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  'HELP SITE' - Added by Anonymous User.  Posted: 1/7/2014
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  'Basic Boiler Controls' - Added by jww1@hotmail.com User.  Posted: 10/24/2006
Hot water boilers share a common set of devices that insure safe and accurate boiler control. Each of these controls should be checked periodically to insure proper operation and none should be disconnected or bypassed to obtain temporary heat.

A pressure relief valve acts as the primary safety device. It has been accurately sized to blow off hot water at a rate greater than the input rate of the burner. Pressure relief valves should be inspected in advance every heating season to insure they will open. Periodic pressure testing done off the boiler is appropriate.

The aquastat controls the operation of the burner by shutting it down when operating temperature has been reached. They have a limit setting, usually 180 F, and a differential setting, usually 20F.

On atmospheric gas boilers a rollout switch should be present near the burner tray. This temperature switch shuts off power to the gas valve should flame roll toward the gas valve.

The blocked vent switch is a similar type device that helps detect a blocked chimney. Should combustion gas spill from the draft diverter the blocked vent switch shuts power to the gas valve.

The gas valve controls the flow of gas, either natural or propane, to the burner. Gas valves provide several functions acting as a shutoff valve, a pilot regulator, a burner gas pressure regulator, and a backup shutoff valve.

  'The Fine Art of Purging Air' - Added by jww1@hotmail.com User.  Posted: 10/24/2006

Air trapped in the piping is the natural enemy of hot water heating systems. Air circulating in the system makes noise. When large enough pockets of air collect, circulation of water (and heat) can be reduced or completely stopped.

Air combines naturally with water as it falls from the sky as rain. Cold water holds surprisingly large quantities of air. When that water is heated it surrenders the air. You have seen this happen hundreds of times when you draw a glass of cold tap water and leave it on the counter. An hour later the water has warmed from roughly 50 F to room temperature and small bubbles cling to the side of the glass.

A well designed hydronic system will purge air as it leaves the boiler. An air purger is usually installed on the supply side of the boiler, right after the expansion tank and ideally just before the circulating pump. Since the water is hottest at this point and the system pressure is lowest the air can be separated from the water before it gets trapped out in the heating system.

Some older more complex systems may require purging vents out in the system but usually the arrangement shown and a careful startup routine are all that is required to purge the system and keep it free of air.

  'The Hydronic Heating Loop' - Added by jww1@hotmail.com User.  Posted: 10/24/2006

Some of the simplest ideas turn out to be the best. Hydronic heat, commonly referred to as hot water heating, offers the essence of simplicity and efficiency in heat distribution. Hot water generated by a boiler, hot water heater, or heat pump is circulated through piping to heat emitters placed strategically throughout a building providing warmth where is needed.

These heat emitters may include baseboard radiation, kickspace heaters, radiant ceiling panels, or in-floor heating loops. Since heat emitters come in a variety of styles they can easily blend with the room decor. Heat emitters provide larger surface areas that quietly and quickly distribute heat to the surrounding area.

Since water molecules tend to stick together the weight of water flowing down a return line offsets the weight of water rising up the supply side. A heating loop works like a continuous chain looped over a pulley. The weight of links rising is offset by the weight of links moving down. Very little energy is needed to keep a flow moving.

Water molecules can hardly be compressed. When we increase pressure at one end of a pipe full of water the molecules move toward the other end. Connecting the piping in a loop and adding a pump to create a pressure differential causes the water to circulate. The pump only has to overcome the friction of the water flowing through the pipes. Unlike warm air heating that looses a percentage of its heating media to exfiltration, the hydronic system returns 100% back to the boiler to be fully reheated and cycled again.

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