Exothermic welding looks very easy and it is, until it isn't. There are times when the welds don't stick, or the weld material all runs out on the ground. There are simple solutions to most of the problems associated with Cadwelding.
A new mold is great to work with. If it is taken care of properly, it will give long term satisfactory use. Do not clean your molds with wire brushes, screwdrivers, pliers or anything that will scratch the mold. These scratches are the start of the deteriorating effects. The weld material doesn't flow properly, the mold doesn't fit snuggly, harder each time to clean it out. The mold manufacturers sell brushes specifically designed to clean the molds. For the price of one mold, you can buy 18 brushes.
Properly cleaning the wire and surface to be welded to are just as important. Impurities have a negative effect on the welds. Make sure all the dirt, oil, grease, water, etc. have been removed.
Pre-heating the wires and/or metal surface before attempting to shoot a weld aids in the welding process. If the wires or metal surface are too cool the welds won't stick.
Sloppy molds are difficult to use, but we have all had to use them at one time or another. To stop the weld material from running out, Cadweld sells mold sealer (looks exactly like duct seal). I have found this doesn't work very well and leaves a sticky mess on the mold. I prefer to get the mold set and then pack moist dirt around the mold. The cool wet dirt makes the weld material cool faster and stops the flow. Duct seal just melts and creates a bigger mess.
Cadweld also sells copper strips that can be used to increase wire size. For example, you have a 4/0 run & tap mold but you need to tap off your 4/0 with a 2/0. These copper strips are wrapped tightly around the end of the wire increasing the 2/0 to the same diameter as the 4/0. Much easier than cutting small strands of wire and trying to fit them in the mold. The strips save time, which saves money.
Wednesday, February 16, 2011
Saturday, February 5, 2011
Rules and Regulations
In our society we have plenty of rules designed to protect stupid people from themselves. We have found the lowest common denominator to abide by. Should the NEC follow suit?
There is another website, a forum for electricians, that I recently joined (a very good website). There have been numerous discussions on multi-wire branch circuits (MWBC). Sharing a single neutral with 2 or 3 phase conductors is perfectly safe if installed properly and maintained by qualified electricians. But there are inherent possible problems. Lifting the neutral at the panel can cause voltage spikes on the phases, damaging connected equipment. Trained electricians know how to avoid this, but what about the guys that don't have a license or apprenticeship schooling. They learned on-the-job from other electricians. These other electricians may or may not have had any schooling either. They may have learned on-the-job too. This leads to a relaxed attitude toward licensing, the "I know what I'm doing, I've been doing it for 20 years" attitude. Doing it wrong for 20 years doesn't make one a qualified electrician. With the growing number of non-licensed electricians performing electrical work, should the code enact stricter rules to safeguard the public? I read numerous statements from opponents on this, "If I install it properly then I have done my job and I can sleep at night. What do I care if some idiot comes along after and screws things up?" I think the real question is how much do we owe the end user. If I install the electrical system per code and another electrician comes in to perform additional work and is either lazy or uneducated concerning the hazards of MWBC's, the end user may suffer equipment losses. This could be very expensive.
Others have stated that we just need to enforce the rules we already have. How do we do this? Is the answer stricter licensing requirements for electricians? Should apprenticeship training be mandatory? If we abolish the on-the-job training only approach we will develop better tradesmen. Requiring apprenticeship training would insure that knowledgeable persons perform electrical work. Those that don't make the grade would be weeded out. Electrical work is dangerous and should only be done by trained people, not homeowners, not plumbers, not A/C techs. If it is done improperly it can , at worst, cost lives or, at least, cause nuisance tripping of ocd's.
Let's hear your thoughts.
There is another website, a forum for electricians, that I recently joined (a very good website). There have been numerous discussions on multi-wire branch circuits (MWBC). Sharing a single neutral with 2 or 3 phase conductors is perfectly safe if installed properly and maintained by qualified electricians. But there are inherent possible problems. Lifting the neutral at the panel can cause voltage spikes on the phases, damaging connected equipment. Trained electricians know how to avoid this, but what about the guys that don't have a license or apprenticeship schooling. They learned on-the-job from other electricians. These other electricians may or may not have had any schooling either. They may have learned on-the-job too. This leads to a relaxed attitude toward licensing, the "I know what I'm doing, I've been doing it for 20 years" attitude. Doing it wrong for 20 years doesn't make one a qualified electrician. With the growing number of non-licensed electricians performing electrical work, should the code enact stricter rules to safeguard the public? I read numerous statements from opponents on this, "If I install it properly then I have done my job and I can sleep at night. What do I care if some idiot comes along after and screws things up?" I think the real question is how much do we owe the end user. If I install the electrical system per code and another electrician comes in to perform additional work and is either lazy or uneducated concerning the hazards of MWBC's, the end user may suffer equipment losses. This could be very expensive.
