# Upgrading My Control Panel (2 Pole Rcd Or 1 Pole)



## mxd (29/4/12)

Hi All,

I am going to upgrade my control panel from 2 boxes to 1 box and thought I'll put some RCD's in as well.

I will run a 15A and a 10A into the control box, the 15 will drive the HLT and Pump and the 10 will drive the HX.

I am thinking of having a switch between each PID and the element under control so I may turn the elements off while the pids are still on (monitor temp without heating etc..). A switch for the pump and anything else I can think of or put in latter 

so for my silly Q.

Do I put in a 1 pole RCD or 2 pole RCD, whats the diff, I would have thought they should all be 2 pole ?

thanks
Matt


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## Filby (29/4/12)

Single pole is fine. RCD just looks at the current through active and out through neutral. If there is a variation of around 30mA then it switches off. This is because the only reason there would be a difference in current is due to current leaking through earth (ie the device is down to earth or it has leaked through a human down to earth). Remember, an RCD protects humans and not the wiring, a fuse/breaker protects wiring, not humans.


Fil


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## eamonnfoley (29/4/12)

As long as your mains (that feeds your brewing area) has RCDs (which is law for new places or when you sell a place I think), you really dont need one in your control panel. But it certainly will not hurt, and is essential if you have an old place without RCDs. Actually you should ensure you house has them.

The RCD is a toroidal CT (current transformer) that detects a small current imbalance between the phase and the neutral (return). So if the current isn't fully making its way back to the source, it is going somewhere else (fault), and this unit detects it immediately. It should save you in the absence of proper earthing. An RCD can break by either interrupting the phase (1 pole), or the phase and neutral (2 pole). 3 pole and 4 pole breakers are related to three phase supplies. The breaking part is what the pole reference is about (not the detection).

Cheers.


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## Filby (29/4/12)

foles said:


> An RCD can break by either interrupting the phase (1 pole), or the phase and neutral (2 pole).
> 
> Cheers.




This is what I always thought until I came across a two pole RCD that only switched active. I queried the electrical wholesaler and he said it was some bad legacy terminology that indicated the DIN rail width ie 18mm single pole, 36mm two pole. Sounded retarded enough to be true.


Fil


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## eamonnfoley (29/4/12)

Filby said:


> This is what I always thought until I came across a two pole RCD that only switched active. I queried the electrical wholesaler and he said it was some bad legacy terminology that indicated the DIN rail width ie 18mm single pole, 36mm two pole. Sounded retarded enough to be true.
> 
> 
> Fil



Yeah there seems to be a habit of referring to unit size by number of poles. But technically that is incorrect. You need to know how many poles the circuit breaker actually switches, when considering its impact (in an earthing/protection design) on the system it is part of. Switching poles becomes particularly important when your looking at 3 pole vs 4 pole breakers, and earthing systems containing transformers, generators and other equipment. I deal with this design issue on mine sites as part of my job.

All this wont matter in your house as long as you have an RCD that detects leakage current and interrupts the circuit. A good example is the DIN-SAFE range from Terasaki. You'll notice they refer to 2 pole and actually switch 2 pole.
http://ecat.nhp.com.au/content/NHPECatData...asaki/DSRCB.pdf


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## Screwtop (29/4/12)

If you have a safety switch (earth leakage) in your switchboard then no advantage using an RCH in your controlbox. A single pole and double pole RCD are basically the same thing, one being larger than the other. Both switch active and neutral, the double pole refers to it taking up two slots in your switchboard, the single pole takes up one, simple as that. The later technology single pole is usually more expensive......naturally if you have limited space in the switchboard, they're gonna hit you up, cos they can :lol: 

Bit of overkill IMHO

Cheers,

Screwy


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## mxd (29/4/12)

thanks all

I have RCD's on my main switchboard, it's just if I'm building a new control box may as well have another level of "safety" the old belt and braces  or if I take it around to someone else's place.


I released smoke from my stc1000 a couple of weeks go and nothing tripped, I tested the switches and they tested ok. So I assume it was just heat rather than shorting, it was rather melted though ?


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## eamonnfoley (29/4/12)

mxd said:


> thanks all
> 
> I have RCD's on my main switchboard, it's just if I'm building a new control box may as well have another level of "safety" the old belt and braces  or if I take it around to someone else's place.
> 
> ...



