# RCDs and cable dimmensions



## dave_h (5/1/16)

Hi everyone,

Im in the process of upgrading my brew pots to immersion elements (from over the side elements) and have a couple of questions.

I have been using two portable RCDs (16 Amp which trips at 30mA)





Am I correct in thinking that these will be sufficient? I do not have a RCD in my main house board. I read some conflicting stuff that 30mAmp would still kill you but all of the rail mounted RCDs ive seen seem to have the same trip level.

Also, Im currently using 3G 1.5mm extension cables, and ive noticed that these are a little warm to touch after an hour, would it be worth upgrading to 3G 2.5mm? Will be using them upto 16Amp.

SSRs to control the boil rate, Im planning on getting them rated to 40Amp.

Thanks in advance

Dave


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## MitchD (5/1/16)

dave_h said:


> Hi everyone,
> 
> Im in the process of upgrading my brew pots to immersion elements (from over the side elements) and have a couple of questions.
> 
> ...


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## TheWiggman (5/1/16)

Do you understand the purpose of RCDs? They are designed to protect someone from getting electrocuted by detecting when there is a path between the source and earth. They aren't designed to protect equipment. Not trying to be patronising, just making sure you have the right intent because if you are able I would install the RCD at the mains instead of locally at the brew system.

Getting larger SSRs isn't a bad idea because they will run at a lower temperature than a 25A under the same current. It's the difference of about $1 from China, and depending on how you're intending to mount it might be a worthy investment.


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## Camo6 (5/1/16)

I was taught that around 50mA is enough to kill you, hence the 30mA limit, but it depends on the path taken through your body, skin resistance at the time, heart condition etc. Regardless to say, no amount of AC current through you would be nice.

What are the sizes of the new elements? If they're more than 2400W you're pushing the recommended limits.

Also, do the plug in RCD's also trip with current overload or is it just their rating? I assume they do but they look a bit like cheap ebay jobbies. If not I'd want to know that my circuit protection was adequate too. Do you have circuit breakers at the board or old style ceramic fuses?


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## DU99 (5/1/16)

the leads do they a straight run and have no loop in the them


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## spog (5/1/16)

If its getting warm it's being stressed = danger.


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## dave_h (5/1/16)

Many thanks for all the replies,


TheWiggman

"Do you understand the purpose of RCDs? They are designed to protect someone from getting electrocuted by detecting when there is a path between the source and earth. They aren't designed to protect equipment. Not trying to be patronising, just making sure you have the right intent because if you are able I would install the RCD at the mains instead of locally at the brew system."

Not patronising at all, I did read somewhere that most of the plug in RCDs were more for equipment safety rather than personnel so I was a little confused. I have been thinking of getting some RCDs put into the main board so might just do this



Camo6

"What are the sizes of the new elements? If they're more than 2400W you're pushing the recommended limits.
Also, do the plug in RCD's also trip with current overload or is it just their rating? I assume they do but they look a bit like cheap ebay jobbies. If not I'd want to know that my circuit protection was adequate too. Do you have circuit breakers at the board or old style ceramic fuses? "

I have not decided on the elements yet, I was thinking of these two 

http://www.aliexpress.com/item/AC220V-2000W-Metal-Electric-Heating-Tube-Water-Heater-Element-Silver-Tone/32411921460.html?spm=2114.01020208.3.153.vyqMZB&ws_ab_test=searchweb201556_3,searchweb201644_5_79_78_77_82_80_62_81,searchweb201560_2

http://www.aliexpress.com/store/product/240V-2500W-Immersed-Foldback-Heating-Element-Screw-In-1-INCH-NPT-Thread-Tubular-Heating-Element/1862595_32546357152.html

Im based in Sweden at the minute and have 230V (223V when tested yesterday), I have been using a 3.2KW over the side element without any issues on a 16Amp circuit. I calculated 230V at 16Amp max was 3.6KW

Currently also trying to determine what their watt densities are and if they are low enough.

