Sunday, May 3, 2020

Design - Solar Collector - Cont'd

The previous post on the solar collector for the AGS system dealt with the mechanisms for trapping solar energy and converting it to usable heat.  This post discusses the factors that go into maximizing the amount of solar energy collected.

Original Assumptions
My early thinking, that appears in at least one prior post, was that the best tilt for the glass and steel would be perpendicular to the sun angle for St Louis shortly after the summer solstice (June 21), say July 21.  Since the choice was empirical, I wanted to flesh it out with data if possible; hence, the following analysis based upon three factors -- optimal sun angle, warm weather collection period and available daylight.

Optimal Sun Angle
NOAA Solar Position Calculator is seemingly a useful tool for knowing the elevation of the sun angle from horizontal. However, Gary, my mathematician brother-in-law, calculated the angles and found the NOAA data to be incorrect. Following are his sun angle calculations (rounded up or down) for St Louis.  The optimal tilt for the glass and galvanized steel roofing in the collector would be 90 degrees from the sun angle during the warm season but the question is what date would be best to use as the default.  For the sake of discussion, the  figures for five scenarios are listed below :  

     June 21:    Sun elevation from horizontal = 75 degrees; collector glass angle = 15                       degrees from horizontal

     July 21:  Sun elevation = 72 degrees; glass angle = 18 degrees

     August 21:  Sun elevation = 64 degrees; glass angle = 26 degrees

     September 21:   Sun elevation = 52 degrees; glass angle =  38 degrees

     January 21:  Sun elevation = 32 degrees; glass angle = 58 degrees

A default date of July 21 with a sun angle of 72 degrees is only 3 degrees less than June 21 and, by observing the play of the sun in the collector shell for a few summers now, I think that the difference between the two is moot, i.e., the additional amount of sun entering the collector on June 21 vs. July 21 is negligible.  

The sun angle for January 21 was included above to contrast the difference between the typical passive solar design that uses the energy from the low-angle winter sun versus the high-angle summer sun that energizes our AGS system.  For solar gain in winter, the optimal tilt for our 38 degree St Louis latitude of, say, greenhouse windows, would be tilted 58 degrees off horizontal to be at 90 degrees to the sun angle compared to the 18 degrees of horizontal that optimizes the output of our solar collector on July 21 -- a difference of 40 degrees.

Parenthetically, the south facing windows of our house are 90 degrees from horizontal rather than the 58 degrees that is optimal for January 21. The 32 degree difference might be important for a classic winter-centric passive solar build but, as detailed in a prior post, maximizing solar gain in winter is not very important for our Annualized GeoSolar System, especially after the first couple of years.

Warm Weather Collection Period
In order to keep cold air out of the AGS system, the north ends of the conduits will be capped during the cold months -- roughly from the end of September until the beginning of April.  Consequently, the question becomes, "Shouldn't the default date for the sun angle fall in the middle of the six-month April through September collection period?"  If so, it would be sometime in June.  However, it is more likely that lingering cold weather in the spring will delay opening the conduits than early cold weather will cause them to be capped prematurely in the fall, thereby skewing the midpoint of the collection period backward to, say, sometime in July.  So, again, any advantage of a June default date over a July date is questionable, particularly in view of the amount of cloudy weather in the spring as discussed below and recurring warmer autumns due to global warming.

Available Daylight
In addition to optimal sun angle and which months are included in the collection period, it is useful to consider the available daylight during the collection period. NOAA's Sunrise-Sunset Calculator is helpful in this regard.  Here are some representative values spanning the seven months that would be in play as the optimal collection period.

