woman setting a thermostat

Sub Cooling and How to Troubleshoot A Central Air System

Understanding Subcooling …

Let’s go back to basics for a moment to make sure we understand what subcooling is, to begin with. During a refrigeration cycle, high-pressure super-heated gas is converted by the condenser into high-pressure liquid so the evaporator may use it for cooling purposes. It does that by removing enough heat out of the gas in order to cause it to condense into a liquid at the prevailing temperature and pressure (saturated liquid point). Any of the added heat that is removed from the condenser is referred to as “subcooling.” The amount of cooling that may be measured at the condenser’s outlet is a good indication of the performance of the condenser.

man with thermostat

When the condenser is operating in an efficient manner, the process of the refrigerant vapor being converted into a liquid is completed prior to the refrigerant reaching the final several passes into the condenser coil. Those several last passes should be only filled with liquid. Since the coil is transferring heat still, from the liquid refrigerant into the last couple of passages, the temperature will continue to drop and subcooling of the refrigerant occurs.

Subcooling is an accurate measure of the amount of time it takes for the refrigerant to pass through the condenser. This is referred to as “stay time.” The proper amount of subcooling for any specific unit may vary with its application and type of system. Subcooling may fall within the 10 to -20 F range with design air flow, clean coils, and at the right charge.

How can subcooling assist with troubleshooting?

Knowing all of that, how can subcooling assist with troubleshooting? Let’s take a look at a few different situations. When there is an insufficient refrigerant charge in a system (under-charged unit), that will cause the refrigerant to flow quickly through the condenser to attempt to satisfy the load conditions. That doesn’t allow a sufficient amount of “stay time” to let the refrigerant condense and be subcooled properly which will result in no or little subcooling.

A system with a plugged or improperly adjusted valve, on the other hand, will exhibit very high subcooling (perhaps 30 F) due to all of the excessive amounts of liquid backing up into the condenser. The strange part about both of those situations is they have the same effect on the system’s evaporator side: high super-heat, low head pressure, and inadequate cooling.

How do we tell what the problem is exactly and how do we properly diagnose it?

There are 2 different situations here that cause the same problem on the system’s evaporator side. So how do we tell what the problem is exactly and how do we properly diagnose it? The only way to know what the exact cause of the problem is to take a subcooling measurement to pinpoint it without having to rely on trial and error processes. When a subcooling measurement is made, the technician can potentially prevent having to do an unnecessary change-out of the expansion valve.  If there is zero subcooling, the expansion valve cannot close due to a plugged orifice or lost bulb charge.

If super-heat is high and subcooling is low, you can assume there is most likely a low refrigerant charge. In order to double check your assumption, take a measurement of the compressor amp draw. It should be a low reading. There should also be a low-temperature difference across its coil.

ac test gauges

An example of how subcooling can assist with troubleshooting …

The following is an example of how subcooling can assist with troubleshooting.

When subcooling is used properly it can be a valuable tool that can significantly reduce the amount of time that is needed to diagnose system malfunctions. In addition to suction super-heat, it is playing an increasingly important role in maintaining and servicing an air conditioner or refrigerant system. Above I just provided you with a few scenarios – can you think of other areas that it could be invaluable for you in making a diagnosis?

Be sure to look at all sides …

It is important to always keep in mind that an air conditioner is a system. All sides of this system need to be looked at – air flow, evaporator, condenser, etc. All of them deter from or contribute to a system operating correctly. Doing a complete diagnostic will allow you to solve problems.


Is It Time for A New Air Conditioner?

Three signs it might be time for you to get a new air conditioning unit

Summer is right around the corner, and that means the time has come for you to think about your air conditioner. If your AC unit is getting up there in years or just doesn’t use the latest in technology, and it seems you’re calling for an AC repair every year, then the time might have come to get a new one. This air conditioning repair service company in Kingston / Gananoque points out the three signs it might be time for you to get a new AC unit.

air conditioners

Increased Costs and Reduced Efficiency

As with any machine, when an AC unit gets older, it wears out more. Just like with a furnace, a lawnmower, or a car, the increased wear and teary can equate to a decrease in efficiency. In regards to air conditioning unit, this would mean it has to run longer just to get to the same temperature level it might have gotten in just half that time several years ago. Be mindful of your electric bill. Should it keep climbing, you need to contact our air AC company. It might be possible that the unit just has to get repaired. However, if we’re able to trace the issue to the age of the unit, then you need to consider buying a new AC unit.

