Home Remodeling Basics: Mechanical, Plumbing and Heating Systems
The electrical system in your home consists of a service entrance, where power enters the house, and various circuits composed of wires, outlets and fixtures that distribute the power throughout the house. Safeguards are built into the system to prevent shocks, overheating of wires, and short circuits between wires that shouldn’t be touching each other. The main disconnect, a switching device that can shut off all power in the house, may be a pull lever, a fuse block that is pulled out, or a main circuit breaker that can be flipped off. If may be housed in a panel box of its own, but it is often in the same panel as the fuses or circuit breakers for all the house circuits.
The main fuse block or circuit breaker has a limit to the electrical load it can carry. If that limit is exceeded, the breaker will automatically shut off electricity to the entire house, which prevents the entrance wires from overheating and causing a fire. The maximum current is called the service rating. Most homes today are wired for 100-, 150-, or 200-ampere service. However, older homes without updated wiring may have only 60- or even 30-ampere service. The rating is determined by the size of the service-entrance wires and cannot be increased unless they are replaced with larger wires.
Once power enters the house through service entrance, it is distributed through the circuits originating in the service panel. You may have from 4 to 20 separate circuits in your house, each protected by its own fuse or circuit breaker located in the panel. When a particular circuit is overloaded, the fuse or breaker shuts off power to that circuit and prevents its wires from overheating. You should know which circuits serve each room in your house. Since circuit wiring is concealed, you may never see it unless you crawl into the attic, open up a wall, or need to wire additional outlets and fixtures.
The service panel itself must be properly grounded by connecting it with a No. 6 wire to a metal water pipe, a copper-clad rod driven deep into the ground, an exposed end of foundation rebar, or a combination of the three. In turn, each outlet and fixture should be attached to a ground wire that leads back to the service-panel ground. When a short circuit or other malfunction occurs, the resulting surge of electrical power flows harmlessly through the grounding wire and to the ground, which is at zero volts. The surge also causes the fuse or circuit breaker to trip, shutting off the affected circuit.
In addition to proper grounding, ground fault circuit interrupters (GFCIs) are now required in all bathroom, garage, and outdoor receptacles. These devices prevent a person’s body from becoming a grounding path should a malfunction occur while handling equipment plugged into the receptacle.
The plumbing system of course is a different animal to deal with. Besides the actual fixtures, the plumbing in your home consists of two basic systems: a water supply system and a drain-waste-vent (DWV) system. The supply system provides water under pressure; the DWV system carries away water and wastes by gravity, and gases by convection.
The water supply lines are as follows: A main or service line supplies your home with cold, fresh water. The main normally comes through a basement wall or lower-level utility area. If your home is connected to a municipal water system, the water enters under pressure and travels through a meter. In private supply systems, water is pumped from a well or cistern into a holding tank. Air pressure in the tank creates sufficient water pressure for household use.
Once inside the house the main water line splits into smaller branch lines. One of these goes directly to your water heater. From there hot-water branch lines travel to fixtures that demand hot water, such as the kitchen sink and the bathroom washbasin, tub and shower. Cold-water supply lines also split from the main into different branches. One branch, for example, may supply water to the kitchen sink, another may supply water to an upstairs bathroom, and a third branch may supply an outdoor sprinkler system.
Shutoff valves, an essential part of your water supply system, are very helpful in remodeling. A main shutoff valve, located where the main line enters the house, will turn off the water to the entire house. Each branch run should also have a shutoff valve, as well as the inlet line to the water heater. Fixture supply valves beneath washbasins and toilets allow you to turn off the water to a particular fixture whenever necessary.
The aforementioned drain-waste-vent system depends on gravity to carry wastes away, which means the direction and pitch of the pipes is critical. A drain pipe must slope downward 1/4th inch for every foot of horizontal run, otherwise water would stand in the pipes and sludge would build up.
Each fixture or drain in the house must have a trap beneath it, a U-shaped dip in the line that remains filled with water. The trap seals off the waste line and prevents noxious fumes as well as vermin from entering the house.
Cleanout fittings allow access to each drain in case of plugging. Drain lines from each trap carry the wastes to a vertical pipe called a soil stack. The stack connects to the main house drain, which empties into a private septic tank or municipal sewage system.
Vent pipes are an integral part of the DWV system. These pipes rise vertically from the drain lines and connect to one or more vent stacks that exit through the roof of the house. The vents brings fresh air into the waste system and carry away unpleasant or dangerous gases that may accumulate.
Both the supply and DWV lines run within the walls and floors of the house. Holes are simply drilled through studs, joists, and plates wherever the pipes need to run. Code limitations on the size of notches and holes prevent the structural strength of the framework from being weakened. In some instances cuts in the studs and joists must be reinforced with metal plates to protect the integrity of the framing.
