Adding grounding through cinderblock

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  #1  
Old 12-03-04, 08:00 AM
FordsTowel
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Question Adding grounding through cinderblock

My recently purchased, 1950s, cinderblock house has several outlets that have no ground connection. I assume I'll have to purchase the appropriate Romex and rerun it through the original paths. Is this possible, do-able, feasible? Is there a better/easier alternative?

The house has standard cinderblock exterior walls, covered by auminum siding. The interior walls are narrow cinderblock (not just the load bearing wall). The service had been upgraded to include a breaker box and GFI outlets in the kitchen and bath.

I'm concerned that modern, expensive, electrical devices are at risk without a ground; and, I need to use a cheater just to run our carpet cleaner and other three-prong devices.

Any help is, of course, much appreciated.
Doug
 
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  #2  
Old 12-03-04, 08:19 AM
SkyKing
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I have a read a number of posts where the solution was to use GFI outlets to solve the three prong problem. Not the most elegant, but if you are thinking of pulling wire through cinderblock walls and are having difficulty, this could be an option for you.

But others will be of more help!
 

Last edited by SkyKing; 12-03-04 at 08:29 AM.
  #3  
Old 12-03-04, 08:26 AM
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GFCI makes it legal and much safer, but is not the solution for electronic gear. To protect your computers and electronics, running a new grounded circuit is the answer. Rerunning it through the original paths offers no advantage. Rerun it the best way now, regardless of the original path.
 
  #4  
Old 12-03-04, 11:55 AM
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Is there an attic or accessable crawl space above the top of these walls? If the answer is yes then you have a better than even chance of being able to run teh new cable or ground wire through the cavities in the cinder block. If not then tell us what you have for base boards and interior wall finish.
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Tom H
 
  #5  
Old 12-03-04, 03:57 PM
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Is this house wired with romex type cable or conduit. If it is conduit it will be easy.
 
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Old 12-04-04, 06:50 AM
FordsTowel
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Smile

Here I've gone and made the classic mistake of not giving enough information, haven't I?

The house is on a slab, no crawl space or basement. The interior surfaces are lath and plaster.

The roof has a nicely tall pitch, so working up top is relatively easy, except at the most outside walls where a lot of the outlets requiring a ground reside.

I believe, from the interior outlets I've had to excavate and patch around, that conduit was used throughout; but the wiring seems to be an old cloth covered variety in some cases.

Might I be able to fuse the new wiring to one end of the old, and just pull it through? This is what I am most hoping to hear, but the top run of blocks seems filled with mortar (probably to limit heat loss, and moisture caused mold), and I'm at a loss as to how to handle the replacement if there are cases where conduit was not used, and the filled areas impede wire movement.

I certainly appreciate the immediate interest in my dilemma. Thanks ALL!
 
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Old 12-04-04, 07:01 AM
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Sorry to be the bearer of bad news, but unless the old wiring is in conduit, using the old wiring to pull the new wiring will be quite impossible. I suggest you consider leaving the old receptacles on the exterior walls ungrounded, and installing new grounded receptacles on interior walls. You may have to move a bit of furniture around to make it work for you. Another option, although not satisfactory to many people, would be to run conduit on the exterior of the house to new grounded receptacles. Remember that you probably just need a few grounded receptacles--they don't all need to be grounded.
 
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Old 12-04-04, 07:02 AM
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If conduit was used then you are in luck. If conduit was used in some places in the walls, then it was likely used everywhere. Remove the receptacles in question and check. Do this with the power off! check where the wires enter the receptacle. You should be able to tell.

If conduit was used then you can use the old wires to pull new wires, but you will need to know where the conduit runs to/from. This requires a detailed "map" of the house and some trial and error. You attach the new wires to the old ones and then pull from the other end. Make sure that you use wire lubricant on the wires. This job takes at least two persons.

Running new wire would be the time to decide if you want to upgrade from 15 amp circuits to 20 amp circuits. I would certainly do this, especially if the wiring is old, when they placed many receptacles on a single circuit.

However, if conduit was not used then you cannot pull new wires with the old.
 
