Do I Need A Seperate Circuit Breaker For An Ac?

[thaibeachlovers]

Had a new AC installed and the electrician just tapped into an existing power line in the roof? This was despite me showing him all the unused circuit breakers available!

I put on all the electrical appliances I could while the AC was going and it doesn't trip the breaker.

Thanks for advice.

[alaninlamphun]

You need a separate mcb/circuit breaker for the A/C,the norm is 20 amps but you need to check specification of your model to be sure,easy enough to do just remember to switch all electric off before starting

[thaibeachlovers]

You need a separate mcb/circuit breaker for the A/C,the norm is 20 amps but you need to check specification of your model to be sure,easy enough to do just remember to switch all electric off before starting

Thanks for replying. I should have said that I know I SHOULD have a seperate breaker, but can I get by without?

I can't go up in the roof- way too heavy for the ceiling, so I'd have to call an electrician, and I haven't had much luck with them doing jobs properly.

[Crossy]

What rating is the A/C?

How about the size of the breaker it's connected to?

And the size of the existing wire?

Yes, it should have its own circuit, but in reality anything up to about 12000 BTU will be OK on a correctly sized outlet circuit provided it's not sharing with the kitchen appliances.

[thaibeachlovers]

What rating is the A/C?

How about the size of the breaker it's connected to?

And the size of the existing wire?

Yes, it should have its own circuit, but in reality anything up to about 12000 BTU will be OK on a correctly sized outlet circuit provided it's not sharing with the kitchen appliances.

Thanks Crossy.

It's 10,000 BTU.

Didn't turn off the breakers to determine which is the one it is using; I'll do that when I get back to the house and let you know. Hopefully it's on the shower heater wire, which is 20 amps. If not, it's on a 10 amp breaker.

I'm pretty sure the existing wire will be 2.5, as that is the wire that comes down from the ceiling to all the plug boxes.

At least the new wire is 2.5. I checked that when they were putting it in.

[bankruatsteve]

Ideally, you have on separate breaker to isolate it when/if you need: like so it's not the same circuit as other high draw and when it needs service you can cut by itself. Otherwise, it's not a big deal as long as everything is properly sized ie: wire, breaker.

BTW: if you have unused MCB's already in the box, then it's just a cost of wire and somebody to run it to the box - that might be a good thing to do.

[electau]

The airconditioner should be wired on its own circuit if over 10Amps total load. if less ie a 7000BTU unit it may be connected to an existing power circuit by means of a plug and socket. Aircon should be earthed and protection by an 20A RCBO at the switchboard.

Do not use the circuit for the shower heater.

Edited January 28, 2013 by electau

[electau]

Circuit protection must comply with the following.

1. The protective device, ie the MCB or RCBO must be rated equal to and not more than the current rating of the circuit conductors to be protected.

2. The protective device must protect against short circuit, overload, and earth fault conditions.

3. Actual current rating of circuit will depend on the method of installation,eg, unenclosed in air, or enclosed in conduit over 50% of its route length. 2.5sqmm will carry 25A unenclosed.in air. subject to voltage drop.

[thaibeachlovers]

What rating is the A/C?

How about the size of the breaker it's connected to?

And the size of the existing wire?

Yes, it should have its own circuit, but in reality anything up to about 12000 BTU will be OK on a correctly sized outlet circuit provided it's not sharing with the kitchen appliances.

I checked the circuits and it's wired to one of the 10 amp breakers. However, not the one that services the kitchen, so I'm thankful for small mercies. The only thing on that breaker that might be on at the same time, other than lights, would be the tv.

If I find that it does trip the breaker, I'll just turn off anything else on that circuit. So, unless the tv plus AC trips the breaker, I'll be OK.

[thaibeachlovers]

Ideally, you have on separate breaker to isolate it when/if you need: like so it's not the same circuit as other high draw and when it needs service you can cut by itself. Otherwise, it's not a big deal as long as everything is properly sized ie: wire, breaker.

BTW: if you have unused MCB's already in the box, then it's just a cost of wire and somebody to run it to the box - that might be a good thing to do.

They did put a seperate switch on the wiring to the AC, so no problem to isolate it.

The problem with getting someone in to run the wire is would they do a proper job, or just wire twisting and tape?

After each encounter with local electricians, I trust them less.

Unfortunately, I'm too heavy for the ceiling supports, or I'd do it myself.

[Crossy]

I checked the circuits and it's wired to one of the 10 amp breakers. However, not the one that services the kitchen, so I'm thankful for small mercies. The only thing on that breaker that might be on at the same time, other than lights, would be the tv.

If I find that it does trip the breaker, I'll just turn off anything else on that circuit. So, unless the tv plus AC trips the breaker, I'll be OK.

Taking my usual pragmatic approach rather than being a slave to another country's regulations:-

A 10,000BTU A/C will pull about 4.5A so on run it's unlikely to be an issue, if it doesn't drop the breaker on start I think you're good to go. That said, it's own circuit is still the preferred way to install.

