Willim's Page 254

254 Air conditioning

I started off sizing the air con on the basis two brochures I was given in Wilcon.

https://www.energystar.gov/index.cfm?c=roomac.pr_properly_sized - this link gives much the same information as the brochures but for more room sizes. This EnergyStar link is a good place to start the sizing of air conditioners.

These are the conversion factors required for Energy Star table for use in the Philippines :-
. . . 1000ft2 = 92.9m2 & 10 000 BTU = 10 550kj/hr

Do NOT use horsepower, HP, to size your air conditioning as I have seen different manufactures showing different cooling rates for the same HP. Use kiloJoules per hour, kJ/h(r).

Florida is another “strip” of land largely surrounded by water so has much the same issues as the PI. Locations in the heart of the US are not troubled by high humidity so have different issues. This link is to Florida Solar Energy Center http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-118-87/index.htm
The Pyschometric Chart, figure 3, shows the ASHRAE Summer Comfort Zone.

80^F, 26.67^C to be exact, but 27^C is close enough, is the upper temperature line used as above this temperature static electricity can be a problem.

From just below figure 3 :-

There are some other points of observation. First, the indoor conditions maintained were outside the ASHRAE summer thermal comfort zone, which is also plotted on the psychometric chart in Figure 3. It shows that the air conditioner maintained higher humidity even in fan "auto" mode. Therefore, air conditioners with a higher dehumidification fraction or lower SHR are required in warm, humid climates. Second, at low temperature settings, although the absolute humidity was reduced, the indoor relative humidity actually increased slightly. ... “ - my bolding of the above - Willim

http://www.wbdg.org/resources/hvac_humidclimates.php This link details the issues with mould (mold -US) in a hotel in Honolulu.

Even before guests began occupying the new guestroom tower of the hotel in Honolulu in 1996, pink spots of mold were visible behind vinyl wallcover and a strong mold odor was present in rooms and corridors. ….

To avoid the types of problems seen at the Honolulu hotel, HVAC systems in buildings in humid climates must do several things to maintain humidity control. The HVAC system must properly condition the building's interior, including the building envelope, and pressurize the building with dehumidified air (called exfiltration). When negative building pressurization occurs in humid climates, the result can be multimillion-dollar moisture and mold> problems from intrusion and condensation of moist outside air. The Florida Solar Energy Center ( FSEC )has found that building pressures as low as +1 pascal (Pa) relative to outside conditions are sufficient to prevent outside air infiltration problems. On the other hand, even a slightly depressurized building (-1 Pa relative to normal outside conditions) in hot, humid climates can develop devastating moisture and microbial growth problems when the building envelope traps this moisture. ….

http://coastalgreenair.com/pdfs/How-to-prevent-mold-and-mildew.pdf a slightly more detailed document 17 pages on the prevention of mould and mildew.

Air Conditioner Selection:

If you are building a new home and can choose, then choose an air conditioning system with a variable speed air handler and an operating selection mode for "enhanced moisture removal"(dehumidifier).

This is a good option for multiple reasons: the units are SEER 14+,they are quiet and they do a better job removing moisture,particularly under part load conditions. They accomplish this by starting the air handler fan at a lower speed during each cycle, which improves moisture removal. ...

they are ideal for use in the Southeast USA and other places around the world with the same hot humid climate.

http://courses.washington.edu/me333afe/Comfort_Health.pdf - Loads of information in an understandable fashion. :-) See page 24 for the "comfort zone."

Maybe I will be hanging carpets on the wall in the new accommodation - see page 8 :-) Due to the mould/ mildew issues maybe not such a good idea in the Philippines Islands.

http://www.trane.com/commercial/Uploads/PDF/520/ISS-APG001-EN.pdf

http://psychrometric-calculator.com/HumidAirWeb.aspx - as it says.

http://www.energy-design-tools.aud.ucla.edu/papers/ASES09-Yasmin.pdf pyschrometric chart tutorial

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-use-psychrometric-chart - as it says If the temperature is above "normal" body temp, 37^C, the human body temperature will increase, albeit more slowly if in an airflow.

Update Feb 2016

We have moved to Cordova. I obtained Airofoam and taped it to the "fly screens" in both bedrooms. I am comfortable in the bedroom that does NOT get the Sun all day with only the fan running.

In the bedroom that the Sun is on in the afternoon the air con is required to reduce the temperature. The aluminium of the "fly screen" becomes almost too hot to touch and this is only February. 

