just out of curiousity.....this was our first winter in this home and we
noticed that from about end of Nov to almost Feb, that the humidity in our
home displayed itself as tell-tale condensation on the lower edge of
windows. (northern ontario canada climate)
That was about 60% humidity...and we still have it. Its not uncomfortable,
in fact its quite nice in here (no static, dry lips, etc). but the moisture
I don't like in the winter. We tried running a borrowed dehumidifier, and
it did NOTHING. Pulled all of 3 drops from the air overnight.
At 60% humidity would the dehumidifier not be working overtime???? What are
my other options to controlling the humidity? I've got a new bathroom fan
installed and shower with the bathroom window open (all year). Older
furnace, no other accessories other than central air (which obviously
controls the issue in the summer). What could be going on? Is it that the
dehumidifier I borrowed didn't work??
any ideas on a more permanent solution? I know an air/air exchanger will
work wonders, but the cost is prohibitive. I heard that running a "fresh
air intake" to the intake side of the furnace works well....any ideas? just
cut a hole in the wall and run a duct to the intake???
60% humidity sounds wrong, what kind of humidistat do you have . Was it
calibrated, Taylor sells them up to 25% out of calibration, Menards, Ace
all had the same junk. I had to find a large display analog and
calibrate it. 60% rh at 10f or less and your exterior walls would be
literaly wet and your windows would have puddles under them. A little
condensation as you describe happens, but depending on window type may
not be a concern.
Do you have dual pane argon, what brand . What temp do you keep the
house in, farenheit. Dehumidifiers can frost some as high as 67f and
not work. What are winter temp ranges in, farenheit.
First you need a good humidistat.
regulated inside temp all winter = about 70 deg
average outside temp during winter = about 0 deg or less
Yes, the humidistat did move up and down some, but still stays at 60% right
now!! The dehumidifier I had
did not frost up. I agree....I'm going to have to get a good humidistat!!
The windows in the house are all wood framed, double pane glass from 1984.
Brand is unknown but the
glass is labelled as Twinsulite II. The windows were essentially sweating
somewhat, no moisture on the walls :)
I don't like the idea of water streaking down the window frame, sitting
there deteriorating paint/drywall and perhaps
getting in behind...
any ideas on how to lower??
You need fresh air , a recircuator , or a way to introduce fresh
air, but im no hvac pro.
Do you have a condensing furnace , one that uses outside air for
combustion , or a real tight house , with tyvek.
Without a good humidistat you cant say how far you need to go. But
yes condensaton should not happen.
To repeat, you don't have a humidity problem (or your dehumidifier would
have collected water). You have a window problem. Your windows have gone
"soft", i.e. the space between the two panes is no longer air-tight. 20
years is just about the average lifetime of double-pane windows made in
those days. I am sorry to be the bearer of bad news, I know replacing
windows is more expensive than running a dehumidifier.
I'm thinking of adding evaporative cooling to my home, and none of my
local stores seem to know much about it regarding a non-standard
installation. So, I thought I'd ask here and see if anyone can spot
potential problems I've missed.
The reason I want to install an Evap cooler is to reduce my electric
bill because using my present AC can cost up to $200 a month. I'd
also like to be able to use the cooler on "fan only" as an alternative
to opening windows when the weather isn't too hot.
First, my install plan;
My home has a combined forced-air heater/AC (gas heater). I was
planning to use the existing ductwork for the evap cooler.
My heater/AC is in a utility room on the lowest floor of my home, and
ten feet from a wall that divides the living area from a dirt and rock
floored crawlspace (the air in there is cool and dry; no moisture in
the crawlspace at all.). The crawlspace has twelve-foot ceilings in
that area, and I plan on installing the evap cooler in the crawlspace.
(outside mounting is not an option; it would cause too long a run of
ductwork to get to an outside wall. Roof mounting is also much too
far, and in any case forbidden by my homeowner's association.
Basically, I plan on running the cooler air into the main forced-air
junction box that's on top of my heater/ac. An alternate plan would be
to run the cooler output air into an AC return duct that passes right
over where I want to put the cooler. That would be far easier, but
it's only a 14" round duct and it does not look large enough. Aside
from easy installation, that configuration would also run the cooler
output air through my air filters, which I would like. In either case,
I plan on installing some sort of flapper valve that will close
automatically when the cooler is not in use (so when I'm using my AC
or heater I won't be losing air back through the evap cooler).