     April 1:  12 hours, 40 minutes

     May 15:  14 hours, 18 minutes

     June 15:  14 hours, 51 minutes

     July 15:  14 hours, 35 minutes

     August 15:  13 hours, 39 minutes

     September 30:  11 hours, 48 minutes

     October 30:  10 hours, 36 minutes

These data seem to indicate that a June 21 date in the middle of a six-month collection period -- April through September -- would provide more available daylight than would a mid-July date with a six-month collection period -- May through October.  
However, according to Climate for St Louis, there is much more rain in April through June than in August through October.  More rain means less available sunlight.  Less available sunlight in spring and early summer therefore makes May through October a more attractive collection period than an April through September period despite the latter's shorter days and makes July 21 a better midpoint than June 21.

Three factors influence the choice for the best date on which to base the angle for the glass and steel panels:  (a) sun angle from horizontal, (b) the timing of the collection period and (c) the available daylight during the collection period.  A close look at sun angles and collection periods results in essentially a wash between June 21 and July 21. But the third factor, the available daylight/sunlight during the collection period, seems to tip the scales in favor of July 21 which validates my original hunch.

Tuesday, April 14, 2020

Design -- Solar Collector

Two 2015 posts detailed the construction of the dry-stacked concrete block shell for the solar collector located in front
Shell for the solar collector showing the AGS conduits
exiting the back wall of the collector 6' below the floor
 level of the house (line of holes near the bottom)the
glass top over the working part of the collector will be
 situated just above the conduits; notice the white conduits
 running to daylight at the back of the excavation for
 the house (beyond the blue tarps) at a distance of about
65 ft from the collector.  (Click any picture to enlarge it for
 better viewing.)
of the house (as opposed to the photovoltaic array behind the house). The two posts were Construction of the Solar Collector and More on the Construction of the Collector.

It is time now to convert the shell into a functioning part of our Annualized GeoSolar system -- something to which, until recently, I had not given much thought beyond realizing that it would not be as simple as covering it with glass as if it were a greenhouse roof.  Fortunately, our friend, Ben, a retired metallurgical engineer, has been sharing his knowledge.
The red arrows bookcase the solar collector, also identifiable
by the ladder protruding from it.  Although it looks as if it
is attached to the house, it is actually 18-20' away from it.
Parenthetically, notice the berm (yellow arrows) that directs
 runoff to a rain garden (magenta arrow).  The garden is the
 third in an interconnected series of four with the first one
 situated beside the garage. 

(If you are new to the blog or unfamiliar with the concept of AGS and the role of its solar collector in eliminating the need for conventional heating and air conditioning, click on "Featured Post" in the left column then follow the links to other posts on the subject. Or, for a quick overview of AGS, go to Wikipedia.)

How the Collector Will Work -- in Layman's Language
The solar collector will function as a heat exchanger.  it will use the sun's energy to heat a stream of air entering the exchanger on its south side and existing through nine 4" conduits on the north side. 
North-south cross-section of the collector. (Click on the
drawing to enlarge it.)
The air will flow between transparent glass that traps the sun's heat and corrugated galvanized roofing panels a few inches below the glass that absorbs the heat then releases it to the passing air (see nearby sketch).  

The hot air passing through the conduits will heat the earth under the house and the earth under the insulation/watershed umbrella behind the house before exiting to daylight.  And, since the conduits are slanted upwards as they fan out and run north, the heated air rises through them passively with no mechanical assistance.

How the Collector Will Work -- in Engineer-speak
According to Ben, the sun must raise the temperature of some material in the collector above that of the air in the collector in order for the collector to function as a heat exchanger.  The heated air is then forced by convection out of the collector and into the AGS conduits (which, as mentioned above, are tilted slightly up -- leaving the collector at 6' below the floor level of the house and passing under the north wall of the house at 3' before bending abruptly upward to daylight behind the house.)  For maximum efficiency, the heated material in the collector must have high solar absorptivity.

However, it is not enough to be highly absorptive.  It is also important that the material readily transfers its heat to the air, i.e., be highly emissive.  The higher the ratio of absorptivity to emissivity, the more efficient a material is for solar collection. Ben has vetted an interesting Table of Absorptivity and Emissivity of Common Materials and Coatings that lists nearly a hundred materials with regard to the ratio (third column in the table) of absorptivity (first column) to emissivity (second column). There are only five materials in the table, such as metals plated with nickel oxide or plated with black chrome, having a higher ratio than the one Ben recommends and all of them hard to find and beyond our budget.