I have applied only one layer of Airofoam to the flyscreens as this allows some light to get through. If I was staying longer here I may have applied more Airofoam insulation on a frame outside to absorb/reflect the heat of the Sun but let in some light much as it does at the moment.

When collecting the car the other day we were in "van" / microbus with Airofoam on 50% of the passenger compartment side windows. I would presume this was to reduce the fuel to power the air con in the vehicle. 

Keep the Sunlight out and reduce your air con costs. The ultimate is Coober Pedy in Austrailia where people live in houses dug into the hillside.

I have no links with Messrs Airofoam there may be other similar products, insulating foam with Aluminium/reflective foil on both sides, on the Philippines market that I am unaware of. 

I am estimating less than PHP 100  per day for our total electricity costs. See page 605.

Update January, 2017

Having had the shipping container emptied, after a year the clothing wrapped in plastic waste sacks and taped with packaging tape was quite fresh. Some of the clothing was unwrapped and left in the open in the non-air conditioned part of the house and then we saw the "mould/ mold/ mildew" issue first hand.

Plastic sacks are not very decorative but appear to a good means of reducing at least if not fully combatting the "mould/ mold/ mildew" issue.

Our ex-UK bed is fabric covered, we/I discovered why they are a rarity in the Philippines, I have seen very few in the shops. Due to the previous regime of switching off the bedroom air conditioner during the day and closing the door the "mould/ mold/ mildew" issue occurred on the bed drawer fabric.

The air conditioners now run 24/7 usually set to "dry" rather than "cool". The temperatures on each are adjusted to target 50% or less humidity.

As both air conditioners are hard wired rather than using plug and sockets I have no means of determining the energy used by each. The electricity supply meter reading is noted on an almost daily basis and the kWh used varies from 8 - 16 with a usual of 11. My best guess is that the high usage of 16kWh is merely due to the Sun on our Southern walls one 135^ and the other 225^ (45^ East and West of South).

As part of my investigation I developed this spreadsheet.

Link to Solar_Surface_W_01.ods [372kb] approx. ODS Calc icon

This spreadsheet calculates the Solar Radiation, w/m2 on the walls, roof and a flat surface for interest. At times there are 1000w of radiation energy on each square metre of outside wall, my air conditioners are approx 1200W max. So less than three square metres of wall is receiving more power than they are using.

As supplied, the Reflectance of the Ground Surface,  rho_g for the walls and roof are all the same, they may be individually set if desired. I have been unsuccessful in tracking down better guidance on the web for selecting the rho_g values.

I prefer changing all together to "see what if." I leave them all the same and set them at 0.2, 0.4 and 0.6 to see "what if" Much the same ratios for the surfaces but higher as rho_g increases.

The methodology seems to be similar if not the same as the ASHRAE Clear-Sky Model. On the links in the spreadsheet it seems that if the co-efficients are revised the Model can produced good results. That is for others, the spreadsheet is a starting point for those interested and I hope it helps. 

The user sets one's latitude, longitude and time zone then selects a year, time difference from noon and whether it is Local Clock Times or Solar Hours. For those in the Tropics I have included two Special Days to hunt down when the Sun is directly overhead at noon and has crossed one's line of latitude on the way North or South. Users may find other uses perhaps to check one's birthday. Or perhaps determine where North or South is when the Sun is not too directly overhead at noon.

I have included what appears in hindsight to be the ASHRAE Standard Profile, ..mtu.edu/.. seems to use slightly different parameters, possibly updated ones, I don't know.

The walls, Cell  L68 and thereby, are set up at 90^ to each other and can be "rotated" by 90^ to cover all points of the compass.

My checks at 0^ and 45^ that the orientation for a square house does not have a major influence, less than 5%, on the total solar radiation gain with no eaves and about 2% with 1.0 eaves 2.4 above the ground. At 5^ North build for wind direction if possible and the windows are to be open. If fully air conditioned perhaps one should build for the best views where possible.

 (As long as the reader uses consistent units metres of feet, it does not matter which as it is mainly the ratio we are concerned with in most of this discussion.) A 2.4 feet canopy/ porch/ eaves is rather small to stand up in.

The roof parameters, Cell P68 and thereby, are much the same except for the roof slope. The slopes can be individually adjusted if required.

The greater the roof slope the less solar radiation per square metre however to minimise the total impact the closer the roof is to flat the better.  At a slope of 22.5^ the penalty is in the order of 1% greater impact than flat on total solar radiation. At 50^ and 60^ roof slopes the penalties appear to be in the order of 10 & 20% for a building at 10^ North.

