7 HVAC informations

Monday, October 22, 2018

air cooled and water cooled chiller difference

Air cooled and water cooled chiller difference

Air Cooled Chiller.
Both air-cooled and water-cooled chillers depend on an air stream as a means of heat transfer. The difference is that the water-cooled chillers or rather the cooling towers use a humid air stream (ambient air stream + water spray) while the air-cooled chillers use a current of ambient air.


Tuesday, October 16, 2018

cooling towers so tall why?

Cooling towers so tall.

Because they are "natural draft" towers. A natural draft tower is very large (tall) and shaped like a nozzle. This allows for cool, dense air from the environment to naturally flow up through the bottom of the tower and out through the top. That flow of air is what drives the evaporation of the fluid being cooled.

Monday, October 15, 2018

working principle of contactor

Operating principle of Contactors
The operating principle of a contactor is very simple. Whenever the electromagnetic coil is energized, an electromagnetic field is produced. This electromagnetic field attracts the metallic rod (armature) towards the gap in the hollow cylindrical magnet.

Difference between contactor and relay

What is difference between contactor and relay

Relays and Contactors are electromagnetic switches. The only difference is that relays are usually used for low voltage applications while contactors are used for higher voltage application. Contactors usually have Overload protection


 

types of contactors

How many types of contactors are.


  • Contactor telemecanique contactor,
  • Magnetic contactor,
  • Siemens contactor 
  • Mitsubishi magnetic contactor
  • Single pole contactor , 
  • 2 pole contactor 
  • Schneider contactor
  • Telemecanique magnetic contactor
  • 4 pole contactor 3 pole contactor ,
  • Schneider electric contactors ,
  • Fuji magnetic contactor
  • AC magnetic contactor 
  • etc

What is the function of contactor

What is the function of contactor.

Contactors are used by electrical equipment that is frequently turned off and on with the opening and closing of a circuit. The function of the contactor is to make and break all power supply lines running to a Load or to repeatedly establish and interrupt an electrical power circuit.

How does a contactor work

How does a contactor work

When a relay is used to switch a large amount of electrical power through its contacts, it is designated by a special name: contactorContactors typically have multiple contacts, and those contacts are usually (but not always) normally-open, so that power to the load is shut off when the coil is de-energized.

What is the working principle of contactor?

Operating principle of Contactors. The operating principle of a contactor is very simple. Whenever the electromagnetic coil is energized, an electromagnetic field is produced. This electromagnetic field attracts the metallic rod (armature) towards the gap in the hollow cylindrical magnet.

Sunday, October 14, 2018

Important Tools Needed By HVAC Technicians

Important Tools Needed By HVAC Technicians

  • Reciprocating Saw Blades
  • Vacuum Pump
  • Mobile HVAC Software
  • Refrigerant Scale
  • Cordless Drill
  • Screwdrivers
  • Pipe Wrenches and Pliers
  • Tin Snips and Shears
  • Multi-Meter and Voltage Tester


Reciprocating Saw Blades

The ability of a reciprocating saw (also known by the brand name Sawzall) to cut through just about anything makes it a valuable and flexible tool that no HVAC technician should go without. Though your technician will likely purchase and maintain the saw itself, you’ll want to ensure that they choose a model with quality construction that will continue to work well through years of daily use. You’ll also want to provide the blades they’ll use, as the cost of keeping them in stock pales in comparison the cost of the time lost when you try to perform a complicated task with a dull blade.

Vacuum Pump

When you put refrigerant into a line with leaks, you basically just throw good money after bad. At best, this represents a waste of time and materials; at worst, it could lead to a failure of your client’s air conditioning system. The costly repairs it’ll take to fix the problem and the disintegration of that client’s trust in you will serve as a painful reminder of the importance of doing the job right the first time. That’s why you should provide each of your technicians with a reliable vacuum pump. The pump’s ability to suck moisture and air out of air conditioning lines can help them determine which lines have leaked before charging the system with refrigerant. The wide variety of models, however, can make it difficult to determine which pump suits the needs of your company and your technicians. This vacuum pump guide can help break down the differences between the models and give you the information you need to make a smart purchase.

