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re: steam heater problems
25 dec 1996
dennis  wrote:
>nick@ufo.ee.vill.edu (nick pine) wrote:
>>bill burdick  wrote:
>> 
>>>also make sure your air vents are shutting off properly and not
>>>letting steam escape...
>
>>or that someone like me hasn't added a humidistat, solenoid valve
>>and needle valve off a t that goes to the air vent... :-)
 
>good idea, nick.

it works, altho there's some temperature and humidity interaction
in controlling this system.

>if he would add a automatic feed water valve powered from the lwco,
>it would be self sufficient.

the 25 unit apartment building in brooklyn where we did this last winter
has one of those, in their one-pipe steam system, but only one thermostat.
a lot of the residents wear t-shirts and shorts all winter, and leave the
windows open. there was no insulation on the 3 steam risers in the apartment
we fixed up, and too many radiators. we took out one radiator, insulated
the risers and added a danfoss mechanical thermostat after the humidity t, 
and now there are only 24 apartments with the windows open.

>put a little menthol in if you're stuffed up. :-)

or some of grainger's concentrated banana scent? :-)

merry christmas.

nick


article: date: thu, 26 dec 1996 00:01:42 -0800
from: automatic digest processor 
subject: re: one way to build a high-performance passive solar house
to: recipients of ae digests 

from:    nick pine 

michael lebeau  writes:

>i think you need to consider a few more items nick:

then let us consider them very carefully, michael...

>> step 1.
>>
>> look up the average outdoor temperature in january, where you live.
>
>and also look up average windspeed.

10.3 mph, at the philadelphia weather station.
now what do we do with that number?

>> the national renewable energy laboratory's free _solar radiation data manual
>> for buildings_ has this information for 239 us locations. nrel's phone number
>> is (303) 275-4099.
>>
>> where i live, near philadelphia, the average january temperature is about
>> 30 degrees f, and nrel's manual says that 1,000 btu/day of sun falls on a
>> south wall here on an average january day.
>>
>define "wall", how big etc.

a wall is a vertical side of a house :-) walls vary in size, but the amount
of sun that falls on a square foot of south wall in january does not depend
on the size of the wall. nor does it vary a lot, over the whole month, at a
particular location. nrel says the standard deviation for sunshine during
the month of january is 42/620, ie less than 7%, and the uncertainty in the
data is +/- 11%. these are two-sided measures of dispersion, and we are only
interested in times with less sun, not more sun, so we can more or less halve
these percentages.

>>step 2.
>>
>>estimate how many btu your house needs to stay warm on an average january day.
>
>what about those days that are twice as cold as average??

that's an interesting question. i wonder what you mean by "twice as cold."
if the outdoor air is 30 f on an average day, there's a 68-30 = 38 f indoor-
outdoor temperature difference. is a day that is "twice as cold" one with
an indoor-outdoor temperature difference of 2x38 = 76 f, ie a day when it's
-8 f outdoors? we don't see many days like that around here, and they are
usually quite sunny, sometimes with snow or ice on the ground, making them
at least 30% sunnier by reflection. we can insure that reflection by making
a shallow pond to the south of a house. a solar heating system should be
designed for the local climate, like any other heating system.

if colder days are sunny, that's not a serious problem, and very cold days
and nights tend to be clear, as mentioned below. it's good to have enough
thermal storage in a solar closet, attic warmstore, masonry house walls, etc,
to bridge a few colder-than-average cloudy days, and sufficient thermal mass
in the house and heat transfer rate between the thermal store and the house
to be able to keep the house warm at the minimum outdoor "design temperature"
for the location. this heating system capacity problem is often addressed to
start with for conventional heating systems by looking up some numbers in the
american society of heating, ventilation and air-conditioning engineer's
(ashrae) handbook of fundamentals (hof), which says on page 24.2, under the
headings "weather-oriented design factors," and "winter,"

   minimum temperatures usually occur between 6 am and 8 am suntime on clear
   days when the daily range is greatest. for residential applications or
   other applications where the occupancy is continuous throughout the day,
   the recommended design temperatures in column 5 apply... studies at several
   stations have found that the duration of extremely cold temperatures can
   continue below the 99% level for 3 days and below the 97.5% level for 5
   days or more (see ecodyne cooling products 1980, sterling 1985, crow 1963.)