Ben's Recommendation
Galvanized roofing
New galvanized steel, with an aborptivity of 0.65 and an emissivity of 0.13, has a ratio of 5. "Exposure to weather" (whatever exactly that means) eventually causes the ratio to drop to 2.90 which is still high compared to most of the materials listed.  Perhaps, under the glass of the collector, the steel will "weather" slower than if it were in direct contact with the elements. And steel panels are cheap enough that replacing them from time to time will not be an issue if the need arises.

The galvanized steel panels will have to be supported by something.  Ben recommends using dirt or sand which will double as a heat sink (thermal mass). When the panels are heated by the sun, most of the heat will be carried away to the conduits by air movement but some will be conducted to the thermal mass below.  When the sun is not shining, some of it will reverse-conduct into the cooler space of the collector and find its way into the conduits. 

In order to be sure that most of the heat in the sand under the galvanized roofing is not lost to the ground below, I am considering laying down at least 2" of foam board insulation before adding the final layer of sand that supports the galvanized panels.  The insulation is depicted with dashes and its label with a question mark in the drawing above because, at the time of this writing, the decision to include it was still in limbo.  .

My inclination, though, is to use it since to do so is consistent with the way we insulated under the nine conduits running between the collector and the house.  In the top photo, notice the pink vertical insulation on the east and west sides of the excavation behind the collector shell. The same insulation had already been laid down under the conduits.  The insulation in the overlying  insulation/watershed umbrella insulates the top.  A single layer of foam board surrounding the conduits was deemed sufficiently insulating because the soil on the outside of the foam is already being warmed by the overlying umbrella but perhaps the case could be made for using more than one layer in the collector.

Air Flow
The collector will have to be designed so that air flows passively between the glass cover and the steel panels.  In order to make sure the volume of air entering the collector is more than enough to replace the warm air exiting into the conduits, the square area of the air intake on the south side of the collector will need to exceed slightly the total area of the openings to the nine 4" diameter conduits.

The collector will have walkable space between the southern edge of the heat exchanger and the south wall of the collector that will not only expose the air intake but will also provide access for clearing leaves and plant growth and for cleaning the glass periodically.  

Sunken Configuration
The glass of the heat exchanger will be situated about 6' below the top of the back wall of the collector and nearly that deep in front due to its cant southward.  At first blush, it might seem that the sunken configuration will reduce the amount of useful sunshine reaching the glass.  While the east and west walls do indeed block some of the suns rays until mid-morning and after mid-afternoon during the majority of the summer collection period, their angle of incidence to the glass would be so low that most would be reflected from the surface of the glass instead of penetrating it.  Even then, the amount of glass that is shaded at 10:00 am and 4:00 pm comprises less than a third of the total.

Another reasonable objection to using a sunken configuration is that it would hold water, which could be more of a problem in the future with accelerating climate change.  It just so happens, however, that the excavation for the collector was deep enough to uncover one of the seven French drains that was installed early on to keep the soil under the house as dry as it has to be for the Annualized GeoSolar system.  The three rock formations seen in the second photo protect some of the French drains as they emerge to daylight.  The one to the left passes through the middle of the collector shell.  Without it, we would have had to install a separate French drain for the collector.

While excavating for the house and trenching for the French drains and the AGS conduits, we encountered a layer of glacial till, also known as hardpan.  As will be discussed in a future post on the actual build-out of the collector, we found that the dirt floor of the collector also comprised hardpan.  All along, rain falling into the collector must have been shunted by the hardpan to the French drain with the drain carrying it away fast enough to eliminate any pooling.  However, as part of the build-out, we removed the hardpan from the walkable space so that the concentrated flow of water from the glass panels of the collector would be carried away quickly -- by finding the French drain or by simply soaking into the newly exposed permeable soil.

