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3.4.3
Recommended Pipe Connections
Installation of flexible connections in the flow and return
heating pipework is recommended to ensure that stress
is not transmitted from the pipework to the heat
exchanger. It may also be necessary to install flexible
connections in the gas line. It is recommended that
inline strainers are provided in the water circuit. The
pipe connections are as detailed in the following table.
Piping
Pipe Connections
Hot water circuit
3 in. BSP
External oil
3/4 in. BSP Cone (for external oil
cooling
cooler)
3.4.4
Micro Turbine Fully Recuperated
System Typical Heating System
Applications
It is not intended here to address all the systems likely to
be encountered when installing a micro turbine. Two
typical systems are outlined below. In both systems, it is
essential that the micro turbine be used as a lead boiler
to maximize the benefits from the system. In both cases,
it may be beneficial to operate with a thermal dump
during summer months. The decision on whether to
include a dump cooler will have to be considered on an
individual site basis.
Series Connected Boilers
In this example, the micro turbine is operated as the lead
boiler and is enabled at all times when heating is
required. Subsequent boilers are enabled as the return
water temperature drops in a manner proportional to
temperature. Firing of other boilers should be controlled
by packaged boiler thermostats on individual boiler
outlets. This is recommended for simple, effective, and
reliable control and is ideal when the minimum heating
demand is predictable and is above the amount
available from the micro turbine.
At low heat demands, set the control to avoid switching
the micro turbine on and off. If necessary, use a dump
cooler. Constant flow is needed in the primary circuit at
all times. Run-on of the primary pump on shutdown is
recommended to dissipate heat. Figure 3-5 shows a
possible arrangement for the micro turbine with a
package boiler.
Parallel Connected Boilers
In this example, the micro turbine is again operating as
the lead boiler that is enabled at all times when heating is
required. As above, subsequent boilers are enabled as
the return water temperature drops in a manner
14
Section 3 Installation Requirements
proportional to temperature. Individual boiler firing is
controlled by packaged boiler thermostats on boiler
outlets.
Maintain constant flow in the primary circuit at all times.
The primary circuit pump has lower power absorption
due to the low resistance of the primary circuit. Some
dilution of flow temperature occurs at low loads and is
normally of little importance but increases with the
number of other boilers. Figure 3-6 shows a possible
arrangement for a micro turbine with other packaged
boilers.
Protective Devices by Installer
Install an independent temperature switch set at 95
°
(203
F) as close to the heat exchanger as possible to
protect against high temperature by shutting down the
hot water system. Installer must supply a pressure
expansion tank on the hot water loop and provide
vacuum relief for the system, if required.
Micro
Turbine
Figure 3-5 Series Connected Boilers
Micro
Turbine
Figure 3-6 Parallel Connected Boilers
Boiler
Boiler
TP-6242
°
C
8/03
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