Assume in total you have 6HP of airconds after adding the new unit.

rule of thumb for aircond power is 1 HP = ~753W

6HP x 753W / (240 V x 0.85 power factor ) = ~22.14 A

So you will have 22.14 A running in total just for the aircond, fridge, PC, TV, smartphone charger etc consume very little power, i assume all turn on together will consume a maximum of 5A, heater will normally consume 9A.

So everything in total will be 22A + 5A + 9A = 36A, so theoretically it should be safe. Aircond compressor / motor is theoretically to spike in initial start up for up to 6 times the normal usage so try to keep your total usage at around 50% of the total supply.

1 thing you have to take note is, your new 2 HP aircond power MUST draw power from new MCBs or that particular power circuit must consume very little power. for this you have to ask the electrician or the aircond guy to do it already.

You can see from your picture there are alot of small small MCBs, lets say there are 20 small MCBs, therefore your DB has 20 power circuits, you should have some spare unused ones, ask the electrician to pull cable and connect to the spare unused 1 and draw power from that spare MCB.

ok got it thanks guise

Our loads are all single phase. Very rarely you will have 3 phase air con for residential.

Let's say we 1ph.
Means 63A max like someone said.
(Also depending on cable sizing they did when they wire the house)

If you have 3ph, u theoretically can have 3x the loads.
This means that 63A x 3 = 189A total since what they do is they alternate the loads on 3 diff Electrical lines.

Is like having a 1 lane road vs a 3 lane highway.

But current always flow 2 ways. The neutral line have to be oversized properly too. So in the end might not be 3x max.

ok..

3 phase supply properly balanced across each phase means no current flows through the Neutral.. The neutral only returns the unbalance current across the phases..

11KV transmission lines is only 3 wires.. It is distributed in Delta with all phase current balanced.. Only when step down by transformer from Delta 11kV/433V Star is where the neutral is introduced where the Neutral is earthed..

From Transformer it goes to a Feeder pillar where there will be an Earth fault protection device before it gets distributed to residential properties where is must also be earthed at the DB.. This is known as a T-T (Terra-Terra) system..

The usual tail into a residential landed property is only 2x25mm(60A) or 2x16mm2(40A) Aluminium cable which only provides you the fuse rated max demand load which is a slow blow high rupture capacity fuse..

This maximum demand can easily be exceeded by the high inrush starting current of inductive motors (your aircon motor)..

3 Phase is the name of an electrical supply.. It can be 3 wire (2 phase lines plus Neutral) or 4 wire (3 Phase lines Plus Neutral) supply..

Single Phase is the name of a electricity supply of a 2 wire (one phase plus Neutral) supply..

If in doubt please get a competent electrical contractor to verify the existing maximum demand to check that your wiring can handle the electrical load..

You can easily overload (think electrical fire) your existing wiring if you change your protection fuse to a higher rating without knowing your maximum demand..

What I am saying is basic electrical common knowledge to all electricians..

If you don't understand what I'm saying please talk to an electrical person who knows something about maximum demand and how to use a clamp on ammeter..

Electricity is not your friend .. It is a known killer held in a copper prison just waiting to kill you..

oh come on, i was running 2KW server (4 GPU each server 950W power draw x 2) thro a 13A extension cord for 2 months 24/7. also use power meter to check.
dont simply scare monger la. use science to count how many Amp per 1HP aircon.. 40amps is alot for 240V, thats nearly 10KW of power.
as long as each 1HP aircon is on one electrical branch it should be ok.
only downside to my extensive server usage was my TNB was over 1.5k per month that two months..

thats why electical and electronics ppl are 2 different breed.
this is not 80s era aircon le.
nowadays all soft start and what not.

Careful ts.... better don't
If u wan to try

Pls remove all the plug first

er, you dont run 4 aircons on one branch of the mcb le.. that might be a cause of wire overloading.

^ mechanical engineer lai liao

one of my friends' house has 6 units of aircon..no issue

You understand .. but no one knows if he has an inverter unit or a conventional DOL start and that pictures shows a DB with 24 SP mcb's single phase..

I have never seen a single phase DB with so many mcb's..

Add to the fact they're all non branded components easily means if that RCD is defective any surge inrush current from a DOL motor will fuse any of those mcbs short circuit and start an electrical fire..

And it's not all soft start.. There's definitely more conventional DOL AC motors out there than inverters..

true, inverter is safer, on this issue.

but also for basic units that is not 20years old,
the compressor motor drive circuits also got ICs, current limiters and various diodes le.

and! when you turn on the aircon, the compressor dont kick in immediately.. its usually 5-10 seconds later than the blower unit starts to run.. and for that 0.1 second during motor start you dont draw 10amps and blow everything on your drive circuit PCB!

When I cook, I got use three stove at once. Multi tasking. But using gas stove la. Hahah

er...those soft start u mention does it applies to newer non-inverter AC?

but then....AC is a very long lasting thing. my house still got NATIONAL name tag AC

sure, refer to my answer above.. compressor kick in later.

anyway if you have 4-5 units of NATIONAL aircon, perhaps you wanna upgrade them to more efficient and higher EER or BTU rating.. 1HP aircon now 800-900 can get liao..got brand ones.

add another breaker laa... 20A rating

well.. is only 1 unit and that 1 unit is in guest room

rarely switch on 1 so....ok loh dint touch

I've been using 4 inverter ac (1x2hp & 3 x 1hp) for the past 4 years. No issue except have to pay a lot to TNB Just make sure it's connected from different MCB.

No sign of wiring overheating or what so ever. (Checked with FLIR thermal camera)

fuyoh use FLIR for hotspots summore..

Borrow from my brother. His company have some project with TNB that uses FLIR.

So far, everything normal. No sign of wiring overheating even though 4 ac are on simultaneously.

And I use this to check each AC current / load. All good

I'm not worried about lighting load as 100% LED light use throughout my house. Too little load.

This post has been edited by haturaya: Dec 26 2016, 10:34 PM