Burnham Series 8H/8HE Boiler Manual De Propietario

3.1    Breeching ducts are generally less flexible in design 

location than are water pipes.  To avoid conflicts for a 

given location, design and layout the breeching ducts 

before proceeding with water piping in this section.

3.1.1 The purpose of the Section 3.0 is to recommend 

piping systems and accessories that can be used with 

Series 8H/8HE Modular Gas Boilers.  Although 

recommended design procedures are presented, the 

final sizing of mains, pumps and compression tank 

must be left to the designer of the total system because 

only that designer has available the requirements and 

capacities of the connected system.

3.1.2  Please consider the serviceman who must periodically 

clean and adjust the boilers and repair accessories.  

Do not block passageways with piping.  Do not block 

access panels on the boiler jackets.

3.2    MANIFOLDS—Selection of the proper manifolds is 

important to the success of the modular concept.  One 

of the prime reasons for using modular boilers instead 

of a single large boiler is to improve the seasonal fuel 

efficiency.  Boiler losses are highest when the burner 

is off and the boiler is still warm.  Thus, if one small 

module can carry the heating load during mild outdoor 

weather by nearly continuous firing, a significant loss 

can be prevented and greater utilization of fuel can 

be made.  However, poor selection of manifolding 

can wipe out part or all of the potential fuel savings 

of the modular system.  Some provision should be 

made to prevent water from flowing through any 

module when it is not being fired.  When warm 

system water is allowed to flow through any unfired 

module, heat is being wasted by convection through 

the chimney and jacket of that unfired module.  For 

example, on an eight module system fired by an eight 

step sequencer, only one module may be required 

to meet the connected load demand on a day that 

is 55°F outdoors.  That would be a highly efficient 

operation.  However, if the system water is allowed 

to flow through the other seven modules, they too are 

kept warm and the total jacket and flue losses of the 

eight modules may be as great as that of a single large 

boiler.  Thus, intended benefit is lost.

3.2.1  Figure 3-1 shows a typical parallel pumping system.  

Parallel pumping of modules does not prevent flow 

through unfired modules as commonly installed.  

Thus, parallel pumping is not desirable unless a 

motorized valve is used on the supply pipe from each 

module and controlled to open only when that module 

is fired.  With motorized valves, the owner may find 

objectionable noise from high velocity water flow 

under light loads when the entire flow of the system 

pump is directed through only one module of the 

group.

3.2.2  By contrast, primary-secondary pumping provides 

positive flow through each module only when that 

module is fired.  Figure 3-2 shows such a system.  

The piping is simple and uses only a single header 

made up of fabricated steel manifolds available as 

optional equipment.  By keeping the head above 

the top of the modules as shown in Figure 3-2, any 

gravity circulation from header to unfired modules 

is prevented.  Flow through each fired module is 

balanced as a result of having its own secondary 

circulator.