Hail Damage?
One of the advantages of our southern-ish latitude is that the sun is more directly overhead, which is good for harvesting solar heat.  But it also bad because it means that the heat exchanger glass is more horizontal and therefore more susceptible to hail damage. The glass panels will be salvaged 1/4" thick tempered plate glass that will probably hold their own against normal size hail but with larger size maybe not so much.  If damage does occur, one option would be to switch to transparent fiberplass or polymer panels having UV coatings.  However, UV degradation would still limit their useful life-expectancy.

The next post will deal with the optimum angles for the glass and the steel panels.

Tuesday, March 10, 2020

Construction - Steel Siding and Soffets; Garage Doors

As early as mid-2015, we weighed several options for cladding and decided that steel siding would be, by far, the most sustainable.  In a previous post, I said.........

Steel siding is ...... "DIY-friendly, it's virtually maintenance-free, it lasts for plus or minus a century and it has a recyclable end-life. If there is a knock against metal siding, it is that it has fairly high embodied energy which,to some degree, is off-set by its recycled content".

In the first of two posts early in 2019, I described our adventures with buying steel roofing from Menards and followed it with a second post on its installation.  Our steel siding also came from Menards so the following discussion covers only the installation although its purchase was not without additional adventure as well.

As an aside, let me point out that installation of the steel roofing can be a one-person job, at least if it is not too windy, because gravity is an ally.  Installation of steel siding is another matter because gravity is the enemy.  Even with a trim piece at the bottom of the wall on which to stand the sheets while aligning and fastening them, tall panels are virtually unmanageable working alone.  And, for a watertight junction between panels, it is absolutely critical that the overlap between panels be fitted precisely before fastening -- something that is a little more difficult to do by one person.

Moisture Barrier
Joseph Lstiburek, in his excellent paper on vapor control, recommends using vapor retarders, such as house wrap or 15# felt, rather than vapor barriers such as plastic sheeting, bitumen-coated Kraft paper and, as often recommended by steel cladding manufacturers, 30# felt.  For a summary of Lstburek's paper, check out a previous post on vapor and air barriers.

In keeping with Lstiburek's advice to use a vapor retarder, our best choices were house wrap or 15# felt paper.  I opted for the felt paper due to atypical dimensions of our walls.  The south-facing walls that were closest to typical were riddled with windows which would mean wasting a lot of house wrap if it were installed first then the window openings cut out.  The rest of the walls were less than the height of a roll of house wrap -- some only a few feet high -- which would necessitate pre-cutting the wrap instead of merely rolling it out on the wall and fastening it.  And, because the joints in the sheathing were taped against air infiltration, there was no need to use the vapor retarder as an air barrier so using large pieces of house wrap that minimized the amount of taping was moot.

Consequently, I chose to use 15# felt paper as the vapor retarder.  It was cheaper, easier for two people to handle, was better suited for the short walls on top of the earth sheltered walls and could easily be customized to fit around the windows that were clustered together and also easily adapted to the sloping tops of rake walls.  We overlapped the courses by at least 6" to thwart moisture infiltration.  We taped the seams between courses with Tyvek tape, not so much as an air or moisture barrier, but to keep the wind from having its way with the felt before we could cover it with steel which proved to be only marginally effective.  Despite fastening the felt with roofing nails instead of stapling it, it pulled loose in a few areas, had to be re-nailed and the pull-through holes in the felt healed with Zip tape.

In retrospect, I would have sprung for the extra cost of the wider and stickier Zip tape that I used to seal the roof and wall sheathing instead of the Tyvek tape.  Not only would it have better protected the edges of the felt from the wind, it would have adhered better and prevented vapor penetration through overlapping edges the felt over the long run -- maybe overkill but why-not?

