Boiler Preventive Maintenance

Hot Water Circulating Pumps	Automatic Vent Damper
Auto Air Bleeders	Pressure Relief Valve

Hot Water Boiler Preventive Maintenance
The following only refers to boiler system in general and is for educational purposes only. Refer to your owners' manual or consult with your local boiler technician for proper maintenance procedures and operation of your heating system. The procedures described here should only perform by a qualified technician. Serious injury or death could result if improperly handled. Boiler Pressure

Look for a temperature Pressure Gauge on the front of your boiler. Normally just above the burners. For most residential and small commercial systems this pressure should be 12-15 pounds. Read the gauge when the boiler is cold and the circulating pump is off. This will show the static water pressure of your boiler set by the water feed regulator. A higher pressure can be a result of the regulator being set to high or leakage.

Expansion tank

As water is heated it will expand and occupy a larger volume. There must be room for this expansion, else the pressure will climb. There are two types of expansion tanks. A Diaphragm Tank, which uses a bladder, filled with compressed air, or a steel holding tank, which traps air in the top, half. The diaphragm tank is charged with air to the same operating pressure of the boiler. Do not release or add air to the tank while it is piped to the boiler system or it will not function properly. Tap on the tank and it should sound hollow. If the bladder has leaked or is not properly charged, it will fill with water. For the steel holding tanks there should be a sight glass on the front of the tank to indicate the water level in the tank. The tank should be about half full. If the tank is filled near the top or completely filled the water will have to be drained off. Turn the boiler off and attach a hose to the drain valve. Close the valve that connects the expansion tank to the boiler and open the drain valve. Drain the tank until it is empty. Then close the drain valve and open the valve to the boiler system. The expansion tank should filled to the half way mark or less and trap air in the top of the tank. If the tank fills again after a few days then there is an air leak in the tank.

Pressure Relief Valve

Every boiler has at least one pressure relief valve. If the pressure climbs too high on your boiler it will open and blow off the excessive pressure and close again when the pressure falls below the setpoint. There should be a tag on the valve to tell you at what pressure it will open. Most residential boilers will be set to 30#. If your boiler is operating close to this setpoint the pressure relief valve will leak. At least once a year this valve should be open to blow off water and make sure it has not plugged up with sediment and scale. Check the boiler pressure before you begin, if it is close to the setpoint the relief valve will not close. The outlet of this valve should be piped to 6" above the floor and to a place where it will not cause water damage if opened. It can be piped directly to a floor drain, but the outlet should be open so any leakage can be detected. Use a bucket to catch the water if needed, but make sure you know where the boiler feed water shut off is, just in case. With the boiler off and cold, lift the manual lever and blow off some water for a few seconds and let the lever snap back. There should be a good gush of water that comes out and be fairly clear water. If the valve has small leaks after wards, just open it again and let some more water out, sediment can become trapped in the seat causing minor leakage. If the valve will not close at all shut the boiler water feed off and remove and replace the relief valve. If no water comes out, then the valve is plugged or there is no water in the boiler. In either case do not use the boiler until it is replaced or repaired.

Circulating Pump

Most boiler pumps require lubrication for the motor and the pump. The motor normally requires a few drops and the pump may have and oil well, which needs to be filled to keep the oil wicks wet. Refer to the manufacturer instructions for lubrication procedure for you pump. There maybe more than one pump on you system. The volume of water circulated by the pump is very important to the boiler operation. Too little water will boil inside the heating coil and plug it with scale. This will sound like a crackling sound inside the boiler when the burner is operating. When the burner is operating check the temperature rise through the boiler. Most are designed for a 10°F TD. If the TD is much greater than that then there is not enough water flow.

Temperature Setpoint

There should be 4 temperature controls on a hot water boiler system. Room Thermostat, Boiler Water Temperature Control, Circulation pump temperature control, and the safety high limit control.
The operating setpoint is normally an external control to the boiler. It controls the temperature of the circulating water. This can be a fixed setpoint set around 160°F to 180°F or preferably an Outdoor reset controls. These will raise the boiler water temperature the colder it gets outside and lower the water temperature the warm it gets outside. Outdoor reset controls can save a lot of money on a boiler system. It also has a minimum boiler temperature of 130°F to prevent condensation inside the boiler and will shut the boiler off it get too warm outside.
The Room Thermostat can be used to open a zone valve, which in turn enables the boiler, or enables the boiler directly.
The circulation thermostats is used start and stop the circulate pump and can be combined in the same control as the high limit, normally set around 100°F
High limit control will shut the burner off if the water temperature gets too high, check with the boiler manufacturer for the proper setpoint. These are normally around 200°F but can be higher or lower. I have often found these being used as the operating control for the boiler because they are shipped with the boiler and the installer does not add the external operating control leaving the boiler without a safety high limit control.

Coil Cleaning

Atmospheric boilers are used extensively in residential and small commercial applications for space heating, potable hot water and for pool and spas. The finned coils on these units plug up externally from the flue gas passing between the fins. This reduces heat transfer and causes flue gas to spill out the front of the boiler. Every few years the draft hood and casing need to be removed and the coil needs to be cleaned. If you notice staining on the face of the boiler or can feel hot flue gas spilling out the front of the burners then coil is likely starting to plug up.

Automatic Draft Damper
Many of the new atmospheric boilers come equipped with automatic draft dampers. These dampers save a lot of fuel by stopping the draft over your heating coil and cooling the water off when the burner is shut down. The damper is interlocked to the burner and is plugged directly into the ignition control. The damper should drive closed when the burner is off and drive open before the burner starts. Over the summer this damper can seize and not open. Stopping the burner from coming on or it may stick in the open position and still allow the burner to operate but not closes off when the burner shuts off. Use a flashlight and have a look in the vent for the damper. Check and make sure it is doing it's thing.