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Energy Recovery Ventilation Systems
Energy recovery ventilation systems provide a controlled way of ventilating a home while minimizing energy loss. They reduce the costs of heating ventilated air in the winter by transferring heat from the warm inside air being exhausted to the fresh (but cold) supply air. In the summer, the inside air cools the warmer supply air to reduce ventilation cooling costs.
Types of Systems
There are two types of energy-recovery systems: heat-recovery ventilators (HRV) and energy-recovery (or enthalpy-recovery) ventilators (ERV). Both types include a heat exchanger, one or more fans to push air through the machine, and some controls. There are some small wall- or window-mounted models, but the majorities are central, whole-house ventilation systems with their own duct system or shared ductwork.
The main difference between a heat-recovery and an energy-recovery ventilator is the way the heat exchanger works. With an energy-recovery ventilator, the heat exchanger transfers a certain amount of water vapor along with heat energy, while a heat-recovery ventilator only transfers heat.
Because an energy-recovery ventilator transfers some of the moisture from the exhaust air to the usually less humid incoming winter air, the humidity of the house air stays more constant. This also keeps the heat exchanger core warmer, minimizing problems with freezing.
In the summer, an energy-recovery ventilator may help to control humidity in the house by transferring some of the water vapor in the incoming air to the theoretically drier air that's leaving the house. If you use an air conditioner, an energy-recovery ventilator generally offers better humidity control than a heat-recovery system. However, there's some controversy about using ventilation systems at all during humid, but not overly hot, summer weather. Some experts suggest that it is better to turn the system off in very humid weather to keep indoor humidity levels low. You can also set up the system so that it only runs when the air conditioning system is running, or use pre-cooling coils.
Most energy recovery ventilation systems can recover about 70%–80% of the energy in the exiting air and deliver that energy to the incoming air. However, they are most cost effective in climates with extreme winters or summers, and where fuel costs are high. In mild climates, the cost of the additional electricity consumed by the system fans may exceed the energy savings from not having to condition the supply air.
Installation and Maintenance
Energy recovery ventilation systems usually cost more to install than other ventilation systems. In general, simplicity is key to a cost-effective installation. To save on installation costs, many systems share existing ductwork. Complex systems are not only more expensive to install, but they are generally more maintenance intensive and often consume more electric power. For most houses, attempting to recover all of the energy in the exhaust air will probably not be worth the additional cost. Also, these types of ventilation systems are still not very common. Only some HVAC contractors have enough technical expertise and experience to install them.
In general, you want to have a supply and return duct for each bedroom and for each common living area. Duct runs should be as short and straight as possible. The correct size duct is necessary to minimize pressure drops in the system and thus improve performance. Insulate ducts located in unheated spaces, and seal all joints with duct mastic (never use ordinary duct tape on ducts.)
Also, energy recovery ventilation systems operated in cold climates must have devices to help prevent freezing and frost formation. Very cold supply air can cause frost formation in the heat exchanger, which can damage it. Frost buildup also reduces ventilation effectiveness.
Energy recovery ventilation systems require more maintenance than other ventilation systems. They need to be cleaned regularly to prevent deterioration of ventilation rates and heat recovery, and to prevent mold and bacteria on heat exchanger surfaces.
Whole-House Balanced Ventilation Systems
Balanced ventilation systems, if properly designed and installed, neither pressurizes nor depressurize a house. Rather, they introduce and exhaust approximately equal quantities of fresh outside air and polluted inside air, respectively.
A balanced ventilation system usually has two fans and two duct systems. It facilitates good distribution of fresh air by placing supply and exhaust vents in appropriate places. Fresh air supply and exhaust vents can be installed in every room. But a typical balanced ventilation system is designed to supply fresh air to bedrooms and living rooms where people spend the most time. It also exhausts air from rooms where moisture and pollutants are most often generated (kitchen, bathrooms, and perhaps the laundry room). Some designs may use a single-point exhaust. Because they directly supply outside air, balanced systems allow the use of filters to remove dust and pollen from outside air before introducing it into the house.
Balanced ventilation systems are appropriate for all climates. However, because they require two duct and fan systems, balanced ventilation systems are usually more expensive to install and operate than supply or exhaust systems.
Like both supply and exhaust systems, balanced ventilation systems do not temper or remove moisture from the make-up air before it enters the house. Therefore, they may contribute to higher heating and cooling costs, unlike energy recovery ventilation systems. Also, like supply ventilation systems, outdoor air may need to be mixed with indoor air before delivery to avoid cold air drafts in the winter. |
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There are a lot of websites giving the information about energy saving tips, but most of the tips are taken from the government website www.eere.energy.gov. Some of these tips are very useful. But some of them very difficult or expensive to implement for your house.
Here I want to give some information what is really working and what did I use for my house.
Also I've discovered a few more energy saving tips by myself – see them below.
· Unless your home was specially constructed for energy efficiency, you can usually reduce your energy bills by adding more insulation. Many older homes have less insulation than homes built today, but adding insulation to a newer home may also pay for itself within a few years.
I added another layer of insulation in my attic maximum R-value available and it is make a big difference.
