Breaker size ?

[Nighttroll]

I need to put in an AC split unit and need to know what size breaker for a 12000 and 18000 btu unit.

[ronsin1]

20 amp for the 12,000 BTU
30 amp for the 18,000 BTU

[Xplode]

well have a 12000 btu unit and the electrician placed a double breaker 30A for the 220V

[ronsin1]

^^^ no necessarily these days the load on an AC is about 5 amps RLA while FLA is 10 amps by installing a 30 amp breaker there is less protection to the cable or equipment in the event of equipment malfunction or cable short circuit

[bluestarz9]

30A recommended for both

[Nighttroll]

I 've got a 12000 btu in work and it says 8 amps so I assume a 20 will work for it

[RBphoto]

20 amp for the 12,000 BTU
30 amp for the 18,000 BTU

^^^ this. These are the maximum values, and once Full load current does not exceed 80% of your breaker rating, you should be fine whatever size you use. Just make sure the cable is at least 2.5mm square if it is being protected by the 20A breaker and 4mm square if being protected by the 30A breaker on a single branch.

[nick009]

20 amp for the 12,000 BTU
30 amp for the 18,000 BTU

^^^ this. These are the maximum values, and once Full load current does not exceed 80% of your breaker rating, you should be fine whatever size you use. Just make sure the cable is at least 2.5mm square if it is being protected by the 20A breaker and 4mm square if being protected by the 30A breaker on a single branch.

what this guy said is very important.make sure your wires are sized correctly. Breakers are to protect the wires not so much the equipment.

[sizzla89]

20 amp for the 12,000 BTU
30 amp for the 18,000 BTU

^^^ this. These are the maximum values, and once Full load current does not exceed 80% of your breaker rating, you should be fine whatever size you use. Just make sure the cable is at least 2.5mm square if it is being protected by the 20A breaker and 4mm square if being protected by the 30A breaker on a single branch.

what this guy said is very important.make sure your wires are sized correctly. Breakers are to protect the wires not so much the equipment.

Are you serious? Breakers are designed to provide that safety factor between increasing load within the circuitry, due to whatever reasons. They should trip once that tolerance has been exceeded.
I am not saying that the wire size is not important. However once it is properly selected the breaker is mainly designed as a measure to prevent over loading of currents within equipment attached to the circuit. Improper usage of these can result in electrical fires within equpiment and burning of wires etc.

[wheelbarrow]

OP the electrical inspectorate advises that in a residential application that size AC should use a 30 amp breaker and 4.0mm wire. Also the breakers are there to protect the wire that is connected to it. [/thread]

[rfari]

20 amp for the 12,000 BTU
30 amp for the 18,000 BTU

^^^ this. These are the maximum values, and once Full load current does not exceed 80% of your breaker rating, you should be fine whatever size you use. Just make sure the cable is at least 2.5mm square if it is being protected by the 20A breaker and 4mm square if being protected by the 30A breaker on a single branch.

what this guy said is very important.make sure your wires are sized correctly. Breakers are to protect the wires not so much the equipment.

Are you serious? Breakers are designed to provide that safety factor between increasing load within the circuitry, due to whatever reasons. They should trip once that tolerance has been exceeded.
I am not saying that the wire size is not important. However once it is properly selected the breaker is mainly designed as a measure to prevent over loading of currents within equipment attached to the circuit. Improper usage of these can result in electrical fires within equpiment and burning of wires etc.

breakers is to protect the conductors. what defines an overload? not the rating of the conductor and the breaker?

[RBphoto]

OP the electrical inspectorate advises that in a residential application that size AC should use a 30 amp breaker and 4.0mm wire. Also the breakers are there to protect the wire that is connected to it. [/thread]

No eh (on the 30A, the rest is gospel). That is for a multi outlet for I believe 6 outlets of 500VA max each for INDUSTRIAL use. There is no 30A recommendation for home use. The next bigger breaker than 20A is 50A for cookers. The recommended for an AC unit is 20A MAXIMUM. For lager units, the 80% FLA of breaker rating applies, where you may use the 30A.

