How a Hot Water Zone System Works | |
In hot weather, a window air conditioner is an energy-and cost- conscious way to cool a specific room or area a house and in the winter a hot water heating system offers a similar option. You can divide the house into zones to heat a specific area, such as lowering the heat in bedrooms while they're not used during the day. Since the flow of water is easily controlled, a system can have several heating zones, each controlled by its own thermostat. Several schemes are used to move hot water to individual radiators or convertors located in the rooms. Most use a pump to circulate the water, which is kept hot in the boiler until the thermostat calls for heat. Then the circulation pump is turned on and moves the hot water from the boiler through the system. When the water in the boiler begins to cool off, the burner turns on to reheat the water. It doesn't matter if the boiler water is heated by gas, oil, or electricity. A non-zoned hot water system can usually be divided into two or more independent zones with the installation of electric zone valves. Depending on the existing piping, zone valves can be located at the boiler or at the head of each zone to control the flow of hot water. The installation is not difficult and the thermostat and control wiring carries 40 volts or less. There are three basic piping schemes used in hot water systems, a series loop, single pipe system and double pipe system. The simplest system is the series loop that uses only one pipe that runs from convector to convector. The water is piped into one end of the convector and out the other end to the next convector. All the water flowing through the system runs through each convector and shuts off any convector blocking the whole system. It's usually used in small, single-story houses. Similar to a series loop scheme is the single loop, where all the water circulates through a single pipe. The difference is that individual convectors tap into the main loop by means of a diverting T that shuts some of the hot water flowing in the main loop through the convector. It allows the flow of water to an individual convector to be regulated without disrupting the flow through the main loop. A large house may have a double pipe system, one forming a supply loop and the other, a return loop. The convectors are connected to the loops like a single pipe system. The water flow to individual convectors is controlled without affecting the others. You can usually tell what type of system you have by looking at the plumbing in the basement or crawl space. A series loop distribution exists when the heating pipes turn up to pass through the floor at a 90 degree elbow and come back down through the floor at the other end of the convector and connect to an elbow attached to a pipe leading to the next convector. Single or two pipe systems are the easiest piping schemes to add zones to. Look for a shut-off valve at the convector, which is one indication of this system. The valve should be able to stop the flow of water to the convector. (Don't mistake the air bleeder valve for a control valve.) Another tipoff is that individual hot water pipes leading from the boiler are a larger diameter than those leading to the individual convectors, which branch off the larger pipe at a T. Since the basic plumbing doesn't have to be modified zoning an existing single or two pipe system is not difficult. You install a zone valve at the convector so water flows through it and is controlled by a thermostat. To have totally independent zones, install zone valves at each convector. With only one zone valve in the system, the hot water can be prevented from flowing through the convector with the zone valve, but then the zone calls for heat and starts the circulation pump. Also, the hot water flows through the other convectors without zone valves. A single valve can be used to control areas that are usually too warm, like the second floor. When the area thermostat is satisfied, it closes the valve to prevent overheating. When the area cools down, the valve is opened but hot water doesn't flow until the rest of the house needs heat, which is usually sooner than the warm area. Zoning a Series Loop System Requires Some Additional Plumbing Modifying the system usually involves breaking the loop in the center and creating two or more zoned series loops. Most houses can be divided into two zones with the installation of an additional return pipe and two zone valves, which can be located at the boiler or at the head of the zones. An experienced do-it-yourselfer can handle the installation of a zone valve in a copper pipe baseboard system, but if you have a system with galvanized steel pipes, hire a heating contractor. To install the valve the system is first drained and then some of the aluminum fins and a short section of copper pipe is cut away from the convector. Then the valve is sweated in place. The flow arrow on the valve body must align with the water flow in the pipe. Apply heat to the end of the valve to prevent damaging it. While soldering, remove the valve actuating mechanism if possible. Wiring a Zone System The zone valves are energized by a small step down transformer located at the furnace. These transformers are usually capable of operating three zone valves, but check the specifications of the transformer. Both the zone valve and the transformer come with complete wiring diagrams. We used a Taco valve found at a heating supply house. In a zoned system the thermostat is wired to the zone valve. It opens or closes the valve which in turn controls the circulation pump and burner. A three conductor thermostat wire is easy to run through the crawl space or basement and fish through walls. One wire is neutral, the other carries the low voltage to energize the zone valve, and the third is wired to the circulator pump relay. In addition, run a two conductor wire between the zone valve and the thermostat. Best Tips: 1. To make room for the zone valve, remove about 8-in. of the aluminum fins from the baseboard convector. Grip the fin with pliers and pry it off the copper pipe. 2. Use a hacksaw blade holder and a fine-toothed blade to cut the pipe about 6 in. from the riser elbow. Heat the elbow with a propane torch until the solder melts; then remove the fitting and the short section of pipe. 3. To install the zone valve on the convector, cut a nipple from the old pipe to fit between the valve and elbow. Clean and flux all joints and then solder the valve in place using old fins as a heat shield. 4. When the valve is in place, wire it to the thermostat, low voltage transformer, and circulator relay. 5. The low voltage step-down transformer must be wired to the 115 volt supply line used to run the furnace. The transformer requires current at all times, even when the furnace burner or circulators are not operating. 6. The wires leading from the zone valve are connected to the thermostat terminals on the circulator pump or primary burner control, which the thermostat is wired to. 7. Most new installation and many older single or two pipe systems can have the zone valves installed at the furnace. This makes wiring simpler because a wire from the valve to the thermostat runs under the house or through the walls. 8. Wiring each zone valve to a programmable thermostat will allow your to regulate the mature through the house to match your family's lifestyle. Only two wires are required between the thermostat and the zone valve. Written by the editors of HouseNet. Copyright HouseNet, Inc. |