As is standard procedure, we used "J" trim at the left and right vertical edges of each section of wall into which the edges of the first and last panel fit as well as on each side of the window and door openings. Then any moisture circumventing
Steel "J" mold used at the edge of steel panels to divert
water downward that will eventually be overlapped and
covered by painted wood trim
the edges of a panel is diverted downward.  In order to make the house look less like a commercial building or rural implement shed, the "J" trim will eventually be overlapped by and hidden behind wood trim.  The top edges or panels below the windows
though not ending in J trim, will likewise be hidden behind wood trim.    Most of the trim will be fashioned from pressure treated 2 x 6s,\ and 2 x 8s, being mindful that pressure treated stock is typically stored wet at the lumber yard and, if not handled right, shrinks and warps as it drys.  I found early on with the mud sills under the walls that pressure treated lumber can be rendered dimensionally stable by drying it on stickers for several months, exactly like air-drying sawmill lumber.  In fact, at the time of this writing, I was already installing the trim.

The bottoms of most of the second story panels
Friend, Glen, is laying out the location of a row of fasteners
In this view, notice several things:  the rows of overlapping
15# felt paper taped together, the cedar trim board over-
lapping the termite shield with the bottom steel molding
 between it and the lower ends of the steel panels; the cedar
 board and the molding give a cleaner, less commercial
 look than if the steel panels simply terminated over the
 edge of the termite shield (click to enlarge for better detail).
overlapped the dormer flashing at the wall-roof junction.  For a more finished look, the bottoms of most of the first story panels rested on a trim piece called "bottom trim" in lieu of having them merely overlap the termite shield slightly as is probably more typical. On the front of the house, as an aesthetic upgrade, we overlapped the top edge of the termite shield with a 5/4 cedar board then rested the bottom trim on it.

Customizing the Steel
In a previous post, I described a jig for assembling trusses for the exterior walls of the house.  Eventually, I modified it as a jig to support the steel roofing while custom cutting. Then I expanded it for cutting the wider siding steel panels.  The manufacturer warns against cutting the panels with power tools, like circular saws or grinding discs, that produce red hot fragments (sparks) that burn spots in the finish of the metal, opening the way for rust.  Instead, we found that metal blades in a cordless jig saw do cut rapidly without making sparks.  The only caveat is that, in order to control vibration, the panel has to be clamped securely to the jig while cutting .  Fine-toothed blades with 30 teeth per inch minimized vibration and still cut reasonably fast.

The extra effort going into making a jig for
The width of the jig that was used for cutting the roof
panels was modified to accommodate the wider siding
 panels; the crosspiece on the near end was used to press
 downward on the panels in order to control the vibrations
caused by the jig saw.
cutting metal panels is definitely worth the effort.  However, its rectangular shape is not ideal for cutting the angles associated with hip roofs and rake walls because the panel is better supported the short side of the cut, than the long side that overhangs the end of the table more.  We tried modifying the table with an angled extension which helped but was suitable only for angled cuts in one direction while hips and rake walls needed to be diagonalized in both directions.  We finally simplified things by using the square end of the table for all cuts.  We used a specially-designed crosspiece at the end of the table for  downward pressure to control vibration.  Sometimes we supplement it by additional clamping.

We padded the foot on the jig saw to keep it from scratching the finish on the panels but two problems caused us eventually to cut all panels upside down.  The duct tape we used for padding left smudges and occasionally the tape would wear through and scratch before we realized it.  The disadvantages of upside down cutting, though, is that the layout for angled cuts is more un-intuitive and takes more concentration and the table must be thoroughly cleared of metal fragments that might scratch the front of the panels.

Fastening the Panels
The self-threading hex-headed fasteners that matched the color of the panels came with elastomeric grommets under their heads. The challenge was to drive the fasteners just enough to compress the grommets to the proper degree.  Squashing them either too much or not enough could compromise the water-tight seal under the fasteners.

