Wednesday, August 28, 2019

Construction - Electric Rough-in - A Lot to Think About

The roof is protected by a layer of 6 mil plastic, 
stick-built walls with plastic or lumber wrap;
 (the photo predates installation of windows).
Ideally, our structure should have been buttoned up before roughing in the electric and plumbing.  However, a combination of wet/cold weather and the slower progress when working alone delayed the steel roof installation to the extent that we had to do the electric and plumbing rough-ins under temporary roof and wall protection and during cold weather in lieu of working outside.

The plumbing rough-in, particularly the waste side, was much more challenging to my DIY skill set than the electric rough-in or at least I thought so going in.  I had done enough electrical work
previously that I was comfortable with wiring a house from scratch once the installation of the service panel and meter box were done by professionals and inspected by the city.  However, it took Rex Cauldwell's quintessential book to make me realize that there was much to learn.  Oh sure, I could make things work but, after reading Cauldwell, clearly not always up to professional standards.  This time around, mere code compliance gave way to Cauldwell's "above code" methods whenever possible.  Moreover, my experience had been limited with respect to upgrades like GFCI and AFCI circuit breakers, surge protectors, dedicated circuits for electronic equipment and multiple ground rods.  To say the least, a lot to think about. 

Circuit Design
The first task was to diagram the circuits so that they were balanced as to the amount of amperage they would carry and, as much as possible, limited to as small of an area as possible.  For example, dedicated circuits for
Click on the drawings to enlarge them for better viewing.
the kitchen, laundry and bathrooms are best.  Circuits for smoke alarms and for electronic equipment such as TV's and computers are dedicated circuits as well.  Circuits that are not dedicated were balanced so that it would be unlikely for any to be overloaded in the future.  Once I was happy with the diagrams (plural because the first and second floors were diagrammed separately), the circuits were numbered and color-coded then glued over

architectural floor plans over a white background such that the architectural drawings showed through the diagrams.  The resulting composites were then posted opposite the breaker box for consultation while wiring.  I plan eventually to cover the diagrams with Plexiglas as a permanent record of the electrical lay-out.  Then, a circuit can be identified on the door of the breaker box simply by the number that corresponds to its number on one of the diagrams.

Electrical Boxes
We are building a two story house with the first story being in compliance with the American Disability Act (ADA) (if a lift were to be added to the stairway, the second story would be in compliance as well). Therefore, I raised the height of the electrical boxes for wall receptacles to 18" above the floor instead of the more customary height of the length of a hammer handle.  The boxes for switches and some receptacles were intentionally situated so
The jig is screwed to the stud (arrow) and the box is
held in place against the jig while the nails are set
that the upper edge of the first course of 48" wide drywall would bisect them, making it easier to make accurate cuts in the drywall to accommodate the boxes.  This would be especially important for the exterior walls where air sealing the boxes is critical.

This venture was my first time to use plastic boxes almost exclusively.  In order to position them to be flush with the finished wall and to prevent distortion of the boxes by over-driving the anchoring nails, I made a jig to hold them in place while driving the nails.  Per Cauldwell, I used boxes with the largest volume the wall would accommodate.  For instance, the truss-supported exterior walls and the 2 x 6 wet walls (bathrooms and kitchen) accommodated single gang boxes with a volume of 22 cu in.  Slightly smaller boxes with 18 cu in were necessary for 2 x 4 walls.

Wiring the Boxes
A Cauldwell "above code" practice was to run the power uninterrupted through the boxes and use pigtails to power a given receptacle.  The alternative is the direct connect approach whereby the power enters one side of the receptacle and exits the other side on the way to the other receptacles in the string.  Using the direct approach, according to Cauldwell, can lead to overheating of the upstream receptacles should the downstream receptacles become heavily loaded, say with a bunch of high amperage appliances.  Also, if any upstream receptacles become disabled or are disconnected, those downstream also become disabled, making troubleshooting much more difficult.