Mobile HVAC Software

Though not a tool in the conventional sense, a comprehensive HVAC mobile software solution can count just as much for the success of your HVAC business as any of the items listed above. The quality of the work done by your technicians won’t mean a thing if you haven’t given them the tools they need to get to the job on time, provide quick and accurate estimates, or communicate effectively with your office/customers. You can get all that and much more with an hvac software and mobile app solution that allows you to more efficiently manage every aspect of your HVAC business and that allows you to instantly provide your technicians with all the logistical information they need to provide your clients with top-of-the-line service. Schedules, contact information, equipment records, service histories and much more become available after a tap of the screen. Your technicians can focus on their work, which will leave you with the ability to focus on growing your business.

Refrigerant Scale

Those not familiar with the particulars of HVAC work might surprise themselves when they learn the precision of many of the tasks involved. Take, for example, the charging of an air conditioning system with refrigerant. If too little is provided, the system won’t be able to effectively maintain the temperature of its assigned space. Too much, on the other hand, creates a high-pressure system within the cooling equipment that can put a life-shortening strain on the compressor and lead to constant and costly maintenance issues. A refrigerant scale helps to address this issue by measuring the weight of refrigerant as it’s added to or removed from the unit’s compressor, giving your technician the necessary information to put in exactly as much as it needs. That same capability helps your technician to identify if the system suffers from a leak, allowing them the opportunity to fix a small problem before it becomes a giant hassle. As with vacuum pumps, a plethora of refrigerant scales exist; studying this breakdown of three of the most popular refrigerant scale can give you a better idea of which scale best suits the needs of your business.

Cordless Drill with 2 Batteries

A cordless drill makes an essential HVAC tool for its portability, power, and versatility. Equip your technicians with a drill of at least 18 volts and do not forget a set of bits, including Phillips, hex, hole saws, and arbors. Keep at least two batteries on hand to help ensure that your technician’s drill can last the entire day without needing a charge.

Screwdrivers with Insulated Handles

Equip your HVAC technician with an arsenal of screwdrivers to prepare them for any HVAC situation. Your set should include a variety of Phillips, flat head, and hex screwdrivers in different sizes to accommodate the different screws and bolts used in HVAC systems. In many cases, a heavy-duty screw driver can serve multiple uses, including prying apart venting. Make sure to also find screwdrivers that have insulated handles, so as to prevent the risk of electrical shock.

Pipe Wrenches and Pliers

While more commonly associated with plumbing, a set of pipe wrenches can work on many HVAC systems involving natural gas line and connections to plumbing. For smaller connections and to better manipulate wiring, keep a set of pliers handy, including needle-nose, channel-lock, open-face, wire strippers, and linesman pliers. Finding pliers with insulated handles reduces the risk of electrical shock.

Tin Snips and Shears

In HVAC, you must own the tools necessary for manipulating sheet metal. Make sure that your HVAC techs equip themselves with all three types of tin snips, including straight aviators, lefts (reds), and rights (greens). Each type of tin snip allows for different positioning and cut direction for better precision. For longer, straight line cuts, a strong pair of steel shears with an insulated handle can help your tech get the job done.

Multi-Meter and Voltage Tester

Safety is incredibly important when your HVAC team works out on the field. Since HVAC systems are very much connected to electrical systems, it is imperative that your techs are equipped with electrical testers to verify the presence of live wires, measure voltage, measure resistance, and quickly conduct other electrical tests out in the field. Electrical mishaps not only endanger the safety of your tech, they can also lead to devastating damage to your customer

Latent and sensible cooling and heating equations



Sensible Heat
The sensible heat in a heating or cooling process of air (heating or cooling capacity) can be calculated in SI-units as

hs = cp ρ q dt (1)

where

hs = sensible heat (kW)

cp = specific heat of air (1.006 kJ/kg oC)

