All posts by indi-air

Energy Savings
In some buildings and structures the cost for air conditioning reaches 60% of the total electrical bill, it is incumbent upon us to take all necessary steps to conserve energy, thus saving us money and reducing the load on the power grid.

1. Tips for the individual builder

a. Plan your home based on materials designed to prevent heat stress penetration, such as Ytong blocks or equivalent.
b. Plan windows with internal and external shading.
c. Plan on double or triple pane insulating glass.
d. Plan a well insulated roof.
e. Plan for hermetically wind sealed windows and shutters.
f. Plan on energy saving lighting which does not emit much heat. There are light bulbs on the market that are more costly initially, but provide a return on investment during day-to-day use.
g. Plan for air conditioners with the appropriate output, with no excess, to lower the load on the power grid. One can use the virtual engineer software program or consult an engineer.
h. The recommendation is to invest a little more up front in purchasing inverters or VRF type air conditioners, which under partial load can save up to 50% of the energy consumption compared with conventional A/Cs due to the higher energy efficiency at partial loads.
i. For central air conditioning systems, it is recommended to add sensors to the windows (micro-switches), so that an open window will prevent the specific room unit from operating!
j. In chiller of VFR type systems it is recommended to connect the units to the alarm system volume sensor so that the specific room unit will shut off when the room is unoccupied.
k. If you are non-smokers, install air conditioners planned without a fresh- air mechanism – you can aerate the house during the morning or evening hours.
l. Purchase air conditioners with high energy efficiency (COP). The higher the efficiency the greater the cost savings.

2. General

a. Avoid using the air conditioning system with a window open.
b. If you have a very old air conditioner, it is recommended to replace it with a new one. The new air conditioners are much more energy efficient than the older units so you will recoup your investment quite quickly (under discussion is a nation-wide program to scrap old air conditioners and install new ones thus saving significantly on electricity usage).
c. Set the temperature for cooling no lower than 23⁰ C – this is a pleasant temperature for most people.
• At night set the temperature to 26⁰ C not lower.
• Each degree costs hundreds of shekels in electricity.
d. If you see someone setting the temperature to 18⁰ C set it to 23⁰ C – there is no need to overdo it.
e. If you have windows or shutters that are not fully sealed, have a craftsperson repair them – it will pay off in the energy savings.
f. If you have standard pane glass windows, attach a radiation preventing coating to them and save energy.
g. Verify that the roof insulation is in tact.
h. If you have several air conditioning systems in your home – activate only the one in the area where you are!
i. Verify that the condenser unit (the outdoor engine in laymen terms) is located in a well ventilated area and that there is no air short circuit – that expelled hot air is sucked back into the system (a unit operating under an air short circuit operates under high head pressure and gobbles electricity). It is recommended to install the condenser unit in a shaded area.
j. Verify that the condenser unit is clean, that no stray plastic bag or newspaper is stuck to it which can reduce the heat exchange area and increase the head pressure and energy consumption.
k. Clean filters every three months to improve air conditioner performance.
l. During the transition seasons and in areas with low humidity at night – opt for using fans, which are over 95% more economical than air conditioners.