Others have stated that we just need to enforce the rules we already have. How do we do this? Is the answer stricter licensing requirements for electricians? Should apprenticeship training be mandatory? If we abolish the on-the-job training only approach we will develop better tradesmen. Requiring apprenticeship training would insure that knowledgeable persons perform electrical work. Those that don't make the grade would be weeded out. Electrical work is dangerous and should only be done by trained people, not homeowners, not plumbers, not A/C techs. If it is done improperly it can , at worst, cost lives or, at least, cause nuisance tripping of ocd's.
Let's hear your thoughts.
Monday, January 24, 2011
PPE
Let's face it, there are times when it is just easier to do our jobs without having to get all the personal protective equipment (PPE). We save time not having to hunt it down, not putting it on, not taking it back off, not putting it back where it belongs. We save money not having to buy it. It gets in the way while we are working, it gets hung up on everything as we try to get to our task, it's uncomfortable. But, you have to ask yourself, are the cons outweighing the pros. PPE saves lives and limits injuries. Can you really put a price tag on that? Did those few extra minutes really payoff against the trip to the hospital?
Many of us "oldtimers" remember the "good ole days" when construction work was fun. We joked around all day, played practical jokes on each other, and got more work done. We didn't have to put on safety glasses to cut anything. We climbed steel and walked beams without having our safety belts attached to anything until we got to where the work was. Looking back now I realize how lucky I was on numerous occasions.
We don't think accidents will happen to us. We pay attention to what we are doing. We have training. We know our jobs. But accidents don't discriminate. They do happen to anybody. It doesn't have to be something you did or didn't do. It could be the person you're working with, faulty equipment, incorrect as-builts you're working from, etc.
Safety harnesses have gotten lighter, but stronger, making them more comfortable to wear. There is never any reason not to wear one when working at heights. Even if the fall is not enough to be fatal, it may still break an arm, leg or possibly spine.
Hard hats protect our most valuable asset.. our brains. Sure they won't do anything if a transformer falls on your head, but the everyday bumps and knocks and small falling objects will be deflected rather easily with minimal or no injury.
Safety glasses protect our second most valuable asset.. our eyes. Sure there are plenty of blind people that lead fulfilling lives, but I still believe it's better to see the world we live in. How many blind electricians do you know?
Face shields add that next level of protection for face and eyes. It provides better coverage and should be utilized when necessary.
Gloves protect our hands from cuts, abrasions, chemicals, heat, and cold. Even minor cuts are a nuisance.
Proper footwear, proper clothing, the list keeps going. They are all designed to make our jobs safer, so we can go home to our families each night. Re-think your opposition to using PPE, it might save your life one day.
Friday, January 21, 2011
Let's Talk Transformers
We use transformers for all types of jobs. There are step-up transformers, step-down transformers, potential transformers, current transformers, auto transformers, buck-boost transformers. Each is designed for a specific use.
Basic design involves a magnetic core with primary windings and secondary windings. The number of primary windings to secondary windings (winding ratio) determines the voltage ratio. A 2-to-1 ratio would give us 120V and 240V, 240V and 480V, etc. Transformers have inherent losses built into them. Designers/engineers try to come up with new ways to reduce these losses. One type of loss is eddy current. Ferromagnetic cores are good conductors and constitute a single short-circuited turn throughout its entire length. Eddy currents flow along the core in a plane normal to the flux (magnetic field developed from the applied voltage and current) and create resistive heating. Heat equals energy loss. Eddy current losses are a complex function of the square of supply frequency and inverse square of metal thickness. Most designers now utilize thinner, insulated metal plates laminated together to form the core in order to reduce the effects of eddy currents. By using this design, however, there is another phenomena created. Magnetostriction is the effect of magnetic flux in a ferromagnetic core that causes the expansion and contraction with each magnetic cycle. This is what causes transformers to hum.
