Repair or Replace An Air Conditioner?

Repair or Replace An Air Conditioner? 

The Right Way to Decide

Why repair or replace an air conditioner this fall?

If you’ve got an aging air conditioner, you may be breathing a sigh of relief when Labor Day rolls around. You made it through another summer with the old unit! But don’t talk too soon. You could still experience a breakdown during a brutal week of Indian summer. Then you’ll need to decide whether to repair or replace the air conditioner.

The truth is, fall is a great time to take control of your air conditioning issues and repair or replace your air conditioner. If you do decide on AC replacement, you’ll have more time to shop around since there’s less pressure to make a quick decision. You’ll also have the opportunity to get a great price on units in stock. (That’s because your vendor wants to make room for winter equipment and next year’s new models). If you decide on AC repair, the best HVAC service experts are less booked up than in the summer.

Repair or replace the air conditioner: why it’s a tricky decision

So, how do you go about making that decision to repair or replace the air conditioner? How can you tell when a piece of equipment has outlived its useful life? Can you get your older unit to last another couple of years by fixing it? Or will you have to continue putting money into it? Newer, more energy efficient units can lower your electric bill, but what about the upfront cost?

The unfortunate truth is, there is no cut and dried answer. But here’s how you can make the best decision to repair or replace your air conditioner. Keep reading to learn what factors to consider about your equipment and its history, and whom to trust for advice.

How to get advice you can trust about air conditioning repair or replacement

It’s no secret that some service providers will try to sell you a new system when your old one just needs a simple repair. (You’ve probably seen the YouTube videos and TV news stories exposing fraudulent service providers!). Other providers that make their money on repeat service calls may encourage you to keep fixing a unit that’s become a money pit. So whose advice can you trust to help you decide whether to repair or replace the air conditioner? Here are two tips for weeding out vendors who might steer you wrong.

DON’T DECIDE ON THE SPOT. Be wary of any service provider that insists you need to rush into a decision to purchase new equipment. Be even more wary if they have not offered an adequate explanation about what’s wrong – or one you can’t understand. You should never decide to purchase expensive equipment on the spot. Under pressure, it’s easy to make the wrong choice and spend more money than you need to. It’s your right to take the time you need to decide whether to repair or replace the air conditioner.

ASK AN UNBIASED SERVICE PROVIDER. Look for an HVAC company that does both new equipment installations and repair service. That way, you can be sure they have no vested interest in advising you to repair or replace the air conditioner. The advice you get will be based on what makes the most sense for your situation, not what’s in the best interest of the vendor.

5 facts that help you make a good decision

Even with the best advice, you need to understand the facts of the situation. Then you can make the most informed decision to repair or replace the air conditioner. Here’s what to consider:

WHAT’S BROKEN?

Some problems, even though they may seem serious, are actually easy and relatively inexpensive to fix. Electrical issues often fall into this category. And if your system is making so much noise that you’re afraid it’s about to die, the news may not be as bad as you think. You may just need some maintenance or redesign work.

Related article: Air Conditioning Problems: Repair or Redesign a Noisy AC Unit?.

However, if the compressor has failed, especially on an older unit, it’s often time to replace. The compressor is the heart of the system, and the investment to fix it may not be worth the cost. Also, many times compressor failure is caused by a secondary issue that won’t be discovered until after you replace the compressor.

Other issues, such as refrigerant leaks, can go either way. One small leak might be an easy fix. But finding the source of multiple leaks on an older system with a lot of corrosion on the coils can be time consuming and expensive. And ineffective, since more leaks will continue to develop. In this case, replacement is likely to be the wiser option.

SYSTEM AGE

Most light commercial air conditioning units are designed to last about 15 to 20 years under optimal conditions. However, if you have a rooftop or other outdoor unit in a large city like New York, you don’t have optimal conditions. If your outdoor air conditioner has been exposed to harsh pollution for more than 10 years, it may not be worth making a large investment in repairs at this point.

