Steam Balancing Protocol

Therm_lag

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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.  

Steamhead

Well, first of all

I've never heard of this book. I'd want to read it before speaking to this. Where can I get a copy?



The one thing I'll say now is that converting steam piping and radiators to hot-water can open up some big cans of worms. Our company does not recommend or perform such conversions. We find we can get similar results by fixing steam systems, at considerably less cost and risk.

Mike Kusiak_2

Steam balancing

Attached is the article regarding efficiency gained from proper balancing of steam systems. More studies and articles can be found here:



http://www.mncee.org/research/technical_publications/index.php

Steamhead

I thought those articles looked familiar

they formed the basis for the book, "Improving Energy Efficiency in Apartment Buildings", published by ACEEE. Released in 1995, it was likely put together before anyone had ever heard of Dan's "The Lost Art of Steam Heating", so some of the information therein is out of date.



Therm_Lag, the best article I've seen on balancing steam systems is in an e-book you can get here:



http://www.heatinghelp.com/products/Books/5/146/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-by-Gerry-Gill-and-Steve-Pajek



Gerry and Steve, through extensive testing of vents and steam traps under controlled conditions, have reduced the selection of air vents to a set of calculations. Once in a while you need to fine-tune the results but their methods at least get you 90% there. The objective is to fill all the mains with steam before starting to heat the radiators- even those close to the boiler. So there shouldn't be any need to over-vent the furthest radiators, which can cause banging on one-pipe systems.



TRVs take control to the next level, letting occupants limit the temperatures in their rooms if they wish.



Besides "Lost Art" and the Gill/Pajek e-book, get a copy of Dan's brand-new book "Greening Steam". It specifically addresses some of the easiest, least costly ways to make steam systems more efficient and more comfortable. They're all in this site's online store- click "Shop" at the top of this page to get there.