manual circuit breakers for air conditioners and hot water units

[pferdy62]

I was wondering why it would be considered "necessary" by an electrician to install the manual circuit breaker type switch for an air conditioner or hot water unit if these devices are properly wired to a regular circuit breaker in the distribution unit and is properly earthed.  The air conditioning man said something about making sure that no electricity is left in the air conditioner after it is turned off.

[bankruatsteve]

Because that's the way it has been done before and what they know.  If it's on a breaker, that's all it really needs.  My AC guy is such a man that he doesn't even ask to turn the power off.  Whatever.

[shaemus]

Do you mean an isolation switch?

[pferdy62]

That's probably what it is.  I couldn't think of a better name for it.  Our current house has one for each air conditioner and hot water unit and the new bungalow we are building is supposed to have state of the art wiring, yet the sparky and air-con people are still talking about using these isolation switches.

 

 

[shaemus]

Its normal practice to have local isolation points for equipment. Its a requirement in a lot of countries. I assume the supply cable is protected by a Fuse/circuit breaker/MCB and this local switch for isolation and maintenance purposes. I bought some ip56 double pole isolators for my AC install in thailand they guy doing the install was quite excited as he said they only use those in banks and fancy installs.

 

The switch should be suitable for its location (weather & heat) and also be rated for switching the Load (A) of the equipment it is isolating.

 

Do they look like these?

[Pdaz]

I remember about 12 yrs ago being asked by a Thai "chang" to turn off the power. I duly flipped the breaker for the kitchen sockets he was to work on and told him it was off.. He pointed at the ceiling lights ( which were on another circuit ) and told me again to turn the power off like I was the dummy . He'd never seen a consumer unit with separate breakers for each circuit before.. Only the more usual Thai style big on/off that isolated the whole house..  

[shaemus]

"Chang" = tradesman, a term used somewhat liberally i believe.

3 minutes ago, Pdaz said:

"chang"

 

[Pdaz]

10 minutes ago, shaemus said:

"Chang" = tradesman, a term used somewhat liberally i believe.

 

Very very liberally... seems to refer to anyone who can utter the phrase " I can do " and hold a cheap screwdriver.

[Pdaz]

To answer the original question. In my place I don't have a separate isolation for my aircons. But I do for my water heater. Oven and Cooktop. The switches were brought from Singapore and are UK standard.

I believe there that you are meant to be able to isolate high amp appliances close to their location.

I have a 30amp lighted switch for the water heater and oven plus a 50amp one for the cooktop.

 

 

You could probably find something similar in Thailand.

[GavinK]

+1 on the flush fitting double-pole switch facias rather than those bulky (often Panasonic) types you find here which they always cut-out at the top/bottom just enough to allow a gecko to move in and nest. 

 

 

[shaemus]

Its a safety thing also. so if someone is hooked up or flames are cooking your dinner faster than you want it too,you can turn it off and isolate the potential source of the fire. They have been mandatory in the the u.k since the dawn of time, they just bought it into in Australia a few years ago. 

 

[tutsiwarrior]

years ago when we moved into our house with a 5/15 supply we had a 18k btu AC and a 3.5kw shower installed both connected to the mains supply upstream of the CU each with their own breaker...

 

recently with a 15/30 supply we had a 24k btu AC and a 4.9kw shower installed both hooked up to dedicated circuits on the CU...the separate breakers (apart from the CU) that the OP described might be required by the rating of the incoming supply...

 

sometime during the before and after interval we replaced the old type fused CU with a modern Safetycut...the supply was changed later by the PEA...

 

 

[Crossy]

As far as I can tell there's no requirement for local isolation in Thailand, and it's only cookers need it in the UK.

 

Provided your water heaters have RCD protection somewhere I wouldn't bother.

[Sophon]

14 hours ago, Pdaz said:

I remember about 12 yrs ago being asked by a Thai "chang" to turn off the power. I duly flipped the breaker for the kitchen sockets he was to work on and told him it was off.. He pointed at the ceiling lights ( which were on another circuit ) and told me again to turn the power off like I was the dummy . He'd never seen a consumer unit with separate breakers for each circuit before.. Only the more usual Thai style big on/off that isolated the whole house..  

Sounds like a sensible precaution to me given the state of the wiring in many Thai homes. I am (very) far from being an expert, but couldn't a borrowed neutral somewhere mean that a circuit could be live even though the breaker for that particular circuit was off?

 

Sophon

[bankruatsteve]

4 minutes ago, Sophon said:

Sounds like a sensible precaution to me given the state of the wiring in many Thai homes. I am (very) far from being an expert, but couldn't a borrowed neutral somewhere mean that a circuit could be live even though the breaker for that particular circuit was off?

 

Sophon

Not really.  The main issue with a "borrowed" neutral is that is could end up carrying more amps than it's rating and it would trip any RCBO connected to one of the borrowed circuits.

[Wirejerker]

Sounds like a sensible precaution to me given the state of the wiring in many Thai homes. I am (very) far from being an expert, but couldn't a borrowed neutral somewhere mean that a circuit could be live even though the breaker for that particular circuit was off?
 
Sophon

Yes it is very dangerous working with borrowed neutrals as you can test and find the circuit dead and when u break the neutral to add something to your circuit you suddenly have full voltage on that wire. So unless you know your installation well isolate everything and live to a ripe old age.


Cheers