CONDITION AND MAINTENANCE HISTORY

How the equipment has been cared for has a major impact on the lifespan of an air conditioning unit. Has it been regularly serviced and cleaned according to the manufacturer’s recommendations? If so, then most parts may be in good shape even if the system is more than 10 years old. Your unit is less likely to keep failing.

RECENT PERFORMANCE

Has this unit been running reliably until now? If the parts are in good shape, there’s a good chance it’s worth fixing. On the other hand, if it’s had a history of breakdowns and poor performance, you’re likely to keep experiencing problems.

Here’s another tip. If the occupancy and usage of your space have changed, your system’s capacity and ventilation design may no longer be adequate. If you fix your old unit you can still be left with temperature variances and even air quality problems. If you are experiencing hot and cold spots, humidity issues, odors, and even reports of “sick building” symptoms from occupants, HVAC replacement is probably the way to go. Your contractor can then evaluate the usage, capacity and location of your unit and ventilation equipment, increasing the comfort levels in your space.

HOW MUCH CAN YOU SAVE ON ENERGY BILLS WITH A NEW UNIT?

HVAC sales literature promises that an efficient new air conditioner will save you money by reducing your electric bill. You might wonder if the savings is worth the cost of a new air conditioner replacement. The truth is, the cash you save each month can be substantial and can add up very quickly. Especially if you have an air conditioner that’s more than 10 years old. To figure out how much you could save with a new, energy efficient system, 

Digital radiography

Digital radiography is a form of radiography that uses x-ray–sensitive plates to directly capture data during the patient examination, immediately transferring it to a computer system without the use of an intermediate cassette. Advantages include time efficiency through bypassing chemical processing and the ability to digitally transfer and enhance images. Also, less radiation can be used to produce an image of similar contrast to conventional radiography.

Instead of X-ray film, digital radiography uses a digital image capture device. This gives advantages of immediate image preview and availability; elimination of costly film processing steps; a wider dynamic range, which makes it more forgiving for over- and under-exposure; as well as the ability to apply special image processing techniques that enhance overall display quality of the image.

Contents

• 1Detectors
• 1.1Flat panel detectors
• 1.2Other direct digital detectors
• 1.3Phosphor plate radiography
• 2Industrial usage
• 2.1Security
• 2.2Materials 

Flat panel detector used in digital radiography

Flat panel detectors (FPDs) are the most common kind of direct digital detectors.They are classified in two main categories:

1. Indirect FPDs Amorphous silicon (a-Si) is the most common material of commercial FPDs. Combining a-Si detectors with a scintillator in the detector’s outer layer, which is made from caesium iodide (CsI) or gadolinium oxysulfide (Gd₂O₂S), converts X-rays to light. Because of this conversion the a-Si detector is considered an indirect imaging device. The light is channeled through the a-Si photodiode layer where it is converted to a digital output signal. The digital signal is then read out by thin film transistors (TFTs) or fiber-coupled CCDs.

2. Direct FPDs. Amorphous selenium (a-Se) FPDs are known as “direct” detectors because X-ray photons are converted directly into charge. The outer layer of the flat panel in this design is typically a high-voltage bias electrode. X-ray photons create electron-hole pairs in a-Se, and the transit of these electrons and holes depends on the potential of the bias voltage charge. As the holes are replaced with electrons, the resultant charge pattern in the selenium layer is read out by a TFT array, active matrix array, electrometer probes or microplasma line addressing.

Other direct digital detectors

Detectors based on CMOS and charge coupled device (CCD) have also been developed, but despite lower costs compared to FPDs of some systems, bulky designs and worse image quality have precluded widespread adoption.

A high-density line-scan solid state detector is composed of a photostimulable barium fluorobromide doped with europium (BaFBr:Eu) or caesium bromide (CsBr) phosphor. The phosphor detector records the X-ray energy during exposure and is scanned by a laser diode to excite the stored energy which is released and read out by a digital image capture array of a CCD.

