boiler replacement help

mcycle

<span>Help,</span> <span>I'm about to convert from oil to gas and have been looking at condensing boilers. The main house (1950) is 1100 sq ft and there's an in-law attachment (1990) of about 1100 sq ft also. Total fin tube baseboard = 135 feet.</span><span>The main house piping is run in series (I think they called it venturi back then) the in-law is the typical one supply pipe one return pipe.</span><span>Does a condensing boiler make sense for this application? I'm not 100% convinced.</span> <span>Thanks</span>

mjcromp

Ideally

a mod/con boiler works well with lower temperatures. The condensing takes place with lower return temperatures. In a baseboard application you have a small delta T. They boast high 90's efficiency but that's with low return temps where the boiler can condense.

Robert O'Brien

Just fine

Condensing boilers work just fine in the majority of baseboard systems. What % of  heating season is spent at temps that require 160 degree plus water?

Jean-David Beyer

Mod|Con boiler and fin-tube baseboard heat

The upstairs zone of my heating system is heated with 14 feet of baseboard in each of the two rooms. One room is 280 square feet and the other is 168 square feet. The heat loss for the first room calculates out to 3467 BTU/hr and the second one to 3006 BTU/hr. The way I decided how much baseboard to use was that I wanted as much as I could physically put in each room without going into creative plumbing. Then I calculated the water temperature I would require on the design day, and it came out to about 140F going in, and about 134F coming out. Actually, the temperature loss will be greater because there is about 65 feet of uninsulated pipe in the floor going to and from the second room. The heat is not wasted as it is  in between the upstairs and downstairs. It is easy to adjust the water temperature in case my calculations are incorrect. But I do expect condensing from that as the outdoor reset is currently programmed to deliver water between 80F to 140F up there.

CMadatMe

Rob is correct

If you really want to promote condensing do not pipe primary/secondary. Use a hydro-seperator (low loss header). 

Jean-David Beyer

Can you explain this?

It seems to me that, except for the convenience of a Low Loss Header (air release, dirt release, slightly less plumbing), closely spaced Ts and LLHs are pretty much equivalent. So I do not understand why, in this case, you recommend one over the other.

Unknown

Things HAVE changed JD,,,

give-it a rest,,,, we`re all sick-of hearing about your Ultra!!!



A LLH is the way to progress(for your stated reasons),,,, try doing that on simple P/S pumping!