Contact/Relay -- Relays are electronically controlled switches that activate the various components of your HVAC system. They manage everything from the power going to the motor to automatic dampers, humidifiers, etc. Most of them are controlled by the thermostat. The most common failure for a relay is being stuck in the "open" position. Separated from its assigned contact point, it fails to complete the connection and send the message to whatever it was supposed to operate. This failure usually occurs from use over time. Each time a relay connects and sends its signal, the electrical arcing from point to point eventually causes wear and tear.
I'm very glad that I found another guy to come replace the circuit board and put it away from the water, fix the water leak, and also find and fix another impending failure.  All of that was for much less than HVAC Service wanted to charge for repair or replacement. The other guy did a great repair, so I'm confident it will not break down again, but if it does, I will not call HVAC Service. Don't get suckered by their Yelp Deal.
PickHVAC Tips: Electricity resistance heat is the most expensive heating type. You don’t want one of these unless you’re heating less than 30 days per year. The upfront cost of an electric furnace is much lower than the cost of a gas furnace. However, operating costs are two to three times higher. If winters are cold where you live, you’ll waste your upfront cost savings in just a few years of high electric bills.
These factors are included in a "Manual J" calculation. Contractors who make these calculations before recommending a size can take a couple of hours collecting the information and making the calculation. If your contractor doesn't do it, there are services that will do it for around $99. If you're feeling particularly on the ball, there are also free online calculators.

The number of years an HVAC system lasts depend on the type and brand of components that make up your system. The lifespan of an air conditioner averages between 15 and 20 years. The life expectancy of a tankless water heater is approximately 20 years, while a storage water heater is closer to 10-15 years. Ducts may need replacing within 10-15 years. Your equipment will have a longer life if you have regular tuneups and maintenance to keep everything in good working order. If you’re having repair problems and your HVAC system is over 10 years old, it’s a good time to consider the costs and benefits of repairing vs. replacing. Energystar.gov provides the following tips to help you decide whether to repair or replace:
The number of years an HVAC system lasts depend on the type and brand of components that make up your system. The lifespan of an air conditioner averages between 15 and 20 years. The life expectancy of a tankless water heater is approximately 20 years, while a storage water heater is closer to 10-15 years. Ducts may need replacing within 10-15 years. Your equipment will have a longer life if you have regular tuneups and maintenance to keep everything in good working order. If you’re having repair problems and your HVAC system is over 10 years old, it’s a good time to consider the costs and benefits of repairing vs. replacing. Energystar.gov provides the following tips to help you decide whether to repair or replace:
Alberto said they were busy but could either install on the upcoming Saturday.  We were going to be out of town and said unfortunately that day did not work.  He then proposed the upcoming Tuesday as a possible solution, but just had to confirm with another appointment.  I said great.  I will review the estimate and call your office to confirm I want to move forward with the install.
The liquid refrigerant is returned to another heat exchanger where it is allowed to evaporate, hence the heat exchanger is often called an evaporating coil or evaporator. As the liquid refrigerant evaporates it absorbs energy (heat) from the inside air, returns to the compressor, and repeats the cycle. In the process, heat is absorbed from indoors and transferred outdoors, resulting in cooling of the building.
Dehumidification (air drying) in an air conditioning system is provided by the evaporator. Since the evaporator operates at a temperature below the dew point, moisture in the air condenses on the evaporator coil tubes. This moisture is collected at the bottom of the evaporator in a pan and removed by piping to a central drain or onto the ground outside.

