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Vents, Registers, & Grilles

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Whether you call them vent covers, floor registers, or air grilles, this article deals with the part of your HVAC’s ducts that you see in the various rooms of your house.  These may be located along the floor, baseboard, or wall, and vary in size depending on the size of the ductwork.  The purpose of a vent grille is to protect the ductwork from damage and tears from things falling into it such as a person’s foot or from scratching by pets or sharp objects – while at the same time allowing air to pass.

A Decorating Statement

It’s become a high-end decorating statement to have vent grilles specially coordinated with your dêcor.  Whether you shop at Home Depot or a boutique home accessories store, you’ll see vent covers in a variety of materials, colors, finishes and designs.  Materials can be brass, bronze, cast iron, metal, steel, or wood, and they can cost anywhere from $3.00 each to $100-200 each!  Regardless, they all serve the same function and there’s more to them than just the aesthetic qualities.

Air Flow Issues

First and foremost, ensure the vents are open and unblocked by drapes or furniture. Vacuuming or stepping on a floor register could inadvertently close the register, making your HVAC system not work properly, so if you’re having uneven heating or cooling, the vents/registers are the first thing to check.

When should vent covers be replaced?

Vent covers only need replacing if they become damaged (bent), corroded (rusted), or will not stay open.  Otherwise, a periodic cleaning is all they need, using a cleaner appropriate for the type of material and finish.

How often should the vent covers be cleaned?

They should be cleaned whenever they need to be, but a minimum of twice per year fall and spring is ideal.  In high traffic or dusty environments, you may want to clean them each time you replace your air filters (minimum of every 3 months).

Protect the Ductwork

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If you are embarking on a home improvement project, such as painting a room, doing drywall repairs, or sanding/refinishing wood floors, steps must be taken to protect the ductwork from paint, sand/dust, flumes, tools, and damage.   Remove the vent registers prior to beginning work. Then, cover the duct completely with a barrier material that can be taped all around. A large plastic garbage bag also works very nicely. If there is danger of someone walking or positioning a ladder or tools near a duct that is covered in this fashion and thus falling in and damaging the duct put the vent grille back on top of the register.  If you have the high-end designer vents (brass, etc.), consider getting a couple of the cheap vent grilles to use temporarily during your home improvement project, so your “good” vent grilles won’t inadvertently be damaged.  The last thing you want is someone putting a foot through the duct or tools falling in and tearing a hole in the duct!

Why it’s so important

Tears in the ductwork or any holes require immediate attention. They will cause your HVAC system not to function properly, and your system will not cool or heat very well.  The conditioned air (the air you paid to heat and cool) will be leaking out and mixing with unconditioned air, which is then blown back through your house.  Not only is there a lot of lost energy – costing you extra money but your HVAC system will be over-worked and wear out quicker.  You may also develop a pest problem from crawling insects, rodents, or reptiles which can come through the holes in the ducts into your home. Over time, you may also develop an odor and moisture problem.  If you are experiencing any of these issues, a hole in your ductwork may be your culprit!

If you are building a new home or an addition, make sure the contractor seals all the ductwork before the drywall is installed. It is almost impossible to clean drywall dust out of ducts, so the best solution is to keep them protected from sources like this from the outset.  For more information on duct cleaning, see our earlier post.

7 Things You Should Never Do

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One of the reasons we write this HVAC News column is to empower you with information.  Many times that means telling you how to do things yourself to save money on your HVAC maintenance or energy bills.  But this time, we’re emphasizing a few things you should never do because they can be harmful or cause injury to you or your HVAC system.  As we always say, knowledge is power!

