Condensing vs Non-condensing Gas Boilers

Old 01-28-05, 08:59 AM
Pat S
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Condensing vs Non-condensing Gas Boilers

I have read quite a bit about the various types of HW boilers and have a few questions. I have a single-pipe, venturi tee HW system (single zone w/circ pump) to cast iron rads and the 60+ yr old nat. gas boiler also provides DHW via an external tankless coil. I'm replacing with new, mid to high efficiency gas boiler w/ indirect fired water heater. I have approx. 50MBtuh heat load (plus 2.0 bath & washing machine for DHW) so I am looking at ~80MBtuh IBR capacity. My question is whether or not to consider modulating output, condensing boilers. I have read that my application (180 F HWS for CI rads + indirect water heater) is not conducive to condensing-type boilers because they require lower HWR temps and I will not benefit from this extra efficiency. The price differential is considerable so I have to determine cost effectiveness, also.

In a related question, I have read many bad things about units that use elastomer gaskets instead of push nipples (Weil-McLain). I know everyone has their favorites - any comments or suggestions on W-M or gaskets vs nipples?
Old 01-28-05, 07:19 PM
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Gas Fired Boilers

Depending on your climate, how long you plan to stay in your house, the cost of gas in your area, etc., a modulating boiler could save you a substantial amount of money over its lifetime. Personally, I do not care for Weil-McLain's "elastomeric seals". I much prefer cast iron or at least steel push nipples. I don't know if it is available yet, but I saw a Buderus, modulating, stainless steel boiler which was most impressive.
Old 02-01-05, 01:44 PM
Pat S
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In theory - yes! That is why I am asking contributors here to chime in, as real world experience and applications are more valuable. Given the previous info, will a condensing boiler really provide increased savings due to 90+ efficiency for my application - or should I go for an 85% AFUE with reset controls?

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