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If you are renovating a house in any way, you will have decided by now if you are going to keep your existing heating system as is, modify or expand the existing service, or completely replace everything. We will attempt to cover all exigencies in this section. However, the scope of this guide requires us to stick to the basics only, with out describing sophisticated equipment. The installation of most room heating units is easy. Electric radiation units are installed by either plugging in the unit to a grounded outlet or hard-wiring it to a grounded, dedicated circuit. See the manufacturer’s instructions and Sections 20 and 35 for specifying and installing circuiting and wiring. Through-the-window and through- the-wall heat pumps are installed like air conditioners and must have grounded, dedicated circuits. Make sure that you have the requisite circuitry and amperage for these units. INSTALLING A NEW SYSTEM OR MODIFYING AN EXISTING FORCED-AIR SYSTEM With the help of Section 19 and a heating expert you should have a plan outlining the ductwork and the various duct sections required. If you are completely replacing your system, you should have selected the location of the new furnace, which should be installed by a heating contractor. As a matter, of fact, you may want to have all or most of the system installed by a professional. In any event, if you are going to cut into the ducts, have them checked for the presence of asbestos. Tools
Materials: The materials required for the ductwork depend on your plan. Fig. 1 shows all of the potential parts of the system. You will most likely have to have your ducts fabricated in a sheet- metal shop. Bring your drawing to the shop and they will custom-make the ductwork to the sizes and shapes specified by the HVAC (heating, ventilating, and air conditioning) designer. There is a small likelihood that you will be able to purchase simple ducts (such as round sections) “off the shelf.” *We have included instructions for the installation of metal ductwork only. You may use fiberglass ductwork for your job if it's permitted in your area. Even if fiberglass ducts are permitted, the code may require that certain parts of the sys tem be metal, so check the code carefully. Fiberglass ducts are easy to install since they are joined primarily with tape and require no additional insulation. Use the proper mask when working with fiberglass. Modifying the Heating Equipment The Installation Procedure for a New System Generally, the furnace is installed first and the pipes and ducts are then assembled. The return-air runs are installed before the supply ducts. Finally the smoke pipe is installed, the fuel supply connected, and , last, the supply-air and return-air registers are put in place. You will probably be taking off smaller ducts from larger, oversized ones. Follow the instructions outlined below for the cutting into and joining of ducts. The most difficult proposition in adding ducts is to make sure that you have an unobstructed run from existing duct (or plenum) to the new register. If you are installing in a ceiling-less basement, you may have to run the duct under joists, beams, and plumbing lines. Remember that the efficiency of the system is reduced (and the noise factor increased) with each additional change of direction. Vertical ducts can be installed in closets or along existing partitions and then furred out. Installing the Furnace Installing Ducts in an Existing House If you are modifying an existing system that's somewhat oversized, it's likely that you can tap into existing ducts and plenums and extend the system a few feet, adding one or two registers. If the new registers are remote from the furnace, you may have to play with all of the dampers in the house to balance the system so that heat is forced into these remote runs. Advanced technology is allowing the furnaces to be smaller and smaller, and if space is at a premium, shop for an efficient, reliable, and safe unit that takes the least amount of space. Some fit in the attic space horizontally. You may even be able to fit one in the upper part of a closet. Make sure that you meet code requirements, that the furnace is surrounded by incombustible materials, and that the furnace has access to the air required for combustion. If the furnace is fueled with oil or gas, the unit will have to be located where it can have a flue or vent. If you are using a heat pump, you will have to find locations for both the interior and the exterior parts of the system, which are connected to each other with a small tube. Hire a heating expert to install the unit and all of its controls. Assembling the Pipes and Ducts There is no precise sequence of steps to follow in installing the ducts. It is, however, a good idea to review your plans to determine if a supply line is to cross the return line or another supply line. If so, it makes good sense to install the upper one (the one closer to the ceiling) first. ROUND PIPE: You can purchase round pipe ready to be installed.