Phosphor plate radiography

Phosphor plate radiography resembles the old analogue system of a light sensitive film sandwiched between two x-ray sensitive screens, the difference being the analogue film has been replaced by an imaging plate with photostimulable phosphor (PSP), which records the image to be read by an image reading device, which transfers the image usually to a Picture archiving and communication system (PACS). It is also called photostimulable phosphor (PSP) plate-based radiography or computed radiography (not to be confused with computed tomography which uses computer processing to convert multiple projectional radiographies to a 3D image).

After X-ray exposure the plate (sheet) is placed in a special scanner where the latent image is retrieved point by point and digitized, using laser light scanning. The digitized images are stored and displayed on the computer screen. Phosphor plate radiography has been described as having an advantage of fitting within any pre-existing equipment without modification because it replaces the existing film; however, it includes extra costs for the scanner and replacement of scratched plates.

Initially phosphor plate radiography was the system of choice; early DR systems were prohibitively expensive (each cassette costs £40-£50K), and as the 'technology was being taken to the patient', prone to damage. Since there is no physical printout, and after the readout process a digital image is obtained, CR has been known as an indirect digital technology, bridging the gap between x-ray film and fully digital detectors.

Industrial usage

Security

EOD (Explosive Ordnance Disposal) training and material testing. A 105 mm shell is radiographied with battery powered portable X-ray generator and flat panel detector.

Digital radiography (DR) has existed in various forms (for example, CCD and amorphous Silicon imagers) in the security X-ray inspection field for over 20 years and has largely replaced the use of film for inspection X-rays in the Security and nondestructive testing (NDT) fields. DR has opened a window of opportunity for the security NDT industry due to several key advantages including excellent image quality, high POD (probability of detection), portability, environmental friendliness and immediate imaging.

Materials

Nondestructive testing of materials is vital in fields such as aerospace and electronics where integrity of materials is vital for safety and cost reasons. Advantages of digital technologies include the ability to provide results in real time.

Industrial CT scanning

Industrial computed tomography

   Industrial CT scanning

Industrial computed tomography (CT) scanning is any computer-aided tomographic process, usually X-ray computed tomography, that uses irradiation to produce three-dimensional internal and external representations of a scanned object. Industrial CT scanning has been used in many areas of industry for internal inspection of components. Some of the key uses for industrial CT scanning have been flaw detection, failure analysis, metrology, assembly analysis and reverse engineering applications. Just as in medical imaging, industrial imaging includes both nontomographic radiography (industrial radiography) and computed tomographic radiography (computed tomography).

Contents

• 1Types of scanners
• 2History
• 3Analysis and inspection techniques
• 3.1Assembly
• 3.2Void, crack and defect detection
• 3.3Geometric dimensioning and tolerancing analysis
• 3.4Image-based finite element methods
• 4See also

Types of scanners

Line beam scanner

Line beam scanning is the traditional process of industrial CT scanning.X-rays are produced and the beam is collimated to create a line. The X-ray line beam is then translated across the part and data is collected by the detector. The data is then reconstructed to create a 3-D volume rendering of the part.

In cone beam scanning, the part to be scanned is placed on a rotary table. As the part rotates, the cone of X-rays produce a large number of 2D images that are collected by the detector. The 2D images are then processed to create a 3D volume rendering of the external and internal geometries of the part.

Cone beam scanner

History

Industrial CT scanning technology was introduced in 1972 with the invention of the CT scanner for medical imaging by Godfrey Hounsfield. The invention earned him a Nobel Prize in medicine, which he shared with Allan McLeod Cormack. Many advances in CT scanning have allowed for its use in the industrial field for metrology in addition to the visual inspection primarily used in the medical field (medical CT scan).

