by Ing. Willian Morales *
We will start this article presenting different topics about new facilities and with equipment already used in air conditioning.
Topics: 1. New installation:
- New equipment
- Analysis of the geographical location of the installation.
- Rational analysis of the location of the Condensing and Evaporating Unit.
- Optimization of the thermodynamics of the equipment to be installed as is the refrigerant.
- Optimum working pressure in the evaporator and condenser, reheating in the evaporator, subcooling in the condenser.
- Correct distribution of air in the evaporator and in the condenser.
- Verification of compliance with thermodynamic, electrical parameters.
2.- Installation with indeterminate time of use: Equipment already used
- Take the photograph of the installation before taking the initial general data
- Data to be taken, system low and high pressure, equipment work amperage, calculation
- From the absorbed power of the system, temperature and RH of inlet and outlet of the condenser, temperature and RH of the entrance and exit of the evaporator, measure of the reheating of the evaporator and subcooling of the condenser, more data can be taken for a better evaluation of the maintenance work .
Search for possible improvements with minimal work and cost:
- Improve the location of the condenser, possible relocation of the evaporator
- Find the right pressure to achieve a cold quality, on the low side and high pressure system.
- Carry out a cleaning of the contaminated refrigerant gas by means of filter driers
- Carry out the correct refrigerant charge by measuring the superheat and subcooling
- Cleaning of impurities in the evaporator coil and condenser coil, as well as the lubrication of fan motors, change of bearings and combing of the fins.
- Measurement of the EER, COP, current system with support of real measurements of evaporator performance, power consumption in the compressor and auxiliary engines.
Methodologies for the correct installation of the evaporator and evaporator condenser: In the case of air conditioning systems equipped with direct expansion evaporators or ice water coils take into account the following:
Air flow according to the thermal load of the room, taking note of the characteristics of the area occupied, we can consider an air flow of 400 CFM per ton of refrigeration if you do not have the means to know the specifications of the product, likewise it can be assumed with good judgment that the supply temperature of the cold air to the room can be 52 ° F, this is by a recommendation translated from a known formula: Tsuministro = Tinterior + 2 times the height of the room that is generally 9 feet (3 meters) all temperatures in ° F.
Direction of the primary air flow in order to achieve a terminal velocity of 0.22 m / s, or 25 feet per minute, at most when joining with the secondary air that is formed by friction between air layers with the primary air currents, in the whole room, considering only the occupied technical area, that is to say a parallelepiped whose measurements are taken inside the room leaving 0.5 m. of the walls and with a height of 1.80 meters from the floor, where the conditions of human comfort must be given.
In case of using air diffusers, these are selected according to performance graphs, considering the coanda effect, which means that the exhaust air flow from the diffusers is attracted to the ceiling by a pressure issue, and then descending towards the users at a relative distance different from what was thought.
The measurement of the evaporator inlet temperatures and RH for a room of 3 meters will be within the following ranges for a normal installation whose sensible heat factor has a value of 0.75:
- Income temperature and RH: 70 ° F - 75 ° F, 45% - 60%
- Output temperature and RH: 48 ° F - 52 ° F, 85% - 95%
With this data you can find the actual and actual cold production of the equipment, that is, if the 60,000 BTUH can be said on the technical specifications plate, however, the real performance of the equipment will come from these measurements and the application of psychrometry.
In the case of having to place more than one 4 diffuser in a room, the location of the same with respect to the distance between them must be followed by the following advice, the relationship between the distance between diffusers and the height of the room should be by reason of 1.5 m.
The recommendations for the capacitors are similar, but not equal to the evaporator.
Before thinking about placing the condenser on the roof I must think differently from an architect who would place them in agreement with the walls of the building so that it is stuck to the walls keeping a minimum distance between them and avoiding the air flows that are already hot to another condenser, this is already a lot to ask for an architect who only sees aesthetics but is not prepared to know the effects of heat transfer by conduction, convection and radiation.
