| In a hot water (hydronic) heating | | | | in a hydronic system, it releases air |
| systems, water is heated in a gas, oil, | | | | which becomes trapped in the convectors, |
| or electric boiler and circulated | | | | preventing hot water from entering. To |
| through pipes to convectors; older | | | | release this air, most convectors are |
| systems use radiators. When the | | | | installed with air vents, which can be |
| thermostat calls for heat, a "circulator | | | | opened with a screwdriver until hot |
| pump" in the boiler return line moves | | | | water squirts out.Efficiency can be |
| water through the pipes to the | | | | improved by insulating pipes, or by |
| convectors, which give up heat to the | | | | partially closing convector shut-off |
| rooms. When the circulator is not | | | | valves in rooms requiring less heat. |
| pumping, a "flow-control valve" stops | | | | Systems can be divided into zones with |
| the water flow to protect the convectors | | | | one or more rooms controlled by a |
| from overheating.Older gravity systems | | | | thermostatic "zone valve". |
| have no circulator pumps and depend on | | | | Alternatively, a separate circulator is |
| lighter, heated water rising in the | | | | sometimes used for each zone, or you |
| pipes to the radiators; and cooler, | | | | could have thermostatic valves installed |
| heavier water gravitating back to the | | | | on each convector, but these options |
| boiler.Single-pipe systems, with short | | | | might be expensive.Boilers are more |
| branch lines to each convector, are used | | | | expensive to install than other systems, |
| in small to medium-sized houses. Two | | | | but are generally trouble-free, very |
| pipe systems use separate supply and | | | | efficient, and last much longer than |
| return pipes, and are more appropriate | | | | other types of heating systems.* |
| for larger houses, because cool return | | | | Some newer systems use non-metallic |
| water from convectors doesn't pass | | | | piping, installed in/under floors, to |
| through others. This maintains a higher | | | | distribute hot water in the rooms to be |
| water temperature at far ends of the | | | | heated. In some cases, a domestic oil |
| system.As heated water expands, an | | | | or gas-fired hot water tank can be |
| air-tight "expansion tank" on the hot | | | | fitted with a circulating pump, and the |
| side of the boiler takes in the excess; | | | | hot water directed to convectors or a |
| and if the tank fills up, a | | | | heating coil installed in a hot air |
| "safety-relief valve" on top of the | | | | plenum.Copyright Gil Strachan - All |
| boiler relieves the pressure. If this | | | | rights reserved.Gil Strachan is a |
| valve leaks under normal operating | | | | professional home inspector, |
| pressure, you can open it (beware of hot | | | | representing Electrospec Home Inspection |
| spray) and close it. If the dripping | | | | Services in east-central Ontario, Canada |
| continues, the relief valve needs to be | | | | since 1994. Visit to learn more about |
| replaced.Twice a year, if the circulator | | | | home inspections."The Home Reference |
| pump and motor are not permanently | | | | Book" |
| lubricated, add a couple drops of oil. | | | | You can probably find a home inspection |
| If you want to work on your boiler, shut | | | | for a little less than what we ask, but |
| off the power, let it cool down and then | | | | you probably won't find the Home |
| drain the system if necessary. Older | | | | Reference Book. A $60 value, this |
| tanks can be drained when they're too | | | | solutions-oriented reference tool comes |
| full, but newer "diaphragm tanks" should | | | | free with every inspection we |
| be drained only by qualified service | | | | perform.It's the first tool you should |
| personnel.When first heating cold water | | | | have around the house! |