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> Please help if you have electrical knowledge, regarding 3 phase electric installation

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ceo684
post Mar 4 2021, 03:57 PM

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QUOTE(hendry91 @ Mar 4 2021, 02:59 PM)
Ops, Thanks Sis. haha

if 300mA RCD is for commercial/industrial, then what should be used for residential? RCD with lower mA?

Let's say la, I take a fork cucuk the 13A socket and kena shock, my MCB / RCD which one will trip and what's the cause(theory) to make it trip?
*
1 size fit all, 30mA whole house for residential.
Lower mA is tighter tolerance/more sensitive for life protection.

I personally use one piece RCD for 3phase supply. In pic is 30mA 4P 40A (the incoming to the unit is only 10mm cable so 40A each phase). Yours is newer place on 16mm then the TNB is 63A, so you need a 63A 4P 30ma RCD.

Generally top tier RCD for MY market easily ibtainable are from these 3, ABB Hager Schneider.

This post has been edited by ceo684: Mar 4 2021, 03:58 PM


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TShendry91
post Mar 9 2021, 12:41 PM

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QUOTE(ceo684 @ Mar 4 2021, 01:45 PM)
Sis actually.  bruce.gif

1. What is the "MCB C20 WH"? is it different type of other MCB?
Standard C20 MCB.
WH denotes the one for WH circuit.

2. if I have 4 header, which mean I will need FOUR 10mA RCD?
Yes correct. WH 10mA RCD is per unit of WH. Each WH should be on its own dedicated circuit as one WH enough to use 15-17A nominal (WH is heavy appliance). Your 2.5mm cable only support 21A. And the 10mA RCD, only come (from branded mfg) up to 25A max current. In short, the standard cable sizing, the RCD current capacity (max 25A) all only suited for single unit WH as it is sensitive device (0.01A /10mA).
Whilst there are champions from china making 10mA RCD that can handle 40A laugh.gif I also dare not use.

3. The purpose of 10mA RCD is to trip when the heater leaking to our body? my current installation if leaking it won't trip?
Your current installation only trips at 300mA - by then, the human dieded 6 times over.
As the mains is 300mA, it allow 300mA leakage before it trip.
A human RIP at 50mA.
[attachmentid=10803044]

4. In short, I only need to have 10mA RCD in between the MCB and Header individually? Any other wiring need to be change/improve?
Yes, correct.
RCD is comparing input and output current difference. Input and output must = equal the same +/- RCD tolerance of say 10mA (0.01A).

Meaning, if WH input is 16A on L, at least 15.99A must return on WH output (N) else it has deemed to be lost somewhere.

Lost somewhere mean could be leaking through human.
So when the return not enough (<15.99) say only 11A return. The 4.99A cannot be lost, it mean it leak. As 4.99A far exceed the 0.01A allowed by 10mA RCD it will immediately trip.

MCB only consider single wire (L) amount of current passing through (short circuit prevention).
For a C20, meaning the speed limit is 20A.
Slight overload at 23A will trip the SLOW thermal overload after say 20 min.
Major overload at 100A will immediately trip the magnetic overload.

5. between I'm quite confusing are ELCB & RCCB the same? can you correct me if the naming in the image below wrong?
The difference is how and where they measure.
ELCB only detect earth current rise >0 leak (L to PE) leak on that appliance's earth. If it leak via anywhere else (L-N, or L-other PE eg wet floor, L-human) it will not bother. Hence in short I just say it protect that appliance only.

RCD because it constantly compare L input =N output + allowed tolerance (like 10.00A in on L, >9.99A must return as allowed tolerance is 0.01A for normal operation things like wire resistance that do NOT constitute a fault condition). It does not care where it leak through, RCD always compare in and out current so if it leak through any method (L-N, L-PE, L-other PE, L-human) it always trip.

Note: There is something called RCBO which do both function of MCB+RCD in one.
6. Appreciate if you can share the image of "MCB C20 WH" and 10mA RCD
MCB C20 is any usual C20 (20A MCB). WH is just designation for the WH circuit.