* Round ductwork comes with one end flat and the other end crimped. To join sections of the pipe together, fit the crimped end of one pipe section into the flat end of an other. The crimped end should always face away from the furnace. Push the ends together for a tight fit. Seal the joints with a liquid sealer (pro vided for this purpose) or duct tape. An alternative is to use sheet-metal screws to secure the joints. Drill two holes through the joint and tighten the screws. Round pipe should be supported every 5’ or 6’. To shorten pipe sections, measure the exact length of the required section onto a section that has not yet been rounded. (It is easier to cut the pipe when it's still open.) Always cut off the plain end, not the crimped end. Open pipe can be cut with tin snips. (If the edge seam gets com pressed in the process, pry it open with a screw driver.) RECTANGULAR DUCT: Large sections of rectangular duct are used as main trunk lines or plenums. (A plenum is a space, generally above the ceiling, that's used to conduct the flow of air. It is more often used as the return for spent air, but is also used at the beginning of the supply-air system.) Rectangular or round duct can be connected to the central plenum. Most rectangular ducts come with S-shaped connectors on the long sides. The two short sides are bent back. Push the section together, joining the S seams on the long sides. Slip drive clips over the two shorter ends. To install the clips, bend one end tab in ward. Start the clip upward and , if required, tap it upward with a hammer. When in position, bend the top tab down. Ducts should be sup ported with hangers every 5’. Some ductwork is shipped flat and will have to be assembled. The pipe will have either a snap lock or a hammer-lock seam. The snap lock is joined by pressing the tongue on one edge into the slot on the other. The seam will snap closed. The hammer-lock seam will require hammering to get the seam to close. Place the pipe around a piece of 2 X 4 and gently hammer the seam closed. To shorten rectangular duct, measure and cut the section before the long seams have been joined. First assemble all of the regulation-length ductwork, and then measure and cut the last piece. Cut the plain end, not the end with the S clip. It will be necessary to reshape the short sides so that they will join with the regular sections. Cut 1” into the sides and bend the short end backward to receive the drive clip. SMALL RECTANGULAR DUCTWORK: This type of ductwork is most often used as wall stack because it's designed to fit neatly in between the studs. It is joined with snap locks.* Fit the snap end of one section into the shaped end of the next section and push gently but firmly together. CUTTING OPENINGS IN THE SHEET METAL: When one duct meets another, an opening must be made in the larger one to accommodate a connection; Make a template by placing a sheet of paper on the opening of the smaller duct or fitting and tracing its size. Transfer the required opening onto the sheet metal of the larger duct. Drill a hole in the center of the required opening. You can then use metal cutting pliers, tin snips, or a fine- toothed saw to complete the opening. Installing the Return-Air Runs Return runs are installed prior to the supply ducts. There are a variety of ways of installing the return-air run, depending on the furnace and the distribution system. Some systems don't have return-air ducts but draw the air from the surrounding area. This is especially true for installations where the furnace is in a utility room on the main floor of the house. For those systems with return-air ducts an opening must be cut in the plenum chamber of the furnace. Having first determined the exact location of this opening, position an offset takeoff collar at that location. (Clear the floor joists or any other combustible material by at least an inch or two.) Trace the size of the collar onto the plenum chamber. Some systems may require more than one collar. Trace all collars before making cuts. To facilitate the cutting you might consider removing the plenum from the furnace. Cut the holes and position the collars in the openings. The collars are secured to the plenum by bending back the tabs. It is unwise to secure a grill directly to the plenum chamber of the furnace. First place a takeoff collar on the plenum and then attach the grill to the collar. Ducts may be joined together by different mechanical locking devices. Some installers further seal the snap-locked joints with adhesives or tape. Return-air plenums can be constructed by lining with sheet metal the already existing stud and joist spaces. These long, vertical and horizontal spaces make ideal ducts. Holes must be cut in the floors and walls to connect the stud spaces to each other. Be sure to block up that portion of the stud spaces above or below the part used as a plenum. For the horizontal return ducts, the space between the joists can be used if the bottom section is enclosed with sheet metal. This situation is viable only if the duct runs parallel to the line of the joists. If it does not, a regular sheet- metal duct must be used below the joists as the return-air plenum. Holes in the floor must be cut carefully and fully blocked. Cut holes at least as large as the required return-duct size. Larger return-air ducts will not hurt the system, but ones smaller than required might cause vibrations and inefficient distribution. The sheet metal can be nailed directly to the structural wood. Installing the Supply-Air Runs Vertical supply ducts in the walls must consist of sheet metal. You want these ducts to be relatively airtight so that the heated air isn't lost through cracks. Build up the sheet-metal ductwork as per plan starting from the furnace and working out ward to the registers. Remember that the snap end of the small ductwork points to the furnace. Holes cut to accommodate the ductwork should be