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Topic Title: Hand-dryer in public toilet
Topic Summary: 1 pole or 2 pole
Created On: 27 September 2007 01:19 PM
Status: Post and Reply
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 27 September 2007 01:19 PM
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charlieroad

Posts: 150
Joined: 24 September 2007

Anyone assist? Hand-dryer in a public toilet is protected by a 'defective (Gov warning)' Merlin Gerin 1 pole RCBO in a 'full' board. I believe it should be protected by a 2 pole device.
I thought a replacement MCB at the board and using a 2 pole Power breaker RCD spur, local to the hand dryer (at high level). Comments please
 27 September 2007 01:22 PM
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philipwright2

Posts: 745
Joined: 28 January 2006

how can you have a one pole RCBO?

The MG devices in the A series DBs only take one way up

-------------------------
Regards
Phil


I will not cease from mental fight,
nor shall my sword sleep in my hand,
till we have built Jerusalem
In England’s green and pleasant Land.


Edited: 27 September 2007 at 01:23 PM by philipwright2
 27 September 2007 01:40 PM
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charlieroad

Posts: 150
Joined: 24 September 2007

I'm probably not explaining myself well. The defective breaker, I have been informed, has a solid neutral. I believed a double pole disconnection was required. The double pole unit suggested by supplier takes up 2 fuseways, therefore won't fit? Am I being led down the wrong road and making this more difficult than it really is?
 27 September 2007 01:56 PM
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philipwright2

Posts: 745
Joined: 28 January 2006

well the RCBO can't have a solid neutral by virtue of it would not work!

You probabaly know if you don't pass the phase and neutral through the RCBO it will trip. "current balance" what comes in must go out - if the difference is greater than the rating of the RCBO (30mA) then it will unbalance and trip.

If it's a relativly modern Merlin Gerin DB fit the following.

Merlin Gern MG C60HC16R30 which takes up only one way in the DB.

-------------------------
Regards
Phil


I will not cease from mental fight,
nor shall my sword sleep in my hand,
till we have built Jerusalem
In England’s green and pleasant Land.
 27 September 2007 02:10 PM
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charlieroad

Posts: 150
Joined: 24 September 2007

I agree with what you are saying but although the neutral is connected to it and the unit trips when P-N balance is lost - does it disconnect both the Phase & Neutral?
I'm being told it doesn't, it disconnects the Phase only.
 27 September 2007 02:20 PM
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khales

Posts: 1271
Joined: 16 January 2002

Originally posted by: philipwright2
how can you have a one pole RCBO?
...


Most RCBOs that take up a single slot/way in a DB are single-pole devices, i.e. when they trip they disconnect only the phase conductor, and not the neutral.

Faulty devices (government health warning), including the Merlin Gerin MG C60HC16R30, are listed here:
Estates and Facilities Division Alert

The Merlin Gern MG C60HC16R30 (RS Stock No. 467-9694) is a single-pole RCBO.

I'm not aware of any regulation that requires 2-pole RCD protection for washroom dryers; so someone please educate me.

-------------------------
khales

Edited: 27 September 2007 at 02:22 PM by khales
 27 September 2007 02:25 PM
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tillie

Posts: 789
Joined: 03 May 2006

Hi, Phil I think you will find that most single pole rcbos nowadays do have a solid neutral.

I did bring this exact query up myself because when I rewired my own place earlier this year I used Hager single pole rcbos which meant that I could not fit an 100ma rcd to protect the whole installation as I wanted to.

Even though it is a tns supply I wanted it to be failsafe .

The new rcbos can now replace an mcb in a consumer unit as a direct replacement. The problem being that a n/e fault on a cct could take out an upstream rcd.

Should the hairdryer not have a local isolator anyway.

Regards
 27 September 2007 02:35 PM
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charlieroad

Posts: 150
Joined: 24 September 2007

Khales - This is exactly where I'm going, we are on the same page. I picked up a power breaker (spur replacement type) at a suppliers which stated that it was a double pole 30 mA trip RCD as required for washroom hand dryer installation.
I didn't pay it too much attention until visiting a site which required the single pole RCBO replacing (feeds Hand-dryer).
What reg? Or is there one?
 27 September 2007 02:44 PM
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charlieroad

Posts: 150
Joined: 24 September 2007

tillie -
Existing set-up is - Fuseboard containing the single pole RCBO feeds a high level spur local to the hand dryer.

My original suggestion was (to get double pole disconnection)- Replace RCBO with a MCB at the board and use a double pole 30mA RCD power breaker to replace the spur local to the hand-dryer.

The question now is...Is there a regulation that states double pole disconnection is required for hand-dryers and other such equipment in public washroom?
 27 September 2007 02:50 PM
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philipwright2

Posts: 745
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penny drops!

I understand what you mean now!

I have the tec sheet here but it's not clear but I will take khales word as true.

If you are isolating for mech maintenance a double pole device is advisable but this could easily be the fuse spur outlet or DP switch.

Sorry - been sniffing welding fumes...

-------------------------
Regards
Phil


I will not cease from mental fight,
nor shall my sword sleep in my hand,
till we have built Jerusalem
In England’s green and pleasant Land.
 27 September 2007 03:47 PM
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rocknroll

Posts: 8865
Joined: 03 October 2005

RCBO 1 phase + solid neutral

BS EN 61009-2-2

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 27 September 2007 04:08 PM
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rocknroll

Posts: 8865
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One of the problems you have with a solid neutral is that discrimination goes out of the window, as the n/e fault is still present in the installation.

This has to be borne in mind as it is still possible for a fault current to continue flowing and could lead to a fire hazard, there are cases where a solid neutral can not be used especially in TT installations and locations where protection against fire from a n/e fault, there is a few more but I cant remember at the moment.

Also testing could be a bit of a nightmare as well, at least with the switched neutral type you dont have to go round disconnecting circuits.

Going back to the original posters query, the LA I do some work for, we dont use RCD's in public toilets, everything is on MCB's, the lights are seperated into two circuits even if there are just two lights to avoid danger in darkness, the hand dryers are protected by an MCB and a fused spur is fitted at high level, even above the ceiling tiles for maintenance, if you look in any toilet or supermarket toilet you will see fused spurs either next to the dryer or at high level, in my opinion your solid neutral RCD does not need to be changed as it is doing the same job as single MCB.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 27 September 2007 at 04:36 PM by rocknroll
 27 September 2007 09:11 PM
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handyosprey

Posts: 2
Joined: 27 September 2007

Why do you need an rcd / rcbo for a piece of fixed equipment .Unless it is in a wet enviroment I would not have thought rcd/rcbo protection is required . Unless it is spec by the client .
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