said it for the wrong reason though - a loose wire which just isn't making good contact won't cause the fuse to blow, but a loose one which occasionally touches the chassis when you give it a knock will. Since you're certain you've checked all the connections, we can probably rule that one out.

My thoughts on possible causes, in order of likelihood:
-Tolerance. You're dealing with a system of components that have very wide tolerance, and you're operating right at the edge of their ratings. Your element is rated to 2400W, but is that at 220V or 240? How tightly do the Chinese manufacturers of the element control the resistance of their elements? Do they just have an approximate length that they work on? Now, what is the actual voltage that you've got at your powerpoint? In Australia, we think of mains power as being 240V, but it's very unlikely that you're actually getting 240V. Since the year 2000, the standard has actually been 230V, to bring us in line with Europe. But the tolerance on that level is +10% -6%, which means that your mains power could be anywhere from 216-253V. This will vary based on the grid in your area, how far you are from the substation, etc. As I recall, it's allowed to go outside these ranges for brief periods of time, so you could be getting spikes which cause the blown fuse. Back to what I was talking about before, as you go over distance the resistance in the cable causes a voltage drop with the current you're drawing from it, so the voltage will be (marginally) higher the closer you are to the source. The upshot of all this is that if your element is a bit heftier than you thought, and your power is on the high side, your element could easily be drawing 12A in normal operation

-Faulty element. An element is a piece of resistive wire surrounded by some non-conductive stuff, then a sheath which is connected to earth. When an element fails, that resistive wire just blows at some point, and the element is an open circuit. But sometimes, one of the broken ends of wire inside the element can short out against the earthed sheath. Current then goes down the active wire, along the first portion of the element, out onto the sheath and back to earth instead of neutral. If this was the case and you had an RCD, it would trip, but I wonder if this sparky of yours has thought to install one for you. The end result is an element which draws more current

-Dodgy transformer. The transformer could have a nick in the insulation of its winding wire, which causes two turns to short together (thus decreasing the overall resistance of the transformer, increasing the current it draws, and blowing the fuse). This could explain the intermittent nature of the fault if the wires were separate when you first turn it on, but come together as the transformer heats up and expands and vibrates. You can check this easily by swapping your two transformers.

-Fuse Gremlins.


By far the most likely is the first scenario - the element is just drawing a bit more than 10A, and the fuse is faithfully popping after running like that for a while. I don't recommend just replacing it with a 15A fuse, though, because the outlet is still only rated at 10A. Why the turkey didn't just install a 15A point for you when he moved it is beyond me. I suggest calling a proper electrician, get him to install a 15A outlet (with appropriate configuration in your breaker box) so you can use whatever element you like. While he's there, get him to check over everything this other clown has done and redo it if necessary.

Otherwise, just get a slightly smaller element and a mains timer. Set it to start heating your water at some time in the morning and sleep in a bit longer on brew day.


EDIT: when i started typing that, there were no replies yet. I need to learn to rant faster. Or less. Or something.

 

[bum]

-the 15A cable may have been "pulling too much" and could be causing a fuse-blow issue: This is the particularly stupid bit. Cable doesn't draw power (at least, not unless you short the two wires together). The load draws the power. The gauge of the cable determines the maximum current you can safely draw down it without causing excessive heat in the cable. 15A cable is heavier duty than 10A cable - it has thicker conductors, which have lower resistance than thinner ones. The lower the resistance, the better, particularly if you plan to be drawing close to the rated current over a significant distance. You can put the 15A cable back on, in fact, I highly recommend doing so.

I wanted to say this, and pretty much everything else in Lethal's post, earlier but am not in anyway a qualified sparky (merely very interested in the field) so I didn't.

Pretty much everything your relate that he has said is bad advice. Get a second (professional) opinion.

 

[JasonY]

I would agree that the likely cause is that you have a 10A fuse on a circuit which designed to hopfully get 10A so given tolerances and all that you are bound to run into problems.

I would ask why you even have the fuse in your circuit? Your outlet will be protected by an appropriate breaker let it handle overcurrent protection. I would be certain you have a earth leakage breaker on your house, best money you can ever spend.

 

[reg]

I agree with what has been stated above about that sparky. But it has been covered so I wont kick him anymore.

Sometimes when something is turned on there will be an initial inrush of current, this can happen on start up or cycling power etc.
You can buy a type of fuse called a motor start fuse, these will stop a fuse from blowing initially on an inrush.
Go to an Electrical wholesaler such as Middys and ask for some motor start fuses or slow blow fuses. should help but get them in 12A if possible.
Remember though that without an RCD you are really only protecting from a short circuit or overcurrent not from earth leakage faults, so that would be a good investment as well.

P.S Revox if you want and you are not miles from Werribee I can come out and have a look and a chat and save you getting another sparky out if you want.
PM me if interested.

Reg

 

[flattop]

Lethal is right, i am not a Sparky but have worked in an associated field for 20yrs and although i don't do circuits anymore i think the most likely problems are,
A) a slow blow on the fuse which means that the current is right at tipping point for a while then off she goes because you are operating right on the edge of the upper limit
B) shorted windings in the transformer which will cause a slightly higher current draw but not enough to trip the switch the moment you turn it on....
C) a shorted element which is less likely as it is more likely to cause the switch to trip immediately.