larger than the ducts. The supply-air plenum at the furnace must be assembled and installed according to the directions supplied with the unit itself. Make all the openings and install the take off collars before permanently installing the plenum to the furnace. Although it's permissible in some areas to run the return air in unlined stud spaces, we don't advise it. Install a volume damper in each run of duct so you can control the flow of air. Place it where it will be accessible. Supply runs that pass through unheated spaces should be insulated. Blanket insulation material with a vapor barrier (which is essential for ducts that are also used for cooling), sold in 1”- or 2”-thick rolls for this purpose, is easy to install and may be purchased at the building supply store. Installing the Smoke Pipe We suggest that this item be installed by the con tractor who is installing the furnace. The smoke pipe leading from the furnace to the outside must be airtight to ensure that there are no leaks of toxic or unpleasant fumes into the house. In addition, the pipe should rise slightly in its horizontal run. The pipe, although light in weight, must be supported properly. The pieces of the smoke pipe should be laid out on the floor in the order in which they will be needed. The crimped end of the smoke pipe faces the chimney (if one is required). Properly adjusted elbow sections will be needed to make the required turns. If the smoke pipe is to be installed into a chimney flue, the last piece of the run is installed in the chimney thimble, with the crimped end forced all the way in. The runs should be assembled starting from the furnace. If a section must be shortened, it should be the last section and a draw-band (a thin strip of sheet metal used to tighten and cover the joint) should be used to make the final connection. Wire is used to support the smoke pipe at every turn and at every other pipe section. Modifying the Heating Equipment Connecting the Fuel Supply Completing the System Registers and grills can't be installed until the walls and floor are completed. If you are installing a new heating system in an old house, the floors are likely to be in place. Even if you are installing ductwork in a brand-new residence, it's easier to cut through an already installed floor than it's to plan for the ductwork while you are installing the subfloor and the finished flooring. There are a number of different kinds of supply registers, and each variety requires a different kind of opening. The rectangular ceiling register requires a rectangular hole between the joists. The round ceiling register requires a round hole cut in the ceiling. The floor register requires a rectangular hole through the subfloor and finished floor large enough to fit the pan snugly. The perimeter baseboard register requires a floor opening cut flush against the wall. The return-air grills are installed in rectangular cuts in the floor. The opening for the grill is the same size as the shoulders on the underside of the grill. To cut the opening in the floor, drill four holes (1” in diameter), one in each corner of the opening, and use a saber saw to complete the opening. If the register is to be located in the wall it must be positioned between the studs. This opening must also be lined up with the joists in the floor below (or above if your plan calls for an overhead supply) to allow for the supply duct from the basement. (If the walls of the house are already enclosed, cut the hole for the register as required. For cutting gypsum board, use a fine- toothed saw and cut continuously around the outline.) The fuel supply should be installed by the heating contractor or a plumber. All electric connections should be made by an electrician. Installing the Air Supply Registers Floor registers consist of two parts, a face and a pan. Slip the pan in the hole cut for it and screw through its sides into the opening edges. Slip the register face into the pan. Perimeter baseboard registers have a register extension, which fits into a hole cut for it. The back plate is nailed to the wall behind it. The register face is then attached. Rectangular ceiling registers have a face and a boot. The boot is designed to fit snugly into the cut hole. Wood blocks are nailed to the joists on each side, and the boot is nailed to the blocks. The face is slipped into the boot and is secured with screws. Wall registers attach to boxes called stack- heads. The wall opening must have the same dimensions as the stackhead. Wood blocks cut to the required width are nailed to the adjoining studs and the stackhead is secured to them. The register face is positioned on the stackhead and screwed to it. Return-air grills fit directly into the openings cut for them. When the grill is in place on the floor, the flanges rest on the periphery of the opening. Wall grills fit between the stud spaces. The grill is supported by wood blocks nailed to the studs. The grill is attached to the blocks with screws. INSTALLING A NEW HYDRONIC HEATING SYSTEM OR MODIFYING AN EXISTING ONE If you are adding one or two more convectors to an existing system (check Section 19 first to see if the system can handle the additional heat loss), you can tap into existing hot-water pipes. If you are installing a brand-new hot-water system, five procedures are involved. First, the boiler and its paraphernalia are installed. Second, the connection to the fuel supply is made. Third, the baseboards are assembled and temporarily placed in their