The last post about our geothermal heating system home project saw the wells being drilled.  Onward and upward...literally. 

All's Well That Ends Well

The drillers come back the next day, and do the whole thing again for our second well. Considering that the depth is 320' (100m), times two wells, into solid granite and other ledge, it's amazing it takes only two days. This well hits enough water that we could pump 60 gallons per minute! Dang. Too bad we don't need water.

Also featured today: the arrival of our geothermal heat pump. This is the heart of the system, where heat is moved from the outdoor loop of circulating water/edible antifreeze to the indoor air that will run through our ductwork. The pump looks like a rectangular, small and slightly chunky refrigerator.  Remarkably unremarkable. Lots of unused space inside. The actual pump is about the size of a large garbage disposal.

One disappointment for us was that we had hoped to place the unit in an otherwise little-used section of our basement where the ceiling is only 5' high. Only about a third of our tiny basement is suitable for standing up, and we didn't want to compromise that space. We had discussed this wish with the engineer, but it appears he had already ordered the "vertical" version of the heat pump and thought it would fit. Alas, upon closer examination today by the installer and engineer, this unit, with ducts, would not fit in the 5' high area. We had a choice of halting progress while they ordered a new one, or losing some walkable space. Since we were already running about a month later than our original target date, we decided to use the vertical unit, but hold the duct and piping installation to strict limits.

TIP: They do make horizontal units -- mainly for cases where the heat pump has to go in the attic.

There are only two skinny guys available to wrangle the heat pump on a hand truck, down our concrete stairs to the basement, and (since it is impossible to hold back a hand truck from the top of the steps) the pump's exterior suffers a big bump on the last step. Turns out no real damage was done, just a bent panel that we decide to call "the shipping panel" and order a new one. (We're on a fixed cost contract, so no epidermis off our gluteus maximus.)

The driveway and environs look like a construction site, with one van, two pickups, two drilling flatbeds, and a Caterpillar digger. All but the Caterpillar depart at day's end, leaving us two capped wells, a heat pump, and assorted sheet metal.

They will need to return to dig connecting trenches 4' deep between the wells and to the house, lay and connect piping, pour in some sand to protect the pipe from rocks, and replace the earth.   

Roamin' Via Ducts

Vini, vidi, ventilatum. In a house with an existing central HVAC (heating, ventilating, air-conditioning) system, you already have metal ducts roaming the house to carry conditioned (warmed/cooled, filtered) air to every room and back to the HVAC system. If you just have heating, and it's by hot water circulation, you are probably ductless, as we were, and have baseboard units.

If you do have HVAC, there is nothing very special about switching to HVAC using geothermal. The only possible exception is if your ducts are undersized, which does happen. Since the conditioned air during heating season is not quite as hot as it would be from a flame-source of heat, more air needs to be moved to ensure adequate heating. The advantage of this lower-temperature, higher-flow arrangement is a more even distribution of heat in a room, and less drying effect.

Do you know which way the joists run in your floors and ceiling? Us neither. It turns out this is important to the duct wrangler who is trying to get HVAC up to the attic, with a pair of rectangular ducts (supply and return air) running through two floors and a ceiling. You don't want to be cutting joists if you can at all avoid it; the ducts are each sized to fit between joists. No problem, you say: the joists in the first floor are visible from the basement, and for the second floor you can use one of those $20 joist finders from the hardware store. Well, they are designed to work through plaster, not floorboards, so you have to use it on the ceiling. We have sand-textured ceiling paint, which utterly defeats the joist finder. So, many test holes, measurements, consultations with original blueprints, tapping with fingers, and even examinations with a fiber-optic peer-through-a-tiny-hole camera (familiar in principle to anyone over 50 who has had a medical exam recently) we discover the ceiling joists run the other way (at right angles) to the first-floor joists. (The second floor ceiling joists match the second-floor floor joists.)  Hmm. Also, we discover there are no mouse corpses in the joist bays, hooray!

The solution to such crossed joists is very much like a modern sculpture, where odd metal shapes twist around each other. [Picture] The two ducts emerge from the first floor one way, then twist around each other and the pair goes through the two ceilings the other way. Cool! Museum of Modern Art, here we come. The industrial visible-ductwork look doesn't quite go with our decor, however, so we will be boxing it in.

To be continued...and in case you were wondering...there are eight parts in total...