The electrical service box is the first thing that is important in any electrical job. It might sound like it is a herculean task to install electrical service at your house, but it is a necessary evil, and nothing can go forward without it. If you need to install an electrical service at your house/dwelling, following these general instructions can help make things easier and make the process more pleasing for those looking to get the value for their dollar in electrical work. Generally, the electrical regulations (and they vary from state to state) allow for a service that is as big as you want but not as small. Generally, in this case, the bigger, the safer – if that can be attributed to electricity – in terms of passing inspection! There is always a definitive minimum, which is usually based on the area of your house above the ground.
In more detail, the service size usually requires 2 considerations:
1) The Load (Calculated) – This is the sum of all your potential loads after general demand factors are applied to the calculation. An average dwelling (about 1076 sq.ft.) has an electric stove and electric dyer, but for gas heating, the demand on the service is around 5000 watts, plus another 7000 watts for the stove (6000) and the dryer (1000). Again this is the load calculation, not the actual number of watts the appliance is rated on. For example, the dryer load is 1000 watts on the system if the dryer is a 4000-watt piece. This is referred to as the basic load of the system. Naturally, adding those watts up (5000+7000) is the 12000-watt load you need. Furthermore, we need to find amperes in our consideration. This is found by dividing the total amount of watts by the service voltage size. In physics, the formula is represented by a = w/v. Surprisingly, although we use 120 volts in the plugs in North America, the service voltage size coming to your panel is 2 wires by 120 each. Thus, the service voltage size total is 240v. Remember, Volts and Watts add up; amps do not! So our minimum amperage required would be 12,000 / 240 = 50 amps. Please remember that this is calculated amperage and not the minimum service size because there is a HUGE DIFFERENCE!
2) The Minimums Service Size – this is the number based on the floor area of your dwelling. Generally – 60 amp – for any dwelling which is LESS THAN 861 sq. ft. The area calculation also includes all the areas of all the floors except the basement / or underground section of the dwelling. The underground/basement area is ignored for the minimum amperes requirement. For any place which is MORE THAN or EQUAL to 861 sq. ft. – you generally need 100 amp service. As mentioned above, this includes all the floors except the basement/underground.
Considerations: Even if your total actual load is way below the service size based on your floor space – i.e., if your calculated load is 50 amps, and your floor space requires 100 amps – you need to install the service size based on your floor space, and not your calculated load amount. This is why you can have a serving size as large as you want but not as small as you’d like. The extra capacity (the difference between 50 and 100) is for future use. Even if you are never going to use it, you might one day sell the dwelling, or your kids will inherit the property, and they might want to do something with it; the extra service size has to be there to allow for this future need. In any case, most jurisdictions will not let you get away with using a service size that is too small for the area/space that you have in your house/dwelling.
60 Amp Service Size – (reminder: can only be used if total floor space is < 861 sq. ft.)- Service switch, fuse, or breaker rating – 60 amps- Hot Wire (Black) – x 2 #6 AWG 90 copper – (other colors can be red or blue)- Neutral (White) - x 1 #6 AWG 90 copper- Service Raceway – 1 inch. Or use #6 TECK Cable.- Meter Base Rating – 100 amps.- Service ground wire – #6 or larger – (this is a bare copper, twisted strand)- Service Panel Size – minimum 16 circuits. This panel can generally supply the usual plugs and central gas/oil heating. 100 Amp Service Size – (reminder: can be used for any property that is less than, equal, or more than 1076 sq.ft.)- Service switch, fuse, or breaker rating – 100 amps- Hot Wire (Black) – x 2 #3 AWG 90 copper – (other colors can be red or blue)- Neutral (White) - x 1 #2 AWG 90 copper- Service Raceway – 11/4 inch. Or use #3 TECK Cable.- Meter Base Rating – 100 amps.- Service ground wire – #6 or larger – (this is a bare copper, twisted strand) Service Panel Size – minimum 24 circuits. This panel can generally supply all the usual plugs, a central electric furnace, a boiler, and a baseboard heater.