Today was an unusually warm and humid day for Maine in June — upper eighties by late afternoon. That made it the perfect day to see how well the A/C function on the newly installed and operating system functions. Unfortunately for the workers they had to work in the heat of the day (finishing in the attic at about 11:00, as the temperature hit 120 there) and couldn’t enjoy the cool air until right before they left.
It was still an intense work day for them. Any retrofit requires working around the idiosyncrasies of a house not built for geothermal. Still, they answered all my questions and cleaned up before the left. One issue is the desuperheater, which sends very hot water directly to the hot water tank when the unit is running. It can send it at either 125 or 150, though 150 is above the state regulation. I can set it there, but the installer couldn’t.
The problem is our water was set at 135, meaning that the boiler would still kick on and we’d save little in summer, even when theoretically we should be getting a lot of “free” hot water. If I set it for 150 that could overcome that, but then there’s danger of severe burns if the kids got under it at its hottest. I lowered the temperature to about 115 instead, so hopefully that’ll help. The most efficient way to use the desuperheater is with an electric hot water heater. In summer it would hardly ever go on, and only sometimes in winter. If we really want to save we could go that route.
While he was explaining this there was some commotion and cold white “smoke” was coming out of the heat exchange pump. “I’m stopping it with my hand,” one guy said. “Move it, you’ll get frostbite,” another responded. The leader of the crew started to work on it and got everything under control. Other than that, things went very well!
The pump draws in water from the well, currently about 52 degrees, and takes heat from the house and puts it in the water. The water is then sent back to the well about five or six degrees warmer. In essence it refrigerates our house by removing heat rather than injecting cool air — though it feels like the latter as cool air comes from the vents. In the winter it’s reversed, heat is taken from the water and colder water is sent back to the well (warming up from the earth’s heat as it makes its way back.)
It’s a split level system so heat is sent up from the basement to the attic for distribution. There are 15 vents upstairs and three downstairs. Basements stay around 50 anyway, so it doesn’t take as much heat — but we were limited by the inability to do much duct work in the basement.
The other bit of maintenance is to replace the upstairs filteres every three months. There are two return vents that suck air out assuring a good flow of air through the house, keeping humidity down as well. To protect both our air and the duct work, it’s important to filter this. It’s possible to buy filters you can clean and reuse, though it’s not expensive to just replace them every three months — and our thermostat will remind us when it’s time to replace them.
One of the beauties of this form of air conditioning is that it isn’t like the rush of cold air that comes from most central AC systems. The air flows gently, meaning that the temperature lowers slowly (they measured air coming out was at about 59 degrees, while the return air at that time was at 75). You don’t have cold air blowing on you, you have to reach up to feel near the vent to tell — but it is effective, the house cooled from 78 to 70 within an hour.
The system is not loud at all. The heat exchange pump does make noise, but it’s less than what the boiler produces. The fan in the attic is hardly noticeable. At least on day one, using the “Cool” mode, it works easily and quietly. The thermostat is easy to operate. It can be programmed, and you work from either “cool” or “heat” mode (there is an automatic, but that can switch back and forth and burn a lot of electricity). We choose to have only one zone to save money, we didn’t see the point of multiple zones, especially if you can dampen the vents individually.
Although this will end my “daily” blogging about the project, I will post periodically about performance and cost — I’ll probably put together a page of posts like I did for the Italy trip. It’s too early to say if the investment was worth it, or if the system will work as promised. Yet I was very happy with both Jeff Gagnon Heating and Air Conditioning, and Goodwin Well and Water. They communicated clearly, did what they said they’d do, were professional, and clearly understood their task (they’re the most experienced at this in the region). RDM Electric (Ryan Morgan) also did a great job creatively dealing with the electrical needs of the system.
Wow. I started asking about geothermal possibilities way back in 2007, playing with ideas, but all the time thinking the high initial price tag would keep this theoretical. At UMF they are now drilling 80 wells for a massive conversion to geothermal for a good chunk of the campus. For the sake of the economy I hope oil prices drop, but it’s nice not having to worry as much about them in planning next winter’s budget!