Do not just upgrade your fuse... You could trial it for ONE test run to see if it solves your problem but you are not playing in a sandbox environment. You will void your house insurance.... If testing on a 15A fuse works then consider....
The wiring (from what i remember) will handle 15A without a problem as a 15A power point has only a larger earth pin. Replace the power point!
Get it done by a good sparky and be safe

The sparky you got in shouldn't have a license as far as i'm concerned, but there are dopes in every field.

 

[Batz]

The wiring (from what i remember) will handle 15A without a problem as a 15A power point has only a larger earth pin. Replace the power point!
Get it done by a good sparky and be safe

The sparky you got in shouldn't have a license as far as i'm concerned, but there are dopes in every field.

I'm afraid you need to rewire the power source first,it needs a 15a feed,replacing just the power point will do Jack sh%t.
When I had a power point installed for my brewing I went straight for 15a,the cost is about the same,I'm surprised your sparkie did not advise this.

Batz

 

[Carbonator]

I would be looking at resistance in the sockets (male and female) at the ends of your lead/s. If the cable feels warm near the sockets, you could have resistance issues with the in the pins and corrosion with age. If they are not shiny, then you got resistance. I know it's a bit hard to see inside the female plug, but thats the risk you take when using old extension cords. (not saying yours is old)

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;

 

[QldKev]

I think the rest has basically covered this but,
a) It looks like you only have small gauge cable in the control panel, if so don't even think about a bigger fuse until this is resolved.
B) The 2400w element may actually be drawing over, you would need to measure the true load.
c) Add 5w for the controller itself (so if actually using 2400w add 5w = over loaded)
d) Please don't take offense to this but looking at that wiring, it is why they made it illegal for us to do it ourselves. No grommets, mixed color coding and with the mess of wires crossing each other there is no way to diagnose anything.
e) 100% get a RCD in there. Don't rely on the main one back at the power box. The closer the RCD is to the work site the more effective they are.

QldKev

 

[Jono_w]

Scary stuff guys,
My only advise is to find a Decent licensed electrician who is willing to test , tag and put his name to his work.
There is alot at stake when these things go wrong not worth the risk.
If I wasn't so far away I would be more than happy to help out.

Jonathon (A grade Electrician)

 

[LethalCorpse]

Guys, it's not a surge current issue. We're dealing with almost purely resistive elements here, not motors or switchmode power supplies. Surge/inrush is only an issue on inductive loads. A slow blow fuse would help if the spikes are being caused by dodgy power or flyback from other motors in the vicinity, though.

Carbonator, go read my post again. Increased resistance in his fittings etc will not cause fuses to blow. They would cause excessive heat, which would cause problems down the track, but that's not the problem we're addressing here.

QldKev, DIY wiring of non-fixed appliances isn't illegal where reVox is (it's only in QLD), but that doesn't mean you shouldn't take every precaution and do it as neatly, professionaly, and above all, safely as possible.

reVox, best course of action is to get a new spark out, get that point replaced with 15A (he may not need to replace anything at the breaker box if it's a dedicated circuit, alternatively, he may decide to increase the fuse and give you two points - he should be the expert on what he's allowed to wire to what), then replace all your wiring with 15A cable (screwing down those terminal blocks and routing the cables neatly so you can see everything), add cable grommets (one for each cable that goes in and out) and then (and only then) replace your 10A fuse with a 15A.

 

[roger mellie]

Guys, it's not a surge current issue. We're dealing with almost purely resistive elements here, not motors or switchmode power supplies. Surge/inrush is only an issue on inductive loads. A slow blow fuse would help if the spikes are being caused by dodgy power or flyback from other motors in the vicinity, though.

Carbonator, go read my post again. Increased resistance in his fittings etc will not cause fuses to blow. They would cause excessive heat, which would cause problems down the track, but that's not the problem we're addressing here.

QldKev, DIY wiring of non-fixed appliances isn't illegal where reVox is (it's only in QLD), but that doesn't mean you shouldn't take every precaution and do it as neatly, professionaly, and above all, safely as possible.

reVox, best course of action is to get a new spark out, get that point replaced with 15A (he may not need to replace anything at the breaker box if it's a dedicated circuit, alternatively, he may decide to increase the fuse and give you two points - he should be the expert on what he's allowed to wire to what), then replace all your wiring with 15A cable (screwing down those terminal blocks and routing the cables neatly so you can see everything), add cable grommets (one for each cable that goes in and out) and then (and only then) replace your 10A fuse with a 15A.

Dont you mean removing the in line fuses?

If a fuse provides no segregation - what use is it? Uprating the entire circuitry to cope with 15 Amps - negates the need for the inline fuses.

RM

 

[LethalCorpse]

Dont you mean removing the in line fuses?

No, I didn't.

 

[roger mellie]

No, I didn't.

Fair enough - but I would have thought that the in line fuse would be a bit superflous. The MCB or rewirable at the fuse board end would give all the protection required.

He already has an effective means of isolation - A 3 pin Plug - lose the fuse - its clearly creating the intermittent trips.

RM

 

[LethalCorpse]

The circuit breaker is to protect against a short in the cable starting a fire. The equipment that you plug into the outlet is supposed to ensure that it doesn't draw more than the upstream components allow - in this case 10A. It clearly is drawing more than it's allowed to, and the fix for that is not to remove the part which prevents it from doing so. Drawing more than the rated current of the wall outlet could cause a fire in the wall outlet. Yes, I know that 12A is extremely unlikely to start a fire in a 10A outlet, but that's not the point. It's not rated to handle it, so don't force it to do so.