* Please remember that you need twice as much hot wire as the neutral wire. Considerations: At least 2 Spare Circuits are usually required to be left in the panel after you’ve connected all of your circuits. This is for future use. The Minimum Panel Size – is used only as a guideline for the minimum size as to your needs. A project/house/dwelling might require more circuits or a bigger panel amp rating. Always ensure you have the necessary amount of circuit space in your panel. Neutral AWG Size: – some jurisdictions require one to use the same neutral wire size as the hot (feed) wire. Check with your local authorities. Usually, it’s a good idea to use the same AWG for both the hot and neutral wires. Fused Switches: – are rarely used in residential settings, but if you plan to install a fused service switch, it must comply with your local authority regulations. Usually, the regulations require that the service conductor ampacity be equal to the calculated service load or around 80% of the switch rating, whichever is greater. For example, if your calculated service load is 120 amps, the service switch must be 200 amps. In this example, the minimum service conductor ampacity is 160 amps (80% of 200), not 120; the load conductors from the switch to the panel must also be the same 160 amps. Neutral – Can, at times, be bare; some jurisdictions will allow a Neutral wire in the service panel pipe to come from the service meter into the service panel. Something else to consider in regards to this is that using a bare wire saves you money and is easier to work with / form when pushing it through PVC piping with tight corners. On the other hand, the insulated wire can be greased easier. When a bare neutral wire is entered into the meter base, switch, or panel, it must be insulated to protect against contact with any live wires. Usually, this is not a problem as the live wires are separated widely enough for any contact with the neutral. Still, in cases where it isn’t, one must insulate the neutral wire (electrical tape) to the same thickness as the insulation of the hot wire. Also, you would insulate from the entrance until the connecting coupling (any exposed sections). ====================gtg ==================gtg ====================gtg ========================gtg A Typical Lightning and Earthing Issue The Problem I have an alternative power system at my house in an area susceptible to lightning. This consists of a wind generator, 4 solar panels, two inverters, various controllers, and a 1200 amp/hour battery set in a small "energy center". I have already been 'hit' by a remote strike which traveled up the phone cable around the walls of the building and took out my new sine wave inverter!! Although all items were earthed and bonded to a single point, it was insufficient. All items in the system are close together. The fall-back diesel generator is also inside the same building. I have read almost ALL the literature I can find on the Web on bonding/earthing systems and the effects of lightning. My biggest problem lies in that - with the equipment available to me - I cannot sink a 3/8" earthing rod very far into the ground around the house since it is on a solid rock mountainside. Therefore, I would be glad for your advice on various issues. Response First, you don't mention either the DC voltage or the duration of backup , or the power level. I have assumed 120Vdc, 1 hour (nominal) 100A inverters. What was the route from the phone line to an inverter? Can you demonstrate that this was the path by damage, or is this an assumption? Experience tells us it is much more likely a ground strike raising the earth potential of your system and thereby causing the damage. Telephone wires are thin and unlikely to carry seriously damaging currents. Specific Questions 1. Should I use earthing rods of larger diameter? A larger diameter will not help, as the surface area is critical. However, in the solid rock, it is unlikely 1.5 meters would be sufficient. The earth rod aims to achieve a low impedance to the earth of approximately 0.4 ohm. A test drilling and rod measurement would answer how deep you need to go, but this seems like a lot of hard work for little return. 2. Since I cannot drive them into the ground more than 1.5 meters should I use several 'grouped' together? Yes, this "Earth Net" or "Earth Farm" approach is advocated by several experts for overcoming high impediments to earth. 3. If so, how many should I use? This is almost impossible to answer, as there are so many variables. I'd suggest that you put in as many as it takes to get your target impedance value. 4. How should they be grouped? How far apart? How should they be joined? If you put them apart, there is a potential for current to flow between them, so whatever links them together must be low impedance. They should be grouped in a star configuration for small earth farms or a network configuration for larger ones. 5. How should I connect the various items of equipment? One expert report suggested copper "strapping" rather than heavy duty copper wire. To be honest, large-diameter copper wire can cause several problems when conducting high current impulse energy; stranded or braided "strapping" is better but more expensive. It is common practice to use large single strands in external rods/nets and braids where appropriate indoors. In addition, you have the "Aerial" effect where a large loop of copper can act like the loop aerial on a TV and pick up high frequency. 6. What size strapping or wire? Back to your target impedance, there is no point getting a 0.4ohm Earth and then connecting such thin copper to it that you reduce its effectiveness; on the other hand, the cost is the limiting factor upwards. 