My main concern is that the utility room is vented, via a duct, into
the crawlspace, for ventilation of the water heater and heater/AC. My
concern is that the cooler will create low relative air pressure is
the crawlspace, and thus a reverse flow in the water heater "chimney",
which is a four inch vertical pipe over three stories tall.
If this is the case, could I just attach an airtight duct to the duct
between the crawlspace and the utility room, and extend it thro9ugh
the crawlspace to outside?
Also, there are not enough air entry points into the crawlspace for
the airflow, so I was going to put a screened cutout in the crawlspace
door (which is on an outside wall).
Plumbing won't be a problem, nor will electrical power. I have a
dedicated 15 amp line in the crawlspace that is used only for one
9-volt fluorescent light. There is a drain line below where I want to
mount the cooler, and also a cold water line nearby, so I do not
anticipate pluming problems. (I plan on putting a drain valve in the
cooler pan, for flushing and seasonal draining.)
I'll be going to city hall to see about permit and code requirements
in a few days, provided this plan still looks feasible. There are no
city or state codes here, just national ones.
A few more details; the climate here (mountains of Northern Arizona,
altitude 7000') is usually dry, but in July, August, and September can
be very humid. Daytime temps in the hot months (May through October)
often run in the 90's.
The house is a little over 4000 square feet, well insulated and sealed
against air leakage.
Anyone see any problems in my plan?
Also, how do I figure out what size evap cooler to get?
My present AC unit (Trane XL-80) is undersized for the square footage
of the house, but due to the house having good insulation and being
built into the side of a mountain it works just fine winter and
Thanks in advance.
Not a good idea. Do what you want, but the ductowrk for the AC isnt sized
correctly for an evap...period.
Then you need to give it up, and purchase a higher SEER AC unit..
Read what I said about AC ductwork not being large enough.
No. Thats called in the trade, just damn stupid.
It is also very illegal.
And your idea violates the International Mechanical Code...the standard
The evap cooler company can tell you...or, you can just go to Home Depot and
buy the biggest one you can find.....LOL
Then its not undersized is it? There are NO Rules of Thumb for SF/Tonnage.
If your unit is working, (altho, I have doubts about how well, since I never
broke $200 in good old Palm Springs, nor did my father in law in Phoneix and
he had over 3500SF of home....) then its not undersized.
And I am looking for criticisms, thanks. I'd rather find out here than
after I rip holes in walls whether this idea will work or not.
No, I don't. I was planning on replacing some attic access hatches
with screens during the summer months (would that count as an actual
upduct?) . The attics are all ridge and soffit vented. I was thinking
that air flow through the attic would also help cool the house.
The ductwork in this house is almost all rectangular box, several of
them leading out from the junction on top of the heater/AC, and I've
seen that used for Evap. Of course, I have no idea if this is adequate
or not. If not, then my Evap cooler is a non-starter.
That's an option... I'll have to phone Trane and see if they have a
SEER rating for my present system (XL 80, about ten years old) as I
can't find one anywhere on or in it, nor on the web (everything on the
web I've found is for newer XL 80's). (this unit was present when I
bought the house, so I wasn't involved with the installation). If I
can get significantly higher SEER, I'll do it if it isn't too
If that's the case (not doubting you, but my ductwork capacity looks
larger than in similar houses I've seen) then that sinks my idea.
Thanks for tipping me off to this potential problem.
I didn't mean attach to the water heater "chimney", but rather to the
duct that vents the utility room into the crawlspace, basically just
extending it a little. Or is that what you thought I meant, and it's a
bad idea (and illegal)?
Which part? Putting an Evap in a crawlspace, or the ductwork issues,
About the only place in town that sells them, other than installation
companies, is the home depot, and they were the ones who wanted to
base it solely on square footage. (I live in a fairly small town).
I've been told it is, but I disagree as it works fine, or seems to. It
does not run anywhere near continuously (more like 10-15 minutes an
hour in severe heat or cold) unless I've just turned it on and it has
to make a major change in interior temperature.
I managed to break $200 in Phoenix in a small apartment on more than
one occasion, but I suspect that was a cheap AC unit.
