Adding central air to house without ducts Q: I saw a ductless air conditioning system used in an older house that did not have a forced air furnace. How does this work? Mark, North St. Paul, MN A: Richard Trethewey replies: A ductless air conditioner, also called a mini-split system, has two major components: a unit mounted on an inside wall that delivers cool air to the room and a unit mounted on the outside of the house. A pair of refrigerant lines run between the two, one delivering electricity, the other taking away condensate (water). The system also has thermostatic control and a variable quiet blower. If your house already has insulated ductwork, air conditioning can be added to the existing furnace. If your house is without ducts, look into a high velocity mini-duct system. If you are looking for the "oasis theory" of cooling one room as opposed to a whole house a split type is a good solution. A split system has several advantages over a traditional window unit, first and foremost a thermostat that can keep the room at a constant, comfortable temperature instead of blasting on and off.

In addition, you don't have to move a spilt system in and out of the window as the seasons change, and you don't have the open-window security concerns of a moveable unit.Most of us take heating and cooling for granted. We expect our heating systems to keep us warm during the winter, and we depend on air-conditioning to keep us cool during the summer. When the house is cold in winter or hot in summer, the natural reaction is to call for professional service. how to fix car air conditioner compressorFortunately, there is an alternative. heat pump vs ac unitYou can cut service costs drastically and keep your heating and cooling systems working efficiently by doing some maintenance and quick fixes yourself. average cost of new hvac unit

But first, it's important to know how the basics of how heating and cooling systems function. The Ultimate Off-Peak Cooling Systems Quiz Keeping Cool: Air Conditioner Quiz All climate-control devices or systems have three basic components: a source of warmed or cooled air, a means of distributing the air to the rooms being heated or cooled, and a control used to regulate the system (e.g., thermostat). The sources of warm air, such as a furnace, and cool air, such as an air conditioner, in a house often use the same distribution and control systems. If your house has central air conditioning, cool air probably flows through the same ducts that heat does and is regulated by the same thermostat. When a heating or cooling system malfunctions, any of these three basic components may be causing the problem. Both heating and air conditioning work on the principle that heat always moves from a warm object to a cooler one, just as water flows from a higher to a lower level. Furnaces and heaters put heat into the air to make your home warmer;

air conditioners remove heat to make your home cooler. All heating and cooling units burn fuel. Air conditioners use electricity. Most home heating systems use gas or fuel oil; other systems use electricity. The heat pump -- an electrically powered climate control unit -- both heats and cools air. In summer it extracts heat from the air inside your home. In winter it pulls heat from the air outside and uses this heat to warm the air inside. When the furnace is turned on, it consumes the fuel that powers it, whether it be gas, oil, or electricity. As fuel is burned, heat is produced and channeled to the living areas of your home through ducts, pipes, or wires and then is blown out of registers, radiators, or heating panels. Older systems use the heat they produce to heat water, which in turn heats the air in your home. These systems use a boiler to store and heat the water supply, which is then circulated as hot water through pipes embedded in the wall, floor, or ceiling. When an air conditioner is turned on, electrical power is used to cool a gas in a coil to its liquid state.

Warm air in your home is cooled by contact with the cooling coil, and this cooled air is channeled to the rooms of your home through ducts and out registers or -- in the case of room air conditioners -- directly from the unit itself. In the next section, we'll review the different distribution systems used for heating and cooling the home.Need Help Finding a System? Our interactive tool will help you select the perfect air conditioner for your family. Heat Pump Buying Guide Save energy with a heat pump. Find out why a heat pump may be smart for your home. Frigidaire 10-YearWarranty & Quality Pledge Quality, comfort and total peace of mind.The heating and cooling units at Bice House are very easy to operate and will provide comfortable space conditions if set correctly. FOR COOLING: The unit switch should be set to the COOL position and the fan switch should be set to HIGH. The thermostat should be set to a position at mid-scale. The unit should operate to maintain space conditions of 72°F at these settings.

If a slightly warmer space temperature is desired, the thermostat can be set to a warmer position. If a slightly cooler space temperature is desired, the thermostat can be set to a cooler setting. However, caution must be used when adjusting the thermostat to a cooler setting, as setting it too cold can create a condition where the space becomes cold and damp and condensation forms on the unit top and front. FOR HEATING: The unit switch should be set to the HEAT position and the fan switch should be set to HIGH. The thermostat can be set to a slightly warmer or cooler setting if desired. It is NOT recommended that the thermostat be set to the extreme cold or warm setting at any time. Doing so will not make the unit heat or cool any faster. The TOP and FRONT of the units MUST be kept clear of obstructions at all times. This includes desks, wardrobes, books, clothes etc. Blocking the airflow through the unit will cause the unit to not heat or cool properly.This air-conditioning unit is too big.

A 4-ton system installed in the Florida home of Chris Marriner doesn't run long enough to dehumidify the house. Florida is not the kind of place where you'd want to be without air conditioning for very long, so when Chris Marriner's old system died last spring, he didn't waste much time in replacing it. But what should have been a ticket to indoor comfort hasn't exactly worked out that way. Marriner's HVAC(Heating, ventilation, and air conditioning). technician decided to replace the 4-ton system with one of the same capacity, even though Marriner knew that because of improvements to the building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; the new system probably would be oversized for the 2200-square-foot home. The tech told Marriner the system could be "tuned." In a Q&A post at GreenBuildingAdvisor, Marriner complains that indoor relative humidity averages 55% or more, and has ranged up to 66% or 67%.