ρ = density of air (1.202 kg/m3)

q = air volume flow (m3/s)

dt = temperature difference (oC)

Or in Imperial units as

hs = 1.08 q dt (1b)

where

hs = sensible heat (Btu/hr)

q = air volume flow (cfm, cubic feet per minute)

dt = temperature difference (oF)
Latent Heat
Latent heat due to the moisture in air can be calculated in SI-units as:

hl = q ρ hwe dwkg (2)

where

hl = latent heat (kW)

ρ = density of air (1.202 kg/m3)

q = air volume flow (m3/s)

hwe = latent heat evaporization water (2454 kJ/kg - in air at atmospheric pressure and 20oC)

dwkg = humidity ratio difference (kg water/kg dry air)

estimate humidity with the Mollier diagram
Latent evaporation heat for water can be calculated as

hwe = 2494 - 2.2 t (2a)

where
t = evaporation temperature (oC)

Or for Imperial units:

hl = 0.68 q dwgr (2b)

or

hl = 4840 q dwlb (2c)

where

hl= latent heat (Btu/hr)

q = air volume flow (cfm, cubic feet per minute)

dwgr = humidity ratio difference (grains water/lb dry air)
dwlb = humidity ratio difference (lb water/lb dry air)

1 grain = 0.000143 lb = 0.0648 g

Psychrometric chart
Total Heat - Latent and Sensible Heat
Total heat due to both temperature and moisture can be expressed in SI units as:

ht = q ρ dh (3)

where

ht = total heat (kW)

q = air volume flow (m3/s)

ρ = density of air (1.202 kg/m3)

dh = enthalpy difference (kJ/kg)

estimate enthalpy with the Mollier diagram
Or - in imperial units:

ht = 4.5 q dh (3b)

where

ht= total heat (Btu/hr
q = air volume flow (cfm, cubic feet per minute)

dh = enthalpy difference (btu/lb dry air)

Total heat can also be expressed as:

ht = hs + hl

= 1.08 q dt + 0.68 q dwgr (4)

Example - Heating Air
An air flow of one cfm is heated from 32 to 52oF. Using (1) the sensible heat added to the air can be expressed as:

hs = 1.08 (1 cfm) ((52 oF) - (32 oF))

= 21.6 (Btu/hr)
Sensible Heat Load and Required Air Volume Chart
Sensible heat load and required air volume to keep the temperature constant at various temperature differences between make up air and room air:

Latent Heat Load and Required Air Volume Chart


Latent heat load - humidifying and dehumidifying - and required air volume to keep temperature constant at various temperature differences between entering air and room air are indicated in the chart below:
The Sensible Heat Ratio can be expressed as
SHR = hs / ht                              (6)
where 
SHR = Sensible Heat Ratio
hs = sensible heat
ht = total heat (sensible and latent)

































What temperature does refrigerant condense.


What temperature does refrigerant condense. 

Splits, Swings, And Loads. In air-cooled condensers, the temperature difference between the ambient and the condensing temperature is referred to as the condenser split. For example, if the condensing temperature is 110 degrees F and the ambient is 80 degrees, the condenser split would be 30 degrees

it possible to have a negative delta T?

it possible to have a negative delta T..

When the pot of boiling water cools, energy leaves the system, so the water is cooler than before(negative delta t). So, when delta t is negative, q is negative, and the process is exothermic. When delta t is positive, q is positive, and the process is endothermic.

delta T in chiller?

delta T in chiller?

CHW systems are all designed for a differential temperature or delta T between the CHW supply and return water between the chiller and the building loads. Selecting a chiller for a higher delta T may reduce other equipment cost and energy use when compared to the traditional 10 F delta T.
basically Delta T,  is the entering temperature 54'F and leaving temperature 44'F then the difference 10'F  

Delta H in HVAC?

