4 Water connections (continued)
Pump Maintenance: Inspect the pump every six (6) months and oil as necessary. Use SAE 30
The boiler is recommended for installation in a primary/ secondary piping system. This type of system uses a separate boiler circulating pump to supply flow to and from the boiler only. The secondary pump is sized based on the head loss of the boiler and related pipe and fittings in the secondary loop only.
A properly sized primary system pump provides adequate flow to carry the heated boiler water to radiation, air over coils, etc. The fittings that connect the boiler to the primary system should be installed a maximum of 12 inches (0.30m) (or 4 pipe diameters) apart to ensure connection at a point of zero pressure drop in the primary system. There should be a minimum of 10 pipe diameters of straight pipe before and after the boiler secondary loop connections to prevent turbulent flow at the secondary loop connections. The secondary loop piping to and from the boiler must have a fully ported ball valve installed in both the supply and return side piping. The ball valves must be fully ported having the same inside diameter as the installed piping. The ball valve in the piping supplying water to the boiler will only be used as a service valve. The ball valve installed in the discharge from the boiler back to the primary system will be used to adjust boiler flow and temperature rise to ensure proper performance.
The boiler primary piping system must have a circulator installed in the main system loop to carry the heated boiler water to the point of use in the main system.
Multiple boilers may also be installed with a primary/secondary manifold system. Multiple boilers should be connected to the common manifold in reverse return to assist in balancing flow to multiple boilers.
The installer must ensure that the boiler has adequate flow without excessive temperature rise. Low system flow can result in overheating of the boiler water which can cause short burner cycles, system noise, relief valve discharge and in extreme cases, a knocking flash to steam. These conditions indicate the need to increase boiler flow to and from the boiler. This is generally accomplished by either increasing the size of the boiler pump or by increasing the diameter of the piping that connects the boiler to the primary system. A larger diameter pipe reduces head loss and increases flow.
CAUTION | At no time should the system pressure be less |
| than 12 PSIG. |
| Do not allow the flow in the primary loop |
CAUTION | |
| to drop lower than the flow in the secondary |
| |
| loop at any time during boiler operation. |
| Improper operation of the boiler(s) and |
| possible tripping of the high limits and relief |
| valves may occur. |
Installation & Service Manual
Minimum boiler water temperatures
Inlet water temperatures below the specified minimum of 140°F (60°C) can excessively cool the products of combustion resulting in condensation on the heat exchanger. Condensation on the heat exchanger can cause operational problems, bad combustion, sooting, flue gas spillage and reduced service life of the related components. See the Low Temperature Bypass Requirements section for boiler system applications below the minimum specified temperature.
Low system water volume
System run time is very important to the overall operating efficiency of the boiler. Short cycling of the boiler creates problems with condensation in the vent stack, condensation on the heat exchanger, system temperature spikes, and mechanical component failures. To prevent short cycling of the boiler, it is important to limit the boiler cycles to six or fewer per hour.
A buffer tank is an effective way to enhance a small system load and increase heating system efficiency (see FIG.
To calculate the proper buffer tank size for a multiple zone system:
(Run Cycle) (Output - Minimum System Load)
(Temp. Rise) (8.33) (60 Min.)
CFN2067
Min. Load = 100,000 Btu/Hr
Min. Boiler Output = 850,000 Btu/Hr
Cycle Time = 10 Min
Temp. Rise = 38
(10)(850,000 – 100,000) / (38)(8.33)(60) = 395 Gallons
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