7. Where should the connections be? I'm aware that they should be to the earth point and any frame, but should they be anywhere else? I'd recommend that you avoid Loops and create Stars to your earth point. You need to make connections wherever energy can be created by fault or coupling effect. 8. Are the connection points themselves a particular problem? Do you have any suggestions? Again a low impedance connection is an aim, as two clean flat surfaces together are better than a clamp on a screw thread. In addition, each connection point should increase the gauge of the conductor so that the preferred path for energy is the desired direction. 9. Do I run a single cable from each item back to the rods, or can I run a "ring main" around them? I'd recommend that you avoid a loop and create a star instead. 10. What size cables/strapping would you recommend for each item? These should be the appropriate size for the likely "energy" associated with a fault and should increase in size towards your earth point. 11. A report that I read suggested that the NEGATIVE side of the battery set (2 parallel racks of 12 x 2v [600 amp/hour] cells) MUST also be connected to the common earth. Is this correct? This depends entirely on your inverter; if your inverter operates with one side of the battery earthed, it should already be connected, although this is down to how good your earth is. If your earth is bad, the connection allows energy into the inverter front end, which is typically susceptible to damage. Conversely, this is probably a good idea if your earth is good. 12. What is the additional effect of connecting the batteries into the earthing system using, for example, more or heavier rods? The only reason for increasing the earthing size by connecting batteries is if they are likely to induce an earth fault, which should not apply in your case. 13. Several suppliers have suggested I include several lightning/surge arrestors. Is this a good idea? This is a vast subject. In basic terms, "lightning" cannot be arrested - the best that anyone can hope to do is divert the energy where it will do the least harm. Electricity Substations do this by using large spark "arrestors" that disconnect explosively, dissipating energy. Large factories and new building installations tend to feature earthing, preventing energy from entering their wiring network by diverting it to earth rods. Typically, this is augmented by "surge suppressors," which can absorb some energy, and "surge diverters," which can divert the excess back into the earthing system. However, there is no point in diverting energy to earth if your earth is so poor, it will dissipate anywhere you have connected to the earth. Moreover, a surge suppressor is expensive and may be a one-shot device for serious amounts of energy. Having said that, a clearly defined approach, identifying good earthing, diversion, and suppression, is what most people look for in these circumstances. However, at least one of these three items will often have little effect. The customer frequently needs to contact an expert when one approach has failed. 14. If I use surge suppression, how many devices will I need? Where do I put them? How do I earth them? You need to adopt a zoned approach, with larger TVSS near incomers/outgoing supplies, large pieces of equipment, and smaller devices on smaller systems. Each unit comes with wiring instructions and recommendations , including the earth cable size. As before, the earth cable should run back to the star point. 15. How do I eliminate the effects of lightning through and around the walls of the building? You can't completely eradicate these effects. The best you can expect is to deal with the effect and limit the damage unless you wish to line your walls with steel and bury them deep in the ground! However diverter/suppressors fitted for transmitted energy will be just as effective for coupling energy. 16. Do you have any other suggestions that could help? Three additional suggestions might help: - a. Consider earthing alternatives. Our recent customer ran a bare cable into the sea because he was on solid rock. b. Consider inverter technologies that are less susceptible to damage. c. Identify the REAL cause of the damage and spend money to fix that problem. The biggest problem with earthing and transient suppression is spending money on the wrong solution. ==============gtg ================gtg =================gtg use in website We’ve been the local electricians for over 40 years. In that time, we’ve firmly established our reputation as honest and reliable electricians delivering the highest quality workmanship at affordable rates. We cater to all your electrical needs, whether residential or commercial. No matter the task, you’ll always find our electricians will arrive on time and complete the work to a level you’re satisfied with. Our first-class service is why we’re the electrician that residents have trusted for over three decades. Although our electrical work is always completed to the highest possible standards, our prices remain extremely affordable. We can keep prices down by remaining local and having our electricians service the area. 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