10mA RCD (must be used in conjunction together with C20 MCB) ie. add this along with MCB C20
ABB= https://www.lazada.com.my/products/abb-f202...i2IABn&search=1
Hager= https://www.lazada.com.my/products/hager-cc...l5n2dU&search=1
Schneider = https://www.lazada.com.my/products/schneide...8t5PsK&search=1

10mA RCBO = RCD+MCB in one package pao kah liao 2 function in one
Schneider RCBO https://www.lazada.com.my/products/schneide...PVCaV4&search=1
The drawback is, officially, their MCB is a C25 equivalent so you need to use with 4mm cable. As 2.5mm cable only good up to 21A rating.

user posted image
First one from left  is MCB 3P (3 pole) C63 (63A)
Second one is 4P RCD but this is 300mA. Only used in commercial/industrial where they use heavy motors. Not safe for residential and its against regulation, as the human has dieded 6x before this trips. (RCD/RCCB/RCCD = same function with diff name like zebra crossing=pedestrian crossing)
Third one is MCB 1P C10 (10A)

You will then ask, why do people still put the 300mA in residential?
Just to save the few bucks for more profit/lower tender cost whistling.gif
*
Hi Sis,
my DB box out of slot, so might need to use RCBO. but the 4mm cable u mentioned is for out going from RCBO to water heater or incoming to RCBO?
My wireman told me like the image below, between can I use 2.5mm cable(To WH) with RCBO?
Can you demonstrate how to connect?
Thanks
user posted image

This post has been edited by hendry91: Mar 9 2021, 12:46 PM
ceo684
post Mar 9 2021, 01:12 PM

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QUOTE(hendry91 @ Mar 9 2021, 12:41 PM)
Hi Sis,
my DB box out of slot, so might need to use RCBO. but the 4mm cable u mentioned is for out going from RCBO to water heater or incoming to RCBO?
My wireman told me like the image below, between can I use 2.5mm cable(To WH) with RCBO?
Can you demonstrate how to connect?
Thanks
user posted image
*
Ideally, per ST WH Guidelines page 14, the RCBO (25A 10mA) is connected after the mains RCD 30mA as well. So you will have the 30mA (whole house) as second level RCD protection.

As RCBO = MCB and RCD in one.
The RCBO unit can be installed like an MCB (replace the existing MCB with the RCBO in-situ).

QUOTE
but the 4mm cable u mentioned is for out going from RCBO to water heater or incoming to RCBO?


The chain is only as strong as weakest link. All the way should be 4mm as the min cable size per ST guideline is 4mm for 3300-3800W WH.
Because typical load is around 15-17A.
Still can get away with 2.5mm if the 2.5mm cable is good quality (full copper and SIRIM and MS2113 certified) as the 2.5mm cable can take a 21A max load, but it is recommended to use 4mm if possible.

This post has been edited by ceo684: Mar 9 2021, 01:27 PM


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Attached File  Guideline_for_The_Design_Installation_Inspection_Testing_Operation_and_Maintenance_of_Water_Heater_Systems__1_.pdf ( 4.49mb ) Number of downloads: 23
TShendry91
post Mar 9 2021, 02:42 PM

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QUOTE(ceo684 @ Mar 9 2021, 01:12 PM)
Ideally, per ST WH Guidelines page 14, the RCBO (25A 10mA) is connected after the mains RCD 30mA as well. So you will have the 30mA (whole house) as second level RCD protection.

As RCBO = MCB and RCD in one.
The RCBO unit can be installed like an MCB (replace the existing MCB with the RCBO in-situ).
The chain is only as strong as weakest link. All the way should be 4mm as the min cable size per ST guideline is 4mm for 3300-3800W WH.
Because typical load is around 15-17A.
Still can get away with 2.5mm if the 2.5mm cable is good quality (full copper and SIRIM and MS2113 certified) as the 2.5mm cable can take a 21A max load, but it is recommended to use 4mm if possible.
*
If I understand correctly, all the Water Heater are recommended to use 4mm cable, no matter use RCD/RCBO correct?
But no choice, already pulled 2.5mm cable, if the cable quality good enough shouldn't have problem right?

RCBO 25A 10mA & 20A 10mA, which one should I use?

This post has been edited by hendry91: Mar 9 2021, 03:27 PM
SUSslimey
post Mar 9 2021, 03:36 PM


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QUOTE(hendry91 @ Mar 9 2021, 02:42 PM)
If I understand correctly, all the Water Heater are recommended to use 4mm cable, no matter use RCD/RCBO correct?
But no choice, already pulled 2.5mm cable, if the cable quality good enough shouldn't have problem right?

RCBO 25A 10mA & 20A 10mA, which one should I use?
*
If use 2.5 mmsq cable, then 20a 10ma trip rcbo.

What’s the water heater rated wattage?
Ideally pull the wire again though.

Most older houses still using 2.5mmsq wire. Running water heater or 3600 watt. Not ideal. But real world usage hardly use 50 percent of the water heater power and usually usage only a few minutes.

