View Full Version : 83% Efficiency Columbia Gas Boiler w/ Heat Manager?
10-24-2011, 09:21 AM
If I'm lookimg for Reliability, how does that system sound? I was told with the Heat Manager I can get an extra 10% efficiency.
I read too many problems with High Efficiency Systems to include issues w/ SS Heat Exchangers, leaking, etc...too many to list.
The Intellicon 3250HW+ is a slightly more sophisticated economizer than the Beckett Heat Manager (which was designed by Intellicon) for about the same money, and is a bit more flexible when dealing with indirect-fired hot water heaters (which is also a good idea for increasing net-efficiency.) But either will do.
But these products don't increase the efficiency so much as the reduce the severe hit you take in efficiency with high-mass boilers that are oversized for the loads. Far more important to both long-term reliability is sizing the boiler correctly to the load. A 150KBTU/hr boiler serving a 4-zone house with a 30KBTU/hr design day load with low-mass fin-tube heat emitters is going to be a short-cycling piece of misery, even with a Beckett or Intellicon. A 50KBTU boiler on the same house would come close to hitting it's AFUE numbers even without the economizer, but would run fewer & longer burn cycles with the economizer control, reducing wear & tear, buying a percent or two reduction in heating fuel if it's cut up into zones, but not too much if it's a single zone.
Most high-mass boilers installed in my area are 3x or more oversized for the actual loads. Using fuel use against weather data with the prior boiler is a more reliable way to size a new boiler than any Manual-J type heat loss calc, since it's an actual measurement, not a best-guess on construction methods & air infiltration rates. Even carefully done Manual-Js hit to the high side, often 25-30% to the high side of measured-reality.
Depending on how big the prior boiler is/was dropping to a right-sized boiler may require a narrower flue liner. In some instances it's cheaper/better to go with a right-sized power-vented 85-88% unit and side-vent it. The lower limit to being able to chimney vent the thing is ~83-84%, above which the risk of condensation in the chimney and back-drafting due to low an exhaust temps becomes an issue, assuming a right-sized flue. If you're replacing a 200kbtu/hr 80% 6-8plate behemoth with a 2-3 plate 50-60K unit you won't be able to use the same chimney (and if you have a hot water heater venting into the same flue you'll have to do something about that too.)
10-31-2011, 09:18 AM
Your information on high efficiency boilers is lacking. As dana properly points out, the proper application, installation and maintenance is the key to safe, efficient and reliable hydronic heating systems of all kinds.
If you have gas, a properly sized condensing boiler will pay for professional installation and service.
If you must have a low efficiency atmospheric boiler, there are boilers on the market with built-in outdoor reset.