7.SYSTEM CONTROLLER
Controlling of these systems is decided mainly by the type of building system controlling desired. A single boiler installation might be controlled directly from space temperature thermostat(s). Multiple boiler installations are more effective when the boilers are sequenced in and out of operation by some form of main water temperature controller. With one or two boilers, individual control settings at progressive temperature may be used. For more than two boilers, electronic sequencing controlling is recommended. Individual controls, or the separate stages of a step controller, should start the boiler loop circulator and fire the boiler. Some large installations may require the firing of more than one boiler per stage.
The system or primary circulator may or may not be controlled by the boiler sequencer. When this pump is operated through the first switch of any type of step controller, care should be taken to determine if a motor starter is needed due to insufficient switch capacity.
Multiple boiler installations are especially adapted to the use of outdoor reset for main water temperatures. This feature is not mandatory, but offers smooth, efficient operation of a modern system.
Normal use of flow control valves is required to prevent cross circulation of zones as with any multiple pump system.
Large systems with multiple boilers should include main water temperature controls (with or without outdoor reset) to sequence the boiler on and off, in relation to the load on the system.
24VAC System Controller (Optional) - VB models require a field supplied 24VAC operating control to be installed in the system such as: loop thermostat, indoor/outdoor reset control, sequencing panel, or energy management system. The connection for such devices is located in the junction box at the rear of the unit. A 24VAC thermostat/aquastat can only be used as an “On/Off” switch for the unit. The actual controlling of the phasing will be through either the inlet or remote probe. To use a 24VAC system controller, dipswitch “4” on the MCB must be switched to the “on” position, see
REMOTE PROBE INSTALLATION.
Internal Contaminants
The hydronic system must be internally cleaned and flushed after a new or replacement boiler has been installed, to remove contaminants that may have accumulated during installation. This is extremely important when a replacement boiler is installed into an existing system where Stop Leak or other boiler additives have been used.
Failure to clean and flush the system can produce acid concentrations that become corrosive, and leads to heat exchanger failure.
All hot water heating systems should be completely flushed with a grease removing solution to assure trouble-free opera tion. Pipe joint compounds, soldering paste, grease on tubing and pipe all tend to contaminate a system
Failure to flush contaminants from a system can cause solids to form on the inside of boiler exchangers, create excessive blockage of water circulation, deterioration of the pumps seal and impellers.
Hot Water Supply Boiler System - General Water Line Connections
This section provides detailed installation diagrams for a typical method of application for the unit.
Piping diagrams will serve to provide the installer with a reference for the materials and methods of piping necessary for installation. It is essential that all water piping be installed and connected as shown on the diagrams. Check the diagrams to be used thoroughly before starting installation to avoid possible errors and to minimize time and material cost.
It is essential that all water piping be installed and connected as shown on the diagrams. Check the diagrams to be used thoroughly before starting installation to avoid possible errors and to minimize the time and material cost.
Hard Water Conditions
Where hard water conditions exist, water softening or the threshold type of water treatment is recommended. This will protect the dishwashers, coffee urns, water heaters, water piping and other equipment. When water softening or water treatment is not practical, a comparatively easy method of periodic lime removal from the unit may be employed.
SHUTOFF VALVES SHOULD BE INSTALLED FOR SERVICING BOILER, HOWEVER, LOCAL CODES SHALL GOVERN THEIR USAGE.
Thermal Expansion (Closed System)
As water is heated, it expands (thermal expansion). In a closed system the volume of water will grow when it is heated. As the volume of water grows there will be a corresponding increase in water pressure due to thermal expansion. Thermal expansion can cause premature tank failure (leakage). This type of failure is not covered under the limited warranty. Thermal expansion can also cause intermittent Temperature-Pressure Relief Valve operation: water discharged from the valve due to excessive pressure build up. This condition is not covered under the limited warranty. The Temperature-Pressure Relief Valve is not intended for the constant relief of thermal expansion.
A properly sized thermal expansion tank must be installed on all closed systems to control the harmful effects of thermal expansion. Contact a local plumbing service agency to have a thermal expansion tank installed.
Remote Probe Installation Procedure
A remote probe is supplied with each hot water supply boiler (VW models). To connect the remote probe to the boiler, remove the cover from the junction box at the rear of the unit. Connect the probe wire pigtails, see Figure 7. Check the field connection diagram located on this cover of the junction box to assure proper wiring.
Once the remote probe has been connected to the boiler, it must be designated as the controlling probe for the system.