  1.  Do not cover your outdoor HVAC unit.  Many people falsely believe they should cover their outdoor unit to protect it from the elements, like rain and snow.  The only time it may be covered is if it’s turned completely off.  While the unit is on and operational, it must have good air flow all around it in order for it to operate, and you will damage the unit if you operate it with a cover on.  It’s ok for the unit to be located underneath an overhang, as long as there are no obstructions for about 3 feet all the way around it.
  2. Do not use a de-humidifier in the winter or a humidifier in the summer.  In the winter, the heat removes the air’s natural humidity, and the dry air increases static electricity, makes respiratory passages uncomfortable (aggravating allergy and asthma symptoms), causes itchy skin, damages the woodwork and wood flooring in your home (causing cracking/splitting), and increases your energy bills.  That’s why you want to use a humidifier (not de-humidifier) during the winter. Here in TN, we naturally have high humidity in the summer so it would be counter-productive to use a humidifier in the summer, plus it would increase mold and insects.  Air-conditioning helps you feel more comfortable in part by taking the excess humidity out of the air, and using a de-humidifier (not a humidifier) can help even more!
  3. Do not use your fireplace as your main heat source.  Some people think that in cold weather, it will help keep their house warmer if they use their fireplace in addition to their HVAC system.  This is dead wrong.  The fireplace causes already warmed room air to be sucked up the chimney and thus makes the house colder… and causes you to use more energy (increasing your utility bills).  The fireplace may be a nice touch for “ambiance” for a few minutes, but should not be used as the main heat source unless it is an emergency and all your heat and power is out.  Additionally, using the fireplace greatly increases indoor air pollution (particulate, soot, and toxic chemicals in the air), and can trigger allergies.
  4. Do not over-size your HVAC system.  When purchasing a new system, it is easy to think bigger is better, but not so when it comes to HVAC systems!  A properly-sized piece of equipment that’s not too large is going to work much more efficiently in maintaining better and more even comfort in your home.  Check out our previous post about this issue here.
  5. Do not ignore small issues like smells, sounds, leaks or minor heating/cooling problems.  These have a way of becoming big problems before too long, and the longer the issue persists, the more money it may wind up costing you.  Money Magazine recommends the best thing you can do to save money is have regular maintenance of your HVAC system twice per year.  Don’t bury your head in the sand and hope for the best.
  6. Do not block registers, air returns, or forget to change your air filters.  These are the number one reasons HVAC systems fail or have problems like uneven heating and cooling.  Set up a reminder on your computer or smartphone to change air filters a minimum of every 3 months. If you’re blocking registers in an effort to deflect air to the rooms that need it most, then read our post on uneven heating and cooling solutions here.  It’s better to get to the root cause of the problem than to deal with a symptom of the problem in this manner, as it will only harm your HVAC system and shorten its life if you block registers or air returns.
  7. Do not turn off your heat when leaving for vacation during the winter.  You may think you’re saving money by not running the heat when no one is home, but if your pipes burst from the freezing and thawing, you could be coming home to a very costly mess!  In fact, it’s a good idea to turn off the water to the house (via the main cutoff valve), and then open up all the faucets so there is no possibility of frozen pipes.  That’s because if the power goes out while you’re gone, the heat won’t work and, if the outage is prolonged, any liquid in the house could freeze anyway. Turn the icemaker off in your freezer and drain the water line, and drain the water from the toilet tanks.

No Heat? What Should You Do?

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Something is not working quite right.  All you know is that it’s cold and your heat does not seem to be working as it should.    Listed below are some common issues, their common causes, and tips on how you may be able to fix the problem yourself, before contacting a service technician for repair.  This can save you time and money.

1.   Filter-related Issues

  • Dirty filters are the most common cause of heating (and cooling!) problems because they restrict airflow.  When the filter is clogged and the system can’t “breathe,” the heat exchanger will overheat and shut off too quickly, and your house won’t warm up. It also causes the blower to run hard and for long periods of time, with little heat coming out, and could shorten its lifespan.  Dirty filters also cause soot buildup in the system, reduces your system’s efficiency (thus costing you more money to operate), and shortens its life.  This is an easy solution: replace all filters. Be sure to check for the correct size (they are sold by size, not manufacturer).  Get the highest-rated ones you can afford to get the best indoor air quality and performance.  Important tip:  When you replace the filters, make sure the arrows on the filter are pointing towards the furnace (away from you).  Never try to skimp by vacuuming and re-using filters.
  • Listen for a whistling sound.  This is a sign that the system is not getting enough air, due to a clogged filter or obstructed airflow.  If you’ve already changed the filters and still hear the whistle, then there may be an obstruction elsewhere in the system. Check to make sure all the registers are open and unblocked.

