Home Electrical MCB, How to size Miniature Circuit Breaker
|
|
 Oct 17 2018, 09:40 AM
Return to original view | Post
#1
|
 
Junior Member
51 posts Joined: May 2012 
|
Hello, I have read through few threads including this thread, I have some questions on RCCB for water heater. My house is using 3-phase power, and currently I have 2x 4-pole RCCB (100mA & 30mA) installed in my DB. Let's say I want to install additional 10mA RCCB for each water heater that I have, what type of RCCB to be used? 2-pole? How will be the wiring diagram looks nice? Appreciate your kind advise, TIA.
|
|
|
|
|
|
Oct 17 2018, 10:24 AM
Return to original view | Post
#2
|
|
Junior Member
51 posts Joined: May 2012
|
QUOTE(slimey @ Oct 17 2018, 09:58 AM) Your water heater runs on single phase right? Then 2 pole it is. Thank you for your slimey prompt response. I understand based on what you explained just now. Could you also enlighten me on questions below?You need to find out which mcb is for the heater currently, and which neutral wire it is using if you plan to install it at the distribution box. If too much hassle doing that, just install a 4 way distribution box next to the water heater switch with a single rcd, 20amp, 10ma tripping value. Wiring diagram is on the rcd.  1) If I have extra space in DB and I choose to install the RCD at DB, will it be less effective compared to RCD nearer to water heater? 2) If I have to install at nearer to water heater, the RCD should be installed before the 20A switch as per sequence below? (Main RCD (30Amp) - Water Heater MCB- RCD(10Amp)-20A Switch-Water Heater Power Inlet) 3) I found Hager 2 Pole RCD only has 16A and 25A rating with 10mA tripping value, which one should I get for my 20A water heater? (See attached photo) Cheers!  This post has been edited by FrankieSiow: Oct 17 2018, 10:57 AM Attached thumbnail(s) 
|
|
|
Oct 17 2018, 01:36 PM
Return to original view | Post
#3
|
|
Junior Member
51 posts Joined: May 2012
|
QUOTE(slimey @ Oct 17 2018, 01:18 PM) 1. Negligible difference. But if the neutral to the water heater switch is shared with other stuff then it is rather troublesome or inconvenient. Either need to pull new neutral line or if not the rcd trip will cause other stuff shared on the neutral line to trip together. Really thanks for your explanation. I understand the whole concept already. I will discuss this with my electrician on this matter. 2. No real difference before or after. 3. Erm....check the wire size going into the water heater. If less than 4mmsq do not use 25a unless it is already protected by a 20a mcb in the distribution board. 16a i think will trip if use full power of water heater. |
|
|
Oct 17 2018, 02:05 PM
Return to original view | Post
#4
|
|
Junior Member
51 posts Joined: May 2012
|
QUOTE(slimey @ Oct 17 2018, 01:39 PM) To add on. If trip the neutral without tripping the live of the appliance that share the neutral is dangerous. Duly noted Sir! All the neutral that share it will actually become live which is more dangerous than before. And since you have 3 phase electric supply , kaboom if different phase mix into neutral line which lost the link to the main neutral link. |
| Change to: |  0.0192sec
 1.14
 7 queries
 GZIP Disabled
Time is now: 27th November 2025 - 07:28 AM |
Quote