After posting the last entry, I realized that I should probably briefly talk about our house wiring – even though we will be off-grid, we still want to be able to run and wire our house for regular appliances and lighting.

In years gone by when people went off grid, they would in many cases use DC lighting and DC appliances, to avoid having the costly inverter in their system.  There are a few problems with this: DC wiring runs have higher losses so distance from the battery bank becomes an issue, DC electrical devices are less common, and the ones you do find are lacking in modern convenience and visual appeal (and are more expensive), and lastly, if you ever did want to connect to grid power at some later point, you would have to rewire your entire house.

Instead, we will wire the house for standard 120/240VAC, be able to use all regular lighting and appliances (except for a gas range, instead of electric, and a gas clothes dryer as well), and if we ever choose to connect to the grid down the line, we’ll be able to do so with a minimum of hassle.  We’ll just run the output of the Xantrex inverter into our standard electrical service panel as though it was a grid power connection.

Thanks again for reading!

Just wanted to get a quick post up covering the core components of our off-grid system – by core components I am referring to the inverter and it’s accessories such as the charge controllers, auto generator starter, and so on.

For a bit of a preamble: the basic premise of an off-grid system is that you have a battery bank to draw on (charged from either the solar array or the generator), and connected to the battery bank is a pure sine wave inverter (MSW or modified sine wave inverters are available, and cheaper, but they produce lackluster power that doesn’t run all appliances well) which is responsible for converting the battery bank power (48VDC) to AC power (120/240VAC) to run our house.

Selecting an inverter is based on a number of factors – budget probably being foremost, but our selection criteria also included the following, listed roughly by importance:

• Continuous power supply
• Surge power supply
• Integrated accessories such as charge controllers, auto generator start, and network monitoring
• Reliability ratings, reputation of manufacturer (availability of repair parts)
• Ability to “stack” inverters for possible future expansion

To satisfy the above criteria we considered Magnum Energy 4000W inverters, and also the Xantrex 6000W inverters.  In the end we chose the Xantrex 6000W inverter as it was most suited to meeting our current and future needs.  While the Magnum inverters are less expensive, we would have needed to start off with two 4000W inverters as I don’t think we would be able to get by with just 4000W continuous load.  Furthermore, the Xantrex inverter has a 12000W surge capacity and can carry that load for a lot longer than the Magnum.  Lastly, the Xantrex’s “load support” feature seems to be more advanced than the Magnum and that would come in really handy if we need to run some really heavy loads.

Our total lineup of Xantrex products is as follows – and I’m just linking out to these on the Northern Arizona Wind & Sun website as that’s where we bought them from – on a July 4th sale, including freight shipping, it came out cheaper than getting them from Canadian suppliers.

• Xantrex 6048 Pure Sine Wave Inverter
• (2x) Xantrex 600VDC, 80A Charge Controllers
• Xantrex System Control Panel
• Xantrex Power Distribution Panel
• Xantrex Automatic Generator Start
• Xantrex Network Monitoring Combox

Also, Northern Arizona Wind & Sun has a great set of forums with tons of helpful members, I highly recommend it if you want to do some more reading on some practical topics.

At any rate, with the above setup we should be plenty good to start, and we can always add up to two more inverters and more charge controllers, if necessary.  I think we will probably be ok with the above but we’ll only really find out once we get the house built and start living in it!  Because the inverters are the core of the system, we will probably purchase a second unit to have available as a standby in case the installed one fails.

Thanks for reading and I apologize for the lack of pictures, but I did promise to do some posts on this stuff previously and I wanted to make sure I followed up!  Again – any questions, hit up the comments section below, or post on Heather’s facebook!

To power our off-grid system, we will rely on solar panels to recharge our battery bank, and, when there hasn’t been enough sun to fully top up the batteries, we have a backup generator that we will use to provide additional recharging as needed.

We can also utilize our inverters “Load Support” feature, whereby if we want to run more electrical devices than our inverter can power alone (6000W), the inverter can pair it’s output with the output from the generator (7000W) to provide power to provide a total system power of 13kW – no doubt this will take care of anything we might wish to run!

Our generator is a Honda EU7000is, which is an inverter type generator that produces a 60Hz pure sine wave electrical output at 120/240VAC, just like the electrical grid.  Right now we use this generator to power the RV (TV/Satellite PVR, Microwave) and my tools (like my table saw, compressor, etc), but when we get around to wiring up the electrical, we will hardware this into our inverter with an automatic generator start circuit so the inverter can bring the generator online as necessary to recharge the batteries, etc.

For our solar array, we are going to start with 26 panels – these are Canadian Solar 250W panels which are currently selling for around 79cents/watt.  This will give us an initial array size of 6500Watts.  We’ll wire this up, for two strings of 13 panels, each string will run to it’s own 80Amp charge controller (connected to the inverter), for a total charging capacity of 160Amps (this is a maximum which will probably not often be seen).  We will start with these panels and see how we get on – if we find we aren’t generating enough power (ie. generator is running too much), we can always add more panels.

Our goal is to be able to support a power draw of around 10kWh/day, or 300kWh/month (a third of our power use in the city!) – so if we look back at the PVWatts tool I previously mentioned, putting in our array size of 6500W with a derate of 0.52 (for off-grid calcs), and a fixed array tilt of 60 degrees (best winter angle, still good enough in the summer), we can see that we are pretty good, except of course for November with it’s particularly meager solar insolation.