Autotransformers utilize a single winding with two end terminals and one or more terminals at intermediate tap points. Primary voltage is applied across the two end terminations and the secondary is usually connected across one end terminal and an intermediate tap. These transformers are cheaper to manufacture but are not as safe as separate primary and secondary windings. Another style utilizes exposed windings in the intermediate area and uses a brush to make the secondary connection. The brush can be moved up or down the exposed section to increase or decrease voltage output. A rheostat is an example of an autotransformer.
Leakage transformers have a significantly higher leakage inductance. This loose coupling between primary and secondary provides an inherent current limiting effect. This makes it possible to create a short on the secondary side and not cause damage to the transformer. Doorbell transformers are an example of this design.
Current transformers and potential transformers, also known as instrument transformers, are used for measuring current and voltage in electrical power systems, and for power system protection and control. These transformers are used where it is impractical or unsafe to use conventional meters to measure voltage or current due to the high values present. Current transformers measure current in a circuit without being electrically connected to that circuit. It consists of a core, usually circular or rectangular, with a single set of windings and two end terminations. The circuit to be measured is routed through the center of the core, and as current flows through the circuit it induces a current in the CT which sends this to either a meter or control device. A potential transformer is designed to be connected in parallel with the circuit to be monitored to provide a consistent value (proportional to circuit values) that can be measured or controlled. These transformers impart a very small load to the circuit, but provide a means to measure the voltage safely and accurately.
Basic design involves a magnetic core with primary windings and secondary windings. The number of primary windings to secondary windings (winding ratio) determines the voltage ratio. A 2-to-1 ratio would give us 120V and 240V, 240V and 480V, etc. Transformers have inherent losses built into them. Designers/engineers try to come up with new ways to reduce these losses. One type of loss is eddy current. Ferromagnetic cores are good conductors and constitute a single short-circuited turn throughout its entire length. Eddy currents flow along the core in a plane normal to the flux (magnetic field developed from the applied voltage and current) and create resistive heating. Heat equals energy loss. Eddy current losses are a complex function of the square of supply frequency and inverse square of metal thickness. Most designers now utilize thinner, insulated metal plates laminated together to form the core in order to reduce the effects of eddy currents. By using this design, however, there is another phenomena created. Magnetostriction is the effect of magnetic flux in a ferromagnetic core that causes the expansion and contraction with each magnetic cycle. This is what causes transformers to hum.
Autotransformers utilize a single winding with two end terminals and one or more terminals at intermediate tap points. Primary voltage is applied across the two end terminations and the secondary is usually connected across one end terminal and an intermediate tap. These transformers are cheaper to manufacture but are not as safe as separate primary and secondary windings. Another style utilizes exposed windings in the intermediate area and uses a brush to make the secondary connection. The brush can be moved up or down the exposed section to increase or decrease voltage output. A rheostat is an example of an autotransformer.
Leakage transformers have a significantly higher leakage inductance. This loose coupling between primary and secondary provides an inherent current limiting effect. This makes it possible to create a short on the secondary side and not cause damage to the transformer. Doorbell transformers are an example of this design.
Current transformers and potential transformers, also known as instrument transformers, are used for measuring current and voltage in electrical power systems, and for power system protection and control. These transformers are used where it is impractical or unsafe to use conventional meters to measure voltage or current due to the high values present. Current transformers measure current in a circuit without being electrically connected to that circuit. It consists of a core, usually circular or rectangular, with a single set of windings and two end terminations. The circuit to be measured is routed through the center of the core, and as current flows through the circuit it induces a current in the CT which sends this to either a meter or control device. A potential transformer is designed to be connected in parallel with the circuit to be monitored to provide a consistent value (proportional to circuit values) that can be measured or controlled. These transformers impart a very small load to the circuit, but provide a means to measure the voltage safely and accurately.
Time For Another Tip
Have you ever been drilling with a holesaw and just when the pilot bit breaks through the teeth on the holesaw grab and snap your pilot bit? Well here is a simple trick to help eliminate that. Place a 1/4" X 1 1/2" fender washer over the pilot bit for holesaws up to 1 1/2" (1 1/4" conduit size). When the pilot hole is drilled, the teeth on the holesaw grab the washer, spinning it instead of grabbing. For larger holesaws you can stack 1/4" X 1 1/4" fender washers until there are 2 washers protruding past the teeth on the holesaw.
Submit your own tips and tricks.
Submit your own tips and tricks.
