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occupants ( internal gains) and solar are the big loads, not the shell<div><br></div><div>ducted systems ( particularly as installed in attics ) have high duct losses and added infiltration losses.</div><div><br></div><div>ductless split systems offer htg and clg and no duct losses at cops of 2-4 and seers of 20 at $2000/ton installed</div><div><br></div><div>and have remote control clickers and hot spot directional fans. google mitsubishi, fujitsu, <br><br><div><div id="SkyDrivePlaceholder"></div><hr id="stopSpelling">From: nick@early.com<br>To: greenbuilding@lists.bioenergylists.org<br>Subject: Re: Central vs window AC<br>Date: Fri, 8 Jun 2012 04:56:54 -0400<br><br>
<div>> NREL says an average year in NYC has 1096 CDDs with a 65 F base... so
a house with no internal heat gains or solar gain and (say) 400 Btu/h-F of
thermal conductance needs 24h/dayx1096F/dayx400Btu/h-F = 10.52 million Btu (note
the units) per year of cooling...<br><br>Oops. That should be
24h/dayx1096F-dayx400Btu/h-F = 10.52 million Btu. A degree-day is a
temperature-time product.<br><br>> or 10.52M/26 = 405 kWh worth $72.84 at
0.18/kWh with a 26 SEER<br><br><a title="http://www.greenbuildingadvisor.com/blogs/dept/musings/window-mounted-air-conditioners-save-energy?utm_source=email&utm_medium=eletter&utm_term=cooling-options&utm_content=20120530-wall-mounted-air-conditioner&utm_campaign=green-building-advisor-eletter
CTRL + Click to follow link" href="http://www.greenbuildingadvisor.com/blogs/dept/musings/window-mounted-air-conditioners-save-energy?utm_source=email&utm_medium=eletter&utm_term=cooling-options&utm_content=20120530-wall-mounted-air-conditioner&utm_campaign=green-building-advisor-eletter" target="_blank">http://www.greenbuildingadvisor.com/blogs/dept/musings/window-mounted-air-conditioners-save-energy?utm_source=email&utm_medium=eletter&utm_term=cooling-options&utm_content=20120530-wall-mounted-air-conditioner&utm_campaign=green-building-advisor-eletter</a> says<br><br>>For
typical residential air conditioners, EER equals about 0.875
SEER.<br><br>Comparing apples to apples, the 10 EER window AC would have a
10/0.875 = 11.4 SEER (maybe more, if the fan doesn't run all the time), so it
would use 10.52M/11.4 = 923 kWh worth $166.10, with a simple payback of
($2100-$210)/($166.10-$72.84) = 20.3 years, compared to a $2100 SEER 26 split
system, without the use of room occupancy sensors.<br><br>>How would this
change for a house with 8 rooms each occupied 2 hours per day, with doors and
lots of wall insulation between rooms and 30-minute occupancy
sensors?<br><br>With no common walls or time delay, a 10-SEER window system
would be like an inexpensive 80-SEER central AC system...</div>
<div><br>> NREL says an average July day is 76.8 F in NYC, with a 68.2
min and a 0.0123 humidity ratio, which is fairly comfortable. Smart night
ventilation on comfortable nights can help.<br><br>How much, if a small box
turns off the window AC and opens a 2-watt outdoor damper or runs a $69 2470 90
watt fan on comfortable nights, using the ASHRAE comfort standard?<br><br><a title="http://www.amazon.com/Lasko-Electrically-Reversible-Window-2155A/dp/B00002N5Z9/ref=sr_1_1?s=appliances&ie=UTF8&qid=1339144279&sr=1-1
