Electrical Question of the Week Archive |
A call comes in that a homeowner is finished his own wiring and he gets it inspected.
He wants you to "Have a look at it" because the inspector found that that
he has too many wires in a box. You check and find there are 1 too many in a 2
gang box for the hall lights. What can you do? You can remove some of the marrettes and solder the connection and tape it. The box fill rule only derates for insulated splice caps, not soldered joints. Yeah, it seems a bit Cheesey, and is not "Common Practise", but it's perfectly legal and acceptable, and will do in a pinch.. 12-112, 12-116, You Can NOT solder the Ground (Bonding) wires 10-808 (2) 10-906 (2) ============================================================================= You are working in a back room at a clothing store. The manager asks you to install another general purpose duplex receptacle for a radio. You notice another receptacle 9 feet away and find that it will be fine to get power from there. All the existing electrical was done on the surface. You go to the van to get a plug and 1110 box, but there is no 1/2" EMT. There is however, a piece 3/8 of Liquid Tite and some free wire, and you have lots of straps to make it look neat. Would this be ok? Nope. 12-1302 (2) says you cant run 3/8" for over 1.5 meters. 12-1302 (3) (b) says you cant use any size as a general-purpose raceway, and 12-1302 (3) (c) says you can only use it where it requires it to be flexible. Just for the record, you could use 1/2" flex (rule 12-1002 (1)), but not 1/2" liquidtite. ============================================================================= A Swimming pool pump and filter shed has been built to house the equipment for a new 20 x 40 foot swimming pool. Because of the landscape features the shed was built of steel, and located next to the home approx 4 meters from the pool. Do you need to install a GFI for the pool pump circuit? No. You do not. Rule 68-068 (7). If it is outside the minimum 3 meters perimeter, it does not have to be GFI protected. ============================================================================= Is there a temperature restriction for the use of Loomex in cold weather? (Hint: Loomex has Thermoplastic insulation). Yes there is. 12-102 says it SHALL not be installed during any time when the ambient is sufficiently low to be liable to cause damage to the insulation. Appendix "B" has a note on Rule 12-100 that says care Should be taken with the installation such as preforming and to move slowly when bending it. Other measures would be like keeping the wire warm in a heated room or vehicle. The CEC Handbook also says that +10 deg C is the lowest temp you shoud use it at.....But that would pretty much wipe out it's use for about 6 months in B.C. I Remember a when all the rolls of Loomex had "Do not use below -18c" stamped on them, but i dont see that anymore. ============================================================================= Are you allowed by code to use a single pole thermostat on 240 volt baseboard heaters, or must you use a double pole thermostat that will interrupt the line current to open all ungrounded conductors? That depends on the thermostat itself. If the thermostat has a marked "Off" position, then it must be a double pole. If it has no marked off position, like the type that say "low and High" or have temperature markings like 10, 20, 30, 40 degrees but have no actual off markings, then you may use a single pole thermostat. Rule 62-118 (2). ============================================================================= When a 2-wire N.M.S.C. (Loomex) is connected as a switch loop for a light, must the white wire be taped black if it is used as hot to the switch and a black wire is used as the return conductor from the switch to the light. No- rule 4-034 (2). It does not have to be taped black if an unidentified (Usually Black or Red) is the return conductor Note: due to lots of inquiries i have posted a picture. (Click Here) ============================================================================= Can I put 2 - 20 amp receptacles in my home kitchen counter on the same circuit instead of having split receptacles? Yes-rule 26-726 (2) ============================================================================= Why does a Standard 3 Phase 4 pole 60 Hz Squirrel Cage motor run slower than 1800 rpm?. It is impossible for the rotor of an induction motor to turn at the same speed as the rotating magnetic field. If the speeds were the same, there would be no relative motion between the stator and rotor fields; without relative motion there would be no induced voltage in the rotor. In order for relative motion to exist between the two, the rotor must rotate at a speed slower than that of the rotating magnetic field. The difference between the speed of the rotating stator field and the rotor speed is called slip. The smaller the slip, the closer the rotor speed approaches the stator field speed ============================================================================= Should the neutral Bonding screw in a 60 amp sub panel in a Garage in a residence be installed to bond to Ground? What rule? No. It should not. Bond the Neutral to Ground at the Main service only. 10-204 (1)(d) ============================================================================= What is current sourcing and current sinking?. What is the difference between them?. CURRENT SOURCING OR PNP Sensors source or supply current which means the output becomes a positive when it is on and floats when the sensor is off. You would connect the load between the output and a negative. CURRENT SINKING OR NPN Sensors Sink current which basically means the output becomes a negative when the sensor is on, and floats when the sensor is off. You would connect your load between the output and a positive. ============================================================================= Do i need to install a ground wire in a rigid metal conduit to my driveway lamp posts. What Rule? Yes. 10-804 (c) (ii) if its in direct contact with the dirt, it must contain a grounding / bonding conductor. ============================================================================= What is the power factor of a 8000 watt load connected to a 240 volt AC single-phase circuit if the current is 36 amperes? Pf = 8,000 / (240 volts x 36 amperes) which equals .93 or 93 percent What is the power factor for a three phase system operating when the wattmeter reads 6,000 watts, the voltmeter reads 208 volts, and the ammeter reads 20 amperes? Pf = 6,000 / (208*20*1.732) which equals .83 or 83% ============================================================================= Do i need to install a bushing on all E.M.T Fittings. What Rule? Yes. 12-906 Bushings or equivilant means shall be used to protect conductors from abrasion where they issue from raceways. Also section "0"- definition of raceway. . ============================================================================= What is the the total capacitance of a circuit with 3 capacitors in series. The capacitors are 1000uf, 450 uf, and 750 uf ? If these capacitors were in parallel, they are just added together, but Capacitors in series are added as 1/ct=1/c1+1/c2+1/c3. Therefore 1/ct = 1/1000 + 1/450 + 1/750 = 1/ct = .001 + 0.00222 + 0.0013333. 1/ct = .0045.= 1/.0045 Which = 219.5 uf total. ============================================================================= What is the minimum size copper conductor that you can use for an overhead feed? What Rule? Consumer service conductors shall be not less than #10 copper and #8 aluminum. CEC Rule 6- 302 (4) ============================================================================= Are you allowed to use standard 2" rigid metal conduit for a residential 200 amp overhead service mast? What rules? No. it must be 2 1/2" rigid metal conduit according to rule 6 - 112 (5). You also have tho option to use an approved CSA mast kit.which includes a special 2" pipe as per rule 6-112 (4) appendix B ============================================================================= Electricity always follows the path of least resistance. Right? Nope! if that were the case and you have 2 lights in parallel, how would the one with the higher resistance ever light up? Electricity will follow all complete paths back to its source regardless of the resistance. It will allow more current to flow in the lower resistance path, and only a little current to flow in the high resistance path..Thats why people get electrocuted in bathtubs and such. Some current will flow through the water to the grounded drain, and some current will flow through you, and it only takes a small amount of current to be fatal!. ============================================================================= Can you connect a home humidifier mounted on the furnace ducting to the same circuit as the 80,000 btu gas furnace? Yes-rule 26-826 It is an accessory that is part of he furnace equipment. ============================================================================= |