Steam Balancing Protocol

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Steam Balancing Protocol





I have incorporated study results from the Center for Energy and Environment in energy audit work and the small amount of

field installation work I’ve done.  MNCEE

(dot ORG) studies include balancing single-pipe steam, boiler vent dampers,

front-end boiler, burner tuning according to a protocol, conversion of steam to

hot water,  (and others).  George Peterson’s “Achieving Even Space

Heating in Single Pipe Steam Buildings, 1985” can be used almost directly

as a balancing guide and specification.  Note

that studies of boiler performance were separate from balancing work, and

Peterson’s work assumes a well-functioning boiler.  Peterson’s studies lead him to say (most below is  paraphrased or re-stated from 32 pgs):





Steam system fill time is a function of mass of the

distribution system (including radiators) times specific heat (thermal

mass).   The main determinant of fill time is the ratio

of the boiler output to the heat capacity of the distribution system.





Fill time for the distribution system is directly related

to initial temperature of the distribution system – cycle needs to be longer in

mild weather,





Further, at

a given pressure the fill time of a radiator varies in proportion to its heat

capacity and  in inverse proportion to

the venting capacity of the radiator air vent. 







Proper air venting can be used to control the relative

speed of steam delivery to various radiators.





Beyond a certain open area, increased vent orifice size

has little influence on fill time.





Balancing can be achieved by following certain steps:





1) Increase main line venting and restrict steam to

radiators near the boiler (TRVs) as an initial balancing step.





2) Establish cycle length sufficient to fill all

radiators (if possible). Thermostat should  have an adjustable dead band,





3) Correct performance problems of radiators (slope,

valve, replace missing, etc.),





4) Reduce operating pressure setting or lower the

temperature in the building until cold discomfort is reported,





5) Increase venting where cold discomfort occurs.  Repeat reductions and “up venting” to balance

the building to the extent possible using variable orifice or adjustable

radiator vents.





6) Place TRVs at locations distant from boiler that

overheat, and possibly thermostatic inlet valve for radiators near a brick set

boiler to restrict steam entry on the off-cycle.





7) Though a formatted approach can be used, at a certain

point in fine tuning, steam balancing transitions from “science” to “art”





Space

temperature control is limited to about 4°F 

for temperature differences between apartments and  swings of temperature within an

apartment.  Energy savings of about

10%  are seen, although buildings that

have areas not kept at comfort temperatures may actually increase in energy

use. 



The original report contains a great deal of detail beyond this quick summary.







I hope to learn if this approach to balancing is

widespread and to hear about different practices and understandings.