Making Boiler Runtime More Efficient

April 1, 2008

With a goal of running your buildings at peak operating efficiency, one of the most effective way to do this is by controlling boiler runtime

Thousands of apartment and office buildings still have boilers that run on a clock. For example, if it's 10 a.m. and 30 degrees F. outside, the boiler is on. If it's 3 p.m. and 54 degrees F. outside, the boiler is still on - and it's probably 80 degrees F. inside, driving tenants/occupants to open windows (wasting money and increasing carbon emissions).

The goal is to run your buildings at peak operating efficiency, and the most effective way to retrofit a centrally heated building to do this is by controlling boiler runtime. Today's energy-management systems (EMSs) can regulate boiler runtime based on indoor temperature - if it's 54 degrees F. outside and 72 degrees F. inside, the boiler turns off. An EMS is advanced technology, but, essentially, it equips commercial property with thermostats similar to the ones that single-family homes have used for decades.

An EMS can, of course, do more. For example, some systems regulate boiler runtime based on indoor temperature, but will also cut off the burner if runtimes exceed calculated norms. This is very important: You don't want to waste fuel if there's a major leak and steam is escaping as fast as the system can heat it. Some systems also monitor make-up water and can detect those leaks, and alert property managers before they become major problems.

Many EMSs can also track stack temperatures to ensure that heat is being transferred efficiently to the boiler and not lost up the chimney. It is also important to monitor mixing valve temperatures to make sure that hot water isn't scalding hot. The object is not to get burned (literally or in the pocketbook).

Another valuable EMS adjustable runtime control is an "aquastat" for buildings that use the same boiler for heat and domestic hot water. On warm days, during the night, and in summer, the boiler doesn't need to maintain water at 180 degrees F. just for hot water; without an EMS, most factory aquastats are left on one setting all day -
every day - year round.

Understanding runtime is also a valuable tool for gauging system efficiency. EMSs can calculate pressure time from when the burner kicks on in response to a call for heat until it first turns off in response to a "pressuretrol." The big question involves how long it takes to make pressure - and then, how long after that it takes for the building to actually get warmer. The EMS sensors can tell you if it takes too long, which may indicate a balance problem or dirty steam traps slowing the dispersal of the steam.

Finally, runtime can be a comparison tool. Why does the boiler in one building run much longer than the one in the similar building next door? Is it just the exposure? Is one boiler sized improperly? Is the maintenance conducted differently? Sometimes, the key to finding answers is to know that there's a question in the first place.

Dan Margulies is COO at Fresh Meadows, NY-based U.S. Energy Group.

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