Tuesday, January 18, 2011
A Few New Code Changes
The new 2011 NEC is out. Hopefully everyone ran out and purchased one for themselves. This year they came with a free .PDF version that can be downloaded at their website, www.2011NECOFFER.ORG. As everyone knows, the code is released every 3 years and it always has tons of changes. I thought I would discuss some of these. I will do more each week so as not to make this one long boring read.
I want to start off with Section 110.11. The new requirement is to protect equipment identified for indoor use, dry locations, or damp locations from damage DURING construction. So don't be hanging panel boxes before the building is dried in unless you have some way to protect it.
110.24 (A) Field Marking. Service equipment in other than dwelling units shall be legibly marked in the field with the maximum fault current. The field marking shall include the date the fault current calculation was performed and be of sufficient durability to withstand the environment involved.
220.5 (B) Fractions of an Ampere. Calculations shall be permitted to be rounded to the nearest whole ampere, with decimal fractions smaller than 0.5 dropped.
Doesn't seem like that big a deal, until you get an inspector that argues you have exceeded the amperage limits. Suppose you calculate 16.4 amps for a 20A circuit, now you can drop the .4 and use the 20A circuit.
250.24(C)(3) Delta-Connected Service. The grounded conductor of a 3-phase 3-wire delta service shall have an ampacity not less than that of the ungrounded conductors.
You may not derate in this situation.
250.30 (A)(2) Supply-Side Bonding Jumper. If the source of a separately derived system and the first disconnecting means are located in separate enclosures, a supply-side bonding jumper shall be installed with the circuit conductors from the source enclosure to the first disconnecting means. A supply-side bonding jumper shall not be required to be larger than the derived ungrounded conductors. The supply-side bonding jumper shall be permitted to be of nonflexible metal raceway type or of the wire or bus type as follows:
So if you install a transformer in a building and the disconnecting means is not located in the transformer enclosure then you must install a supply-side bonding jumper along with your ungrounded and grounded (neutral) conductor. Do not forget the rest of the requirements in Article 250 regarding separately derived systems.
More to come.....
Sunday, January 16, 2011
Troubleshooting
I'd like to pass on an experience we had recently at one of our new projects. We had just finished installing the parking lot pole lights and were power checking them. As soon as the breaker was turned on it tripped out. The electrician assigned to the task of troubleshooting decided to start at the panel checking for shorts. He then moved to the lighting contactor, then the electronic time clock before he moved to the first pole. He spent 4 hours taking off covers, checking, replacing covers and moving on before he finally found the problem in the first light pole. A good place to start would have been at the first pole. He would have isolated the interior section of wiring from the exterior section. It would have cut the circuit almost in half. Even if the problem had been in one of the other poles he wouldn't have wasted all that time removing and replacing covers.
Troubleshooting should be looked at in a logical manner. What is supposed to be happening? What type of problems could cause this not to happen?
Having the proper testing equipment will also save you time and more importantly keep you safer. I was reading on another forum about an old school electrician that uses a homemade buzzer with a 9 volt battery for a continuity tester. What happens if he were to place his tester on a live circuit by mistake? Chances are it would blowup in his hands. Todays meters are built to stringent standards to comply with not only the technical specifications but the safety specifications too. Having the right type of meter will also make your job of troubleshooting easier.
Here is another example. We received a trouble call from a new client. He had been using one of our competitors for quite some time, but they were swamped and not able to take care of this call. This customer had some nice accent lighting in their display room. It uses a transformer converting the 120V to 24V. It is connected to 2 wires that are run exposed 6" below the ceiling on insulators spaced 36" apart. The light fixtures lay on the two wires and set screws clamp the fixtures to the wires. The problem they were experiencing was the transformer kept going bad. The previous contractor had replaced it twice at a cost of $300 each. We counted the number of fixtures, calculated total watts, checked the transformer output. Everything was correct. We used an ammeter to check circuit amps. It was higher than the calculated load. We removed all the fixtures (there were 8). We used a true RMS DMM (digital multimeter) to check continuity of the two 24V wires. They tested fine. We used the same meter to test each fixture individually. They tested fine also. I decided to bring in the megohmeter and retest the fixtures. We found a high impedance short in one of the fixtures. We ordered a new fixture and the circuit has been trouble free since. Would we have figured this out without the megohmeter? Probably not. Would we have figured this out if we hadn't known to check for a high impedance short? Definitely not. Schooling, equipment, trade experience, interviewing are all necessary parts to becoming a successful troubleshooter.
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