One problem with this house is the design; it's sort of staggered up a
mountainside, so it has a disproportionatly large surface area. It
also has a large cubic area due to having twenty foot ceilings in some
areas. It also has a heck of a lot of windows and walls with full
$200 was for a month with record heat. $70 to $110 is more common (but
that's just the increase caused by the AC, not the total electric
Thanks for your comments and help.
NP...installed, and ripped out and RE installed more units than I care to
remember...I have a pic on the office wall on my last evap install...on a
rooftop in CA, and everytime someone asks me about one here, I tend to look
at it and go....No.....way.....
Altho..most people dont understand why I dont like working on the duct
design n this are for them...since they are about as easy as anything...
It would, but an UpDuct is a barometric duct. You dont have to worry about
heat from the attic, putting a cover back in place, etc....you just put one
in each room that you want cooled, or two, depending on the size and area,
and the amount of airflow you have from your ducts from the cooler, and when
the cooler comes on, badda bing, you have no windows to open, no doors to
worry with, and a cooler home.
And the #1 design of western AC ducts...(Drumroll please.........) is what
you describe. Now, granted, Ihave said it before, and will say it again, *I*
cant see it from here, but I can promise you one thing....AC ducting, is NOT
adequate 99% of the time for a swamp cooler.....particularly a MasterCool2
10 year old XL80 would be a max if 10SEER, the lowest rating there is
currently. ARI has jumped the min standard from 10, to 13 starting Jan 1st,
06. In your area, a 14 SEER would actually be a big jump now, and in a year
and a half, it will be the equal to todays 12 SEER.
Ok..heres something to think about...6 inch duct....100CFM...roughly.
Depending on the tonnage of your current AC, you prob have either 8 or 6
inch take offs going to each run to the room.
Unless you have about 20 of them, 6 inch would be too small to properly get
enough airflow to each room, and be able to benefit from the
cooler.,...unless you are installing a tiny unit....and even then, its a
possibility that they are too small for that.
Most installs even with the smallest MasterCool unit or similar, used a min
of 8 inch duct, and most were 10, some even as large as 12...evaps need, and
demand airflow. in, and OUT of the home.
No..I know what you mean, and what you propose would create a negative
pressure zone, OR, the possibility of it. You cant do that. Your water
heater is going to fire up at some point when the coolers running, and all
that exhaust, will be pulled into the home.....granted, it SHOULD be heading
right out the open spaces to the outside...but its still not a good idea,
ever, to introduce exhaust gassses to the living enviroment...its also very
The crawlspace idea, while novel, might run into a couple of issues....its
going to depend there on your inspections department. The
ductwork...Umm...doubt anyone there in the department has a clue about
that....its the gas water heater issues that I can see that kill the idea
from the word go.
Let me explain one thing to you...HD employees are drones....total,
complete, idiots for the most part.
Go to the website for the brand of unit you are looking at, Adobe and other
brands all have a sizing chart that is fairly simple to understand.
The ONLY way to know, is to have a manual J load calc done....to insure its
proper. Too large of a unit will short cycle, and cost you more to run......
Or sized wrong..:)
See it all the time.
No problem, but keep in mind, that you have other alternatives still yet to
Just curious...how much attic space do you have?
If I had any sense, I'd probably shy away from doing this project
Could I fit those into the attic access hatches? The hatches are just
sheet drywall, but I could replace that with wood or steel and paint
<moved from lower down>
More like 40 of them...
The reason I thought mine might be adequate was that the configuration
is different from most I've seen (I'm a realtor so I see a lot).
On top of the Trane unit is what I call the "main junction" (Sorry, I
don't know the correct terminology for any of this). It's basically a
square box, and out of it come three "main ducts", which are approx
12"X24" (giving me an outgoing ductwork cross section total of about
six square feet). one of these "main ducts" has five wall registers
directly into it and also a few standard floor registers on six-inch
pipes. The other two have smaller standard floor size registers, off
of 6" pipes. There are a total of about five large wall registers, 25
floor registers on 6" pipes, and a dozen more even smaller registers
(such as under-cabinet, bathroom, etc.) on 4" pipes.
When the blower on the Trane is running full power, the air (hot or
cold) comes out of registers more like a draft. But, one nice thing is
it's totally silent.
If you still think this is insufficient ducting, I'll scrap the
project, but I just wanted to be sure I'd described it adequately.
