Tuesday, November 11, 2008

Freeze protections

When I got back from the Passive House Conference on Sunday it was down to 53 F in the house.  I hadn't left any heat on, the weather had turned colder, and I wasn't there to open the door to the greenhouse to let the solar heat puff in.  So far this fall I'd been getting by with said passive solar and a 1500 watt space heater on cloudy days.  It was sunny on Monday and I got a lot of good heat into the house, but come the night the little space heater couldn't keep the house above 60.

I find if the temperature is below 64 my nose gets cold, which I dislike.  So late Monday night I decided to torch the planet's future for the sake of my short-term personal comfort, and turned on the Big Heater.  That's the 5000 watt electric boiler and the in-floor hydronic radiant heat.  Right now there's no thermostat control - a simple on/off thermostat probably wouldn't work very well anyway, because of the huge time delay between turning on the power and heating the air.  There is an aquastat for controlling the boiler outlet water temperature, which I set at it's minimum of 90 F.  Over the past day the boiler has been cycling on and off.  On the HUGnet monitoring it looks like the boiler outlet water is averaging about 88 F, the return about 78 F, and the air temp in the house about 64 F.  This was with the water heat loops to the greenhouse floor shut off.

The temperature sensors on the septic line have been trending down, faster on the E-W section which is the shallower leg now.  It's now about 37 F.  Typically it is coldest at around 1 pm and warmest at around 1 am, that is, there's about a 10-hour delay from the daily cycle of the air temperature above.  It seemed like a good way to run the deicing cable might be, to turn it on for awhile midway through the daily cooling-off period, which would be about 10 am.  I've set it on a timer to run from 9 am to 11 am each day, we'll see how that works out.

I also set up a heater to keep Big Foamy, the aboveground root cellar, from freezing.  It's just a work light with a piece of polyiso insulation board taped over it to keep the potatoes in the dark.  I've got a little line-voltage winter watchman thermostat to control it, set at 40 degrees.  It's also plugged in to a Kill-a-watt meter so I can monitor how much energy it's using.

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