I have old school ceramic breakers, but also have three phase power (with 3 phase to single adapter), so each brew circuit is on its own with nothing else!

The RCDs I have are Everflourish EMP200S


An integrated earthed socket, with child protection IP44 for operation in indoor or outdoor use (outdoors or in damp areas, observe the operating position) Switching Current: 30mA switching time <30ms Bipolar disconnection
Can be connected to grounded mains power socket, 230V ~ / 50Hz Max. Total connected load 3680W (230V ~, 16A) resistive load

So they are supposed to trip within 30ms so should be ok? But they dont have overload protection so would have to rely on the fuses.


DU99

"the leads do they a straight run and have no loop in the them"

They are quite straight, they are not really hot but warmer than the surroundings, just thinking that if Im going to make some cables up (as I will put a PWM and SSR in ) then I could go a cable with more safety margin in. Ambient temps are not really too much of a problem here (no 40C here, currently -6C.......).

Thanks for the help guys, Im planning on getting an electrician to check it all out before use but its good to get things as close to right as I can before I get one out.


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## Diode (5/1/16)

*Cabling is designed with a working temperature of 60c-110c when used in 40c ambient temperature, 1.5mm of a reputable brand can take 16a.*

Are you F^&^%$G serious

I hope those cables are very short

You need to spend a lot more years in the game my friend


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## MitchD (6/1/16)

Diode said:


> *Cabling is designed with a working temperature of 60c-110c when used in 40c ambient temperature, 1.5mm of a reputable brand can take 16a.*
> 
> Are you F^&^%$G serious
> 
> ...


Thank you for your insightful responce, do you care to elaborate or provide some assistance to the OP?


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## Pokey (6/1/16)

The temperature that will start to damage your cables will depend on what they are insulated with. Personally if they are warm I would use bigger cable.
If you're looking at putting in RCDs at the board get the breakers changed as well, new breakers are better than old ones and significantly better than rewireable fuses.


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## TheWiggman (6/1/16)

Big entrance there by Diode


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## Diode (6/1/16)

Ttry running 1.5mm with 16A over say 30-40m and see how you go. Betcha it gets warm


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## burrster (6/1/16)

What Diode is trying to say is the cable size is not the only factor in how much current a cable can carry. Cable length and how thermally insulated it is play a big part too. 16A through 1.5mm cable is not the best idea in my opinion and using 2.5mm cable would be a better/safer option.


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## Diode (6/1/16)

15A cct requires min 2.5mm


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## Camo6 (6/1/16)

MitchD said:


> *Cabling is designed with a working temperature of 60c-110c when used in 40c ambient temperature, 1.5mm of a reputable brand can take 16a.*


Nothing untrue about this statement. _Flex_ wiring in 1.5mm2 has a max recommended current rating of 16A. The OP never mentioned fixed cabling. Certainly de-rating factors still have to be considered but MitchD didn't allege otherwise. Hardly worthy of such a vehement reply Diode but eloquently rephrased by Burrster.

On the subject, try and find an extension lead in any hardware store with a greater diameter than 1.5mm2. Even the heavy duty type are generally 1.5mm2 it's just that they use a heavy duty insulation. I've been told flex has a greater current carrying capacity than stranded or solid due to the greater surface area and the skin effect in an AC circuit but I'll leave this to the experts. But the old adage bigger is better is generally true in this regard.

If I was the OP I'd be ensuring my circuit protection and RCD devices were all up to scratch and upgrade to 2.5mm2 wiring. Beats burning your house down.


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## spog (6/1/16)

Diode said:


> 15A cct requires min 2.5mm


The diagrams you have posted means bugger all to many here,including dumb bastards like me.
Could you please put your explanation in dumb bastard words for us.
Please understand I'm not having a go at you but electricity is lethal ( oh so many comments in other posts) so others may benefit from advice.
And now this thread is likely to go off the rails, re: get a sparky get a sparky......


