69 in a Eurocave

gasfolk

From your recent experiments, would you recommend placing the outdoor temperature sensor on the north or south side, and if the latter, would you place it in shade or sunshine?

gf

Mike T., Swampeast MO

Vitodens with TRVs

Return temp avg: 69°

System Supply avg: 75°

Single Occupied Room Temp (TRV setting 1) avg: 64°

Unoccupied Room Temp avg: 55°

"Wild" Radiant Floor Spaces: 59° (floor feels cool)

Electric Radiant Space avg: 55° (floor feels warm)

Standing Iron Temp: 72°

Outdoor Conditions: Whenever above 32°

Reset Ratio: 0.8 slope, 0° shift.

Sun Dial: 72°; Moon Dial: 72° RADIATOR TEMP: 72°

---------------

2-day and 4-day data attached. (Original pdfs were rather blurry. Have changed to ones with more detail.)

jp_2

why would the 59F room floor feel cold and the 55F room floor feel warm? what are the details?

what is meant by system supply ave.? what the are highs and low temps and more importantly how long are the high temps high? you could have ave temps low but be in the high region more often, does the boiler consider time in these average recording? then we are really talk power and not just temperature.

Mike T., Swampeast MO

These numbers are positively freaking me out.

6° system delta-t. 6° radiator delta-t in my office (the one room with a higher TRV setting of "1").

Heat loss in the study must be at least 1,300 btu/hr when that rad averages 72° surface temp. This MUST be the true average as system supply temp is 75° and system return temp is 69°.

Flow in that radiator works out to 0.43 gpm. 75 sq.ft. of EDR, so with a loss of 1,300 btu and a temp difference of 8° (64° room, 72° radiator) each square foot of the standing iron must be giving off about 2.17 btu/hr. That alone blows away "standards" for cast iron output.

Entire house must be loosing at least 20,000 btu with outdoor temp is in mid 30s. With a 6° system delta-t, flow rate must be around 6.6 gpm. The circulator built in to the Vitodens is rated to move 6.16 gpm with zero head loss–and this rating is at 100% circulator speed. The Vitodens doesn't report the current circulator speed and literature doesn't give any way to determine, but I know that the circulator was operating at MUCH less than 100% speed as I forced it into full speed and could hear and feel it a tiny bit and the Grundfoss Indicator for AC Magnetic Fields began spinning significantly faster.

We've had reasonable and often gusty winds throughout the period. I'm reducing Manual J (HVAC-Calc) heat losses in these conditions by 30%+!!

While I said "radiator temp" was 75° that's ONLY the rad in my office. I did not measure the rest, but all were significantly cooler and a number felt ambient.

Something is really strange...

jp_2

looks like you have a good amount of sun loading. will be interested in same data when you have 24 hour temp below 32F and no sunny days.

jim

addition: I've left my cabin in the morning, indoor temp 50, woodstove winding down, come back during a sunny afternoon and have cabin temps 70F with outside temps below 32F, good ol sun! if I come back an hour after sundown, cabin temps are more like 5F-10F above outdoor temps.

Mike T., Swampeast MO

Definitely solar gain, but don't forget that the outside temp data is collected on the South side and often in the sun. Significantly cooler on the North but I can't get my solar-powered outdoor temp sensor to work back there.

Actually I kind of like having the outdoor temp being solar influenced. Makes for some very interesting comparisons to boiler operation. Am not yet using the dual (N & S) temp sensors for the Vitodens--its input is coming strictly from the N.

Yes, it will be interesting when outdoor temps are constantly near or below freezing. The 0.8 slope, 0° shift shouldn't be able to heat the house--even at these rather low indoor temps.

jp_2

average temps

does the boiler factor in 'time' when it gives average temps? as you can understand, 'time' is very important when talking about operation here, we are really talking about power, average temps on their own is kind of meaningless.

jp_2

dT

"""Heat loss in the study must be at least 1,300 btu/hr when that rad averages 72° surface temp. This MUST be the true average as system supply temp is 75° and system return temp is 69°. Flow in that radiator works out to 0.43 gpm. 75 sq.ft. of EDR, so with a loss of 1,300 btu and a temp difference of 8°(64° room, 72° radiator)...""""

wouldn't your real delta T be 3F. if the feed is 75F and surface is 72F then 3F is missing?

or is the boiler putting out 75F but the rad sees only 72F, giving up 3F to the room for a return temp of 69F?

I would think the surface vs room temp would give you the rate of transfer, which again brings up 'time'

jim

Mike T., Swampeast MO

The temps I call "average" come from the attached graphs. As you can see, the temps are quite tight. These are measured (not reported) temperatures. The boiler has mainly been in what I call "pulse" mode, injecting small amounts of heat at regular intervals.

Mike T., Swampeast MO

Top dead center of radiator 72F. Supply @ TRV 75F. Did not measure return at radiator.

Supply @ rad TRV same as supply 3' away from boiler. Return 3' from boiler 69F. Room temp in that space 64F.

I did assume (based on those number) that the return at that rad was 69F. 75 - 69 = 6 delta-t. Don't believe it could be lower than 69. If higher then the output per sq.ft. EDR of that rad is even further into the realm of [supposed] impossibility.

True constant circulation. Boiler is injecting very small "batches" of heat (at a temp significantly higher than 75F) into the two pairs of very large mains (converted gravity system).

I agree that time matters!!!! It would however seem that the radiation instantly "sees" the batches of higher temp water produced by the radiant burnered Vitodens. Can a tiny "tunnel" of significantly hotter water somehow pass through the huge piping?

Mike T., Swampeast MO

Graph From Comparable Period Last Fall

Unoccupied spaces were maintained at about 60° (as opposed to 55°) and occupied spaces at 66° (as opposed to 64°), so really not that much difference in space temperature.

Unfortunately however I've nearly lost the "wild" bath radiant floors. Even copper in Thermofin can't do too much with 75° supply although they're still maintaining 4° above the average surrounding space temp!

WHOPPING difference in the graphs and I presume there will be a significant difference in fuel consumption (for this sort of weather) as well...

jp_2

figured it out

it just hit me today.

"""I did assume (based on those number) that the return at that rad was 69F. 75 - 69 = 6 delta-t. Don't believe it could be lower than 69. If higher then the output per sq.ft. EDR of that rad is even further into the realm of [supposed] impossibility. """"

your delta T is only 3F, not 6F, you need to use rad temp and not supply temp. heat transfer depends on the boundry conditions, air/rad boundry which would be 69F/72F and not 69F/75F. this corrisponds to a 50% error!

jim

Mike T., Swampeast MO

Not sure. Have all the components to hook up a simple diversity system but didn't do it this year. Will do so when I'm not keeping most of the place so cool.