Eaves for shading have been included the parameters, Cell BR68 and thereby, are quite simple eaves width and eaves height, each can be set differently for each wall. If the eaves are "working" there will be differences in the individual columns U-X and Y-AB. For a quick glance I find it easiest just compare Columns BM and BN. A quick check for the effectiveness of the shade is to set the eaves width as 0 and Columns BM and BN row values match.

I have a brief investigation of eaves lengths for a 2.4 height :-

1.0 eaves reduces the radiation on the walls by 40%

2.0 eaves reduces the radiation on the walls by 56%

3.0 eaves reduces the radiation on the walls by 63%

This would explain the large porches in front of traditional pre-air conditioning houses in Australia and USA.

Rather than walls and eaves one may "check" a window and "overhead sun screen canopy". The Shadow Pole height may be adjusted to give an indication if the distance to the side of the window required.

The length of a shadow from a vertical pole, height set in CG71 is displayed for a further "reality" check on the shading.

Summing the radiation per square metre for the walls and roof is slightly meaningless but a staring point if the building is almost square. For accurate work areas need to be considered rather than individual square metres.

For the purposes of the spreadsheet it is assumed the walls / house stands alone and have/has no barriers or shade between them/it and the the Sun at all times. If there are barriers less Solar Radiation and so less air conditioning maybe required if in the Tropics so this may be a good thing. Especially if the barriers are trees and/or other vegetation.

To generate one's own table copy and paste special  B18 - J18 and B30 J30 into, say row 100 onwards to build tables for the location and times being considered.

Treat the output as INFORMATION ONLY there are no guarantees, otherwise enjoy. The spreadsheet results may start one thinking on what route to pursue next. NOTE the limitations of the tab 01_NOAA NOAA calculations.

The spreadsheet tends to confirm that most air con will be required when the Sun is in the South at the begining and end of the years. There are houses screening our house to the East and North so we are protected to some extent from when the Sun is in the North of 10^ North.

Update 09-Feb-2017

Link to Solar_Position_Algorithm_SPA_10.ods ODS Calc icon  [17312kb] approx. = 17Mb approx.  Solar Position Algorithm Spreadsheet. There are 1350+ rows and 430+ columns and most cells are active – it takes time, 10-20 seconds, to enter data in the cells while the sheet is being re-calculated.

The spreadsheet bears heavily on the .PDF of the steps for the Solar Position Algorithm. One or more adjacent cells in a row cover an equation in the PDF. There are links to the SPA web site and others in the spreadsheet.

There are two tabs as supplied 01_Calc and 02_InOutput.

01_Calc should NOT normally be changed. Each row of 01_Calc calculates the Solar Position for the matching row on 02_InOutput. The top rows, 1-10+, of 01_Calc have the “constants” for the algoritm. Normally one should not require to view 01_Calc. 01_Calc can be viewed to compare the results with those parameters on the SPA PDF file

On tab 02_InOutput Rows 1 – 40 should not require changing. Rows , 41 – 1001, sufficient for 24 hours at 1.5 minute intervals Rows 1004 – 1016 “further data set for year, i.e. Solar Noon for each 21st. Adjust Cell F1007 if using a leap year to keep all the days at 21st. Rows 1017 – 1352 as supplied show 00:00 – 23:59 for 21-Dec-YYYY-1 to 21-Dec-YYYY.

As stated the surface directions are the Whole Circle Bearing (N=0 E=90 etc.) directions one is looking when one's back is to the surface. The “roof” surface is the same as the walls but there is NO shading, set the slope to 90^ and the results will be the same as for un-shaded walls. The surface outputs are watts per square metre. Each roof slope can be varied as require if desired. As supplied the four roof surface slopes are “linked” in Cells V35, W35 … .

The wall shading can be varied for each surface although supplied linked as above, the relevant Cells BX35, BY35 …. and BX35, BY35 … .

A suggested procedure is shown in Cells S2 - AS20. After experience is gained to speed up the spreadsheet rows could be deleted if not required.

The spreadsheet  was sufficient for my needs. It may prove to be a starting point for others. The spreadsheet my give some indication of the solar radiation on the human body so may be useful in other ways rather than just for solar panels and buildings.

Treat the output as INFORMATION ONLY there are no guarantees, otherwise enjoy. The spreadsheet results may start one thinking on what route to pursue next.

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