Repairs Cost More

Even machines built better than others are going to need routine repairs and maintenance in order to keep smooth operating levels. However, as age creeps up on the performance of an air conditioner, it’s possible that you’ll start seeing the very same parts needing repair with a growing frequency. One instance could be the heat pump of the AC unit. If you wind up calling to get service on this particular item multiple times per year, then that’s a definitive red flag. If things get to the point that you start winding up getting repairs for more than one item, it probably makes sense to stop wasting money on individual issues and just buy yourself a new air conditioner. The frequency with which system failures happen goes up with age, which means you’re smart to just deal with things directly instead of continuing to sink money into something that isn’t going to be fixed.

air condioners

More Than 15 Years Old?

At this point, you’re likely wondering what the average lifespan of most AC units is? The short answer is typically 10 to 15 years. This is of course based on the kind of AC unit you have, the frequency with which you run it, and if you clean it periodically or have parts replaced as need be. If you have an AC unit that reaches 15 years of total service and is still running really well, then consider yourself fortunate. Just be ready for what is likely going to be a sudden downshift in its performance level.

You have two choices here, as already alluded to. You can work to get every last minute of service from your AC unit by keeping up with services and repairs. Alternatively, you can invest into a new unit. In the end, it’s a lot more cost-efficient to just buy a new AC unit, although homeowners typically have timetables of their own based just on usage, budget, their current AC unit, and the like. If it makes any sense to you to push your current unit for another few years, then by all means do so. However, don’t flush too much money down this hole, and keep in mind you’re going to need a replacement anyway.

If you want more information about AC installation, repair service, or longevity, then consult an experienced air conditioning professional.

heat pump repair

7 Tips to Repair Your Home’s Heat Pump

Heat Pump Repairs ….

Winter’s is over, so I’m quite sure everyone is looking ahead to the finale of this heating season. Even though the title mentions heat pumps, this could really apply to any equipment that’s out there. It really just boils down to competence, which comes from knowledge and training. You can see how this might apply to nearly anything if you swap out heat pump for whatever kind of equipment you focus on, be it furnaces, packaged units, or what have you.

heat pump

Everyone gets hit with a heat pump which just doesn’t work. It happens sooner or later. The issue might be a defective part, old age, misuse, or just a loose connection.

Are you a service technician?

If so, then you want to try these following techniques. They’re not actually guaranteed to give you results, but they’re certainly going to give you something to do as you figure out how much you’re going to charge your customer 🙂

STEP 1: Approach the heat pump in a confident manner. This will tell the machine, mistakenly, that you know what you’re doing. It should also impress anyone watching, so if the heat pump suddenly starts working, you’re going to be credited with the successful repair. If this doesn’t work, move on to STEP 2.

STEP 2: Wave the manufacturer manual at said heat pump. That should make the heat pump assume you’re familiar with the source knowledge. If that fails, move on to STEP 3.

STEP 3: Forcefully recite OHM’s Law to said heat pump. (Before you take this step, make sure you actually know Ohm’s Law.) This will definitely prove your knowledge to the heat pump. Is the machine still unimpressed? Go to STEP 4.

heat pump repair technician

STEP 4: Slightly jab the unit. That might involve a 3- or 6-lb. hammer. On the other hand, you need to be careful in this step, so you don’t damage the pad.

STEP 5: Wave around a large screwdriver menacingly. This shows the machine that you personally know the fatal short-circuit technique.

STEP 6: Should nothing else work, just add a bit of refrigerant. This will now confuse the heat pump, thereby increasing your advantage.

STEP 7: If that heat pump doesn’t have any sentimental value and you’re just done messing with it, then it’s time to sell a new model. On the other hand, if you’d like to make some last-effort in saving it, then call your preferred factory representative. Also, avoid displaying any further ignorance by giving the customer a bill right now.

ecm motor

All There Is To Know About ECM Motors

Behind today’s high-efficiency furnaces and A/C are higher efficiency motors designed to reduce the total electrical consumption, thereby raising the overall consumption of the system. This equipment also maintains the proper cubic feet per minute, better known as CFM across the various parts of the system, including the condenser coil, the heat exchangers, and the evaporator coils. Airflow is critical for these devices to operate properly. As such, the use of ECM motor technology helps in both these fronts.