2.   Thermostat-related Issues  

  • If the display on your thermostat is blank, it could be there is no power to the thermostat.  A tripped circuit breaker or fuse could be the problem, possibly caused by a power outage, power surge, lightning strike, or storm. Reset the tripped circuit breaker or replace the fuse. Make sure all the wires going to the thermostat are connected and not loose.  Useful tip: If you’ve lost your owner’s manual for your thermostat, most major-brand manuals can be found on the web-just go to the manufacturer’s web site.
  • Check that the thermostat is in heat mode. If it’s a programmable thermostat, switch it to manual control and set it for 5 degrees above the room temperature, and wait to see if the heat cycles on.   For programmable thermostats, check that it is set to the correct day and time (am or pm).
  • If your thermostat is battery-powered, or relies on battery for backup power in case of a power outage, it could be that the battery needs replacing.  If you have a programmable thermostat, and had a recent power outage, it could be that without a functioning battery backup, all of your settings have been wiped out by the power outage and the thermostat reverted to its default program.
  • If your thermostat has a switch to control the furnace fan, switch the fan “On” (as opposed to “Auto” or “Off”).  If you do not hear the fan coming on, go to one of the supply registers and see if you can feel any air coming out. If the fan is not running, there may be no power to the furnace.  If the fan runs, but the air coming out is cold, you have a problem with the furnace (or heat pump) itself.

3.   Electrical-related Issues

  • Check to see if the circuit breaker or fuse controlling the heating system is tripped or blown.  If a breaker has been tripped it will be in a position that is between ON and OFF. Reset the breaker by turning it all the way OFF, then back ON. If your home has fuses, check to see if the fuse for the furnace is blown. If so, replace it with the same size and type of fuse. Do not increase the size of the fuse. Important Tip:  If a breaker keeps tripping or a fuse keeps blowing, contact a qualified service technician to inspect your system to determine why you are having problems.
  • Check to see if the switch located near the heating unit is switched on.  This often looks similar to a light switch and easy to mistakenly turn off.  (In one house, the switch was mounted upside down, so the unit was actually “on” when the switch was in the “down” position!).  Useful tip: Most thermostats get their power from the same electrical circuit that feeds the HVAC system.  So, if your thermostat is not responding, turning on the switch by the HVAC may be the solution!

4.    Furnace-related Issues

  • Check to see if the pilot lot has gone out (if your furnace has non-electric ignition).  The solution is to relight the pilot light.  If you are unsure how to this, contact your gas service provider.  If the pilot will not light or stay lit, call a service technician.
  • Most furnaces today have electronic ignition switches rather than a pilot light.  If that gets stuck, try switching the furnace off, wait a minute, then switch it back on. If your furnace has a reset switch, press it. After another minute, you should hear the furnace fire up.
  • Make sure the gas is turned on.  Trace the gas line back from the furnace to the meter, and if there is a handle that’s perpendicular to the gas pipe, turn it so it’s parallel. There should be no obstructions or kinks in the gas line. Also, if you have other gas appliances and they are all working, then you know the gas line is on and not obstructed.
  • Some furnaces have emergency cut-off switches that are activated when a door or service panel is removed. If the furnace door is not closed properly (such as after a filter cleaning, or accidentally bumped open), the cut-off switch will prevent the furnace from coming on.  Check to make sure all access doors are properly closed and secured.
  • Make sure the exhaust line or flue is clear.  I’m not talking about the chimney flue in your fireplace, but the part of your furnace that exhausts to the outside, usually through a metal duct.  Sometimes birds, drawn by the warmth, build nests in it.  To clean it, you’ll need to turn off the furnace first.
  • High-efficiency furnaces can drain off several gallons of water a day during the heating season. If the drain lines become restricted by sediment or mold growth, the furnace will shut down. If the drain line is in unconditioned space, and the water in the line freezes, that, too, will cause the system to shut down.  Check the drain hose, and if it looks dirty, remove it and clean it with a mixture of 25% bleach + 75% water, and after flushing it for several minutes, replace the hose.