Analysis and inspection techniques

Various inspection uses and techniques include part-to-CAD comparisons, part-to-part comparisons, assembly and defect analysis, void analysis, wall thickness analysis, and generation of CAD data. The CAD data can be used for reverse engineering, geometric dimensioning and tolerance analysis, and production part approval.

Assembly

One of the most recognized forms of analysis using CT is for assembly, or visual analysis. CT scanning provides views inside components in their functioning position, without disassembly. Some software programs for industrial CT scanning allow for measurements to be taken from the CT dataset volume rendering. These measurements are useful for determining the clearances between assembled parts or the dimension of an individual feature.

An industrial computed tomography (CT) scan conducted on an aluminum casting to identify internal failures such as voids. All color coordinated particles within casting are voids/porosity/air pockets, which can additionally be measured and are color coordinated according to size.

Void, crack and defect detection

Flight through a 3D reconstruction of a disposable pepper grinder. Glass in blue.

Traditionally, determining defects, voids and cracks within an object would require destructive testing. CT scanning can detect internal features and flaws displaying this information in 3D without destroying the part. Industrial CT scanning (3D X-ray) is used to detect flaws inside a part such as porosity, an inclusion, or a crack.

Metal casting and moulded plastic components are typically prone to porosity because of cooling processes, transitions between thick and thin walls, and material properties. Void analysis can be used to locate, measure, and analyze voids inside plastic or metal components.

Geometric dimensioning and tolerancing analysis

Traditionally, without destructive testing, full metrology has only been performed on the exterior dimensions of components, such as with a coordinate-measuring machine (CMM) or with a vision system to map exterior surfaces. Internal inspection methods would require using a 2D X-ray of the component or the use of destructive testing. Industrial CT scanning allows for full non-destructive metrology. With unlimited geometrical complexity, 3D printing allows for complex internal features to be created with no impact on cost, such features are not accessible using traditional CMM. The first 3D printed artefact that is optimised for characterisation of form using computed tomography CT 

Image-based finite element methods

Image-based finite element method converts the 3D image data from X-ray computed tomography directly into meshes for finite element analysis. Benefits of this method include modelling complex geometries (e.g. composite materials) or accurately modelling "as manufactured" components at the micro-scale.

See also

• Industrial radiography
• Cone beam computed tomography

Types of AC Units

Types of AC Units: What’s the Difference and What’s Right for You?

If your air conditioning system is getting older and performing poorly, it’s a great idea to plan for proactive system replacement in advance instead of waiting for a breakdown to force your hand. That way, you won’t have to deal with the inconvenience of going without AC while the replacement is in the works. For businesses, or even for homeowners who rely on AC for health reasons, living without AC for weeks or longer can cost you much more than that.

As you begin to shop for a new system, educate yourself by learning a little bit about the types of AC units. This article will help you do that in 10 minutes or less!

Chances are, it’s been a while since you had to think about buying an air conditioner, and there are modern air conditioning options that you may not know about. Also, be aware that some air conditioning installation vendors won’t bother to tell you about the newer types of AC systems. Unfortunately, many are in the habit of just recommending a newer version of what you already have. If you don’t know any better, you could miss out on the chance to get something that will work better for your needs.

Here’s an overview (intended to help the consumer who is not an HVAC expert!) of the types of AC units that are suitable for residences and businesses in the NYC area.

 6 types of AC units and their uses (an overview)

1. Variable Refrigerant Flow (VRF) systems

VRF systems are the HVAC system of choice in Europe, Japan, China and other parts of the world, and the technology is becoming popular in the US over the past 10 years.

Like older types of AC units found in suburban homes, VRF systems use refrigerant to cool the air via outdoor condenser units and indoor fan coil units. But the similarity stops there. These systems have variable-speed compressors that run only at the capacity needed for the current conditions. VRF systems can be designed with individually-controlled zones to provide customized comfort throughout the space. And, VRF technology is capable of providing not only cooling, but also heat, and even both simultaneously to different areas within the space.

