Feeling the Pressure: Smart vents, sensors and pressure

Feeling the Pressure: Smart vents, sensors and pressure
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Keeping the Pressure on HVAC Pressure Measurement

By now, you’ve read our ongoing series on how HVAC works. If you haven’t, now’s a great time to go back ….

OK, we’re back. We’ve talked about ductwork, heat and air conditioning. We’ve even thrown around the term “forced air” a number of times. Today, we’re going to fully define “forced air” and talk about its greatest enemy—pressure that reduces airflow. We’ll use a simple Q&A format to outline the process.

What is forced air?

At its essence, forced air is pressure that moves hot or cold air throughout your home’s ductwork to maintain comfortable temperatures. For HVAC systems, this pressure is created by a blower fan. Low pressure is created on the intake side, high pressure on the return side. The pressure difference is what moves the air through your ductwork, heating system and cooling system.

Acting as obstacles to that pressure difference is every physical item in the path of the airflow: The return grill, the air filter, the ducting, the heat exchanger, and the supply vents. Your HVAC contractor will specifically choose the blower so that it can work in the system in your home, creating sufficient pressure difference to generate the level of required airflow into the heat exchanger and through all of the flow restricting obstacles.  Any change to this carefully balanced system can create issues.  An air filter getting clogged, a kink in a flexible duct, and closing vents all increase the resistance to flow and change the balance of flow and pressure.  With too much blockage in the system, and without proper monitoring, pressure will rise, and pose a serious threat to your HVAC equipment.

So airflow is key to safety?

Exactly! You see, to keep your heater (and your home) safe, it’s imperative that there be sufficient airflow through and around your ductwork to prevent over-pressurization or overheating. Sufficient airflow is the only way to keep your heater or AC safe. If you’ve tried to solve your home comfort issues by closing vents around your home, you’re setting a ticking time bomb for your HVAC equipment because when blockages occur, airflow is reduced. Aside from manually closing vents, there are other things that can affect airflow too—like, say, HVAC air filters. If enough dirt gets trapped in the air filter, then blockages occur, reducing airflow.

Ok, so i guess i should stop tinkering with my vents. So how often should I replace my air filters to keep my system safe?

There’s no hard and fast rule here, because current HVAC systems don’t actually measure the airflow of the system, so they can’t tell when the filter is actually clogged. So a rule of thumb was created to ensure that the airflow remained high enough at the expense of changing perfectly clean filters sometimes.  What is really needed, and Ecovent brings to the table, is a way to constantly measure airflow in the system.

How do HVAC professionals currently measure pressure in a duct?

Until very recently, sensors capable of measuring pressure and temperature in a duct were expensive and required professional installation. Typically airflow was only measured when something went wrong with the system and a professional visited to diagnose the problem.  The professional would make two static pressure measurements in the system, one on either side of the blower.  These measurements are used to calculate the total external static pressure, or TES.  With this measurement and knowing the characteristics of the blower, the professional can calculate the total volume of airflow and determine if it’s too restricted across a system.

At the same time the technician can also measure air temperature and humidity readings at the return and supply vents to diagnose any other problems with the heating or cooling system beyond the blower. What would be best for HVAC equipment, and homeowners, is if there was a solution that could constantly make and report these measurements so that problems could be identified before they arose.

Where did you learn this stuff?

We’ve been working with HVAC professionals with decades of experience for years now to better understand HVAC system dynamics and safety. They’ve helped us better understand how to walk the fine line of providing increased comfort and control, while maintaining system safety, efficiency and performance. We’ve also been working with HVAC giants like Emerson Climate Technologies and industry leaders to develop a system that learns how your HVAC equipment operates, and uses that information to ensure your comfort without compromise. We love geeking out about this!

So how does Ecovent make sure my HVAC system stays in harmony?

The Ecovent system has integrated the latest low cost and high accuracy pressure, temperature, and humidity sensors available into our Smart Vents and Smart Sensors.  Some of our secret sauce is in having integrated pressure sensors in our Smart Sensors in every room, because you can’t accurately measure pressure in a room and across a system with only sensors in the vent. Remember those two measurements the professional has to make in the system? Ecovent uses the pressure sensor on the vent as the first measurement, and the pressure sensor in the room as the second measurement.  This comparison allows us to compute the airflow through each vent, and once we have that, we can calculate total airflow volume in the home. This is the golden measurement needed to ensure that the blower is supplying sufficient airflow for the HVAC system. It’s also why you need measurements from, and control over, vents across an entire system, rather than just a handful of rooms.

Ok, I get how the sensors relate to pressure and airflow, but how do they keep me comfortable?

The room sensors serve a couple of other purposes as well.  It primarily gives multiple temperature readings of the room, which help us accurately measure the temperature you feel when you’re in the middle of the room. If you only measure temperature at the vent, the true temperature of the room would be masked by the conditioned air coming out of the vent, and any “smart” system would be left in the dark. Any home comfort solution needs to be able to accurately measure temperature in a room, to give the homeowner real control over their comfort, otherwise it’s no better than a thermostat. Temperature, pressure, humidity and several other variables all have a huge impact on your home comfort, which we’ll discuss in a later blog post.

With the combined measurements from room and vent sensors, Ecovent knows how to keep you comfortable, and how to keep your system healthy instead of hurting. Get Ecovent for your home today, and get comfortable.



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