Another practice that I had not always followed in the past had to do with switched circuits.  The "above code" method is to run the power to the switch box first rather than to the load first from which then to run a round-trip leg to the switch.  In the switch box, there are two options.  If there is only one load on the circuit, the power is simply run through the switch to the load.  However, if the power needs to feed other receptacles or other loads, a pigtail is used to run power through the switch for the dedicated load while the rest of the power continues downstream.  The nearby photo demonstrates this arrangement.  The yellow 12 ga conduit brings power to the box from the top and continues out the bottom to receptacles downstream.  In the box, pigtails will run power through three switches to three loads on the white 14 ga conduits exiting the box from the top.

Still another new practice for me was to use push-in wire connectors (pictured below to the left) instead of wire nuts. Not only were they much faster to use but they required much less space in boxes that were crowded by multiple wires.  Click on the picture of the switch box to appreciate how much they can de-clutter a box.  And it is not
always easy to be sure that all the wires inside a wire nut are in proper contact, even after twisting them, while push-in connectors have see-through sides for visualizing the stripped ends of the wires to be sure they are fully seated.  Finally, the local building inspector requested that I use the type of staples pictured at the right instead of the more ubiquitous wire staples in order to lessen the chance of damage to conduits by over-driving the wire staples.

Cauldwell also schooled me on taking care to
make sweeping turns with Romex cable as seen in the nearby photo.  If the cable is bent sharply around a right-angle corner, dangerous overheating can result. 

Ground-Fault Circuit Interrupters and Arc-Fault Circuit Interrupters
I adopted another "above code" feature by using Ground-Fault Circuit Interrupter (GFCI) and Arc-Fault Circuit Interrupter (AFCI) circuit breakers rather than individual GFCI or AFCI receptacles at the point of use.  (Actually, to be more precise, I used the modern GFCI-AFCI breakers on most of the circuits and the combination AFCIs that are described below.)  Using GFCI and AFCI breakers instead of individual GFCI and AFCI receptacles has several advantages:  (a) longer lifespan for breakers compared to receptacles, (b) receptacles have to remain accessible (can't be hidden behind furniture, appliances, drapes, etc.), (c) both types of receptacles are bulkier than conventional receptacles and require a box that is deeper than is always available, (d) AFCI receptacles "come with a long list of inconvenient installation rules" (Cauldwell), and (e) since all GFCIs and AFCIs need to be tested regularly, it is more convenient to check them all at once at the service panel than sorting out their many locations downstream. 
The edgewise 2 x 4s frame a plywood runway in the
 "vertical basement" that channels most of the circuits
 towards the service panel (arrow).  Eventually, the
 runway will be covered with plywood that can be easily
removed for future access to the wiring.

Code now requires GFCI and AFCI protection in so many areas of the house, garage, porches and patios that the cost of our using circuit breakers was probably not much more than the cost of distributed GFCI and AFCI receptacles.  Since our house is partially earth sheltered, we are living in contact with a lot of soil, much like living in a basement where GFCIs are advisable if not mandated by code.  Even though the soil in contact with the house would ordinarily be moist/wet and therefore a ready ground for any short circuits, the soil under our house is drained dry by a series of French drains and the insulation/watershed umbrella keeps the soil behind the house dry, making it safer.  However, I decided to error on the side of caution by protecting all circuits with either a GFCI-AFCI or combo AFCI circuit breaker (the old style AFCI breaker no longer meets code in most places).
Trench holding daisy-
changed grounding rods

And one last thing that I probably would not have thought of without Cauldwell is that our hard wired smoke alarms daisy-chained on an AFCI circuit could be a deadly combination if the backup batteries in the alarms are not checked regularly and kept fresh.  Then, if a fire were to damage the circuit, the AFCI would kill the power but the alarms would still function on battery power.