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## SBOB (6/1/16)

spog said:


> The diagrams you have posted means bugger all to many here,including dumb bastards like me.
> Could you please put your explanation in dumb bastard words for us.
> Please understand I'm not having a go at you but electricity is lethal ( oh so many comments in other posts) so others may benefit from advice.
> And now this thread is likely to go off the rails, re: get a sparky get a sparky......


the symbols in his signature have nothing to do with wire current ratings or RCDs


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## spog (6/1/16)

Ahh thanks,see I am a dumb bastard.


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## dave_h (6/1/16)

Thanks guys,

My cables are around 5m extension type, store bought, they are not as well insulated as some of the longer/more industrial ones I have. I will make some cables up with 2.5mm for use with SSRs. Cant see any plugs rated higher than 16Amp but will talk to my sparky

I will get a sparky to put in some RCDs when he has a look at my elements/pots.

These are the type of fuses I have in my main board.



After having a sparky out for something else I said that I wanted to upgrade them and he recommended not to, cant remember his reason. He thought it was a good idea to put in some RCDs anyhow.

But party back to one of my original questions, are these portable RCDs any difference to the rail mounted ones, or do the rail ones trip faster. 

Ive also read somewhere that you should not have two RCDs in the same circuit for some reason, but can talk to the sparky.

Thanks

Dave


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## Camo6 (6/1/16)

I thinking having more than one RCD in a circuit can cause nuisance tripping but I've never experienced it with my controller.

If those RCD's are of decent quality and have the same ratings then they should function the same as one in a switchboard except obviously it'll only isolate downstream from the unit. Most worksites run on portable rcd's until the power is commissioned.


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## lael (7/1/16)

I bought a couple of power boards with RCDs on them. They definitely work. I was hoping that the power board RCD would mean the main board wouldn't switch, but the main board had triggered as well each time so far.


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## jibba02 (7/1/16)

As long as the rcd has an Australian standards sticker on it. It will be fine


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## Camo6 (7/1/16)

Or a Swedish standards sticker?


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## spog (7/1/16)

lael said:


> I bought a couple of power boards with RCDs on them. They definitely work. I was hoping that the power board RCD would mean the main board wouldn't switch, but the main board had triggered as well each time so far.


Double up,I don't see any harm in that.


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## lael (7/1/16)

Yeah, no harm, but curious why it triggers both. I was hoping that the powerboard one would stop the current fast enough that the main switch would continue operating.


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## TheWiggman (7/1/16)

I'd say because both would detect the earth leakage. If you're talking 30ms on a solid state device it would be on its way to tripping before the downstream one tripped at a guess.


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## lael (7/1/16)

yeah, that is what I was guessing, or that the current isn't immediately clamped, and so trips the first one, which clamps/goes off, but not before the differential travels past and trips the second


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## jimmy_jangles (7/1/16)

Diode said:


> *Cabling is designed with a working temperature of 60c-110c when used in 40c ambient temperature, 1.5mm of a reputable brand can take 16a.*
> 
> Are you F^&^%$G serious
> 
> ...


Great way to reply to people that don't know what they are talking about and are after advice. I assume by the use of the bridge rectifier in your signature you would like people to think you are superior in regards to your electrical knowledge? Maybe just share that knowledge next time instead of pointing out peoples mistakes.


So i've had my rant, now what old mate means is that when you increase a cable's length, you increase the resistance in the cable, which in turn decreases the amount of current that it can carry, If you wanted to search for the standards, it's AS 3008 that we use here ( it may be a diff standard over there) and check out table 10 that shows the capacity of twin and earth cables. Keep in mind there are derating factors that apply too, so it's not just the number that the table says, rather that is the number you plug into an equation to give you your capacity. I would be using 2.5mm cable for peace of mind, however the lads were right that most extension leads are made from 1.5mm cable.

The thing you need to keep in mind about that is that these are made with 10amp plugs on the ends of them. Meaning they are really only rated to 10amps. If they were rated higher, for example 15 amps, they would have a different plug on them that does not fit into a 10amp General power outlet. The difference is the size of the earth pin is larger so they can't be plugged into lower rated outlets.

