AboutMorgan M. Audetat Expertise Radiant floor heating. Snow Melting. Boilers. Indirect water heaters. Tankless water heaters. Current owner BadgerBoilerService.com Minneapolis based mechanical contractor specializing in Mod/Con based, integrated heating systems. System design, consulting and technical training world-wide.
Currently designing hot water based heating and snowmelting systems for spaces ranging from 50 to 50m square feet. Consulting fees start at $500.00US
Experience 30 years. Organizations: Charter Board Member - Radiant Panel Association, former manufacturer of the first American-made wall-hung, sealed combustion condensing boilers, son and apprentice of mechanical & plumbing contractor.
Continuing Education: Uponor/Wirsbo advanced design school 2007, Power Limited License (low voltage controls) 40 CE credits 2005, B&G Little Red School House 1993, Tekmar Controls residential and commercial 1993, Division Manager and Advanced Hydronic Seminar Host for the first Hydronic Radiant Floor Distributor in the USA 1990, Hydronic Heating Association Workshop participant with Richard c. Bourne, PE spring 1988, Master Plumbing/Hydronic/Solar Course Red Rocks Community College 1987.
Education: B.S. University WI 1981, 26 yrs. continuing education.
Licensed CO, MN & WI. Home Inspection license WI exp.
Awards and Honors: My momma's favorite son.
Past/Present Clients: References upon request.
Expert: Morgan M. Audetat Date: 5/15/2008 Subject: *Cast iron boilers vs. Mod/Con boilers*
Question I'm researching new heating options for my 1901, 2200 SF house (cast iron radiators) in northern MN. I'm in the process of adding additional insulation and some new windows, but feel that upgrading from the current Weil-Mclain oil boiler (10-12 years old) to a more efficient, natural gas boiler will make the most difference. However, I've talked with a couple contractors who claim that a NG condensing/modulating boiler would not be as efficient as a NG cast iron boiler due to my old cast iron radiators (somethng about the water needs to heat to 170-180 degrees in the winter). This seems contradictory to the research that I've done on Cond/Mod. NG boilers--most efficient type available, especially when paired with an indirect boilermate (I currently have a stand alone fuel fired water heater) and an outdoor reset device. Before moving onto specific brands/models, I need to clear up this important issue/question. Any input that helps me clear up this question is appreciated! Thanks.
Answer Mod/Con boilers are the most efficient LTW boilers available today!
Let me take a moment to castigate my fellow heating contractors: many are ignorant and many more are deliberately obtuse. This is not a matter of opinion but a scientific fact.
The argument goes; high temperature emitters such as fin-tube baseboard-normally designed for 180 average water temperatures at outside design temperatures-will not work or be well matched to condensing boilers. HOGWASH.
First I would like to point out that the vast majority of cast iron radiator systems installed at the turn of the century were designed top operate at 170F maximum! Yours is not a high temperature 190F emitter! Lets keep in mind that these were conservative individuals and that the heat load of your house has surely gone down with improvements such as windows and insulation.
Your system operating with outdoor reset -an uncommon upgrade with cast iron boilers but universal for ModCons -will operate below design conditions all but a week or so when the coldest days -design conditions- occur.
This disinformation has been promoted for years- in fact; just last year I attended a three-day "Advanced Radiant Design School" hosted by one of the largest producers of radiant floor tubing in the country. They tried to convince others and me that "controls" could some how make a 1940's technology cast iron boiler -82%AFUE- MORE efficient than a Mod/Con boiler! Incredible.
For those who persist in this nonsense whether through simple ignorance or misguided self-interest, I point to the stack or flue temperatures of the boilers in question: 350F for cast iron and around 100F for condensing boilers.
In your particular situation the cast iron radiators are a near perfect match for properly sized Mod/Con boilers. They are oversized which means they will heat the home most the year with return water temperatures below 140F, condensing flue gasses and recovering 970 BTUH of energy per pound of condensate. Furthermore, outdoor reset will control the extra mass presented by large heavy cast iron radiators and match water temperatures to outdoor temperature reset by the minute instead of worst case "design temperature".
Shame on our industry for being so ill informed and betraying the trust the unknowing public puts in us.......