Other AC installations I've seen have just one or two of the 12X24 or
similar sized ducts coming out of the main junction. I've never seen
<added from your other post>
Thanks.. you just saved me a major job, if I do end up being able to
put in the cooler.
Also, if there is some flow through the AC unit and back out the three
AC return registers, that effectively adds to my ductwork capacity.
Does increasing the SEER by 40% roughly reduce electrical usage by
40%, or am I misunderstanding the ratio here?
Due to the age of this system, I'd be willing to spend a few grand for
a new, high-SEER one to save 40%, but I wouldn't to, say, save 10%.
I've got at least that, plus several larger registers that are
installed directly into the box ducts.
Why wouldn't a larger number of smaller ducts equal a few larger ducts
How? The utility room would be isolated from the crawlspace by what I
propose. The Utility room would be vented to the exterior instead. (by
running an airtight duct through the crawlspace to an exterior wall),
so how would it be different from venting the utility room elsewhere?
Other then the present vent duct from the utility room to the
crawlspace, there is air connection between them (they are not even
adjacent). I'm not trying to refute what you say, I'm just making sure
I didn't explain myself badly and give you a false picture of what the
end result would be.
Agreed that I definitely don't want any chance of exhaust gasses in
Unless I can resolve the ductwork and the water heater issues it's a
definite no-go. I'm not worried about the gas furnace part of the
Trane, as it's a powered exhaust, and I can't imagine wanting to run
the heater and the cooler at the same time anyway.
I know that (:-)), but they also are about the best informed people in
this area. (says a lot for the area, huh?).
I'll go to several, thanks!!!!!! (I have no idea on brands yet so I'll
If I understand the term right, I'd need to hire someone with a lot of
experience; there are too many unusual factors here (it's kind of a
weird house, but I like it.). The construction is non-standard in many
areas; multiple roofs of different (and non-conventional)
construction, exterior walls of non-conventional construction (and
also in some cases non-vertical) several custom made windows of odd
design and shape (such as protruding half-pyramids) etc. Walls with
alternating brick overlayed by polished granite, and conventional
frame construction in diagonal bands (which change in width as they go
up, making it worse), etc. No way I know of to figure R-values for
much of it.
When I had my AC serviced last year, I asked about calculating the
correct size, and the service guy (from a place that does
installations) looked around and shook his head, telling me he had no
idea how it could be done.
I remember the AC ran just about continuously on hot (over 115) days.
That would indicate a wrong size, if I'm understanding correctly?
That's complicated. I've got three main attics, and a couple of
smaller but separate attic-type areas. The attics (most of them) are
odd because the interior ceiling is peaked, but the exterior roof is
peaked at a sharper angle, so it's a weirdly shaped space. Kind of
like an inverted V under a taller inverted V. The attics are separated
due to the odd design of the house (the house is three stories,
staggered up a hillside, so parts of all are ground level but in some
areas the stories overlap) Some parts of the house have no attic (wood
ceiling, a couple of feet on insulation, then the roof directly
attached) but others have attics. Total attic square footage is around
900 sq. ft, with an average height of (guessing) two feet, but going
from a few inches near the Soffits vents to a few feet under the ridge
vents. All are accessible.
Are you thinking of putting the Evap cooler inside an attic? There is
space, and I did think of that, but I didn't think it would work. The
attic interior is warmer, and also the utility room is in a part of
the lowest floor that would have a three story vertical with a few
zig-zags, then a twenty foot horizontal run of duct to get from the
cooler to the main ductwork junction in the utility room. Not only is
it a long way, but installing the duct would be a truly massive
project, far, far more than I'd ever want to attempt.
If I had any, I would have never gotten into HVAC..LOL..or left Palm
You could, but you would want them in the ceiling in EVERY room you want
cooled, and, you will need enough to keep the air flowing and not build a
static pressure in the home...
ok...your at about 4,000CFM then, IF they are 6 inch, and what you gonna do
wtih the other 2500 from a MC64?
Large home...gonna be like that. We just finished a log cabin thats about
5600SF...proably got a mile of duct in the place.
Then it sounds like it had a complete manual D and J on it when the home was
No..the big issue would be using the same ducts as the AC unit. you can not
completely seal the unit, even with a jack for the unit that would be
automatic when the coolers on..