What is an Electronically Commuted Motor, better known ECM motors? ECM motors, also known as variable speed motors, are motors that can vary the RPM of their motors. However, variation in speeds only happens when conditions within the system change. In the case of A/Cs and furnaces, the changes occur in an effort to maintain a programmed CFM.

ECM motors have 3 parts components:

1. The motor

ecm motor

The motor does not have windings like typical motors. The motor uses DC voltage and magnetic fields drive the stator. The starting procedure involves the motor rocking back and forth while aligning the magnetic fields in order to drive the motor. These motors can operate with 220 volts as well as 110 volts, depending on the five pin power plug configuration.

This system rarely breaks down and features exceptional reliability. The only instance where failures will occur is when someone drops the module with the motor plugged in, therefore, breaking the wires that connect the motor.

2. ECM Microprocessor Module

This is the brains of the motor. The board send programming information from using a 16 pin harness and thereafter translates it for the motor. This allows the motor to produce the right CFM. As such, it functions as the brain, controlling the relationship between torque, speed, and the airflow the system yields. The module is programmed at the factory for each specific unit. Modules are customized for a specific model and are, therefore, not interchangeable.

You can mount at one end of the motor or install it remotely.

3. Control Board

The control board is the component that stores the desired CFM for the application. As mentioned above, it connects to the module through the 16 pin harness.

OK, so how does it work …

The ECM motor is capable of maintaining a programmed CFM whilst responding to changing torque. When there is a change in torque, the motor increases or decreases the RPM, therefore, maintaining the predefined CFM. I admit it, it can get a tad confusing.

For a better understanding, let’s consider how an ECM motor works on an electric car that has cruise control on. The cruise control is the program that pre-defines how fast the car should move. It set the speed limit in mile per hour.

Obviously, as you set the cruise control, the motors will have a certain RPM. When you get to a hill, the cruise control will sense a change in torque and will rev up to maintain the predefined speed. The same case applies when you travel down a hill. The motor senses less torque and therefore, reduces the RPMs to maintain the predefined speed.

This is the same principles that the ECM motor uses. It functions by tracking the torque, RPM, and CFM (in the place of the mph). In the place of the steering column is the board, which controls the ‘direction’ in the sense that it controls the furnace or AC profiles – delay, heat, adjust, and cool. After programming the desired CFM, the motor and the module will automatically work out what to do.

residential air conditioner unit or central air

Let’s think of a hypothetical AC – 3 ton AC. For the AC to function correctly, we need a total of 1200 CFM or 400 CFM per ton. You program the board appropriately and both the adjust and cool profiles to as close to 1200 CFM as you can. Note that you should always use tables provided by the manufactures when you want to set up the ECM motor.

When you want the cooling function, the motor will start and thereafter try to maintain the ideal CFM as much as possible despite the variety of operating conditions. As the AC runs, the evaporator will naturally get wet, which causes the static pressure to go up. And as the static pressure goes up, the motor will sense some changes in torque. This can be equated to a car going uphill. As such, the motor will start to increase the RPM in order to maintain the ideal CFM expected of the system.

This motor process is experienced when the filter gets dirty. The return static will increase and the motor revs will increase to maintain the ideal CFM.

Under normal circumstance (with a clean filter), when latent heat decreases and there is less water or humidity around the coil, static will reduce. This results in a torque reduction, causing the RPM to decrease, thereby maintaining the predefined CFM. You can expect the system to react in this same manner after changing the filter.

This same process occurs under the heating mode. With heating, you program the board to instruct the motor to maintain the desired increase in temperature for the system. The motor will, therefore, operate to deliver the appropriate CFM to maintain that specified increased in temperature. However, if the filter gets dirty, you can expect an increase in motor RPM to maintain the desired CFM for the predefined temperature rise.

Finally, you can set a “Delay” profile. This function is used for cooling. However, it allows users to further fine tune the motor response when called upon to start to end a cooling call. Generally, you can set Humid, Dry, Normal, or the factory default profile using the control panels.

By maintaining the appropriate temperature increase in heating function and the proper CFM while cooling, you are able to eke out maximum efficiency out of your AC or furnace. Moreover, the ECM motor uses less wattage than the traditional PSC motor, further increasing the energy efficiency of the system. You can now appreciate why the ECM motors are fast becoming the industry standard for comprehensive energy efficiency.