Metal Soffets
The ventilated soffets were also made of steel. 
Intersecting longitudinal perforated steel
soffets framed with recycled lumber (yet
 to be painted); notice the Rain Handler
 System (arrow) in lieu of a conventional 
gutter and downspout system.
(Click on picture to enlarge for details.)
Instead of short multiple pieces running cross-ways between the fascia and the wall as is typical for most soffets today, the steel comes in long lengths that are 16" wide.  Since the soffets are 24" wide on the house and 36" wide on the porch, it was necessary to frame the metal panels with wood -- wood that, in a former life, was fir roof sheathing on a house that I salvaged previously .  By rabbeting one edge of the wood, the edges of the panels could be tucked under the framing and, 
for a better seal against insects, caulked where necessary.

Rain Handler System
In order merely to disperse the runoff from the roof instead of directing it to a few places using a gutter and downspout system, we used the Rain Handler System.  With a 2" overhang of the steel roof panels, the water falls onto the perforations in the Rain Handler and, essentially, becomes rain drops again before falling to the ground.  The dispersal adds moisture to the shallow backfill over the insulation/watershed umbrella that, because of its lack of volume, stores less moisture to nourish plant life and can use the extra water collected by the roof.  The two places where we did use conventional gutters was a short section over the front entry and another on the side of the porch under a roof valley where the amount of water often overshot the Rain Handler and eroded the soil below.

Garage Doors
Installation of the garage doors was a new experience for me but the manufacturer's detailed instructions made it relatively easy.  I will focus here only on the extra carpentry that was necessary to provide support for the ends of the tracks and the garage door openers in the presence of a vaulted ceiling.

We used a couple of long 2 x 4s that were
Boxes appended to the beam for supporting the closures
(green arrows); notice the one large window instead of
smaller windows within the doors. (Click to enlarge)
(salvaged from a pallet on which steel roofing was shipped) nailed together to form a beam spanning the width of the garage and positioned to be +/-10" above the top of the door openers and aligned with the ends of the door tracks.  It is supported in the middle by a nailer dropped from a roof truss.  Boxes were added to it over where the closures would be located so that the closures could be hung with short lengths of perforated angle iron as would be typical with a conventional 8' ceiling.
 After going the extra mile to insulate the garage walls, floor and ceiling and to use insulated doors, it made sense to minimize the number of potential air-leaking penetrations through the ceiling drywall.  Using the beam meant that there would be only three penetrations as opposed to the 15-20 that would be necessary with individual angle iron supports for the rails and closures.  And the aesthetic difference is a nice plus.

We elected to forego windows in the overhead doors and go with a large window above them.  Doing so eliminates the weight of the glass in the doors and provides more privacy.  And the large window, to my eye, is not only more interesting architecturally, but seems to provide more useful solar gain in winter.

Saturday, October 12, 2019

Construction - Plumbing Rough-In Completed - A Challenge for This DIYer

The plumbing rough-in was started in late summer
The original rough-in under the slab floor showing the PEX
 lines emerging from PVC conduits; the black gas pipe was
inserted between the PEX and the PVC to protect the PEX
while shortening the conduits (see photo below).
of 2015 when the waste system and supply lines were installed before the concrete floor was poured.  (Curiously, the
 blog post describing it is by far the most visited post in the blog -- by a factor of 5 to 1 over the next most visited post (rice hull insulation).)  

The supply lines were encased in PVC pipes for protection while slinging the crushed rock base for the concrete and pouring the concrete itself.  Both the waste and supply lines were stubbed up high enough to avoid accidental clogging by concrete.  The present post takes the rough-in from there.  (Clicking on the photos enlarges them for a closer look.)