Altho....you COULD have a White Rodgers low voltage control added to the
swamp, and it would be able to control with a little relay and creative
thinking, a bypass for the AC, so that if you were running the swamp, the ac
would never come on, and then you could have dampers added that would
automatically close it off...humm...gotta think on this one for a sec...or
Yes...no...depends. Its basically a method that tells you how many BTUS your
getting for your dollar spent.
Nor would anyone with a bit of sense, but its talked into people daily.
I have never told anyone that a unit will pay for itself, unless after
running the numbers, like an old Arkel Servel unit that will cost about 500
a month in NG to run the AC, since they dont really. Its like buying a new
car that gets better gas mileage...you STILL have to buy the new car...
Nope..I think I see it ok, and you would STILL be creating a negative zone,
and even with a power vent, you have to remember, air is fluid and seeks
Nor does anyone else...go to sleep...........and....thats...it...
Again...a bit of relay work, and you never have to worry about it.
Oh fuck....you got to be in Sierra Vista..but you said northern...so that
Good...you really need to.
Everything in your home that is used in contruction has an R value that can
be determined, U values, T values..etc...with the right guy using manual J.
Manual J isnt that hard..its complicated.
Then NEVER let that company back in your home...ever...period.
Actually, that for your area, sounds almost perfect.
it will run on the hottest days, all the time....normal.
Idea to consider, and its common in the upper class strict neighborhoods in
Palm Springs...and surrounding areas...
The cooler, a side draft, is mounted outside, on the side of the home, with
a support made for it. IT will have to be custom fabricated, and will need
of course to be secured to the home via the studs, with long bolts. The unit
will be secured to the stand after its mounted, and will need to be able to
get the doors off to service it.
The duct run can be pulled throughout the attic, and as long as you can
access the entire house from there, you have it made.
Thats what I was thinking...
There are a few rooms that would be lack flow, such as bathrooms and
one large room, but mostly there would bee good airflow just using the
attic hatch locations. The large room I mentioned couldn't have
upducts of any sort in it due to it being right under living space,
and having no exterior walls. It's not an issue though, as it stays
fairly cool as is, due to being half underground. .
Except for a few four inch and a few more large wall vents directly in
the main ducts, they are.
The ones I'd seen so far were side-draft, around 3000 CFM... For most
of the warm months I need only a little cooling, and I have the AC for
times when the evap can't handle it. If I need 5000 CFM, I think I can
handle that by routing some of it through the AC return ducts, but any
more and I'm probably sunk.
One brand I've found so far is Champion, but I'm by no means done
Could be, but I have no idea. The company that did it went out of
business, and the guy I bought the house from (who designed it and had
it built) is in a mental hospital. (I'm not kidding).
One way I was thinking of handling the situation was by powering the
cooler from the line to the AC, but switched so it would be to one or
the other, but not both.
I'm pretty good with electronics, so putting in relays, even building
control circuits, would be a snap if I need to do it. It would be very
simple to use a live circuit in the cooler as a trigger for a relay
that would kill power to the AC.
Given that I'm willing to attempt this project, that wouldn't apply to
My favorite reply to any salesman who uses the "it will pay for
itself" line on me; "Great! Nice to know I'll never have to make any
OK, how would running the utility vent the way I propose be any
different from putting in an entirely new vent that avoids the
crawlspace entirely (and sealing off the present one into the
crawlspace)? This is also an option...
I keep CO2 alarms for that reason... A friend of mine almost died of
CO2 from a furnace a few years ago.
I'll definitely do that. it would preclude accidentally turning them
both on at the same time.
ROFL!!! I've been to Sierra Vista a few times, and I know what you
mean, and my area isn't too different. The city I live near is
Prescott, and just about all businesses here have a "couldn't give a
damn" attitude. I'm actually several miles outside (and about 1700
feet higher than) Prescott.
The problem is determining what, exactly was used. Without opening
walls and ceilings, you just can't in some areas, due to oddball
They actually have the best reputation in the area, and probably with
good reason. But I did get the impression that they don't know what
they are talking about in some cases. For example, they saw no
problem, until I explained it, with my humidifier (attached to the
heater) installation (done when the house was built, and not by me.)