What I also find interesting is that March and February are the two highest solar producing months in the Ottawa area.  I would have initially thought that June and July would hold that position.

Anyway that’s some information about our solar panels and our generator setup, if you have any questions feel free to post them as comments and we’ll be sure to respond!

Well today was the day the basement floor slab was poured.  In preparation for this, I cut through my 4″ of rigid foam at the location where our four support columns will be located, so that they will sit directly on the concrete footings, and inserted a segment of 4″x4″ post in each one.

Before putting these placeholders in place, I wrapped each one in my 6mil poly vapour barrier, which concrete won’t stick to.  This should make it easier to pull these out later when we are ready to install the four support columns.  I also wrapped the bottom of the 2″x10″ that is supporting the manifold so I can remove this more readily later.

I also took the opportunity to ensure the radiant heating system was still pressurized to 80psi for the pour (to ensure the concrete doesn’t collapse the tubing).

This morning the concrete crew showed up bright and early and got right to work.  They backed the truck right up to the house and were dropping loads of concrete directly from the truck into wheelbarrows, which they would then transport across the basement and drop it where needed.  The following gallery captures some of the progress of the pour:

After the concrete is poured, they give it what is called a “hand trowel finish”, really this is done by quite a crazy little gas-powered machine with four paddles that rotate to smooth out the concrete.  They go over the floor a number of times with this machine and in the end the floor is really smooth.  Here’s a short little video of them in action:

Because it’s quite sunny and warm today, especially in that basement with all that insulation, the crew advised that I keep the concrete watered down a few times a day to slow the concrete curing and ensure it cures with maximum strength.  Heather took a couple pictures of me carefully dousing the concrete (thank god we can get water from our well!)

You might think that connecting the manifold and pressure testing it would be a straightforward affair – and it does most certainly appear so at first glance.  Connecting the supply / return loops to the manifold is actually not so bad, you just cut the tube to length, drop a 1/2″ ProPEX ring with Stop onto the end of the tubing, and then expand the tubing using your tool of choice (I’m using a cordless Milkwaulkee ProPEX Expander Tool which is pretty slick!) – once expanded you drop in your fitting and let the tubing shrink back around it (which takes only a minute or so).  From there you connect that fitting to the manifold – again, about as straightforward as it gets.

Where it gets tricky, is pressurizing the system.  I ordered and received a “Pressure Test Kit” which you can see attached to the left side of the manifold in the above picture.  The problem was, that this kit came as unassembled pieces, and after assembling them, it would not hold pressure.  After dis-assembling, and re-assembling the kit several times, each time using progressively more aggressive pipe sealing measures, I finally got all the leaks sorted and the system seems to hold 80psi of air well for several hours.

You can also see that I re-mounted the manifold to be level before I connected all the tubing!

Yesterday and today we spent our time furiously installing the Uponor 1/2″ hePex Plus tubing for the radiant in-floor heating in the basement.  When the concrete floor is poured the tubing will be completely encased and ready to heat the floor.  In the last few pictures you can see that I “scabbed” together a beam to suspend our distribution manifold from (an Uponor 5-loop engineered plastic manifold):

Next step is to use our compressor and get the system up to 80psi, and make sure it’s holding air and leak-free!

Well the last few days have been reasonably eventful.  Continuing on from the work in the previous post, we managed to complete the rest of the basement wall insulation and the interior of the basement insulation is now 100% complete!

In the midst of it all we had some rain so we made some efforts to protect the basement with a tarp (with all that insulation it’s basically like a big water-holding tub) – this did not initially go as planned but in the end we managed to collect most of the rainwater on a tarp and direct it down the sump pump pit to be rid of it.

In that last picture in the above image gallery, I am just doing a test of gluing the exterior insulation to the exterior wall – I usually prop some stuff against each board as I go to make sure they are well secure as the adhesive sets up.  When I checked on it this morning, it appears to be attached well, so that’s a good sign.

Today we will get started laying out the radiant heating 1/2″ PEX tubing (we purchased Uponor 1/2″ hePex Plus, a 1000′ roll), so we will be taking some photos as that progresses and  be sure to share them a little later on!

Note to self: Always secure your garbage in the country – the night before last a coyote got into a bag of garbage I forgot to secure and made quite a mess – also, not the kind of animal you generally want to attract!

Day 3 of the work progressed much better as I was significantly less sore from the day before.  I got the second layer of insulation completely down and taped about 30% of it.  Heather and I also moved a whole bunch of insulation into the basement so I can more readily fetch it when I’m putting up the walls.

Lastly, I got out the PL Premium (construction adhesive) and glued up a couple sheets on the wall just to see how it would go – hopefully I evened out the wall enough for this to go up quick!

It looks like rain may be on the way in a few days so I shall begin day 4 with a renewed pace in the hopes of getting most of the walls completed today!  Thanks for reading!

I was very sore from all the work on day 1 – so not nearly as much got done on day 2.  I was able to complete taping all the seams on the first layer and started laying the second layer of insulation:

I got maybe 25% of the way done laying the second layer, but got most of the fiddly stuff out of the way like around the sump pump pit and radon ventilation pipe.

After a liberal application of Icy-Hot ™ I feel day 3 will be more productive!