Waste Lines
The red circles enclose the shortened PVC conduits; the 
green circles enclose PEX stub-outs for two bathroom
 sinks; the OSB is left-over roof sheathing that will provide
 secure anchorage for cabinetry and mirrors
The layout of the waste lines followed standard protocol but was definitely a stretch for this DIYer even after plenty of research ahead of time.  My thanks go out to my stepson, Keith, who, by virtue of owning and managing a host of rental properties, could add his expertise to the project.  And I am almost embarrassed to admit to the amount of pipe we wasted getting to an workmanlike result.   

Despite being so challenging, the waste system is sufficiently standard that it merits little description here.  There were two minor complications though -- a last-minute addition of a full bath adjacent to the second floor bedroom that required a long waste run to the central stack.  And the vent from the auxiliary kitchen sink located on the south wall had to travel quite a distance to avoid protruding through the roof in view of the public or close to a window.  The lack of partitions on the second floor in which to conceal the central stack vent made for a longer run as well.

Supply Lines
The PEX supply lines were far more interesting than the waste system.  It took some online research and a few new and borrowed tools (like a crimper for the crimp rings that secure tubing to fittings) to bring the task into the realm of this DIYer. 

Each supply line originates from a manifold located next to the incoming water main in the "vertical basement" and terminates at a single faucet or appliance -- a "home-run" system.  The cold water passes directly through the manifold from the main into the cold water (blue) PEX lines.  Hot water takes a bypass through the water heater before traversing the manifold to the (red) PEX lines.  Cut-offs are located on the manifold rather than under faucets or next to appliances such as the dishwasher or washing machine.  This means that, in the future, when a line needs to be closed for some reason, like changing a faucet, it will be shut off at the manifold, sort of like flipping a circuit breaker at the service panel for working on an electrical circuit.  
Notice PEX lines entering the PVC
conduits that protrude from the floor;

also notice above the PEX the race-
way containing Romex cables on their
 way to the service panel and,above
 them, the gas line to the water heater
and kitchen range.

As described in the post mentioned in the first paragraph, all the PEX lines were run below the floor inside PVC pipes.  In addition to protecting the PEX until the floor was poured, the PVC also affords the opportunity to use an existing PEX line to pull a new line in place in the unlikely event of a leak below the floor or some other unexpected problem crops up. The nearby photo shows the blue cold water lines taking circuitous routes from the manifold to the PVC pipes while the red hot water lines emanate from the bottom of the manifold and enter the PVC pipes immediately thereby minimizing the time it takes for hot water to reach its destination.

Tankless (on demand) Water Heater
The ubiquitous tank-type water heater heats water ahead of time, then, if it isn't used right away, it keeps heating it anytime the temperature in the tank falls below a certain mark.  A tankless heater is much more energy efficient because water is heated only once when it is actually being used.  Also, the amount of energy needed to heat a given amount of water the first time is much less for the tankless heater than for the tank type.  Still another energy-saving feature of tankless heating is that heaters come in many sizes for matching hot
Tankless water heater before the
  gas line and vent were connected.
water demand with, say, number of bathrooms.  And it seemed to me while researching water heaters that there are more Energy Star models available among tankless vs. tank type.

Flood Protection
Red arrow points to the master cut-off valve;
the green arrow points to the automatic emergency
cut-off valve.
As is typical, the water line from the street has a master cut-off valve that controls the flow to the entire house.  What is not typical is a secondary emergency-activated cut-off such as the Water Cop System that automatically closes an auxiliary valve just upstream from the master cutoff should any of its wireless senors on the floors of the bathrooms, kitchen and laundry room detect excessive water on the floor from a leak or overflow.  This backup system will give us peace of mind, especially when no one is at home.

Gas Lines
The gas lines to the water heater and kitchen range were also a challenge.  My prior experience had been with black pipe so using flexible tubing required considerable prior research and new-found familiarity with unique fittings.  It helped to have, a phone call or email away, a plumber acquaintance in a distant state who didn't mind sharing his expertise.  My fears that the system would not pass pressure testing were realized at first but, the only leak was finally found and fixed and air pressure was maintained for the requisite 20 minutes.

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.