In regards to why the rcd at the boards trip before the portable ones, it would be a timing issue, i'd be willing to bet that the rcd installed in the board is set to trip slightly quicker than the portable one, or may be calibrated a bit better and in turn detect the leakage quicker. Would love to be told i was wrong on this if anyone else has had experience with the prob and knows a bit more about it.

Dave if you have any other questions that you wanted to ask before your electrician comes, feel free to shoot me an email [email protected]

anyway, enough yabbing from me, my glass is empty so it's time to go and refill!


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## dave_h (8/1/16)

Thanks Jimmy_jangles, should be good to go.

I will upgrade the cables, I think the plugs on my extension leads are 16amp ones but when I get new ones I will make sure they are.

Dave


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## GibboQLD (8/1/16)

jimmy_jangles said:


> when you increase a cable's length, you increase the resistance in the cable, which in turn decreases the amount of current that it can carry


Don't you mean voltage?

All things being equal (except cable length in this case), it can carry the same amount of current, but the voltage drop increases with cable length.


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## jimmy_jangles (8/1/16)

GibboQLD said:


> Don't you mean voltage?
> 
> All things being equal (except cable length in this case), it can carry the same amount of current, but the voltage drop increases with cable length.


 Yes you do get voltage drop, but your supply voltage will not change, so the increase in cable length will decrease the current carrying capacity at that supply voltage

that makes sense to me, but i could be explaining it wrong


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## Pokey (8/1/16)

jimmy_jangles said:


> Yes you do get voltage drop, but your supply voltage will not change, so the increase in cable length will decrease the current carrying capacity at that supply voltage
> 
> that makes sense to me, but i could be explaining it wrong


You're combining different issues. Current carrying capacity is based on thermal limits of the cable, there are specified limits on voltage drop that also need to be met, 5% voltage drop I think from point of supply to end of the circuit.


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## klangers (11/1/16)

Just clearing up a bit of confusion here:

RCDs - Residual Current Devices. These detect a current imbalance between the terminals (active and neutral). If there is an imbalance this means that some current is escaping through another path (eg your body). The RCD trips when an imbalance of (usually) 30mA is detected. 30mA flowing through your heart is enough to kill you. Designed to protect you.

CBs - Circuit Breakers. These simply trip when the rated current is exceeded. Designed to protect equipment.

Often, these two functions are combined together into one device. Often they're not too, so be sure what you're doing.

Electricity is like water*. Try pumping heaps of water through a small pipe - you need lots of pressure. Try pushing heaps of current through a small cable - you need lots of voltage.

*for layman comparison purposes


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## sponge (11/1/16)

Afer re-reading what I had posted, I'll happily put my hand up for biggest brain fart of 2016. Klangers is completely correct (below)!

This is why I shouldn't jump straight back into work after a month off..


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## klangers (11/1/16)

sponge said:


> Voltage drop at final load (heating element for example) will increase current draw. Ie, 220V at 3.2kW element draws 14.5A compared to 13.3A at 240V. The smaller the cable size, the larger the voltage drop over the same distance and current..


Not quite. The resistance of the element is constant, and so is the cable (since we're talking a purely resistive load, rather than inductive or capacitive and a constant frequency, and assuming negligible temperature rise). So at your source you have (ideally) 240 V. The 240V is applied to the cable and element, which induces a current to flow. The higher the resistance (longer cable, smaller element), the lower the current that flows. The lower current flow = lower power.

So, if a 3.2 kW element draws 13.33 A at 240 V (at the element), it is an 18 Ohm element (V=IR; R=V/I; R=240/13.33). Assuming your cable has zero resistance for this exercise, if only 220 V makes it to your element then it will only draw 12.22 A, effectively de-rating your element to 2,689 W.


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## sponge (11/1/16)

Completely agree with you mate and have edited my post.

By far one of my silliest mistakes.. Carry on.


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