What about gas lines? Your remodeling project may involve altering gas lines. Although some homeowners are able to do this work themselves, with proper permits, you will probably need professional help. Among other things, gas lines must be sized carefully to ensure a steady flow of gas under pressure to the farthest fixtures. Also, only certain kinds of pipe, fittings, and joint compounds are allowed for gas lines.
Septic systems are not the same. For some remodelers, adding a bathroom or building a room addition may mean enlarging a septic system or even relocating it. This will involve installing a septic tank of the correct size, providing a vent (if needed), and laying an adequate array of leach lines. You should be familiar with the type and age of your system before going further with septic systems.
Unlike electrical and plumbing systems, which are essentially the same everywhere, heating systems vary widely in the type of energy they use and the means of distributing it. Some homes rely on space heaters, woodstoves, fireplaces, portable heaters, or wall and floor heaters. More commonly one of four types of central heating systems is in use, with solar alternatives becoming more prevalent in certain areas. Forced air is the most common central heating system. The heat producer is a furnace that burns oil, gas, wood, or coal inside a combustion chamber. Waste gases are vented outside through a metal flue and masonry chimney. When the air surrounding the combustion chamber gets hot, it’s distributed through the house in a network of ducts. In a slab foundation the ductwork is generally embedded with concrete. With a crawl space or full basement, sheet metal ducts run underneath and between the floor joists. In a two-story house the upper-level ducts run up the walls, hidden between studs or inside closets.
The furnace is turned on and off automatically by a thermostat, but the heat supply to each room can also be controlled manually. Dampers inside the ducts and at each register open and close to regulate the incoming warm air.
In a hot-water (also called hydronic) system, the furnace is a boiler fueled by oil, gas, electricity, or coal. The boiler heats water to about 200 degrees Fahrenheit, and small pipes (1/2 to 1 inch) made of galvanized steel or copper distribute the hot water to each room in the house.
If steam and cast-iron radiators are used, the system works with gravity. Pressure from the boiler and lighter density cause the steam to rise naturally within the pipes. Once it circulates through the radiator and condenses, the cooled water returns via the same pipe to the boiler, where the cycle begins again.
In a modern hot-water system, water is forced through the pipes by a circulating pump. Like a plumbing system, the hydronic system has a main supply line that branches from the boiler into two or more supply runs, or zones. After serving each room, the cooled water is cycled back to the boiler by a return line. Separate temperature controls are provided in different parts of the house.
The heat is dissipated into the room by baseboard heaters, which fit unobtrusively along the floor, most often along the outside wall of the house. Generally they’re only 8 to 10 inches high and 2 to 3 inches deep.
Homes equipped with electric radiant heat have no furnace, ducts, flue, or chimney. The source of heat is electricity flowing through resistance wiring, which can be installed in the ceiling between two layers of wallboard or beneath the plaster.
In mild climates the wiring if often located in the floor, embedded in the concrete slab. If the wiring is not in the floor or ceiling, baseboard panels are mounted along the floor. Some electric baseboards use only resistance wiring to heat the room. Others use electricity to heat water permanently sealed in copper tubing. Each heater is a self-contained hydronic system that needs no plumbing or separate water supply. Air drawn from the floor passes over the fins of the tubing and circulates upward to warm the room. The hot water continues to provide heat after the electricity is turned off by a thermostat.
The heat pump is a combination heating and cooling system that operates like a central air conditioner, with a reverse cycle for heating. Electricity is the energy source. In the summer the system withdraws heat from inside the house and dispels it outdoors. In the winter it extracts heat from the outside air and pumps it inside. The air is distributed through the house via sheet-metal ducts just like a forced-air system. If the temperature drops below a certain level, auxiliary electric resistance heaters kick in to provide supplementary heat.
Until recently heating systems were usually chosen on the basis of output of BTUs, fuel cost, and convenience of installation. Skyrocketing energy costs have caused homeowners, builders, and architects to consider heating systems from the standpoint of energy efficiency as well. Furthermore, they are not only concerned with how efficiently the heat is produced, but with how well the home retains it. Conservation measures like insulation, weather-stripping, and caulking are at least as important as installing an adequate heating system.
The most efficient and innovative designs are now tapping direct sunlight as the major heat contributor. The means of collecting it can be as simple as increasing the number of south-facing windows or attaching a hot-air collector to a south wall. Or it can be as complex as a complete redesign of the home to incorporate additional south glazing, substantial amounts of heavy mass, and a floor design that creates an optimum flow of natural air currents. In all cases solar heating designs require a home site with continuous exposure to the sun during the cold winter months for at least four hours in the middle of the day.