The benefits include:

·         Consistent cooling and superior, customized comfort, even for very large spaces

·         Extremely quiet operation

·         Reduced energy consumption

·         Smaller units and small pipes allow for higher ceilings in living and working space

·         Longer life span due to more efficient design that reduces wear on parts

COMMON USES OF VRF SYSTEMS: Manhattan’s brownstone townhouses, apartment buildings where possible, restaurants, retail stores.

2. Variable Air Volume (VAV) distribution systems

Some large buildings, typically 30+ story high-rises, have water cooled base HVAC systems that serve the entire building. Water-cooled systems, as the name implies, use chilled water rather than refrigerant to remove heat from the air in your space. Chilled water is pumped from a large chiller unit that serves the whole building (probably located in the basement or a mechanical room) through pipes to a central fan coil units for each apartment or commercial space in the building.

If your building has a water-cooled base system, you’ll need to install equipment in your space that ties into the building’s base system and circulates the air throughout your space. VAV distribution systems are often installed for this purpose.

VAV distribution units direct varying volumes of air from the central fan coil unit (as needed) to different rooms in your space, using a series of ducts. Using VAV technology is a way to create customized, zoned air conditioning using a water-cooled system. 

The advantages of VAV systems over constant-volume systems include:

·         more precise temperature control

·         reduced compressor wear

·         lower energy consumption by system fans

·         less fan noise

·         additional passive dehumidification

COMMON USES OF VAV DISTRIBUTION SYSTEMS: residential apartments and offices located in high-rise buildings with a water-cooled base system

3. Rooftop packaged units (RTU)

An HVAC rooftop unit also (known as an RTU or packaged unit) provides the heating, cooling and most of the ventilation for large, single-story light commercial spaces. As the name implies, it’s typically installed on the roof. An RTU is a single assembled unit that includes a condenser and an evaporator coil for cooling, a heat source and a fan for forced air heating, and an opening for the intake of outside air.

While they often can’t be used in high rises, RTUs are often easier (read: less expensive) to install and maintain than other types of AC units, since all the equipment is self-contained in one box. However, it’s important for your installer to conduct an evaluation of your space and its usage to determine the duct work design and plan for where the supply and return grills are located.

COMMON USES FOR ROOFTOP UNITS: big-box stores, shopping centers, warehouses, and sometimes for restaurant kitchens.

4. Ducted split systems

Split systems get their name because they have two major components: the compressor and condensing unit (often called the outdoor unit) and the evaporator coil and air handling unit (often called the indoor unit). In a ducted system, air ducts are used to distribute cooled air from a central air handler to the various areas within the space. A ducted split systems can cool a space up to 10,000 square feet.

The indoor unit can be installed in the ceiling if there is adequate clearance, or in a closet space. Sometimes the indoor unit is also connected to a furnace or heat pump that supplies heat to the space. The outdoor unit, which releases the heat absorbed from the air, is typically installed under a window on the outside of the building, or in a mechanical room if available.

Depending on the size of the unit and where it is installed, ducted split systems are quieter than some types of AC units including PTACs (described below) but can be louder than ductless systems. However, they tend to be better at removing humidity than ductless systems.

As little as 5 years ago, these systems accounted for 75% of new residential air conditioning installations in the city. Today, their popularity is down to about 25% due to the development of VRF technology.

COMMON USES FOR DUCTED SPLIT SYSTEMS: suburban homes, apartments or smaller commercial spaces with access to outdoor space or a mechanical room.

5. Ductless mini splits

Ductless systems (often called “mini splits”) are often smaller, supplemental systems intended to cool a specific, contained area such as a room addition. In buildings where duct work cannot be installed, they can sometimes be used as the primary cooling system. However, they are not a practical choice for a large space.