Depends how you've connected various loads etc. If the STC100 is not rated for the current you putting through it (i.e. the load it is driving (fridge, heating element, etc), it could be overloaded and may smoke up. It wont trip the mains because there is not fault (yet) and the mains breakers are set to protect the cables throughout the house, which are probably rated higher than your load.

RCDs may save your life, but they will not save you equipment if it not designed properly.


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## Wolfy (29/4/12)

mxd said:


> Do I put in a 1 pole RCD or 2 pole RCD, whats the diff, I would have thought they should all be 2 pole ?





Filby said:


> ...
> Remember, an RCD protects humans and not the wiring, a fuse/breaker protects wiring, not humans.





foles said:


> RCDs may save your life, but they will not save you equipment if it not designed properly.


Given that the Ebay auctions call both them "RCD/MCB" isn't that just another way of saying that it's _both _ an Residual-current device and Miniature circuit breaker, or Residual Current Circuit Breaker with Overload protection (RCBO) or whatever the correct and current acronym is?
In other words, does it acts _both _an RCD and Circuit Breaker to protect both humans from earth leakage and equipment from overload or short circuit?

Unlike *mxd *we have old house wiring with ceramic-wire fuses and no Safety Switch at all, so I've also been looking at the exact same items.

*mxd*, this guy will sell the RCD's and an enclosure for the same price (counting the free postage) as 2x RCD's from the listings you mentioned.


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## eamonnfoley (29/4/12)

Wolfy said:


> Given that the Ebay auctions call both them "RCD/MCB" isn't that just another way of saying that it's _both _ an Residual-current device and Miniature circuit breaker, or Residual Current Circuit Breaker with Overload protection (RCBO) or whatever the correct and current acronym is?
> In other words, does it acts _both _an RCD and Circuit Breaker to protect both humans from earth leakage and equipment from overload or short circuit?
> 
> Unlike *mxd *we have old house wiring with ceramic-wire fuses and no Safety Switch at all, so I've also been looking at the exact same items.
> ...



Yes an rcd is also a mcb that protects equipment. But if you are pulling more current through equipment than the equipment (example - stc100) is rated for you will damage it. And your breaker won't trip because it is likely set higher than your load.


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## Wolfy (29/4/12)

foles said:


> Yes an rcd is also a mcb that protects equipment. But if you are pulling more current through equipment than the equipment (example - stc100) is rated for you will damage it. And your breaker won't trip because it is likely set higher than your load.


Yup, that makes sense - also means I'm not totally confused about all this. I'll just have to make sure I pick the correctly rated RCD/MCB so that I can readily reset it and not the fuses at the meter.


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## Screwtop (29/4/12)

mxd said:


> thanks all
> 
> I have RCD's on my main switchboard, it's just if I'm building a new control box may as well have another level of "safety" the old belt and braces  or if I take it around to someone else's place.
> 
> ...



Use the STC1000 contacts to switch the coil of a relay such as this. Switch the load with the with 30A contacts of the relay.

Screwy


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## eamonnfoley (29/4/12)

Screwtop said:


> Use the STC1000 contacts to switch the coil of a relay such as this. Switch the load with the with 30A contacts of the relay.
> 
> Screwy



Yep thats the way to go. I have an auberins PID and the max that can be driven directly from the PID is 7A at 240V. Any higher and an external relay (I use an Auberins SSR type) is required.


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## alford_j (29/4/12)

If you are running a 15A AND a 10A (assuming different circuits) into your box you would need 2 RCDs- 1 for each circuit regardless of each RCD being 1 or 2 poles. Everyone else is probably assuming this already. I'm also looking at running 2 circuits into my control box. I've already got both circuits covered by a 40A RCD before the breakers in the fuse box.

Alf


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## mxd (29/4/12)

Alfie said:


> If you are running a 15A AND a 10A (assuming different circuits) into your box you would need 2 RCDs- 1 for each circuit regardless of each RCD being 1 or 2 poles. Everyone else is probably assuming this already. I'm also looking at running 2 circuits into my control box. I've already got both circuits covered by a 40A RCD before the breakers in the fuse box.
> 
> Alf



thats what I have, 2 circuirts and 2 or so SSRs 

cheers
Matt


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