  #9  
Old 12-04-04, 10:58 AM
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The conduit itself may be in good enough condition to serve as the Equipment Grounding Conductor (EGC). The first order of business is careful testing. You will need some sort of Volt Ohm Meter (VOM). Take a radio and plug it into each outlet in turn. Test deenergize circuits until the radio goes silent. You could also buy a tracing set for about thirty dollars at a home center that avoids the need to deenergize the circuits repeatedly.
http://www.twacomm.com/Catalog/Model...7X1AJH0U925XA1
Once you have all of the receptacles mapped as to what Over Current Protective Device (OCPD) [i.e. fuse or circuit breaker] protects the wiring that supplies them you can move on to the next step.

If you can rent or borrow a Ground impedance tester such as the ideal sure test
http://www.twacomm.com/Catalog/Model...7X1AJH0U925XA1
the task of testing for ground impedance becomes very easy. Without one you will have to make up some test loads and do a lot more work. The first test load is a male cord cap or plug end with a resister installed in it. Use a 1200 ohm resister that is rated for at least two watts. In theory it will only be subjected to one watt so the two watt rating provides a margin of safety. The resister is wired between the ground pin and the short blade of the cord cap and the cover is installed over the resister to avoid any possibility of electric shock. You will also need a battery operated head lamp to light your work. With the panels main fuses or breaker open and the circuit under test isolated by opening it's OCPD you conduct a preliminary test of each outlet by measuring the resistance between the hot conductor and the EGC at each outlet in turn.

WARNING NOTICE DANGER If the testing cannot be done with the everything except the panels main supply lugs deenergized do not proceed. If the testing will put you at risk of contacting the main lugs then do not proceed.

If the resistance measures higher than 1260 ohms the circuit will need work before installing the grounding type receptacles. If all outlets on a given circuit measure fairly close to 1200 ohms you will move on to the second test.

Make up a three foot cord with the ground and neutral conductors reversed in the cord so that you can apply a load between the hot and ground. Use a triple tap to plug in the test leads and your dummy loads to the the test cord. The dummy loads will consist of a sixty watt incandescent bulb and adapter to permit it to be plugged into the test cord. At each outlet to be tested you connect a three wire adapter to the cover plate screw of the receptacle, plug in the test cord, plug in the meter and note the voltage, and plug in the test bulb and note the voltage again. This imposes a test load of half an ampere on the EGC which in this case is the conduit. If the voltage drops measurably the Conduit will not serve as an adequate EGC. If the voltage remains stable go on to the third test.

The third test uses a portable hair drier or an electric heater as the dummy load. Best results will be obtained with a dummy load that draws fifteen ampers. That is 1800 watts. Note the no load voltage. Apply the load on it's lowest setting only long enough for the meter to get a new voltage reading. If a stable voltage reading is not obtained in three seconds shut off the test load. The circuit impedance is too high and the EGC has failed testing. Shut off the load and calculate the percentage of voltage drop. If it exceeds five percent the EGC is inadequate. Repeat the test at the test loads highest setting. Again the voltage drop must not exceed five percent.

Remember test loads are never applied for more than three seconds. If the test fails at one level do not go on to another test. The circuit will need work before you can use it's raceway as an EGC. This testing regimen is not appropriate for circuits that are contained in any form of armored cable or BX. If there is any such cable in the circuit arcing and fire could result from application of the test loads.

Every receptacle that passes all three test can be replaced using a self grounding receptacle.
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Tom H
 
  #10  
Old 12-08-04, 06:18 AM
FordsTowel
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Thank You Everyone!

John: I'll certainly consider moving furtniture over new outlet installation. I certainly wouldn't want to try and install wiring under (or over) my siding.

Racraft: Thanks for the reminder about lubricant. I can see myself going through a lot of unsuccessful effort before this even might have occurred to me.

Hornet: Wow! That's a finely detailed plan. Without it, I wouldn't have had a clue how to run a test like that!

I have a volt-ohm meter, and a five-dollar socket tester (the three-LED type).
I got the tester because I knew that several of the sockets had reversed polarity and I wanted to be able to check them after fixing that.

I did try attaching the ground to the outlet box, to see if the socket registered as grounded. My assumption was that, with the box attached to the conduit, I'd know if it was sufficiently grounded. It occurred to me, later, that the conduit must also be attached to a ground if that is to work. That's when I decided to research the wire replacement option.

I'll be checking my outlets this weekend, and if possible begin the testing.

Thanks again, everybody,
Doug
 
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