Anecdote
Several years ago an old man showed up unexpectedly in my office and asked me to come check the air conditioning system that was installed in his house and to prepare an opinion for the court against the installer who had installed the system as the system was not cooling as expected.
I regretfully informed him that I could not accommodate his request as I was overloaded with work and I stayed away from any legal dealings, recommending that he consult an engineer instead for this work.
The following day the old man was at my office again with no appointment. He begged me to come and said he and his wife were suffering immensely from the system and that he had been wronged.
I did not enjoy seeing the old man begging, so I agreed.
During my visit to the apartment in Netanya I saw a 4 room apartment with a 3.5 HP system installed – an output that should at first glance be sufficient (for the old man and his wife) except that the living room had a large glass door facing the balcony and a large glass window both pointing west.
I ran a detailed calculation of the load for the apartment whose walls amongst other face east and south and realized that the output of the unit installed fell about 13,000 BTU per hour below the requirement. The executed air flow was so bad that the dining room received a very large quantity of air while the rooms and living room less than the required amount, and a noticeable temperature difference was created within the apartment, causing discomfort when moving from one space to another.
I submitted my professional opinion to the court.
In the court case, the old man won, and the contractor was required to install a new greater output system for him.
(I asked the installer how he had determined the air conditioner size? His response was that it was based on tables of output vs. space size that he received from the manufacturer).
I visited the old man’s home during the installation and witnessed his stress when his decorative ceiling with spot lights in it was taken down again so a new and larger system could be installed, walls were broken to pass the gas lines through and install the distribution units in the room based on the plan that I had prepared, changes to the electrical board from single phase to three phase were made, and more…
His wife suffered from seeing all the dirt and upheaval in the house.
When the work was completed and the new unit was turned on I finally saw the old man smile. “You know I should have come to you two years ago, before installing the initial system, then we would have been spared all this suffering” the old man said.
“The truth is I am not sure I would have had the time to serve you” I replied.
When I left his home I thought that in fact there was a whole sector of “residences” in this country that does not receive the appropriate engineering attention (due to the high cost of engineers) and is at the mercy of the air conditioning installers, not all of whom are capable of providing the appropriate solution for the apartment or house. After all the output of the air conditioning system is determined not only by the apartment footprint, but there are other important variables in determining this output, the directions of the walls, the type of glass in the windows, the type of wall material, the number of inhabitants, the type of lighting (standard bulbs or spots), electrical equipment in the apartment, animals in the apartment, are the residents heavy smokers (an important factor in determining whether to incorporate fresh air or not) – all these and more are important parameters one must consider when calculating and determining the air conditioning unit size.
On the other hand installing a unit that is larger than required is also a failure – as you have spent unnecessary money on something you only partially use, your energy consumption is greater, the wear on the unit is more rapid due to “short work cycles” with frequent starts and stops, unnecessary load on the phases, loss of space, higher noise levels, etc.
Since to the best of my knowledge most of the engineers specializing in air conditioning do not plan apartment units and avoid planning private homes due to the high cost of their labor and their involvement in larger projects, I have thought it appropriate to offer you basic principle advice on apartment and home air conditioning.
After watching the guidelines from Yasmin and you learn to fill out the data for your home, you will get a fairly accurate idea of the type of air conditioner you need and the quantity of air required for each of the air conditioned spaces.
This service is provided “free of charge” with the perspective that if each one of us makes an effort to do the utmost in his area of specialization for others around him – at the end we will all be better off!

So good luck!!

Isaac Barrabi, consulting engineer.

Air conditioning methods

There are several methods for air conditioning homes/apartments.

A. Chilled Water Air Conditioning System

This system generates cold/hot water (depending on the season) in a device called a chiller.
The water is distributed by a pump and pipes into interior fan coil units.
Eventually, each air conditioned room or space is equipped with a fan coil unit that can be turned on and off to regulate the temperature (for example, hotels).

Method Advantages

  • Compact device
  • Maximum reliability
  • System lifetime: ~15-20 years
  • Maintaining homeowners’ value – Serves as a factor among realtors and real estate professionals. When a chiller is installed in a home, it is considered to be of greater value. Low maintenance requirements.
  • Saving on the main electrical service size as compared to the method of split or mini-central air conditioning units.
  • Approximately 20% savings on electricity as compared to a mini-central system due to duty factor (you cannot be at all places at once and the system automatically regulates itself). MethodDisadvantages
  • Very expensive in homes.
  • Not many companies are capable of providing long term, rapid and reliable service for these systems in private homes. Compared with mini-central and split air conditioner systems Expensive ongoing maintenance annual costs.
  • Spare parts supply that is not always readily available.

B. Mini-Central Unit

In this method, a mini central unit is installed, air conditioning several rooms simultaneously (in private homes, it is usually one unit per floor – for example). This system is the most popular in Israel due to its price.

Method Advantages

  • Relatively low price, approximately one third the cost of a chiller system (depending whether the system is installed with sheet metal ductwork or flexible duct). The price sometimes includes ceiling height adjustments, depending on the type of unit and the installer.
  • A compact system in which the condensing unit is usually situated near the laundry balcony. The internal unit is concealed over an acoustic ceiling.
  • Low maintenance requirements (where installation was performed properly). There are systems whose maintenance only involves cleaning the filter once every few months.
  • Leading air conditioning companies have achieved high levels of production and reliability. A high level of product reliability means that where the installation was properly performed, the unit will operate without fault for many years.
  • Spare part and of the shelf product availability for immediate supply – as soon as the repair is required.