Anywaaay...*Disclaimer* I have been working with industrial electrical for a while, and not residential/ commercial, so if I am wrong about that don't sue me.

[ronsin1]

OP the electrical inspectorate advises that in a residential application that size AC should use a 30 amp breaker and 4.0mm wire. Also the breakers are there to protect the wire that is connected to it. [/thread]

Since when can you quote the clause in the TTBS 171:Part 1 :2002 Low voltage Installation

[RBphoto]

^^^^Annex c to be precise.

[ronsin1]

^^^^Annex c to be precise.

Oh gosh let me man find the thing nah

[wheelbarrow]

Yeah well , de few inspectors ah tagged along wit on sum residential inspections have advised electricians to use ah 30A for the ACs and tank-type water heater outlets... I'm jus tellin de OP what ah heard from the ppl who supposed to know.... And advised is de key word here.... But if it black and white well ah stand corrected...

[RBphoto]

Um, sizzla89, the conductor is sized for the load, and the breaker is sized to protect the conductor.

[ronsin1]

yuh should ask the man what an Overload is for

[Sasquat007]

jus remember fastest thing to out electrical fire is red sand so keep some close by !

as ah man say here 30A for ac units and water heaters !

[RBphoto]

jus remember fastest thing to out electrical fire is red sand so keep some close by !

as ah man say here 30A for ac units and water heaters !

Reading these two statements I was like:

[ronsin1]

jus remember fastest thing to out electrical fire is red sand so keep some close by !

as ah man say here 30A for ac units and water heaters !

Reading these two statements I was like:

[RBphoto]

Ok, for a sensible post, dry chemical extinguisher will work much better than the sand, nobody keeping a bucket of sand in their house.

For the second part, Annex C of the T&T electrical code has all the nesescary recommendations (really Rules of thumb) You still should do a calculation or look up in a table the ampacity of cables required for your install and size the breaker to the application. Let's not have any more anecdotal statements about how yuh uncle/ faddah/ piper fren would size a breaker.

[~Vēġó~]

too much headache...buy ah 2-3 lasko fan

[wheelbarrow]

too much headache...buy ah 2-3 lasko fan

Agreed....

[fordfanatic]

20 amp for the 12,000 BTU
30 amp for the 18,000 BTU

^^^ this. These are the maximum values, and once Full load current does not exceed 80% of your breaker rating, you should be fine whatever size you use. Just make sure the cable is at least 2.5mm square if it is being protected by the 20A breaker and 4mm square if being protected by the 30A breaker on a single branch.

what this guy said is very important.make sure your wires are sized correctly. Breakers are to protect the wires not so much the equipment.

Are you serious? Breakers are designed to provide that safety factor between increasing load within the circuitry, due to whatever reasons. They should trip once that tolerance has been exceeded.
I am not saying that the wire size is not important. However once it is properly selected the breaker is mainly designed as a measure to prevent over loading of currents within equipment attached to the circuit. Improper usage of these can result in electrical fires within equpiment and burning of wires etc.

breakers is to protect the conductors. what defines an overload? not the rating of the conductor and the breaker?

20 amp with either 2.5mm or 4.mm conductors for 12000btu
30 amp with 4.0mm conductors for 18000btu

you can underfuse a conductor but never overfuse it. mean you can put a 20 amp breaker or 4.0mm wiring but not put a 30 amp on 2.5 wiring reason why is that in the event of a short circuit the 20 amp will trip before the conductor burns but in the case of a 30 amp the 2.5 will burn before the 30 amp trip......

i've installed electrical for numerous air conditions in residential using these methods i have never had a failure on one of my jobs,

[fordfanatic]

oh .........on another note breakers and to insure the safety of conductor directly behind it, not the appliance or equipment further down the line......

[Around]

nice to see some men got the ttbs low voltage to advise the rest

[RBphoto]

nice to see some men got the ttbs low voltage to advise the rest

No problem sire