42/52 - Geothermal Installation Begins!

25 Oct 2015 This is a big week in the life of River Ford Farm. After losing our primary heat source last fall and weathering a winter with only a wood stove, we are finally starting the installation of our new heating system!

We had many constraints on our options. Our house has a water-based heating system, with a combination of baseboard hydronic radiators in the log portion of the house and in-floor radiant heat in the great room addition. Using a different heating mechanism would require lots of changes to the log structure of the house, something we wanted to avoid. There was nothing wrong with the existing plumbing, so finding a new system to heat and circulate the water was our goal. As it turns out, there aren't too many options. There is a company that makes a heat pump air-to-water system, but none of the local HVAC companies we talked to had ever dealt with it. We had LOTS of issues finding someone in the Gorge who knew how to work on our old, somewhat esoteric propane-based system. Finding a system that had some local expertise was also important.

In the end, it came down to two options: a new propane boiler or a geothermal system. We ran the rough numbers for the two systems: propane would be cheaper up-front but would have recurring fuel costs similar to what we had previously. When factoring in the 30% Federal tax credit for qualified geothermal installations, we estimated the payback time for the geothermal investment to be about 10 years. Geothermal it is.

Technically, what we are having installed is actually a ground-source heat pump. True geothermal heating systems require a high temperature source in the ground, such as a hot spring, and simply transfer the heat directly. Our system involves using the temperature of the earth to drive a heat pump. Water is equalized with the temperature of the earth by circulating it through long pipes through the ground. Drilling vertically to run the pipe requires minimal land but is expensive, since you may have to drill several hundred feet. But we have the land available to do a horizontal system with "racetrack" trench. Time for a call to the utility line locator!

We had a couple options for locations. We ended up choosing the open space north of the house, between our house and Mt. Adams. We figure that we'll never want to put anything else there that might obstruct our mountain view, so having piping beneath the ground would be safe.

The "racetrack" through which the water pipe will run will be about 800' long, with the water circulating through the entire length. Here is the quick rough sketch of the path that was marked on the ground.

Square is the house; drawing not to scale

Excavation was planned to start on Tuesday, so we arranged for the polyethylene pipe to be delivered to us on Monday. Corinne's father and step-mother run Superlon, a polyethylene pipe company in Tacoma. We'd have family-made, high quality pipe for our heating system!

But over that weekend, Superlon's delivery truck was totaled and wouldn't be able to bring the pipe to us. So we would pick up our 800' of ¾" pipe and 300' of 1" pipe ourselves. 1986 Dodge farm truck to the rescue!

Quick trip to Tacoma, in style (not)

Now that we had the pipe, it was time to start digging! We would need 800 feet of 5-foot-wide by 5-foot-deep trench. The biggest risk of the whole project was encountering large rock deposits. The installer spot-checked his proposed path by poking a metal rod into the ground, but there's always a risk of missing something. Thankfully, only once did the excavator find a spot that required using the hammer attachment.

We knew where the trench would be dug, but we didn't truly grasp how large it would be until we saw it. The main trench area covers about half an acre. Enormous.

Anders looking at giant trenches

Trench pattern

Early morning trench, with steam

The connection to the furnace closet in the house had to go right through a cluster of three Port Orford Cedar trees. One of the trees' branches had started to hang down on the roof, even after pruning them up 16'. So we decided to remove it to make room for the trench.

The path to the house didn't need to be as wide, since it only housed two 1" pipes, out and in.

So many roots! Oh, and the white things sticking out randomly are irrigation lines for our sprinklers. We'll repair that at the end. The last several feet of the trench to the house were dug by hand.

Each trench in the racetrack will contain 6 separate pipes, to maximize heat transfer between the water and the ground. These connect to the 1" main lines at a junction point.

Pipe in trenches with spacer

Junction between 3/4" track and 1" supply

By the end of the week, the trenches were dug and the pipe was laid. The trenches have been mostly filled-in, to be finished off with another piece of equipment.

The old furnace was ripped out and the new geothermal heat pump installed inside. But there is still much work to do on the inside. With any luck, in another week it will all be done, we can put the house back together, and we'll have heat!

- Mike, Corinne, and Anders