That's apparently because the oversized AC equipment doesn't run long enough to lower indoor humidity. When Marriner spoke to the HVAC installer about the oversized equipment, he got some strange advice. "I talked to him about it and he wants to bring some attic air into the return so [the AC] will run longer," Marriner writes. "I think that adding a whole house dehumidifier, like the Williams Air Sponge, or Aprilaire would be the best solution. Saving Energy With Manual J and Manual D Green Basics: Cooling Options Q&A: Excess humidity — HVAC system too large Humidity, Mold, and Indoor Air Quality That's the topic for this Q&A Spotlight. Nathaniel G finds the suggestion to bring hot attic air into the system to extend the run time nothing more than an "inefficient Band-aid." The system should have been sized correctly in the beginning. "Sounds like your HVAC tech is less interested in doing his job properly than doing it the way grandpa did and upselling you on a bunch of crap to patch up his own mistakes when grandpa's approach doesn't cut the mustard," Nathaniel says.

"Bring some attic air into the return?" writes David Meiland. "You mean deliberately and needlessly increase the load so the unit will run longer in hopes that it will also decrease humidity adequately? in fact it might be one of the worst ideas I've ever heard — it's about the same as opening a window." It's not clear what the tech might have meant when said the new system could be tuned, Meiland adds, but the real solution is longer run times and an indoor coil that's not so cold. Marriner has already explored the possibility of replacing the outside compressor and scaling back the air-handler. The manufacturer told him that won't work. "To compound this," Marriner adds, the HVAC technician is a friend. "If he were not, I'd have raised hell. He got indignant when I asked him about the humidity and said he will not change the unit ... He was trying to cut me a deal, so I don't know if he had an extra one at the warehouse or what. But I've learned a valuable lesson."

senior editor Martin Holladay suggests that Marriner begin with a stand-along dehumidifier. "It may work well enough for you to tolerate your system," he says. "And it is a cheaper solution than starting from scratch." To help the existing AC equipment get more water out of the air, Holladay says, is to lower the blower speed of the air handler from 400 cubic feet per minute (cfm) per ton to 350 cfm per ton. "Of course, lowering the blower speed (especially below 350 cfm per ton) carries its own risk," he adds, "namely, freezing the coil." Holladay's suggestion for a dehumidifier is a good one, Dana Dorsett says. "If the house is reasonably tight it should do the trick," he writes. "A 600-watt stand-alone dehumidifier converts the latent loadCooling load that results when moisture in the air changes from a vapor to a liquid (condensation). Latent load puts additional demand on cooling systems in hot-humid climates. into a sensible loadThis is the heat content of just the air;

it does not include the heat content required to remove (condense) moisture from air. Sensible heat is measured by dry bulb temperature. Latent heat is measured by wet bulb temperature., but it doesn't increase the total cooling load by more than ~2000 BtuBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. /hr (the 600 watts it's using while running). (For more on sensible and latent loads, here's an explanation from a website called The Engineering ToolBox.) "I wonder how many other HVAC technicians there are out there who take the approach of increasing the load as the 'solution' to an oversized AC system?" he adds. "If it's a vented attic, it would also increase the latent load. You may end up pretty much in the same place, but be using significantly more electricity." The indoor humidity levels sound normal, says AJ Builder. "I have no AC and my summer humidity is 50-85% in my home, about 10% less than outside," AJ writes.

"No mold except for bad tile work in one shower. Fifty-five seems right considering Tampa, where outside humidity is high along with the temperature." People are healthy and comfortable, Dorsett replies, when the indoor relative humidity (RH) is between 30% and 50% and the temperature between 68° and 75°F. "When it's above 50% RH, dust mite populations begin to grow (a problem primarily for those with allergies or asthma)," Dorsett says. "Above 60% RH @ 75°F, humans are more susceptible to skin fungus/yeast infections. Above 70% RH it can be pretty uncomfortable, mold spore counts take off, and the risk of respiratory tract infection (fungal or bacterial) goes up." In Tampa, where Marriner lives, high dew points mean that any infiltration of outside air brings in a lot of humidity. "The airtightness of the house and ventilation rates matter quite a bit," he says. AJ isn't buying it: "People who live in a 'clean room' are screwing up their immune systems," he says. "

We need to interact with the real world to have healthy immune system understandings IMO and finally in some research published of late. "And Florida, to reduce humidity to 55% (which he has) is fine," AJ adds. "Dehumidify maybe just a bit; but in cooler weather, open windows and be part of this great planet." Like it or not, Dorsett replies, but at 65% humidity "you won't have serious mold issues, but if you have dust mite allergies you're pretty much screwed — they breed faster than flies at that RH." Moreover, dew points tend to be a lot higher in Tampa than they do in New York (where AJ Builder lives) or in Massachusetts (where Dorsett lives). "That 70°F/55% RH outdoor air you're currently experiencing has a dew point of 53°F, whereas in Tampa right this second it's 92°F, with an outdoor dew point of 72°F (down from the mid-70s from earlier in the day)," Dorsett tells AJ. "Tampa's average outdoor dew point is about the same as our absolute summertime peak dew point so far this year.

( data sets — which was the highest reading of the season.)" Here's how GBA technical director Peter Yost sees it: Higher interior relative humidity can easily feel uncomfortable when you are also dropping the air temperature with air conditioning. Sure, some folks actually do just fine with plenty of air movement at 80°F and 55% RH, but many folks don’t. There is no excuse for any HVAC technician not to size an AC system based on the real loads, or to fail to specify the appropriate sensible heat ratio (SHR – the portion of the total cooling load handling the sensible load) for the climate. SHR for a Florida climate should be 0.70 or below. As Martin Holladay notes in his blog, Climate-Specific Air Conditioners, most air conditioners have an SHR in the 0.75-0.80 range — much too high for a hot humid climate. Installing a dehumidifier to drop the interior relative humidity will likely do the trick, but most dehumidifiers are meant to work in just one room or space, unless the unit can be configured into the central forced-air system.