It's got an overflow drain that is a piece of clear tubing. To get
that connected to the sewer, they had tapped into the AC drain line
*downstream * of the trap, did not add a trap, then ran the PCV
diagonally across the front of the Trane unit (making getting the
front panels on and off a nightmare) and then hung the open end by a
string (!!!!) from the humidifier. They had stuck the clear drain line
in there, and "sealed" it in by stuffing a paper towel in around it.
Amongst other things, this arrangement was putting sewer gas directly
into my air ductwork! And this company I am talking about "didn't see
a problem with it" when i asked them to look at it. I fixed the
This was in an apartment down in Phoenix, which has a much warmer
I've got my AC on today, with a high of 91 (hot but not
record-breaking for this area, and the AC is handling the afternoon
load (the worst, due to Western exposure) by running 22 minutes out of
the last hour. Sound ok?
The heater runs about 45 minutes an hour when it's 15 below zero and
windy, which is the coldest I've seen here.
That would be great, but unfortunately it won't work. Due to the
layout of the house, the attics are above different stories, and don't
connect. There is no possibility that I can see of running ducting.
The only way I can see would be to have three of the setups you
describe, and given the cost and complexity of that and the new
ducting, I think I'm much better off even with my existing AC.
My main concern would have to be running all that water laden air over
your heat exchanger in the furnace. A furnace is not designed to
handle that level of moisture. If you have a lot of condensation on
the heat exchanger you could shorten the life of your furnace.
I'm surprised you spend so much at 7,000 feet in Northern AZ. NREL says
July is the warmest month in Flagstaff (el 7005', with an average air
pressure of 11.4 vs 14.7 psi at sea level), with a 66.3 F 24-hour average
daily temp and 50.5 and 81.9 average min and max and humidity ratio
w = 0.0081 and a 97 F 30-year record high. Prescott (el 5023') has 57.9
and 73.1 and 88.1 average temps and w = 0.0091 in July. Phoenix has 81.0,
93.5, and 105.9, with w = 0.0105 and a 30-year record high of 118.0.
Opening windows at night might do a lot, or reducing indoor electrical
energy use or the amount of sun that shines in windows, or increasing
the thermal mass of the house. At 10 cents/kWh, $200/mo is 67 kWh/day,
which could move 200 kWh or 682K Btu/day of heat, with a COP of 3.
$70 is about 10K Btu/h.
With no indoor electrical use or sun into windows, you might cool
a 5K Btu/F house thermal mass with a 200 Btu/h-F house-to-outdoor
thermal conductance (RCday = 25 hours) to T (F) at dawn and warm it
to 75 F at dusk, where 75 = 81.9+(T-81.9)e^(-12/25), so T = 70.7.
If 70.7 = 50.5+(75-50.5)e^(-12/RCnight), RCnight = 62.7 hours, so
R = 62.7/5K = 0.01253, eg a mass airfilm resistance of 1/5K h-F/Btu
in series with a 1/cfm fan resistance, with a tiny 81 cfm fan or
open windows at night. With an 8' height difference and an average
23 F temp diff, 81 = 16.6Asqrt(8'x23F) (using one empirical chimney
formula) requires an open window area A = 0.36 ft^2, eg a 3" slot
in each 2' window.
If the ambient vapor pressure Pa = 29.921/(1+0.62198/0.0081)11.4/14.7
= 0.2983" Hg, 100(Pw-0.2983)/(Tw-66.3-460) = -1 (using Bowen's 1926
formula) at the average wet bulb temp Tw (R). If Pw = e^(17.863-9621/Tw)
(using a Clausius-Clapeyron approximation), Tw = 9621/(22.47-ln(556.1-Tw)).
Plugging in Tw = 510 R (50 F) on the right makes Tw = 516 on the left,
Plugging in Tw = 516 R (56 F) on the right makes Tw = 512 on the left,
then 514.8, 513.1, 514.2, and 513.5 R, ie 53.5 F, or less, if the cooler
runs more at night.
You might install it on top of a water reservoir (eg a plastic 55 gallon
drum) and cool the house indirectly with an indoor fan-coil unit that adds
no humidity to the house air, or evaporate some water inside the house to
make it cooler still. A $150 2'x2' MagicAire SHW2347 duct heat exchanger
or a $35 used auto radiator and fan might have a water-air conductance of
00 Btu/h-F. With 53.5 F water and an indoor heat gain of 10K Btu/h, it
might keep the house at temp T, where (T-53.5)800 = 10K, so T = 66 F.