The installers are not guided by the beauty of a roof, but rather we must make a preliminary study of the direction of the wind in each city and even in each district of the city, to know what direction and speed it has for wind maps that are of knowledge through the internet; in the case of Lima, the historical direction of the winds is mainly from the South, in smaller scale of the SE and the SO, then the air inlet to the condenser must receive the air in that direction, even if that forces the condenser to be located in a direction other than the roof wall, preferably the condenser must be high and have no obstacles as adjacent walls.
By a wrong criterion sometimes roof top equipment or air-cooled condensers are plugged with a concrete wall, so that they do not look outside from the street, this is absurd if you do not want them to be seen it is better to build an ornamental brick wall with holes or a metal grate with holes that do not let you see the silhouette of the air conditioning equipment, but let air flows through at least so it is a palliative to place a concrete wall, as I have seen Many times, it obstructs the flow of air to the condenser. The additional energy consumption that the equipment spends for being partially covered by the air flow goes from 10% to 35% more than electric power, if it is well ventilated, if the recommendations are followed, this will result in a much lower monthly electricity payment .
Verify a refrigerant pressure that produces a quality cold in accordance with the evaporator data. Normally during hot weather we use a pressure gauge of 22 psig for the R-60 and for the high pressure of the system we use the 220 psig reference, if we see this information in the PT rule, we will see that they correspond to an evaporation temperature of 34 ° F (1 ° C) in the evaporator and in the condenser the condensation temperature will be of 108 ° F (42 ° C), in this way we can find with 1 ° C and with 42 ° C, the pressures of any refrigerant that we want it to work the same as it does with the refrigerant R - 22, in this case for the R - 410 a, observing in the rule P - T the pressures of 105 psig and 360 psig are obtained respectively.
The color of the condenser unit should be clear, it can also have a roof, so that its metal structure is not heated, of course the roof should not obstruct the air flow of the condenser fan, place a roof to the condenser equipment contributes to a decrease of the electric consumption of the order of 5% to 7.5% of the electrical consumption of the air conditioning equipment.
The installation of the condensing unit must be done in such a way that continuous maintenance can be done without danger of falling over the precipice, it is ridiculous as some colleagues make the installation of the condensing unit in a wall of the facade without any access to future maintenance. That is completely irrational. To do this, a large and safe scaffold would have to be placed in a routine maintenance, that can be expensive, the owner of the equipment rejects a maintenance because it is very expensive, the lack of maintenance causes a high consumption of electrical current of the equipment that will have to pay that high cost the owner of the equipment.
The routine of minimum maintenance for equipment with a normal location in Lima, in a place not very dusty should be every three months, be it summer or winter, this will ensure that the team is always ready to work economically, for areas of greatest pollution environmental this time should be reduced, especially in mining areas that are close to the city.
Installations poorly made by the refrigerator
Regarding the suction insulation, it has a life time with effective insulation, after the 5 years must be completely changed.
The refrigeration technicians think that the insulation is placed forever, but it is not, since the insulation gets wet due to contamination by the water vapor condensed in its interior in climatic reasons that has to do with its protection with a barrier of steam and the dew point temperature, even when wet, leave it that way, but it must be replaced by new dry insulators, otherwise consumption increases by 5% to 7% due to wet or damaged insulation.
The user and the graduated temperature
According to Peruvian law, RNE Title III.1 Chapter IX Article 54, for reasons of conservation of the environment, the temperature must be between 24 ° C + - 2 ° C, with a relative humidity of 50% + - 5% . Published in the newspaper El Peruano on the 118 page.
The user of the air conditioning equipment must learn that with a light clothing does not need a temperature lower than that dictated by the law, thus saving a lot of electrical energy achieving a thermal comfort in their environments, because of this reason can achieve savings of consumption of energy of the order of 10% up to 25% of the air conditioning equipment, thus reducing its payment of the electricity bill and the conservation of the environment.
* Ing. Willian Morales Quipe. Mechanical Electrician UNI - CIP N ° 93846. General Manager RETER EIRL - PERU. You can be contacted by email: email@example.com