 Delta H in HVAC..

heat Q, often stands for BTUs in their language. But that's not the language most of us use in the field. Delta H stands for enthalpy change. It's the difference in measured enthalpy as air enters and exits a cooling system. Simply measure the wet bulb temperature before and after the equipment in the appropriate locations.

Saturday, October 13, 2018

STANDARD and OPTIONS ACCESSORIES For Chiller

STANDARD ACCESSORIES

UNIT ON-OFF SWITCH: ON-OFF switch is provided for manually switching the unit control circuit.

INDICATOR LIGHTS: LED lights indicates power ON to the units, MENU adjustment and FAULT indications due to trip on
safety devices.

ELECTRONIC EXPANSION VALVE: Electronic expansion valve is used to regulate the refrigerant flow to the water cooler and maintain a constant super heat and load optimization.

FILTER DRIER (REPLACEABLE CORE TYPE): Refrigerant circuits are kept free of harmful moisture, sludge, acids and oil contaminating particles by the filter drier.

SIGHT GLASS: A moisture indicating sight glass is installed in the liquid line. An easy-to-read color indicator shows moisture contents and provides a mean for checking the system refrigerant charge.

LIQUID LINE SOLENOID VALVE: Closes when the compressor is off to prevent any liquid refrigerant from accumulating in the water cooler during the off cycle.

CONTROL CIRCUIT TRANSFORMER: On 460V-3Ph-60Hz power supply factory mounted and wired control circuit transformer
is furnished eliminating the need for running a separate 220 volt control circuit power supply.

OPTIONS

(All options are at extra cost. Please check with your nearest dealer/sales office)

HOT GAS BYPASS SYSTEM: Hot gas bypass is provided on the lead circuit to permit operation of the system down to 50% of its unloaded capacity. Under low ambient condition, it controls temperature by eliminating the need to cycle the compressor on
and off, ensuring narrow temperature swing and lengthen the life span of the compressor.

WATER FLOW SWITCH: Paddle type field adjustable flow switch for water cooler circuits. Interlock into unit safety circuits so that the unit will remain off until water flow is determined.

UNIT MOUNT SPRING ISOLATORS: This housed spring assemblies have a neoprene friction pad on the bottom to prevent vibration transmission.

LIQUID COOLERS: ASME code stamped liquid cooler.

PRESSURE GAUGES: Suction & discharge pressures gauges.

SUCTION SERVICE VALVE: Compressor suction port service valves.

NON-FUSED MAIN DISCONNECT SWITCHES: De-energize power supply during servicing/repair works as well as with door interlock.

CONDENSER COIL GUARD: Protects the condenser coils from physical damage.

COMPRESSOR/COOLER GUARD: Protects the compressor from vandalism.

COMPRESSOR OIL LEVEL SWITCH: This monitors the oil level inside the compressor.

COMPRESSOR ENCLOSURE BOX: Reduces compressor operating noise and keeps the compressor clean.

FLANGED COOLER CONNECTION: Easy on-site piping connections.

COOLER HEATER WRAPPED: Prevents freezing up of water on low ambient temperature.

COPPER FINS/TUBES CONDENSER COILS: For seashore salty corrosive environments. Provided with 12 FPI as standard

COATED COPPER FINS/TUBES CONDENSER COILS: For seashore or acid corrosive environments.

BMS: BACNET-IP, MODBUS-RS485, GSM and stand alone remote display panel.

POWER LINE ANALYZER: Performs motor current limitation. Protects against high motor current & over/under voltage.

EXTERNAL COMPRESSOR MOTOR OVERLOAD RELAY: Added protection for compressor motor thermal overloading and prolonged stalling of the motor.

HAND HELD CONTROLLER: Enables the chiller technician to monitor and serve the chiller by plugging this portable wired controller into the chiller controller. With built-in magnets, it provides convenient access for chiller status diagnoses and
trouble shooting

air cooled and water cooled chiller difference

Air cooled and water cooled chiller difference Air Cooled Chiller . Both  air - cooled and water - cooled chillers  depend on an  air ...