ECMI and eTracLogic Systems has developed an easy way to determine
approximate space-heat boiler efficiency for comparative purposes. It is a
valuable way for facility managers to get an idea on how efficient a
space-heat boiler (or cooling tower) is operating over a given period of time.
We describe the value as **rFactor**, (meaning boiler **r**un-time
**factor,** not to be confused with r-value). The concept is
actually quite simple. We wanted to arrive at a value to show how many
"miles per gallon" a boiler is getting. We arrived at the conclusion
that to determine this, one simply needs to take the daily boiler
runtime divided by the Heating Degree Day value for that day. (a
Heating Degree Day is the average temperature for the day subtracted
from 65). The resulting value is a ratio or **factor**
which indicates how the
boiler is reacting to varying outside temperatures at a specific site.
**For example:** If the degree day value for a day is 23.5
(an average temperature of 41.5 degrees F) and the boiler ran for 10.98
hours that day, then the rFactor value would be: **10.98
divided by 23.5 = .46723**
**Note that the one caveat to using the rFactor method is that
days for which the boiler runs less than 2 hours should be omitted to
get valid average data values. This is because we have found that
dividing into a value (or by a value) approaching 1 significantly skews
the data set.**
To use the formula for yourself, monitor a boiler's daily run-time, get the Heating Degree Day information for the
monitored period, and perform the daily calculations. (this can also
easily be done by creating a spreadsheet)
Be aware that rFactors will vary quite a bit from site to site. We have monitored
numerous boilers and have arrived at a basic data set that gives a good
indication of how efficient a boiler is operating. Use this
information only
as a guideline. **Note that higher rFactors indicate better
overall boiler
efficiency.**
More on
Improving Boiler efficiency |