Wednesday, April 13, 2011

Buildings and code...

Ok since we've had some comments about our electrical system, and I'm sure we probably had some comments about plumbing, or the structure, or whatever.

If you are planning to build a place the very first thing that you'll need to do is figure out whether you are governed by any building codes, and if you are which codes apply (from foundation to wall structures, to electrical and all points in between). Know and understand if you are in a regulated zone and know what permits and codes apply.

If there are building codes you are required by law to follow them, and have inspections and permits to ensure you meet the code. We're "lucky" in that we're in an unregulated zone, this means that we need to ensure that we feel confident that the systems and structures we build are safe for us, and anyone else who enters that structure. To this end we try to stay within established codes and standards where they apply.

Building codes are created to ensure that standard built structures with standard systems are safe for use by anyone who owns or may inhabit that structure. However the problem is "standard". For example standard residential electrical code is for grid tied systems, have an input panel of 200A (or more) with a 220V line split into 220V, and 110V circuits, with associated safety devices both internal to the house (breakers/fuses) and external (company breakers at the entry and along the grid lines) electrical may also have requirements placed by the utility company too. Similarly plumbing needs to take into account any sewer hookups, materials need to take into account any chemicals that may be off-gassed into the structure, or ground and ground water. For instance 50 years ago lead pipes were used, not so now, makes a lot of sense.

Whenever you're using alternative building materials or systems, then the "standard" code may not be applicable, or grossly under/over engineered. So if you're not in a regulated area, it's important to understand why a building code is in place, so that you can derive an alternative system that addresses those safety issues. If you don't feel comfortable in your ability to do that, take the time and money to enlist an engineer, or stick to code and convention (and abandon the alternative method and/or system).

Now on to our systems...

Structure, post and beam with alternate inside/outside studs 4' between studs a side, no applicable code, however the load bearing structure is the post and beam, not the infill walls, structural rigidity is maintained by the shear panels and bracing. Confirmed load bearing capacity with several structural engineers.

Plumbing, pex, internal from storage tank, drains to greywater leech field, no applicable code.

Electrical, no applicable code (code only covers residential grid tied systems), wiring all +2 gauge on internal wiring codes (12 gauge where 14 is code, 10 gauge where 12 is code), grounding wiring +9 gauge (code is 8 gauge for a 100amp panel, we have 2/0 gauge for a 20amp panel). All junctions, sockets, and connectors installed to general NEC electrical codes.

Networking installed to Microsoft Datacenter standards.

HVAC, no AC, heating/stove installed to Fairbanks code.

Now one point of apparent concern is our grounding...

Well, that's kind of you guys to worry, but it's not a problem, here's why.

In a grid tied system, you have your main breaker (100A, 200A, etc.) the neutral is ground tied (so that Neutral and ground have the same potential, we do the same). If for some reason on the house side of the system there is a ground fault (hot shorts to ground), then the circuit breaker will blow or the main panel breaker will because it appears to the system as a short between hot and neutral; even if that doesn't blow, then there are service breakers installed in the lines by the supply company.

These breakers will blow regardless of what is connected or not to the ground rail as long as you have tied the neutral to the ground rail (in essence you're tying the case of your electrical appliances to neutral).

If the same happens on the supply side, then the same thing happens, but higher currents could cause some issues, for instance the supply breaker may not trip (the one you have no access to), so you could be running branch current to ground unless the breaker at the branch blows, if there are 10 or so houses on that branch that's a 2000A breaker at least.

We have a total of a 20 amp main breaker on a completely isolated system, that has a breaker on the circuit (this may be 5 amps, or 10 amps), there is the inverter over current system that will shut down in case of overload, there is a 100A breaker in the battery line if that doesn't shut down. So the failure chain would need to be to cause any serious harm, the circuit breaker fails, the panel breaker fails, the inverter over current fails (and the inverter doesn't burst into flames), and the 100A battery breaker fails.

The only big advantage in having heavier grounding is for lightning protection. After careful review we have decided against installing a lightning rod it's not something that sprang to mind when we were planning. We're not higher than any other structure, we're not on the top of a hill, and we're surrounded by higher trees.

Now a for instance, if you have an RV that has a 110V 20A supply, how much hard grounding (to ground) do you make sure you have? If any? Because this is pretty much the same thing we have going on with our electrics.

5 comments:

Anonymous said...

Good info for everyone.
The temps above the zero mark helping you two get back into the building phase? Or is it just too wet and snow packed?
ps. The word verification characters are "she sins". :) What's with that?

Plickety Cat said...

We are back building a bit, but the wet/melting snow pack is still a problem. We've still got several feet of snow left, and it just dumped more on us last week. Although it's packed down pretty good around the cabin, it's melting a little irregularly making very slippery little hummocks which are treacherous when carrying heavy materials. So we're taking things slow and cautious.

A friend of ours is coming to stay with us for a couple of weeks, so we'll have some slave labor :) Hopefully with two manly-men to lift and tote, we can get the last of the current round of heavy projects done (the drywall) so that I can focus on the artsy-homey interior finishing. If we're really lucky, it'll get above 40 for a day or two while he's here so we install the sill membranes around the doors and windows. We can't install the windows, or the doors permanently, until we can membrane and caulk around them... and can't install the siding until the doors and windows are installed... and neither caulk nor membrane stick below 40 :(

Walkntom said...

There's no need to fear, Under Dog is near! The clock is ticking till your new TC55 series pseudo-uman automated robot arrives to solve all your philosophical, socioeconomic, theologic, anthropomorphic supercalafradgalistic construction problems. All while serving you mint juleps out on the front veranda in the cool of the evening on a daily basis.

Anonymous said...

I realize when you put yourself out there and tell people what your doing, it can result in comments that range from helpful food for thought to uncalled for negativism. On the grounding issue I think there are at least 2 issues maybe more that systems need to be designed for. First the potential max current so the system holds up in a nasty short situation. Secondly in the event of a short to equipment ground you want there to be a extremely low resistance path to earth ground so that if you are touching equipment ground the path to earth ground through you is at a much higher resistance level.

Plickety Cat said...

Tom, we'll appreciate all your hard work while you're here. You'll have to tolerate camping out in the unfinished cabin while we work around your gear, and then suffer my cooking... but it'll be an adventure :)

With grounding issues... yes, the reason behind the codes is to safely provide the electricity a path of lesser resistance than going through you.

Humans aren't the best conductors when compared to almost any metal... we're only slightly more conductive when we're standing in liquid or touching metal in two places creating an arc circuit (ask me how I know!!)

Having been accidentally zapped by our batteries during installation, I definitely appreciate this... which is why I told everyone to install the ground FIRST and the hot lead LAST. And be very careful leaning across battery terminals if any part of your anatomy dangles a bit (um, like breasts) ;)