You might improve the cooler controls by adding a room temp thermostat
and a Honeywell RH sensor that turns off the fan-coil when the room is
comfortable and a differential thermostat that turns off the cooler when
the water inside the cooler is warmer than the reservoir water. You might
also improve the water-air ratio inside the cooler: too little airflow,
and the RH inside the cooler rises to 100%, with no evaporation and no
cooling; too much airflow, and the water temp inside the cooler is the
same as the outdoor air temp, with no cooling. Weather conditions change,
but this air-water ratio doesn't, in most swamp coolers.
For more heat storage, you might sprinkle a 4' or 8' cube or cylindrical
rock gabion with water at night, under an updraft fan.
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On 5 Jun 2004 09:58:51 -0400, email@example.com wrote:
That was my total electric bill, so I'm guessing $140 for the AC, but
that was an unusually hot month. I also could not open windows as we
were in the ash fallout area of a major fire, and my screens would not
have stopped all the ash blowing around (that hung around for weeks
after the fire). A more normal usage for June or July would be $80 for
Correct, Flagstaff is at the same elevation, and it's only 80 miles
away, but it's a little warmer here due to fewer trees and also
airflow up from the nearby low deserts. My warmest month is usually
June. (Monsoons start in July, and often have a massive cooling
However, the evap cooler wouldn't be much use in July or August, due
to very high humidity.
Prescott is only 15 miles away, and I'm on average ten degrees cooler,
but wind direction affects that a lot. BTW, your data is old; Phoenix
had an official high of 123 over a decade ago. I was there.
That's one big reason I want an evep cooler and air filters; It's
often 30 degrees cooler at night, but there are lots of tiny flies in
this area that can get through window screens and they are attracted
to coming inside, both day and night, which often precludes open
windows during the summer. Pollen and Dust are also an issue, though
not as serious. So, I'd use the cooler for non-evap air inflow quite
often, basically as an alternative to opening windows.
Sun in the windows is a big issue; I've got lots of them with a
Western exposure. I have thermal windows in most places, and vertical
blinds that I close, but some windows aren't practical to cover, due
to being 20' off the floor.
Thermal mass seems to be fine; The home has a very low heat loss or
gain over time when the AC or heater is off. I've got a great deal of
brick, granite, marble and tile, which helps.
I wouldn't mind some extra humidity; the air is extremely dry right
I'm very interested by the fan-coil concept you mention, though. I've
never heard of it.
The thermostat is a great idea, I'll definitely do that. I'm going to
have to study all the math you cited, though, as it's a bit beyond me.
However, thanks very much for posting it; I'll definitely look into
I need something automated, or I'll never remember to do it. Also, I
can't see the rock Gabion you describe being that effective in a 4000
Sq. Ft. house?
I haven't needed to fire up my air-conditioner much since I installed
thermostatically-controlled window fans that draw cooler air into the house
to a preset temperature. They really do cool the house a lot. When it's
really hot, the fans work most of the night cooling down the house for the
next day, and then other forms of cooling aren't really needed until later
in the day.
Evap coolers can be excellent air-cleaners if designed properly. A
wet-sponge filter used as an evaporator can trap nearly all foreign objects.
A small amount of chlorine or copper sulfate and a water-filtering system
should keep it fairly clean.
Using a heat exchanger to reduce the humidity is a great idea, but it
wouldn't really work, because any form of air-cooling drops the air to near
or below the dewpoint anyway. That's why air-conditioners have water
drains. I've never seen an air-conditioner or a swamp cooler that could
produce low-humidity cool air.
OK, OK commercial air-conditioners do this to a small degree. The
temperature of the air going over the evaporator fins can be a bit colder
than the mixture that comes out the vents, so you could say that the output
air is a bit above the dewpoint, therefore not at 100% humidity.
Funny, I've never seen an air conditioner that didn't produce very low
RH air. In a normal air conditioner the coils are very cold, well below
the dew point, and water condenses out of the air. This cold air is
then sent into the building where it becomes very much warmer and it's
Swamp coolers are another thing entirely, they work by putting water
(humidity) into the air so they can not produce low humidity air.
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