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Posted by HeatPro on May 03, 2008 at 10:58:35:
In Reply to: Do high efficiency boilers make sense for baseboard? posted by Tim_Anchorage on May 03, 2008 at 00:40:21:
Unfortunately, condensing boilers haven't been on the market for long, so don't have a track record for longevity yet, so all is a guess.
The conflicting advice about baseboard use with condensing boilers is due to the learning curve of people thinking about how the difference requires some changes. A condensing boiler goes out of condensing mode when the water temperature goes over 140F, so there is little incentive to use it at higher water temperatures -
until -
you remember that a properly-sized boiler (and most condensing boilers become properly sized because they have fire modulating controls to match the fire input to the need. So condensing boilers should operate for at least half the year in condensing mode in fall and spring.
If you want a condensing boiler to condense all year to double the savings to a full year, then add twice the baseboard to the room, that is, design the baseboard to emit heat at a maximum of 140F instead of 180F, so the boiler never needs to get warmer than 140F to supply heat to the rooms. Baseboard is a lot less expensive than a boiler. This wasn't done before because running a cast iron boiler at no more than 140F would have rusted it out from long condensing times. The condensing boilers built now are meant to take the wet - as is the Mestek rAy condensing cast-iron boiler.
An extra $4000 a year discards the 5% more fuel savings. That is, if your bill is $3000 a year, you spend $150 less a year; so you get to save that money 20 years or so after you paid the extra for the new boiler.
Buying a Takagi for $1000 means you don't get the $150 savings, but you have to figure if you have 20 years left to see savings. Boiler manufacturers saw that coming 15 years ago when the CAEFRA law was proposed, so they aren't happy with not much chance to make big fuel savings claims to replace boilers that are already 85% efficient. 'Dumbing-down' to keep people unaware of that makes bigger sales opportunities.