But for peace of mind, 4mmsq is better

This post has been edited by slimey: Mar 9 2021, 03:39 PM
TShendry91
post Mar 9 2021, 03:38 PM

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QUOTE(slimey @ Mar 9 2021, 03:36 PM)
If use 2.5 mmsq cable, then 20a 10ma trip rcbo.

What’s the water heater rated wattage?
*
Haven't bought a water heater yet.
20A support up to 4800 watts? which mean if I use 20A, then I need to buy the water heater below <4600 watts?

This post has been edited by hendry91: Mar 9 2021, 03:44 PM
ceo684
post Mar 9 2021, 03:45 PM

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QUOTE(hendry91 @ Mar 9 2021, 02:42 PM)
If I understand correctly, all the Water Heater are recommended to use 4mm cable, no matter use RCD/RCBO correct?
But no choice, already pulled 2.5mm cable, if the cable quality good enough shouldn't have problem right?

RCBO 25A 10mA & 20A 10mA, which one should I use?
*
Yes correct recommended 4mm per ST spec. Regardless RCBO or RCD.

Per cable mfg spec 2.5mm is safe up to 24A single phase max load - http://www.megakabel.com.my/A-1.pdf
Attached Image

If cable is from proper mfg (u see there is MS2112-3, SIRIM QAS certified, and mfg name on the cable) then OK.
Attached Image

Between RCBO 25A 10mA & 20A 10mA, for safest choice 20A 10mA when using 2.5mm cable.
Whilst going 1A extra may not be much difference above the cable mfg spec but for insurance claim (in case fire occur) this kind of technicality can and will void the claim validity, so if on 2.5mm cable pls use a RCBO 20A 10mA,
or pair RCBO/RCD in conjunction with a 20A MCB (DB box space limitation).

This post has been edited by ceo684: Mar 9 2021, 03:48 PM
SUSslimey
post Mar 9 2021, 03:46 PM


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QUOTE(hendry91 @ Mar 9 2021, 03:38 PM)
Haven't bought a water heater yet.
20A support up to 4800 watts? which mean if I use 20A, then I need to buy the water heater below <4600 watts?
*

I won’t recommend anything higher than 3600 watt although in ideal scenario, a perfect 2.5 mmsq can handle 24 amp
ceo684
post Mar 9 2021, 03:54 PM

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QUOTE(hendry91 @ Mar 9 2021, 03:38 PM)
Haven't bought a water heater yet.
20A support up to 4800 watts? which mean if I use 20A, then I need to buy the water heater below <4600 watts?
*
Hello, cannot use 4800W.

4800/230=20.8695652173913 A (21A for easy calculation)
by 80% derating factor (same as you don't redline your car every time) you should use cable that can support 26.25A ie minimum 4mm cable.

the minimum (as per ST spec) recommended is 4mm cable to use a 4800W heater (highlands model, usually from Pana or Hitachi).

In the market usually 3kw class is 3000W for storage, and 3300-3800W for instant WH. These are the recommended type (max power) for the 2.5mm cables typically installed.
Next step is 4800W.
Normally rare to find anything in between 3800 and 4800W.

QUOTE(slimey @ Mar 9 2021, 03:46 PM)
I won’t recommend anything higher than 3600 watt although in ideal scenario, a perfect 2.5 mmsq can handle 24 amp
*
If quality cable used.
If unknown/substandard cable.. insulation very thick, copper all substandard or adulterated so only 3kW class is safe option.

This post has been edited by ceo684: Mar 9 2021, 03:55 PM
SUSslimey
post Mar 9 2021, 03:55 PM


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QUOTE(ceo684 @ Mar 9 2021, 03:54 PM)
Hello, cannot use 4800W.

4800/230=20.8695652173913 A (21A for easy calculation)
by 80% derating factor (same as you don't redline your car every time) you should use cable that can support 26.25A ie minimum 4mm cable.

the minimum (as per ST spec) recommended is 4mm cable to use a 4800W heater (highlands model, usually from Pana or Hitachi).

In the market usually 3kw class is 3000W for storage, and 3300-3800W for instant WH.
Next step is 4800W.
Normally rare to find anything in between 3800 and 4800W.
If quality cable used.
If unknown/substandard cable.. insulation very thick, copper all substandard or adulterated so only 3kW class is safe option.
*
I haven’t seen before a instant water heater of 3kw class
ceo684
post Mar 9 2021, 03:57 PM

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QUOTE(slimey @ Mar 9 2021, 03:55 PM)
I haven’t seen before a instant water heater of 3kw class
*
Storage heater Rated Power : 3000W - Centon current series (QNQ RNQ SNQ)

Instant WH 3kw class = 3xxx W (typically 3300-3800W)
Older National/Pana is 3300W
Current series Pana 3600W
Current Toshiba 3800W

This post has been edited by ceo684: Mar 9 2021, 03:58 PM
TShendry91
post Mar 12 2021, 11:22 AM

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QUOTE(slimey @ Mar 9 2021, 03:46 PM)
I won’t recommend anything higher than 3600 watt although in ideal scenario, a perfect 2.5 mmsq can handle 24 amp
*
https://shopee.com.my/EPS-20A-25A-2P-10mA-6...0848.2764232010
I would like to buy this(20A), am I getting the correct item?