column 5 on page 24.13 of the 1993 ashrae hof shows 99% and 97.5% winter
design dry-bulb temperatures of 10 f and 14 f for philadelphia. that says
something about the statistical distribution of outdoor winter temperatures
in philadelphia, as well as the maximum required heat transfer capacity of
a heating system, ie it says that we expect to see outdoor temperatures less
than 10 f less than 1% of the time in the winter, and temperatures less than
14 f less than 2.5% of the time, which in turn says something about the
amount of heat the house has to store in order to stay warm during these
colder times. of course if there are colder than average days in a month,
there have to be warmer than average days too, to make the monthly average
come out to the monthly average. during those warmer days, the house needs
less heat and stores more heat. it's a bit like putting money in the bank
and taking money out, and looking at the balance over a month, if you are
a gambling casino.

as the number of cold days in a row increases, the average outdoor temperature
approaches the average monthly outdoor temperature, statistically-speaking.
it is not very surprising to flip a coin twice and see 2 heads in a row;
it is much more surprising to flip a coin and see 30 heads in a row. it is
surprising to heat houses by such coin-flipping. people are used to more
cause-and-effect heating systems. but if the system is well-designed, these
systems can have equivalent performance. norman saunders, pe, calculates
how often his 100% solar houses will need non-solar backup heat in the same
way that some engineers calculate 100 year floods :-) he estimates that some
of his new england houses will only need backup heat every 35 years, and some
of his houses with long track records have no backup heating systems at all,
since the frugal occupants prefer to put on a sweater every 35 years instead
of buying a small electric space heater that so rarely turns on.

the few simulations i've done and posted here using detailed hourly nrel
weather data for a typical meteorological year in philadelphia show that
houses designed with this particular scheme have no problem keeping warm.
their heat stores are never less than 80 f. they are overdesigned.

>>for example, a very-well-insulated 30' x 30' 2-story house with about 2,000
>>square feet of average r20 walls and 1,000 ft^2 of r40 ceiling needs about
>>2,000ft^2/r20 + 1000ft^2/r40 = 125 btu per hour to stay 68 degrees f inside
>>when it is 67 f outside...

>you don't get an r20 average per square foot value very easily.

that's why i said "very-well-insulated." including the windows, which would
mostly be a part of the thermally isolated sunspace, in a new house with few
windows in the house itself. in an existing house, we might better insulate
the windows by covering them with foamboard during the winter, fashioned as
air heaters for south windows, with only tiny exposed patches of bare glass,
as malcolm wells did in his underground office in new jersey and one of my
friends who lives in a conventional house with a $300 heating bill does in pa.
it seems to me that present day houses have too many uninsulated windows at
night and during the dead of winter. even during the day, we don't need much
window area for views and light. direct sunlight is about 200 times stronger
than a brightly-lit room, so if we can diffuse it nicely, we can have have
fine daylighting with 0.5% of the floorspace as windows or skylights with
concentrating south sunscoops above them, eg a 2000 ft^2 house with a single
3'x3' south window, vs a more typical house today with 10% of the floorspace
as windows. (imagine a powerful beam of 10 "sameshine suns" ie 10 kw of heat
and light entering that small window over a whole clear day from a simple
outdoor concentrating heliostat in albuquerque, new mexico--a sheet of
newspaper held in that light would burst into flame in a few seconds.)

>you have around 30% framing in a typical stud wall.

thermal shunts. they don't have to be so serious, as we've already discussed.
the energy crafted homes spec and dutt and nisson's _superinsulated home book_
show many ways to minimize this.

>you're also claiming that you have no air change happening

no...

>which is most of your losses in many standard homes.

i read that the average air infiltration loss in a home was about 30%, as of
15 years ago. things have improved since then, but so has insulation. again,
things don't have to be this way, eg if we use a few gaskets when building
a house, as they do in scandinavia. and the electrical usage in many houses
makes up for the air infiltration loss. take a look at the detailed thermal
analysis in the designs in nisson/dutt's book, if you like, michael, or try
a few numbers yourself: that 30x30x16' tall 14k ft^3 r20 house would lose
about (70-40)14k/55 = 10k btu/hr with 1 ach or 1k btu/hr with 0.1 ach, and
a typical house using 1000 kwh/month of electricity makes about 5k btu/hr
of internal heat. this can all be done with simple arithmetic. we also use
and waste far too much electricity...

>air change through leaks driven by wind and stack.

and gloom of night? where's the verb? what's your point?

>intentional air change via ventilation.

that's a happier matter with more simple arithmetic, like this:


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