Method Disadvantages

  • It is impossible to regulate the temperature for each room unless an electrical damper and thermostat is installed in every room, rendering the system more expensive and complicating its maintenance.
  • Maximum electrical connection to the home (since it is impossible to plan the system with a duty factor, as with the chiller, the electrical hookup must include all air conditioning units inputs in the house).
  • Average lifetime: ~8-10 years.
  • Multiple condensing units (private homes, not apartments) cause higher maintenance requirements over time.
  • Relatively high electrical consumption compared to other methods.

Split Air Conditioners

This method entails the installation of a split air conditioner in each room.

Method Advantages

  • Relatively inexpensive, about 15% cheaper than the mini-central method, depending on the manufacturer.
  • Electrical savings – The unit is operated in rooms requiring air conditioning and not in unoccupied rooms.
  • Extensive savings with inverter air conditioners.
  • Allows for pacing the monetary investment over time. Units are installed where necessary and the system is completed when the budget permits it.
  • Low maintenance level in which, if correctly installed and if the condensing unit is placed in a clean and ventilated area, the filter is cleaned once every few months.

Method Disadvantages

  • Multiple condensing units (“external engines”) create an architectural problem and there is not always enough room for them (there can be 6-7 units in a private home, causing a problem for the placement of the external unit, unless there is an available roof).
  • If all units are operating in the house, there will be a greater level of electrical consumption compared to the other methods seeing that the small compressors are not maximized (but usually, not all units are operated at the same time), unless the air conditioners are operated by the inverter method, in which case there are high electricity savings.
  • Design level – Some architects are not pleased with air conditioners in the house and prefer concealed solutions.
  • The level of distribution does not allow maximal comfort. In large spaces, such as the living room, the temperature near the air conditioner is different from the temperature when standing far from the unit. This is especially evident for heating and may cause colds due to the temperature difference (thus, split air conditioners are not recommended for large spaces, but rather mini central units with proper distribution). In addition, it is important to ensure that the bedroom air conditioner is installed in a manner that prevents the air from being directly blown onto the occupant seeing that the air temperature when leaving the air conditioner is very low and may cause neck pain, sneezing etc.

VRF (Variant Refrigerant Flow) System – Such as Mitsubishi, Daikin or equivalent.

This system is innovative and popular in Japan and Europe. Applying this method, a central condensing unit is equipped with variable speed compressors, which regulate their operation according to the home utilization.
When usage is low, the compressor will rotate more slowly and consume less electricity. When the consumption level increases, the compressor will spin faster in order to meet the demand and will consume more electricity.

Method Advantages

  • Savings on the size of main electrical service at home.
  • Saving on electrical consumption – This is the most economical method of all.
  • Smaller interior units and saving on physical space in the home.
  • High technological level.

Method Disadvantages

  • Very expensive – About 15% more expensive than the chiller system, depending on the manufacturer.
  • There are not enough installers who are proficient with this method – an average installer who did not undergo training by the companies marketing the unit, is unable to successfully install the system. Thus, if you have decided to install such a system in your home, be sure to obtain a list of installers recommended by the engineer or marketing companies and get a quote from them only.

Mini Central Unit

with a variable speed Compressor based on Output – Regulating with electrical dampers in the rooms.
Same as above, but the compressor has variable speed, which reduce output and save on electricity when lowering the load.
The technology is different than the VRF method and not as economical on electricity. However, it is economical compared to a regular mini-central system.

Advantage

  • Saving on electricity

Disadvantage

  • Significantly more expensive than mini-central units. The return on the investment between the original cost of installation and the cumulative savings on electricity over time, is 5 years and even more in private homes and apartments (in offices, where air conditioners work more than in residential units, the difference between costs and savings may be repaid within 3 years and this is where such units are worthwhile in planning and installation.
  • The compressors are not available for immediate replacement in the event of failure.
  • Incorrect system planning will cause air flow noises when the dampers in the room close upon reaching the desired temperature.
  • A system with electrical dampers requires more maintenance over the years.
  • The annual service cost (insurance) is higher than with simple mini units.
  • These units are slowly coming off of the production lines and are being replaced by inverter air conditioners!