Gas Boilers

[ps]

I've tried other forums (heatinghelp, boilerroom) but I am still undecided. I know you aren't psychic - but I'll settle for accurate info based on real world experience.

Application - New gas HW boiler w/ indirect fired DHW heater. Heat load = 50 MBtu/h, + DHW (1.5 ba, washing machine).
Single pipe & zone w/ circulator, diverter tees to cast iron radiators (not considering changing).
HDD ~ 7000 (Worcester, MA), Design Temp = -10F.

I understand condensing/modulating units w/ reset (Munchkin, Buderus,etc) - but I am unsure if enough condensing efficiency can be captured to offset extra cost. I understand low HWR systems (radiant) benefit 100% - but no one will speak to my application (CI rads & indirect loop).

Should I just go with a more reasonably priced 85% AFUE w/ reset? Are there any non-condensing, modulating boilers out there? Any one have any experience w/ similar setup? I have read everything - looking for some help!

[beenthere]

You said single pipe with diverter tee's, do you mean mono flo?

[nutshell]

Teledyne Laars makes a couple of great boilers. Some are condensing and some modulate. I would go with Buderus myself. I have installed and serviced many of them and you can't go wrong. I install Buderus boilers with indirect Superstore tanks all the time with great outcomes. A couple points here or there on efficency, you're just splitting hairs. Go with a good name proven product.

[johnsp]

I can't justify the extra cost and the cost of expensive modulating gas valves and variable speed induction blowers replacement parts on a high temp system. Just get a condensing boiler like the Dunkirk Quantum with a tekmar boiler control with outdoor reset. Now you can set up the boiler to cold start and you could even set the reset curve to drop down to 120-140° supply temp water without worrying about condensation damage from cool return temps. You'll be pushing 90% efficeny while saving almost a grand on the boiler.

[ps]

Pardon my ignorance. I have seen the MonoTee pics, they are definitely not those. Look like normal copper tees - some have called them venturi tees. System is circa 1940, boiler was originally oil-fired, converted to NG ~ 1970. The tees are spaced out the same as radiator length, can't see any difference between supply and return - told restriction should be on return side. Actually, no problem getting heat to the radiators.

Most concerned about getting the most bang for my buck Oover entire boiler life), plus reliability. I am concerned with all the bells/whistles (blower/burner, controls)on the condensing/modulating units - needing expensive replacement before boiler.

Have read only good things about Buderus. I did look at the Quantum - different design seems tailored more to my application, although not modulating (definite savings there). You say I can use TekMar OA & DHW priority controls with this unit? What about the Aluminum HE - I have heard some concerns. Is this a proven material (like stainless), or is it relatively new? I know WM uses Al HE in the Ultra - but they also use gaskets on their CI sections, so ...

[Edited by ps on 02-10-2005 at 08:49 AM]

[ps]

Anybody out there have 2 cents to add?

[johnsp]

All the high efficency boilers only give you a 15yr limited warranty. The HX in Ultra and Quantum are alum casting, so there's some mass to them. Stainless steel dosn't mean anything if it's thin pressed metal. The Ultra is the pricier of the top names: Ultra, Quantum, Munchkin.
All have only been out a few years, so none can tell if they'll last 15 or 20 years. I'd stick with a major player and find the lowest price. Plan for a replacement after 15 years.

[ps]

15 years - are you kidding me? I hope you are referring only to the condensing/modulating units, in which case i think I will go with a standard boiler. Is a standard 80 - 85% CI boiler going to need replacement that soon? No disrespect intended, but my old boiler (w/ ~ 60% eff) is 65 years old! I'd be better off trying to restore and upgrade controls than replace it and never have the increased efficiency (aka $ savings) pay for it!

[johnsp]

We don't have history on the modulating/condensing boilers to tell how long they'll last. I doubt any new CI 80% eff boiler will last more then 25 years anymore. They're not made of 600 lbs of CI like the old models. All the lifetime waranties on the CI boilers are pro-rated and only on the CI sections. When one leaks, they'll send you a single section to replace. You pay the labor. Probably cost more to fix then replace. I think the days of 30+ year old boilers is over.

[beenthere]

The ultra only has a 15 year on the hx.

And like others said, the jury is still out on how long they will really last.

I like the Ultra's, but if you want to be reasonably sure of a long life span, stick with the standard boilers.