CTRL + Click to follow link" href="http://www.amazon.com/Lasko-Electrically-Reversible-Window-2155A/dp/B00002N5Z9/ref=sr_1_1?s=appliances&ie=UTF8&qid=1339144279&sr=1-1" target="_blank">http://www.amazon.com/Lasko-Electrically-Reversible-Window-2155A/dp/B00002N5Z9/ref=sr_1_1?s=appliances&ie=UTF8&qid=1339144279&sr=1-1</a></div>
<div><strong><font color="#4b0700" face="Courier New"></font></strong><br>The box
might look something like this: <a title="http://www.youtube.com/watch?v=wexdNx_StRc
CTRL + Click to follow link" href="http://www.youtube.com/watch?v=wexdNx_StRc" target="_blank">http://www.youtube.com/watch?v=wexdNx_StRc</a></div>
<div><strong><font color="#4b0700" face="Courier New"></font></strong><br>My
Quaker friend Thom Styles could build one. Any takers? This could work well in a
massy brick house or brownstone.<br><br>Phila has 1101 CDD, with an average 67.2
F July min and a 0.0133 humidity ratio...<br><br>Nick<br><br>50 CLO = 1'clothing
insulation (clo)<br>60 MET=1.1'metabolic rate (met)<br>70 WME=0'external work
(met)<br>80 TA=19.6'air temp (C)<br>90 TR=19.6'mean radiant temp (C)<br>100
VEL=.1'air velocity<br>120 RH=86'relative humidity (%)<br>130 PA=0'water vapor
pressure<br>140 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure,
kPa<br>150 IF PA=0 THEN PA=RH*10*FNPS(TA)'water vapor pressure, Pa<br>160
ICL=.155*CLO'clothing resistance (m^2K/W)<br>170 M=MET*58.15'metabolic rate
(W/m^2)<br>180 W=WME*58.15'external work in (W/m^2)<br>190 MW=M-W'internal heat
production<br>200 IF ICL<.078 THEN FCL=1+1.29*ICL ELSE
FCL=1.05+.645*ICL'clothing factor<br>210 HCF=12.1*SQR(VEL)'forced convection
conductance<br>220 TAA=TA+273'air temp (K)<br>230 TRA=TR+273'mean radiant temp
(K)<br>250 TCLA=TAA+(35.5-TA)/(3.5*(6.45*ICL+.1))'est clothing temp<br>260
P1=ICL*FCL:P2=P1*3.96:P3=P1*100:P4=P1*TAA'intermediate values<br>300
P5=308.7-.028*MW+P2*(TRA/100)^4<br>310 XN=TCLA/100<br>320 XF=XN<br>330
N=0'number of iterations<br>340 EPS=.00015'stop iteration when met<br>350
XF=(XF+XN)/2'natural convection conductance<br>360
HCN=2.38*ABS(100*XF-TAA)^.25<br>370 IF HCF>HCN THEN HC=HCF ELSE HC=HCN<br>380
XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC)<br>390 N=N+1<br>400 IF N>150 GOTO
550<br>410 IF ABS(XN-XF)>EPS GOTO 350<br>420 TCL=100*XN-273'clothing surface
temp (C)<br>440 HL1=.00305*(5733-6.99*MW-PA)'heat loss diff through skin<br>450
IF MW>58.15 THEN HL2=.42*(MW-58.15) ELSE HL2=0'heat loss by sweating<br>460
HL3=.000017*M*(5867-PA)'latent respiration heat loss<br>470
HL4=.0014*M*(34-TA)'dry respiration heat loss<br>480
HL5=3.96*FCL*(XN^4-(TRA/100)^4)'heat loss by radiation<br>490
HL6=FCL*HC*(TCL-TA)'heat loss by convection<br>510
TS=.303*EXP(-.036*M)+.028'thermal sensation transfer coefficient<br>520
PMV=TS*(MW-HL1-HL2-HL3-HL4-HL5-HL6)'predicted mean vote<br>530
PPD=100-95*EXP(-.03353*PMV^4-.2179*PMV^2)'predicted % dissatisfied<br>540 GOTO
580<br>550 PMV=99999!:PPD=100<br>580 PRINT
TA,RH,CLO,PMV,PPD<br><br>19.6
86
1
-.4778556
9.769089<br>23.9
66
1
.4732535
9.676994<br>25.7
15
1
.5239881
10.74283<br>21.2
20
1
-.4779105
9.770202<br>23.6
67
.5
-.4747404
9.706658<br>26.8
56
.5
.5145492
10.53611<br>27.9
13
.5
.5003051
10.23146<br>24.7
16
.5
-.4883473 9.982468<br><br>Innova AirTech
Instruments has an excellent comfort web site...</div></div></div> </div></body>
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