final locations so that holes can be drilled through the subfloor. Fourth, the hot- water pipes are run from the boiler to the base boards and connections are made between boiler and household plumbing. Last, the baseboards are permanently installed after finished walls and floors are completed. We recommend that you hire a heating con tractor to do this work. At the very least (and it's usually required by law), have the contractor install the burner and boiler, connect the fuel sup ply and smoke pipe, and make the electric and thermostatic adjustments. Tools: Most of the tools required for joining and cutting pipe are outlined in the prev. section. Materials: • Copper tubing: the sizes outlined in the design drawings. Always order about 5 % more than the lengths measured off the drawings, which are never completely accurate. Extra pipe length will be required where fittings have to be made. • Elbows, air vents, etc., as required • Flexible connectors used as expansion joints • Baseboard units, as designed All equipment required for the installation of the boiler and burner • Smoke pipe Installing the Boiler and the Smoke Pipe All boiler manufacturers make their products differently. Some are shipped preassembled; others are shipped in parts. Have a heating specialist install the burner and the boiler to ensure that all of the safety equipment is in place. Instructions for installing the smoke pipe can be found in the section on forced-air heating above. Locating the Baseboard Units Before installing the hot-water tubing, it's a good idea to determine the exact location of the base boards even though these units will not be in stalled until later. Place the units in their anticipated locations (most likely under the windows). If the gypsum- board walls aren't yet installed, allow for their thickness and , if the finished floor isn't in place, the thickness of the flooring. Slip on all fittings and connections and temporarily assemble all end panels and accessories. To determine the location of the supply and return risers drill exploratory holes to make sure you are clear of the joists and any other obstructions. If the assembly coincides with the joists, the baseboard units on the floors above can be shifted a few inches to clear the structure. In the case of a corner baseboard installation, the base board can be cut slightly or a flexible connection can be arranged. The exploratory hole is drilled with a 1/4” bit from above in the center of the projected pipe. The hole is inspected by going down to the floor below. If the exploratory hole should prove to miss the framing and provides a clear path, enlarge it to accommodate the size of the actual riser. Metal expands as it's heated, and the entire system is expected to move somewhat depending on the temperature of the water circulating in the pipes. To accommodate this movement, oval holes— larger than the risers themselves, with the long side of the oval parallel to the long run of pipe in the basement—are cut through the floor. Drill two holes and cut in between them. For up to 25’ of baseboard the long end of the oval should be 1 1/2”. If the length of baseboard assembled in the room exceeds 25’, add another 1/8” to the hole for each additional 10’ of baseboard length. Installing the Hot-Water Pipe The directions for installing the hot-water pipe are the same as those for the installation of the domestic water supply system. Since all of the connections are to be made from rigid copper tubing, directions for cutting the pipe, connecting it, and running it through the walls and across the floors can be found below. Install the pipe system, making all connections permanent except those to the baseboards. If there is more than one loop to the system, one entire loop should be completed before another loop is started. Begin at the supply end and assemble the pipe lengths according to plan. Assemble each connection and be sure it's watertight before going on to the next connection. Support the pipe every 10’ or 12’ as you progress. Hot-water pipe will expand and contract. (Copper tubing can expand as much as 1 1/2” per 100’ of run.) To accommodate this expansion without placing stress on the pipe you can construct expansion joints from elbows as shown. It is much simpler, however, to use flexible connectors, which not only take care of expansion but reduce vibrations, eliminate soldering connections, and compensate for errors in measurement. The flexible pipe is made up of ring-like corrugations of copper, allowing the pipe to bend. Installing the Baseboard Units Install the baseboards after the finished walls and flooring are in place. The baseboard units are designed to be screwed to wall framing and rest on the finished floor. Remove the innards from the units—that is, the heating element (the fins) and the front panels—and nail the rear panels to the wall. Use a punch to start the holes, and always nail the panels to the studs. (These can be located by tapping the walls with a small hammer and listening for a solid thunk.) Replace the heating elements and reassemble the units. Install the air-vent elbows at the return end of the baseboard. (You will not need to install valves for baseboards in a series loop.) The assembly now can be permanently joined. Solder the various components together, removing them, if possible, from the floor to an elevated working area. Soldering instructions for rigid copper conduit can be found above. Next: Modifying the Electrical Wiring |