5.   Heat Pump-related Issues 

  • Check to see if the outdoor unit is covered in ice. It is normal for the coils to frost-over, especially if there is lots of moisture in the air (mist, rain, or sleet).  Your heat pump has a defrost cycle that normally melts this frost.  However, if the ice on the coils is extremely thick, never seems to melt, and only seems to get worse with time, then there could be a problem with the defrost cycle.  Try switching the system to “Emergency Heat” at the thermostat. Wait until the sun melts the ice off, then try turning the system back to “Heat.”  If you do not hear the heat come on, or if you hear loud noises, turn the system back to “Emergency Heat” (thereby shutting off the outdoor unit) and call for service.
  • When outdoor temperatures stay below about 35 degrees, it is normal for the backup or auxiliary heat light (usually a blue or green light) to come on. The colder the temperatures, the longer this light will stay on. But if the light comes on and stays on, even when outdoor temperatures rise above 35-40 degrees, then there is a problem with your outdoor unit and you’ll need to call for service.
  • Clean away leaves and debris around the outside unit that could be restricting the airflow.  Be sure the outside unit is not covered if you are trying to use it!

Never fear.  If none of these fixes your problem, we’re always here to help!

Case Study: Ductless HVAC at Brentwood Middle School

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Jeff Owens, Project Manager, describes the major project at Brentwood Middle School that installed a green, ductless, HVAC system expected to save 25%-30% of the energy previously required to heat and cool a large school building.

Objectives

Brentwood Middle School opened in August 1972.  It’s a large school with 1,250 students in grades 6 through 8. In 2014, it was named by thebestschools.org as one of the top 30 schools in theO USA.  Learning can be hampered by environments where students are distracted by noise, or in temperatures that are too hot or too cold. In 2013, it was decided that the 41-year-old school should replace its antiquated HVAC system.  They chose a system that would need no ducts for conditioned hot and cool air, would keep classrooms quiet, would let teachers control their individual classroom’s temperature, and would use no floor space for equipment.  The project required removing all the ceiling tiles, all lighting, all the old ductwork, all floor-mounted air handlers, and all roof-mounted equipment.  The work was done during two summer breaks so there was no need to close any classrooms.

Mitsubishi VRF

The system uses  a Mitsubishi VRF (Variable Refrigerant Flow) system. In each of the classrooms we have a ceiling cassette that takes care of this particular room and it’s thermostatically controlled by a white thermostat on the wall. The teacher can control the temperature in each room. Before there was one central thermostat controlling all the rooms.

Ductless

This is called a ductless system and you have no ductwork above the ceiling and you have four directional blowers with air flowing in four different directions in the classroom. There are approximately 74 units throughout the building.  Another good feature for these Mitsubishis is that they’re quiet – only 30-35 decibels. You can’t even hear the thing running in the classroom. It is very quiet unlike a conventional system. Each cassette is connected to a condensing unit on the roof. There are eight condensing units on the roof and each feeds 15-20 air handlers. There is a flow of refrigerant and as the system requires heating or cooling it will flow the refrigerant needed to heat or cool a particular room.  This is a two-ton capacity unit so it can use as much as 24,000 BTUs of refrigerant.

Fresh Air

Of course there has to be a way to bring fresh outside air into each classroom and that does require ducts and vents.  Reznor make-up units on the roof filter the air, and blowers pump the air to the vents. There are no return air ducts. The fresh air pumped in by the make-up units result in the rooms having a positive air pressure, which then exits through leaks around windows and doors.  There are five makeup air units on the roof that condition the outside air. 100% outside air goes in and is heated or cooled as required and then is directed into each classroom.

Energy Savings

As the sun comes up in the morning, one side of the building requires cooling while the other side does not. An energy management system determines which of the eight condensing units to run.  This saves energy. The energy used is being measured by the energy management system and is expected to be 25 to 30% less than the old system.  Data from the old system has been retained and in a year we should be able to report exact figures.