Unique Grounding Issues
The electrician used the typical single grounding rod driven into the soil just below the electric meter.  However, it did not occur to either of us that the insulation/watershed umbrella next to the house would render the soil bone dry and therefore useless for grounding the electrical system.  Luckily, within a few weeks, our solar panel vendor will be installing behind the house opposite the electric meter a free-standing photovoltaic array.  The underground cable between the array and the service entrance to the house will overlay the insulation/waterproof umbrella and therefore be shallower than the 18" depth dictated by code for buried electrical lines -- a problem easily handled by encasing the cable in concrete.  I intend to include in the concrete a #4 copper wire between the service entrance and then add several daisy-chained grounding rods driven into the wet soil outside the perimeter of the umbrella.  The use of several rods 8 to 20 ft apart and 8' in length instead of a single
Grounding rod  with #4 copper wire
attached with an acorn clamp
rod is another Cauldwell "above code" recommendation.

Before an online search, I assumed that the steel roofing and siding would be susceptible to lightning strikes and would need to be grounded either directly or through the service panel  (Cauldwell recommends the latter). As counter-intuitive as it may seem, though, a metal roof is actually safer than a conventional roof in that the surge would be dissipated over a large area, particularly for a house with a footprint as large as ours, and metal roofing is non-combustible.  All bets are off however if there are metal vent pipes through the roof that could funnel a surge into the building.  Our PVC plumbing vent stacks are non-conducting so, for now at least, our metal siding and and metal roof are not grounded.

Surge Protectors
My research reveals that there are two main locations where surge protection is mandatory to protect electrical and electronic equipment throughout the house.  One is at the main service panel primarily to arrest large pulses entering through the power line such as lightning strikes and surges caused by the utilities working on transmission lines.  For this purpose, Cauldwell recommends what looks like a pair of common single-pole breakers with a green and red indicator lights (circled in the nearby photo).  The second location is at the point of use for filtering out smaller pulses that fall below the range of the breaker surge protectors.  Here it takes only a good quality surge protector receptacle strip with plug-in cord.  He also warns about using snap switches for electronic equipment that is not protected by surge protector strips.  He also recommends buying surge protector strips with coaxial cable ports so that incoming coaxial cables can be run through the surge protector before continuing on to electronic equipment. 

Circuits for Electronic Equipment
In addition to surge protection, there are two other considerations for electronic equipment ---  electrical noise and phantom loads.

Electrical noise that compromises electronic equipment can be controlled by stand-alone circuits with sufficient grounding back to grounding bus bar in the service panel.  The question then becomes.....what works best for new residential construction -- dedicated circuits or isolated ground circuits?  A fairly thorough search of the internet leads me to understand that new construction circuits like ours utilizing Romex cable affords the opportunity to use dedicated circuits having conventional receptacles to the exclusion of the much more complicated circuitry with isolated ground receptacles.  The latter is typically reserved for commercial and industrial applications having intricate interconnected metal conduits and electrical boxes.  Consequently, I ran dedicated combo-AFCI breaker-protected circuits for each potential location for TVs, computers, printers, amplifiers and, eventually, receptacles for incoming coaxial cable equipment.

A quick web search of "phantom load" reveals that the electric bill for the average home today is increased by at least $100/yr for energy consumed by modern conveniences that look turned off but are actually in standby mode.  Computers, microwave ovens and remotely-controlled appliances such as TVs consume electricity when not being used as do more obscure devices, like garage door openers, charging stations, answering machines and doorbells.  Some phantom loads (sometimes called "vampire" loads) are unavoidable such as those associated with surge protectors, smoke detectors, doorbells, garage door openers, answering machines and alarm clocks.  The remainder can be controlled simply by using switchable power-strips or by unplugging them.  However,  since we are not very diligent even with off-switching much less unplugging, I outfitted all of the dedicated circuits, as well as the the kitchen counter and laundry circuits, with wall mounted switches conveniently located (with the assumption that they do not qualify as "electronic equipment" for which snap switches are contraindicated).  Then, with a little self-discipline, we can easily control vampire loads to our surge-protected electronics as well as to appliances such as the coffee maker, microwave oven, toaster, dishwasher, automatic washer and dryer.

Unfinished Business
At the time of this writing, all that remained to complete the rough-in was connecting the cables to circuit breakers in the load center.  The advent of warmer weather, however, caused a postponement in favor of more critical outside work.  I plan to chronicle this phase as an addendum to this post in due time. 

1 comment:

As a do-it-selfer-in-training, I welcome your comments.