Understanding Residential Wiring

Imagine we are living a century ago when Thomas Edison and Nikola Tesla were only starting their discoveries on AC and DC.

We would have a hard time adjusting. We would only be using candles and fires for light. We would have to chop woods to cook for food.We would have to spend hours just doing our home chores since appliances since we would not have appliances and electrical machines doing the jobs for us.

We are really lucky today to receive all the benefits of the hardwork of our scientists before.

Now, with only one click on the switch, we have our lights on. With one press on remote control, we have our TV shows displayed in front of us. With one push on electric fans switch, we have automatic fan running to fight the heat and with only few settings for washing machine, we have all our laundries done without any effort.
Our power supply comes very convenient to us nowadays and is one of the everyday necessities we have. In this regard, it is also important to at least be able to recognize the components of our electrical system. Aside from the series of wires on mind, being aware of its other components is also important and can be very helpful during emergencies.

 

• Electric meters - From the pole where our transformers are, the wiring are then connected to a an electric meter located near our homes for the power consumption monitoring. Our Electric Cooperative staff usually has to seal this meter to prevent any illegal connection such as inserting jumper wire so that the meter will be bypassed. In the Philippines, electric meter is located just before Service Entrance. However, in other countries like US, it is usually common to see the Service Entrance first on the top before the meter.

• Service Entrance - This  should also be familiar to a homeowner. This serves as the Connection and Disconnection point of electricity from electric company to the houses. We can see service entrance as joint for two wires from the transformer going to our Electric panel. If we are not able to pay electrical bills, then Electric Cooperative staff will just have to locate it and disconnect power from there.

• Electrical Panel Board - We rarely think about this one until power goes out in the kitchen because we turned on our water heater or until our house has all circuits tripped just after turning on an AC Unit. Once or twice a year, we visit our home's panel board because of emergencies. All of a sudden, it becomes important. Oftentimes it is also either poorly marked or there is no directory at all. If it is the Main breaker that goes off, the electrician or the person in charge has to shut down and reset the breakers one at a time during troubleshooting.

• In some residential designs, we have Isolator Circuit breaker in an Enclosure for convenience. Then the electrician just makes use  of main lugs  in the panel board so that the cable can be connected to the circuit breakers through the busbars. There is also a Ground bus or Ground Screw for the grounding wire. Panel boards have also a deadfront, a GI sheet, to cover wires and protect users from any electrical conductors.

• Outlets - These are where we insert of appliances' plugs. They can come as two-prong or three-prong type latter is also referred to as Ground Circuit Fault Interrupter (GFCI). It can also be indoor or outdoor type. Outdoor type or weatherproof outlets have enclosures. In our electrical standard, a circuit can have up to 10 - 12 circuit depending on the design. Our electrical code states that there should be at least 12 feet distance between outlets. However, in common homes, 6 feet is already an average distance.

 

Motor Control Starter Basics (Direct-On-line)

The term "Motor Control Starter" is actually confusing for some people. Technically, the main purpose ng motor starter is not to start the motor, but to let motor start and run without damage.
The term starter is based only on the overload relay that is used to protect the motor from starting current.

In simplest form, motor control starter can be seen in a Direct-On-Line circuit which is composed of MCCB, Magnetic Contactor and Overload Relay.

1)  Molded Case Circuit Breaker (MCCB) - Ang circuit breaker ay may tatlong functions: (a) Isolator, (b) Proteksyon a circuit sa Overload, Grounding at Short Circuit (c) Switching purposes. Sa Control Panel, nasa itaas ang breaker dahil ito ang unang main protection na kakailanganin sa motor. In case may exposed wires na nagcause ng electrical leak o short circuit, agad agad itong magtritrip.

 Kadalasan din itong ginagamit para mahiwalay ang power supply sa motor sakali may preventive or corrective maintenance na gagawin.

2)  Magnetic Contactor  - Ang magnetic contactor ay isang klase ng relay na ginagamit para sa frequent switching ng isang circuit.  Para lang itong "pinalaki na auxiliary relay" - may electromagnectic coil at nagproprovide ng karagdagang contacts sa circuit para sa ON-OFF mode.

Importante ito sa Motor Control.  As per definition ng mga nauna kong articles, ang relay ay power device na kayang kontrolin ang mas mataas na boltahe. Sa concept ng magnetic contactor, halimbawa, ang may 24VAC coil na contactor ay pwedeng kontrolin ang mas mataas na 220 VAC switched circuit. Dahil sa magnetic contactor,  naging posible din kabitan ng ibang mas maliliit na devices para sa motor.  (For instance, ikonekta lang sa contactor ang ilang auxiliary relays at pwede nang lagyan ng karagdagang pushbuttons, pilot led lights at selector switches)

Ang magnetic contactor ay gamit para sa Manual Control or Automatic Control System.

Paano naman ito gagana? Simple lang. Ang Contactor sa Direct-on-line ay nasa Normally Open (N.O) na position. Pag dadaan ang current sa coil (or maenergize ang coil sa technical term), ang contacts na magkahiwalay ay magdidikit, magcloclose ang circuit at mag-Start ang motor.

3) Overload Relay - Sa baba ng magnetic contactor ang overload relay. Ipinapares  ito sa magnetic contactor pasa sa Overload Protection. Ang OL Relay ay hinahayan ang mga short current overloads na dumadaan sa motor sa unang andar nito ngunit automatic na nagtritrip pag naging tuloy-tuloy ang overload current.

Sa principle ng magnetic induction, ang isang motor ay kailangan ng malakas na current para maset up ang electromagnetic field. Ibig sabihin, isang malakas sa sipa ng kuryente muna, para mapaandar ang motor. Ang disadvantage dito, pag parati itong mangyayari, madaling mag-iinit ang motor na pwede ikasira kaagad nito.

Ang overload relay ang solusyon sa isyu ng high starting torque. Dahil dito, naging posibleng gamitin ang motor nang hindi nasisira kaagad. Naiiwasan nating maoverheat ang motor. In short, iwas sunog sa motor windings.

Additional notes:

• Magnetic Contactor + Overload Relay = Motor Starter. Ang simpleng motor starter ay kailangan lang ng dalawang devices.  Kaya lang, walang kakayahan ang magnetic contactor na magcause ng power intteruption sa tuwing may short circuit. Dito pumapasok ang MCCB.

•  Molded Case Circuit Breaker + (Magnetic Contactor + Overload Relay) = Combination Magnetic Starter  

Capacitor Basics

Why is capacitor needed for a motor? Capacitor is needed for a motor for starting and also is used for keeping a motor from running. To help you understand, think of a motor at rest first. The  motor capacitor provides extra winding for the circuit to run. It stores charge, then releases that stored electrical charge to help start an electrical motor (starting capacitor). In short, it gives the motor a "start up". Then it gets disconnected after the motor reaches a certain speed.

However, in case the motor drops below a required speed, another capacitor switches back into electrical circuit and to keep it from spinning (run capacitor).


Now that capacitor is explained, how can we test it if it is a good capacitor or not?
Well, the most common and recommended way is the use of multitester.


As per electrical standards, we can measure if there is electrical resistance. As per sample photo, we can see that there are 3 terminals - for F for, Herm (hermetic compressor) and the third is C for common. First make sure tester is in zero amps when the positive and negative probes are connected. After that, check resistance of the folowing : Common-fan and Common-herm. If there is still a resistance, then it is a good capacitor.