Air conditioner size is measured in “tons.” However, the tonnage of an HVAC unit is not actually based on its weight. A “ton” is simply a measure of an air conditioner’s ability to cool your home. One ton is the ability of your air conditioning system to cool 12,000 BTUs (BTU stands for British Thermal Unit) in an hour. Likewise, a “2-ton” central air conditioner is able to cool 24,000 BTUs per hour.
Alberto said they were busy but could either install on the upcoming Saturday.  We were going to be out of town and said unfortunately that day did not work.  He then proposed the upcoming Tuesday as a possible solution, but just had to confirm with another appointment.  I said great.  I will review the estimate and call your office to confirm I want to move forward with the install.
If you’re anything like most of our readers, you’ve spent hours online researching HVAC information in preparation for replacing your old heater or air conditioner. I’m the same way; it’s a big investment! You may want to consider saving yourself some time and money by getting an HVAC-Facts Report from this online HVAC installation cost calculator.  Take a look:
An EER certifies the cooling efficiency of HVAC units. It's calculated by the rate of the cooling in British thermal units (Btus) per hour and divided by the rate of energy input in watts at a specific temperature. The calculation goes as BtuH/WATT at dry bulb (db) versus wet bulb (wb) temperatures. The optimal rating for a cooling unit is about 80db/67wb inside and 95db/75wb outside.
Installation: Replacement is quite easy, especially when an old refrigerant line set can be used. If the set is worn, it’s much better to pay the extra $400-$600 to replace it rather than risking it leaking later. When your AC loses refrigerant, you lose your cool air and the compressor is at risk of failing. A new installation means installing a coil in your furnace or air handler, running the line set between it and the coil in the condensing unit and adding refrigerant, if needed. Most ACs come pre-charged for 20-30 feet of line. If the line set is longer, a small amount of refrigerant is added.
A Full Installation is the most common type of HVAC installation for a reputable contractor. The ductwork adds two days of labor and about $2,000 to $3,000 to the price, but realize that this is a very important part of your HVAC system. Although it might sound like a good idea to reduce HVAC installation cost and get a quick change-out, realize that there is dirt and debris collecting in your ducts, and the ducts themselves develop holes and full breaks over the lifetime of your unit, all of which may be hidden from sight by insulation. Remember, many contractors will push a quick change-out on you because it is easy and good money for them – you need to be involved and ask questions.

Some of these components can be repaired or replaced by the homeowner, such as filters, fuses, and clogged up drain lines. Coils, compressors and the other components are best left to a professional. In some cases, you may have a system that is so old that parts are no longer available or else they aren't up to code. In this case you will have to consider replacing the entire system.
Fuses -- Anyone who has worked with electrical systems knows all about fuses and how they fail. They can burn out over time, may just be loose, or can blow out during an electrical storm or due to overload from another failed component. Of course, that's what they're supposed to do; they stop surges from going through and damaging the rest of the system. When a fuse fails, whatever system it was protecting will stop working.

DIY: We don’t recommend a DIY approach. Depending on the system, working with gas, electricity and refrigerant create dangers. Beyond that, it is essential that split system components be selected for compatibility. DIY installation of an HVAC system will void the warranty of most brands. The manufacturers won’t stand behind the warranty when anyone other than a certified installer does the work. This is true since improper installation is the main cause of poor system performance and mechanical breakdowns.
When central air conditioning service fails during a heat spell, you may have to wait days for an HVAC repair technician or an ac contractor to show up, and you'll probably pay at least several hundred for the repair. But if you're comfortable working around electricity and are willing to spend about $50 on parts, you can probably repair your air conditioning service yourself in about two hours and save about $225 on parts markup and labor.
So, naturally I respond with, “you don’t tell your doctor which medication to prescribe you, do you?” The point is, on the residential level, who you get to install your HVAC unit is far more important than which unit you choose.  Keep your options open and let your HVAC contractor make a few recommendations – that’s why you spent time finding a reputable contractor!
Ventilation is the process of changing or replacing air in any space to control temperature or remove any combination of moisture, odors, smoke, heat, dust, airborne bacteria, or carbon dioxide, and to replenish oxygen. Ventilation includes both the exchange of air with the outside as well as circulation of air within the building. It is one of the most important factors for maintaining acceptable indoor air quality in buildings. Methods for ventilating a building may be divided into mechanical/forced and natural types.[16]
Be careful with HVAC change-outs.  Change-outs are only about 15-20% of the HVAC installation industry. Decrease HVAC installation cost by investing in new ductwork now if needed. Your ducts wear out too, and make sure that your ducts are in fantastic shape if you do this. Many contractors push this because it’s easy and cheap for them, with good pay-off. Do your research and replace them if you need to in order to avoid doing it later, as well as avoid potential health hazards from using old, broken ductwork.
Central home air conditioner service systems consist of two major components: a condensing unit that sits outside your house, and the evaporator coil (often referred to as an A-coil) that sits in the plenum of your furnace or air handler. The refrigerant in the A-coil picks up the heat from your home and moves it to the outdoor condensing unit. The condensing unit fan blows outside air through the condensing coil to remove the heat. The condensing unit houses the three parts replaceable by a DIYer: the AC contactor, the start/run capacitor(s) and the condenser fan motor. The condensing unit also houses the compressor, but only a pro can replace that. The A-coil has no parts that can be serviced by a DIYer.
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