Installation & Service Manual
4Water connections
Primary/Secondary Boiler Piping (continued)
A primary/secondary piping system is ideal for systems filled with a propylene glycol and water mixture. A glycol and water mixture is more dense than water only and may result in a lower boiler flow rate. A lower boiler flow may cause noisy operation or short cycling of the burners. A larger secondary pump may be used on a primary/secondary system to provide an increased boiler flow rate. A glycol and water system may require from 10 to 20% more flow to compensate for the increased density of the glycol and its effect on the heat transfer process in the boiler. The exact increase in flow that may be required is based on the type and percentage of glycol added to the boiler system. Consult the manufacturer of the glycol for additional recommendations when using a glycol and water fill for your boiler system.
The installer must ensure that the boiler has adequate flow without excessive temperature rise. The temperature rise on a multiple zone system should be made when only the zone with the longest length and/or highest head loss is open. Low system flow can result in overheating of the boiler water which can cause short burner on cycles, system noise and in extreme cases, a knocking flash to steam. System noise may also indicate an oversized boiler.
CAUTION | At no time should the system pressure be | |
less than 12 PSIG. | ||
|
A boiler operated with an inlet temperature of less than 140°F (60°C) must have a bypass to prevent problems with condensation. A bypass as shown in FIG.
Full Flow Application
It is acceptable for the Solution boiler to be installed in a full flow application, as long as the following requirements are met:
1.The performance loop is in place and functional.
2.The system flow is not lower than the minimum boiler flow.
3.The boiler setpoint is 140°F or higher.
4.If water temperature is below 140°F you must install a low temperature bypass, VAL30000, and follow the piping diagram shown in FIG.
WARNING Varying the flow through a Solution boiler can cause harmonic noises and high limit
trips if the flow is below the minimum boiler flow rate found in Table 4A.
Low Temperature Bypass Requirements
Inlet water temperatures below 140°F (60°C) can excessively cool the products of combustion resulting in condensation on the heat exchanger and in the flue. Condensation can cause operational problems, bad combustion, sooting, flue gas spillage and reduced service life of the vent system and related components. The bypass allows part of the boiler discharge water to be mixed with the cooler boiler return water to increase the boiler inlet temperature above 140°F (60°C). This should prevent the products of combustion from condensing in most installations. The bypass should be fully sized with a balancing valve to allow for proper adjustment. A valve must also be provided on the boiler discharge, after the bypass. Closing this discharge valve forces water through the bypass. Start boiler adjustment with the bypass valve in the full open position and the boiler discharge valve half open. A small amount of the higher temperature boiler discharge water is mixed with the system water to maintain the desired lower system temperature.
Boiler Flow Rates
CAUTION The maximum flow rate through the boiler with a copper heat exchanger must not
exceed 30 GPM.
The heat exchanger is generally capable of operating within the flow rates of a residential heating system. Should the flow rate exceed the maximum allowable flow rate through the boiler 30 GPM) an external bypass must be installed. The bypass should be fully sized with a balancing valve to allow for proper adjustment of flow. Flow rate can be determined by measuring the temperature rise through the boiler.
The basic guide for minimum flow in this boiler is based on a 40°F temperature rise in most installations. Lower flow and a higher temperature rise is acceptable if the boiler system is specifically designed for the characteristics of a higher temperature rise. A system not specifically designed for a higher temperature rise may experience overheating of the boiler water. This can cause short burner on cycles, system noise and in extreme cases, a knocking flash to steam. These conditions can lead to operational problems and
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