Cottage heat loss coefficient

On my list of things to be thankful for, category wonk, subcategory building science, is a thing that happened during the first few hours of Nov 16 - the cottage settled into a thermodynamic steady state with the boiler running full out and all four radiant floor loops turned on.  (I was trying to warm the greenhouse floor for painting.) Because of steady state I know that the boiler electric power, the heat delivered by the distribution loops, and the heat leaking to the outside are all the same.  That plus the air and water temperatures from the monitoring system allow me to estimate the building "UA" or heat loss coefficient, and the flow rate of the hydronic circulation pump.

Data from the 2-3 am hour of Nov 16:

Boiler power 17061 Btu/h (5000 W)

Outside air temp 22.72-23.31 F

Inside air temp 70.3-73.78

Greenhouse air temp 55.53-57.69

Inside to outside temp difference 49.025 F, 27.236 C.

Building UA = 17061 Btu/h / 49.025 F = 348 Btu/hF

Building UA = 5000 W / 27.236 C = 183 W/C

Lower is better.  It would probably look better if I hadn't been heating the greenhouse, but in order to get steady state with just the cabin zones heated, it will have to get colder outside.

I'm actually more interested in the circulation pump right now as I'm trying to figure out the solar hydronic system.  The data I have is:

Boiler outlet 97.85 F

Cabin return A 90.27

Cabin return B 91.41

Greenhouse A 94.05

Greenhouse B 90.09

I really wish now I had a sensor on the boiler inlet to measure the mixed return water temp.  As it is I don't have much choice but to assume all the loops are carrying an equal share of the flow, and use the average of the four return temps.  

Distribution loop temp difference: DT = 97.85 - 91.44 = 6.395 F

Qdistrib = m cp DT = Pboiler, in steady state.

m = Pboiler/(cp DT) = 17061 Btu/h / (1 Btu/lbF * 6.395 F) = 2668 lb/hr * 1 gal/8 lb * 1 hr/60 min = 5.6 gal/min.

I looked up pressure-flow curve for the Taco 007 circulator, which is (irritatingly) labeled curve number five (dark green).

At 5-6 gpm the 007 is almost maxed out on pressure.  I wanted to put flow meters in the distribution loops but I can't find any (cheap) ones that drop less than about 1 psi @ 4 gpm, which is like two feet of water and it looks like that would choke this pump off entirely.

Must-read septic system update

It looks like the septic-line-insulating-dirt-berm-operation (SLIDBO) on the 18th has halted the coldward temperature trend on the east-west section of the line (middle trace on the graph below).  That is good because it is only 4 degrees from freezing.  Air temp outside has been below freezing for a week.  Now that there's more dirt on top I hope some heat from the ground can migrate upward and warm the line or at least offset the cooling trend.  It's only November.

Solar Water Heat, Phase Uffda

J and Grandmaster-J, from RREAL.org, swung by today with Solar Water Heat parts, including the two 120-gallon solar storage tanks.  Lookatemgo.

These are Richmond S120HE-1 tanks.

In other exciting news, our pal Pigpen replaced the seal on the toilet and "retrained the operator."  

[Photo omitted.]

I on the other hand had a rough day of sitting in my cozy cabin and working on the computer.

Survival spud diet update

As Jerry Reed sang in She Got the Gold Mine, "why didn't you just learn how to cook?"

My many loyal readers (hi Mom) will recall the 600 pounds of potatoes I grew this past summer.  I think I'm running behind on eating them, at a rough guess maybe 30 lbs so far.  It occurred to me that if I made a big batch of mashed potatoes ahead of time it would be more convenient to reheat them for quick lunch breaks etc.  Mashed potatoes make a great extender for canned chili, soup, hash.

This is a form of what I think of as Bachelor Chow, where you take a processed food product and bulk it up with extra vegetables, usually in a one dish.  Here's another example: a breakfast salad I made from a gas-station breakfast sandwich and broccoli:

Actually that one didn't turn out that great (a little dry).  

I once saw KP making potato pancakes; it looked like she was just frying patties of mashed potatoes.  I haven't been able to get that to work, they crumble when I go to turn them.  Adding milk and even egg makes the potatoes smoother and creamier but they don't add any strength to the patty, and seem to make it even more likely to stick to the pan.

What did work was adding mashed potatoes to corn muffin mix and making pancakes out of that:

Here's my recipe for Corntato Pancakes:

2  1/2 cups Bob's Red Mill Cornbread Mix

2 cups mashed potatoes

1  1/4 cups water

1/4 cup oil

1 egg

Makes about 1 dozen.  Yummy.

I've also been working on mastering the no-scramble, one-egg cheese omelet:

Another round of freeze protection

Mr. and Mrs. Universe donated their trailer home.  Last week the nice men came to take it away, ha ha.  (I mention this in case you'd wonder where it went in subsequent photos.)

I'd been monitoring the septic line temperatures via the sensors Neo and I installed t'other week, and got a bad feeling.  I showed a chart like the one below to Edie D. the Executive Director, and Pigpen, learned with drain expertise.  The light blue line shows that from noon on the 4th to midnite on the 11th, the outside air temperature dropped from 65 to 17 F.  The dark blue line shows the temperature on the downstream leg of the septic line which we recently bermed over, that temperature barely moved.  The gray line shows the temperature on the upstream leg which was only about a foot down.  It responded much more quickly to the air temperature and had dropped into the thirties already.  We decided maybe we'd better hurry up and throw some more dirt over the upstream leg of the septic line.

That dirt-berming operation took place today.

I decided we'd better bring the berm right up to the house.  Glad I didn't spend too long setting the pavers for the walkway.

Pigpen must've brought out at least a ton of straw - four or five of the 8-foot bales.  We talked about throwing some manure on it in the spring and planting it.

I had to reroute my walkway which looks a little goofy now.  

Greenhouse floor sealing

Next week the Rural Renewable Energy Alliance comes to install solar water heat equipment.  It'll be one for the ages, the heat storage tanks will hold one ton of water and once installed will not be moving for a while, God willing.  I thought it would be a good idea to do something about the greenhouse floor before they went in.  The cob-crete floor has been wearing away into a fine powder.  Redbeard came up with a scheme to seal it using ordinary water-borne polyurethane and came out to do a test patch.  

It seemed to basically work.  Not a super-tough surface but it was a lot better than before so I went ahead and did the rest of it.  Redbeard says to me, "try and mix the poly and dirt into a slurry and fill the cracks in the floor.  And don't get ahead of yourself."  I sort of did that, but as much dirt and dust as there was on the floor, it still wasn't enough to fill the cracks, and it seemed crazy to dig up more dirt outside for that purpose.  That could still be done some time I suppose.  It took three gallons @ $40 to do the whole floor.  I wanted to hurry up and finish it so I could stop using electric boiler heat to warm the greenhouse floor.

I had a lot of stuff stored in the greenhouse which I had to move inside.  The upside of this is that there's much less floor to sweep in the house.

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.