· Adequately insulating and air sealing the access to an attic— especially to unconditioned attics—will help lower your heating and cooling bills.
A home's attic access, which could be an attic hatch, pull-down stairs, or a knee-wall door, often, goes uninsulated. This gap in the attic insulation increases heat loss in the winter and heat gain in the summer.
These accesses also often aren't sealed properly. A 1/4-inch gap around the perimeter of an attic access can potentially leak the same amount of air supplied by a typical bedroom heating duct.
I also used this tip in my house.
· Air leakage, or infiltration, occurs when outside air enters a house uncontrollably through cracks and openings. Properly air sealing such cracks and openings in your home can significantly reduce heating and cooling costs, improve building durability, and create a healthier indoor environment.
· Caulk and seal air leaks where plumbing, ducting, or electrical wiring penetrates through exterior walls.
You should use silicon to implement this recommendation.
· Check for open fireplace dampers.
I don’t use fireplace at all, so I just sealed a damper and blocked the inlet pipe.
· Check your ducts for air leaks. First, look for sections that should be joined, but have separated and then look for obvious holes.
It is very important to do because otherwise air just moving from the supply duct to the return duct in the basement without conditioning your living aria.
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There are some more energy saving tips, but almost all of them designed to increase time between cycles when furnace or AC actually working. Because less energy the house is loosing to the outside, less often the furnace or AC starts up to work.
Meanwile I have discovered a few more energy saving tips which do not only increases time between cycles, but reduce the cycles itself!!!
When temperature outside was 29’F I reduced actual working cycle of my furnace from 18 to 15 minutes what gave me another 20% energy saving to my bill on top of what I already have been saving by using all the tips above and some I've discovered by myself:
• Closing a supply register: some websites give you an advice how save energy with this one but nobody presents the right way how to put it in practice. R.F.C.*
• Closing a cold air return grill: some websites give you an advice how save energy with this one but nobody presents the right way how to put it in practice. R.F.C.*
• Programmable thermostat: it is not about that you can lower a temperature when you out of house. I.I.C.**
• Fresh air intake: it is about right, energy saving way of using this one. R.F.C.*
• Combustion air intake: why it is necessary to have and how to install it. I.I.C.*
• Bath fans: it is about right, energy saving way of using them. R.F.C.* & I.I.C.**
• Humidifier: it is about right, energy saving way of using this one. R.F.C.*
• Garage door: it is about right, energy saving way of using this one. I.I.C.**
• High efficiency water heater: it is not about lowering the water temperature to 120 degrees. I.I.C.*
• Duct seal: everybody talking about this one but nobody explains what actually should be done and the right way of doing that. R.F.C.*
* – this item Reduce Furnace Cycle.
** – this item Increase Idle Cycle.
So, as you see here are 10 items which all together helped me to save 20% of my energy bill on a top of what I am saving by using well known energy saving tips (see above).
Now all the energy saving tips are available for free!
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PROBLEM: Heat either Does Not Reach or Exceeds the Set Temperature
Heat Either Does Not Reach or Exceeds the Set Temperature
Possible Causes
• Thermostat mounted crooked.
• Heat anticipator not set correctly.
Possible Repairs
• Remove cover of thermostat and loosen screws holding unit to wall. Level the thermostat. Re-tighten screws and replace cover.
• To adjust the heat anticipator, please see Heat Anticipator Adjustment.
Thermostat Heat Anticipator Description
Thermostat Heat Anticipator
The heat anticipator is an electrical resistor device mounted in the center of many mechanical thermostats that fine tune the point at which the thermostat turns off the furnace burners. It anticipates the flywheel effect of a space heating up and turns off the burners a short period of time before the space reaches the desired temperature.
The heat anticipator essentially consists of a simple thin wire mounted to a disc which is attached to the bimetallic coil. There is an adjustment arm which touches the wire and functions to vary the electrical resistance of the wire which in turn varies how hot the wire gets. This in turn warms the bimetallic coil causing it to shut down the gas burners early as determined by the heat anticipator.
Adjusting the Thermostat Heat Anticipator
Thermostat Heat Anticipator Detail
When the heat anticipator is out of adjustment it can cause the furnace to exhibit symptoms of short cycling (turning on and off frequently) or to exceed or never reach the desired thermostat heat setting. To adjust the heat anticipator perform the following steps:
• Remove the thermostat cover
• Make sure the thermostat is level. If it is not level the mercury switch will not work properly.
• At the center of the thermostat find the small disc with calibration marks as shown in the photo above. It will probably have the word "longer" on it. The disc will have fastened to it a lever arm and indicator relating to the calibration marks. This is the heat anticipator adjustment lever arm.
• If the furnace is cycling on and off too frequently, move the heat anticipator adjustment lever closer to the "longer" setting by one calibration mark.
• If the furnace is exceeding or never reaching the desired set temperature, move the adjustment lever away from the "longer" setting by one calibration mark.
• Once the appropriate adjustment is made let the furnace run and the temperature stabilize for a period of 2-3 hours.
If necessary, repeat the above procedure.
• If the problem persists and you cannot resolve the problem with these steps, you may need to replace the thermostat.
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