Hot-Water (Hydronic) Boilers
Recommendations for operating and maintaining hot-water (hydronic) boilers are as follows:
1. Keep the boiler and the pipes in the heating system filled with water when not in use. Keeping the pipes filled with water reduces the possibility of rust and corrosion.
2. Check the water level in the boiler before starting it. The heat- ing surface can be damaged if the water level is too low.
3. Always add water to a boiler gradually. Never add water to a hot boiler. Shut the boiler down and allow it to cool first.
4. Check all boiler accessories to make certain they are function- ing properly. Movable parts should be inspected and oiled regularly. Such maintenance should also include the pump in a forced-hot-water heating system.
5. When operating a hot-water space heating boiler, make cer- tain all flow valves are open.
6. Never allow a boiler to exceed the upper safe temperature limit recommended by the manufacturer (usually about 200°F).
Boiler Water
Boiler water should be clean and kept clean for efficient operation.
This is true for all boilers. Never add dirty or rusty water to a boiler. Even hard water may eventually interfere with the efficient operation of a boiler and should therefore be chemically treated before being added.
The Steel Boiler Institute adopted a chemical conditioning com- pound for treating water used in low-pressure steam and hot-water space heating boilers. Many manufacturers provide this chemical compound with their boilers. Always treat the water immediately after the boiler and the heating system have been cleaned.
Note
Boiler water contains suspended solids that are held in sus- pension during boiler operation by the circulating water and the action of treatment chemicals. Unless care is taken when draining the boiler to remove these suspended solids along with the water, they remain in the boiler, dry and stick to the heating surfaces, and require chemical cleaning to remove.
A system compatible antifreeze, such as propylene or ethylene glycol, can be used in the water of a hot-water (hydronic) boiler, but only when absolutely necessary. Additional information about the use of antifreeze in boilers is contained in The Hydronics Institute’s Technical Topics Number 2A publication.
Some boiler heat exchangers are made of aluminum instead of steel. Only antifreeze solutions certified for use in aluminum boilers should be used.
Warning
Never use an RV-type antifreeze protection solution or an automotive-type antifreeze. Both types can damage the boiler and other system components.
Cleaning Boilers
A boiler should be inspected at least once every year for the accumulation of soot and other deposits that could impair its operation. This inspection should take place before the start of the heating season.
The accumulation of soot will result in improper combustion. The soot can be removed with a chemical cleaner or a flue brush. Many boiler manufacturers provide access to the heating surfaces through a removable top jacket panel and cover plates. The flue brush is used to push the soot down between the sections or fins to collect in the combustion chamber below. It can then be removed from the combustion chamber without much difficulty.
Oil burners, gas burners, and coal stokers should also be inspected for dust accumulations and cleaned. Always follow the manufacturer’s recommendations for cleaning the boiler and auto- matic firing equipment. If you do not have an owner’s manual, con- tact a field representative or write to the manufacturer.
Troubleshooting Boilers
Boilers are subject to numerous problems, many of which are due to improper type and design or poor servicing. The following are some of the problems usually encountered:
1. Boiler does not deliver enough heat. This is a very common complaint, but the boiler may not be causing the problem. The problem may be caused by a problem with the burner or the automatic controls. Even a pipeline with improper pitch will
cause the heat from the boiler to be blocked or trapped. If the boiler is found to be the cause of insufficient heat, the problem can be traced to any one (or more) of the following causes:
a. Boiler too small for the heating system
b. Improper arrangement of boiler sections in cast-iron boilers
c. Poor draft
d. Poor fuel
e. Heating surfaces covered with soot
2. Boiler delivers no heat. The automatic controls should be checked first. Sometimes a low-water cutoff on steam boilers will shut off the burner or stoker before enough steam has formed. Another possible cause is that too much water is being fed into a steam boiler. As a result, not enough space is provided for the steam to form at the top of the boiler. Too lit- tle water in a hot-water space heating boiler can be caused by the limit control moving down to a lower setting.
3. Too much time is required to get up steam in a steam boiler.
This common problem can be traced to the following possible causes:
a. Too little or badly arranged heating surface
b. Heating surfaces covered with soot
c. Heating passages too short
d. Poor fuel or fuel firing
e. Poor draft
f. Boiler too small
g. Boiler defective
4. Boiler is slow to respond to the operation of the dampers.
Slow response to damper operation can be caused by any of the following:
a. Air leakage into the chimney or stack
b. Poor fuel or fuel firing
c. Boiler too small
d. Clinkers on grate or ashpit full of ashes (coal-fired boilers)
5. Water line is unsteady. The problem of an unsteady water line may simply be due to connecting the water column to an extremely active section of the boiler. Therefore, it is extremely unlikely that the actual water level in the boiler can read from the water column. Other possible causes of this problem are:
a. Dirt or grease in the water
b. Varying pressure differences on the system
c. Excessive boiler output
6. Water disappears from the gauge glass. The complete loss of water from the gauge glass could be due to priming (i.e., water globules being carried over into the steam). Other causes include:
a. Foaming
b. Pressure drop too great in return line
c. Improper water gauge connection
d. Valve closed in the return line
7. Water is carried over into the steam main. This problem is usually caused by one of the following:
a. Priming or foaming
b. Water line is too high
c. Outlet connections from boiler too small
d. Steam-liberating surface too small
e. Boiler output excessive
8. Flues require cleaning too frequently. A frequent buildup of soot and dirt in flues can be caused by any of the following:
a. Combustion rate too slow
b. Poor draft
c. Smoky combustion
d. Excess air in firebox
9. Low carbon dioxide. This condition can generally be traced to one of the following causes:
a. Air leakage between cast-iron sections
b. Improper conversion job
c. Problem with burners
10. Smoke from boiler fire door. The following conditions may be the cause of this problem:
a. Dirty or clogged flues
b. Incorrect setting of dampers
c. Poor or defective draft in the chimney
d. Incorrect reduction in the breeching size
Boiler Repairs
Repairs to the boiler itself should be done by an experienced and skilled worker. They should never be attempted while the boiler is under pressure. Always shut down the boiler first and allow it time to cool before beginning any repairs.
Installing Boilers
All new boilers are shipped with a complete set of installation instructions. Usually these instructions will also contain an inven- tory list of the contents in the crates and cartons. Always check the contents off against this list before you do anything else. Missing or damaged parts should be immediately reported to the manufacturer or its local representative.
A boiler should always be located so that the connecting flue pipe between the boiler (or draft diverter) and the chimney is as short as possible. Another important consideration is the recom- mended minimum clearances between the boiler and combustible materials. These factors plus the design considerations of the system will dictate where the boiler is located.
The manufacturer’s installation guide will also contain instruc- tions on how to light and operate the boiler. The instructions will differ in accordance with the automatic fuel-burning equipment used (e.g., oil burner and gas burner).
After completing the installation of the boiler, inspect all the con- trols to make certain they are operating properly. Start and stop the burner or stoker several times by moving the room thermostat setting.
All local codes and regulations take precedence over the installa- tion instructions provided by the manufacturer. In the absence of local codes, the installation must conform with the boiler manufac- turer’s installation instructions plus regulations of the National Fire Protection Association, and the provisions in the latest editions of the National Electrical Code (ANSI/NFPA70) and the National Gas Code (ANSI Z223.1).