In a ductless split system, the outdoor and indoor units are connected by a small conduit with refrigerant and electrical lines. The outdoor unit is typically installed under a window on the outside of the building, or in a mechanical room if available. Indoor units are needed in each area to be cooled, and can be wall mounted, or installed in the ceiling if there is adequate clearance.

Since they don’t require ducts, mini splits are often quick and easy to install. Ductless split systems are quieter than PTACs, since the condenser is outside, but indoor units can have noisy fans. However, some brands have packages available to muffle sound.

COMMON USES FOR DUCTLESS MINI SPLIT SYSTEMS: Supplemental cooling for room additions, storage areas, or computer rooms, or for smaller spaces without existing duct work.

6. Packaged Terminal Air Conditioner (PTAC)

PTAC units look like window air conditioners, but are installed through the wall of the building. Some units can provide heat as well as air conditioning (you often see these in hotels).

PTACs are older technology with many drawbacks:

·         They can only cool a single room (and sometimes require more than one unit even for a large room).

·         They cycle on and off frequently, so comfort levels are inconsistent.

·         Units can be quite noisy.

·         Access to an outside wall is required.

However, in an apartment situation where you are not allowed to make new penetrations in exterior walls, you may have little choice but to replace older PTACs with new ones that fit into the existing holes.

COMMON USES FOR A PTAC SYSTEM: Older hotels and historic landmark buildings in Manhattan (where occupants are not allowed to make new modifications to the structure).

Turn heat into useful energy

A new way to turn heat into useful energy

An international team of scientists has figured out how to capture heat and turn it into electricity.

The discovery, published last week in the journal Science Advances, could create more efficient energy generation from heat in things like car exhaust, interplanetary space probes and industrial processes.

"Because of this discovery, we should be able to make more electrical energy out of heat than we do today," said study co-author Joseph Heremans, professor of mechanical and aerospace engineering and Ohio Eminent Scholar in Nanotechnology at The Ohio State University. "It's something that, until now, nobody thought was possible."

The discovery is based on tiny particles called paramagnons -- bits that are not quite magnets, but that carry some magnetic flux. This is important, because magnets, when heated, lose their magnetic force and become what is called paramagnetic. A flux of magnetism -- what scientists call "spins" -- creates a type of energy called magnon-drag thermoelectricity, something that, until this discovery, could not be used to collect energy at room temperature.

"The conventional wisdom was once that, if you have a paramagnet and you heat it up, nothing happens," Heremans said. "And we found that that is not true. What we found is a new way of designing thermoelectric semiconductors -- materials that convert heat to electricity. Conventional thermoelectrics that we've had over the last 20 years or so are too inefficient and give us too little energy, so they are not really in widespread use. This changes that understanding."

Magnets are a crucial part of collecting energy from heat: When one side of a magnet is heated, the other side -- the cold side -- gets more magnetic, producing spin, which pushes the electrons in the magnet and creates electricity.

The paradox, though, is that when magnets get heated up, they lose most of their magnetic properties, turning them into paramagnets -- "almost-but-not-quite magnets," Heremans calls them. That means that, until this discovery, nobody thought of using paramagnets to harvest heat because scientists thought paramagnets weren't capable of collecting energy.

What the research team found, though, is that the paramagnons push the electrons only for a billionth of a millionth of a second -- long enough to make paramagnets viable energy-harvesters.

The research team -- an international group of scientists from Ohio State, North Carolina State University and the Chinese Academy of Sciences (all are equal authors on this journal article) -- started testing paramagnons to see if they could, under the right circumstances, produce the necessary spin.

What they found, Heremans said, is that paramagnons do, in fact, produce the kind of spin that pushes electrons.

And that, he said, could make it possible to collect energy.

Ohio State graduate student Yuanhua Zheng is also an author on this work. The research was conducted in partnership with additional researchers at the U.S. Department of Energy's Oak Ridge National Laboratory and was supported by the National Science Foundation, the Air Force Office of Scientific Research and the U.S. Department of Energy.