Electromechanical System Inspection

Client: Jacqueline Ozols
Part I: Single-phase electrical system to 1920V
Part II: Water and Mechanical Distribution system
Place: Atenas, Alajuela
Made by: Ing. Luis Antonio Oviedo Rojas
ElectroMecanical-Technical Service Engineer Date of execution: March 2008

Part I Description of Electric System

The property currently depends on a single-phase electrical system with a tension of operation of 1920v; it is made up of six posts of concrete of 11mts of height, fed on the primary system on ICE (Institute Costa Rican of Electricity in Spanish) of means of a primary overhead lines measurement installed at the entrance of the property.


The six posts support air lines with aluminum conductors calibrates 1/0AWG, and a neutral one of similar characteristics, the six posts include a length line.


In the transition of systems aerial-underground, there is protective equipment against short circuits, surge arrester, and lightning rods; the underground conductor is 1/0AWG caliber with neutral at 133%, fulfilling the effective norms for construction by an underground canalization up to a transformer, according to the ICE' construction regulations for underground distribution systems of this type of works.

The end of the underground conductor is protected in the section of the post with a steel tube of 7.5cm in diameter (3 inches) until the arrival to the first box of registry located at the foot of this post.

The underground conductor starts from the first box of registry towards the enclosure of the transformer by means of PVC tubes of 7.5cm, in each box of registry are metallic covers to facilitate the inspection and with a ladder leaned against the wall in case it is necessary to enter.


At the end of the electrical system the tension is reduced from 19920v to 120v or 240v by means of a 50kVA transformer, single-phase, conventional, and installed in a very appropriate concrete enclosure to offer the transformer protection against the climate inclemency and the entrance of animals or weeds that could cause interruptions in the electrical service.

The secondary side of the transformer properly feeds a board of distribution wiring, of which a load equivalent to 1515m2 of construction can be served; this comes off the calculation from article 220.3 of the NEC, in which it states that 33VA is required to feed a square meter of construction.


The previous commentary is amplified, when saying that 10 residences, without the minimum fear, will be able to be fed to incur overload of the installed transformer at the moment.

On the other hand, the limited factor of the present capacity is the transformer, in case it requires greater power the capacity of the transformer could be increased up to a maximum limited by the line that limits the primary current to 100A, which is equivalent to a 1.9MVA power, approximately 40 times the power of the present transformer. For practical effects keep in mind that the line is complete to that which services a whole town.

Part II Description of the Water and Mechanical System

In the case of the water system distribution in the property, it has its own water source in a well of 60m (200 feet) in depth located in the lower zone of the property. In an enclosure of concrete, there is installed a pump submerged with a power of 5hp, this pump is reconciled to a PVC pipe SDR17 with a diameter of 7.5cm (3 inches), whose maxima pressure of work can arrive at 175mca (water column meters).

The level differences between the unloading point of the pump and the tank of pick up is approximately 55mca, only 30% of the pressure capacity that can support the tubes. The service pipes are PVC, SDR 17, 5cm in diameter (2 inches), count on branches towards several points of the property that could at any time be used like potable water supplies.

Tank and Water Capacity/Dowry

The tank capacity is 23.775 gallons or 90m3. The water pick system connects the unloading of the pump with a tank of pickup of 90m3 capacity. This capacity is sufficient to supply 120m3 that, according to the "Technical regulation for Design and Construction of urbanizations, Condominiums and Division" of the AYA are equivalent to the sufficient dowry for 450 people.


The pickup tank serves so that a system of hydro pneumatic tank feeds the system on potable water; this adjustment allows one to depend on a very stable pressure in the system and allows the water use in any level of the property.

The hydro pneumatic tank is provided with a compressor from Campbell Huosfeld of 3Hp of power, a pump of 1Hp and a system of control Hd Star Rite with a charge of 30gal per cycle (146lts) sufficient to supply 10 luxurious houses.

The amount of water in the tank is controlled with a system of level sensors from the control pump house. In addition the system counts on an anti-return valve in the unloading of the pump that prevents that the pipes drain by reverse flows. Just like a pressure gauge next to this valve which facilitates the level in the pickup tank.

System of Coloration and Filtration

The water distribution counts on a system of particle filtration and on an automatic chlorine dispenser that operate in parallel form to the starting system - when the pump stops. According to tests made in the property the well has the capacity to supply the tank so that it works as tank of daily use.

Commentary on the Electrical and Water/Mechanical Systems

It was observed at the inspection, that the electrical systems as well as the one of water distribution are in GOOD CONDITIONS to operate in the following conditions:

Electrical System:

It can serve 10 houses, however, if more energy is required, changing the transformer, would give enough energy to supply a small town.

Water Distribution System:

It can equip the amount of water that 450 people require.