It's certainly not unsafe from a loading point of view, obviously grotty taped joints or the absence of grounding are a different kettle of fish.

[thaibeachlovers]

The airconditioner should be wired on its own circuit if over 10Amps total load. if less ie a 7000BTU unit it may be connected to an existing power circuit by means of a plug and socket. Aircon should be earthed and protection by an 20A RCBO at the switchboard.

Do not use the circuit for the shower heater.

I checked, and it's not on the shower circuit.

Earth. You're joking, surely. Of course they didn't earth it.

I installed a SafeT Cut RCD before the main wires enter the CU, so at least I do have protection.

However, your suggestion of using a plug has just solved my problem. I can't go on the ceiling myself, but my wife can, so if I get her to run a wire from the CU to the hole they made in the ceiling for the wire, I can install a wall socket in the room and put a plug on the AC wire. Then I can insulate the ends of the existing wires and it'll be back to the situation prior to the AC installation. I think the AC feed wire has an earth wire, so will not be a problem to run a wire to the ground earth just outside the room. Unfortunately, they didn't run an earth wire to the compressor unit, so I will have to look in the junction box and see if it has an accessible earth connection.

Thanks.

[thaibeachlovers]

I checked the circuits and it's wired to one of the 10 amp breakers. However, not the one that services the kitchen, so I'm thankful for small mercies. The only thing on that breaker that might be on at the same time, other than lights, would be the tv.

If I find that it does trip the breaker, I'll just turn off anything else on that circuit. So, unless the tv plus AC trips the breaker, I'll be OK.

Taking my usual pragmatic approach rather than being a slave to another country's regulations:-

A 10,000BTU A/C will pull about 4.5A so on run it's unlikely to be an issue, if it doesn't drop the breaker on start I think you're good to go. That said, it's own circuit is still the preferred way to install.

It's certainly not unsafe from a loading point of view, obviously grotty taped joints or the absence of grounding are a different kettle of fish.

Thanks for the prompt response, Crossy, which you made while I was writing a response to electau.

However, if you see that reply I made, you will see that I have an action plan to install a seperate circuit to an unused CU breaker, and install an earth.

[Crossy]

Yeah, saw that, stick a plug on it

[electau]

You should earth the shower heater to minimise the effects of minor leakage currents. These will not trip an RCBO.

An aircon with a load of 4.5amps can easily be accomodated on a circuit of socket outlets. 2.5sqmm/20A.

The RCBO should be tested by means of the test button at least once every 3 months.

Edited January 28, 2013 by electau

[electau]

Any individual load with a max demand in excess of 10amps should be wired on its own individual circuit from the switchboard.

Small items such as exhaust fans and ceiling fans may be connected to lighting circuits on a 10A MCB, These items are usually 60 watts or less.

[Crossy]

Any individual load with a max demand in excess of 10amps should be wired on its own individual circuit from the switchboard.

Small items such as exhaust fans and ceiling fans may be connected to lighting circuits on a 10A MCB, These items are usually 60 watts or less.

Agreed, and that ties up pretty well with the UK regs although you are allowed to put a 3kW immersion heater on our 32A rings via a 13A FCU (Fused Connection Unit).

For relevance an aircon that pulls 10A is about 22,500 BTU. I would still give all aircons their own circuit as putting more than one on an outlet circuit would be pushing the loading.

[electau]

The UK (British Standard) and some countries that use this standard with local requirements are the only ones that use the 32A ring circuit with spurs at 16A.

The usual power circuit in a typical domestic electrical installation is usually 20A and 2.5sqmm. Each socket outlet is given a rating of 1A. The max demand is the rating of the protective device. For a single permanently connected equipment on a final sub circuit the max demand is the input current of the individual equipment.

A mixed circuit of lighting points and 10A socket outlets may be connected on a 2.5sqmm circuit, this method may be used to supply a small external building on a residential property, eg a garage etc. Now not often used.

Yes, it would be normal wiring practice to install an aircon rated at between 5A and10A on its own circuit,and the cable size may then be 1.5sqmm with a 16A protective device.

Where there is a minimum of 2 power circuits of 10A socket outlets both circuits should be run through the kitchen area of a domestic installation.

Source: AS3000. Other countries standards may vary from this. The ring circuit is prohibited in Aust/NZ along with the 13A BS fused plug top and the !3A socket outlet in permanent wiring as they do not comply with AS/NZ standards for plug tops and socket outlets.

[Crossy]

Indeed Electau, I only mentioned the ring / spur out of interest.

In fact the ring topology is going out of favour in the UK as it is difficult to fault find and could subject the 2.5mm² cable to overload in the event of an open ring (32A MCB).

There is a lobby to actually outlaw rings, they have served their purpose (of reducing the copper usage during the post-war shortage) and their replacement with either a 2.5mm² (on 20A MCB) or a 4mm² (on a 32A MCB) radial/tree architecture is being mooted, many commercial installations are already wired this way.