This post has been edited by hendry91: Mar 12 2021, 11:23 AM
SUSslimey
post Mar 12 2021, 11:40 AM


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QUOTE(hendry91 @ Mar 12 2021, 11:22 AM)
https://shopee.com.my/EPS-20A-25A-2P-10mA-6...0848.2764232010
I would like to buy this(20A), am I getting the correct item?
*
Looks correct to me
ceo684
post Mar 12 2021, 12:18 PM

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QUOTE(hendry91 @ Mar 12 2021, 11:22 AM)
https://shopee.com.my/EPS-20A-25A-2P-10mA-6...0848.2764232010
I would like to buy this(20A), am I getting the correct item?
*
Yes, correct, RCBO 20A 10ma.
TShendry91
post Mar 13 2021, 10:54 AM

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QUOTE(ceo684 @ Mar 12 2021, 12:18 PM)
Yes, correct, RCBO 20A 10ma.
*
Received the item, this one correct? 0.01A=10mA?
user posted image
SUSslimey
post Mar 13 2021, 01:05 PM


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QUOTE(hendry91 @ Mar 13 2021, 10:54 AM)
Received the item, this one correct? 0.01A=10mA?
user posted image
*
looks right to me
ceo684
post Mar 13 2021, 03:07 PM

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QUOTE(hendry91 @ Mar 13 2021, 10:54 AM)
Received the item, this one correct? 0.01A=10mA?
user posted image
*
Correct. Note that this RCBO is single direction connection to LINE/LOAD as top LINE/bottom LOAD ya.
TShendry91
post Mar 13 2021, 11:19 PM

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Thanks ceo684 & slimey :-)

This post has been edited by hendry91: Mar 13 2021, 11:20 PM
TShendry91
post Apr 21 2021, 11:11 PM

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QUOTE(ceo684 @ Mar 9 2021, 03:54 PM)
Hello, cannot use 4800W.

4800/230=20.8695652173913 A (21A for easy calculation)
by 80% derating factor (same as you don't redline your car every time) you should use cable that can support 26.25A ie minimum 4mm cable.

the minimum (as per ST spec) recommended is 4mm cable to use a 4800W heater (highlands model, usually from Pana or Hitachi).

In the market usually 3kw class is 3000W for storage, and 3300-3800W for instant WH. These are the recommended type (max power) for the 2.5mm cables typically installed.
Next step is 4800W.
Normally rare to find anything in between 3800 and 4800W.
If quality cable used.
If unknown/substandard cable.. insulation very thick, copper all substandard or adulterated so only 3kW class is safe option.
*
Hi, need your advice, can I use this heater? The electrical rating is 4.2kW, your mentioned the 3.6kW is fine for 2.5mm cable, but how about this?

user posted image
ceo684
post Apr 21 2021, 11:37 PM

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QUOTE(hendry91 @ Apr 21 2021, 11:11 PM)
Hi, need your advice, can I use this heater? The electrical rating is 4.2kW, your mentioned the 3.6kW is fine for 2.5mm cable, but how about this?

user posted image
*
Hi,
4200W / 230V = 18.26A


https://www.electrical-installation.org/enw...a_of_conductors
Per reference method B1 (single circuit, solid stranded cable enclosed in conduit) able to handle up to 21A with 2.5mm² cable.

This 21A is assuming that quality cable (eg Mega Kabel, Caramay, or any of the MCMA cartel members) is being used.. biggrin.gif
If elcheapo or fake cables - you might be running a risk that it is undersized for the load devil.gif

Also the length should be kept to reasonable length.. if the cables are too long then voltage drop will be a problem as well
Because if effective voltage drops, the amps go up
e.g. 4200W / 200V = 21A.
So there is about a 10% reserve capacity of the cable current capacity with 2.5mm² cables.. insofar as ST regulations go, officially they recommend minimum of 4mm² so that no need to worry or calculate so deeply.

This post has been edited by ceo684: Apr 21 2021, 11:40 PM

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