Replacing Burnham 140,000 BTU Gas/Hotwater system

I'm thinking about replacing my Burnham 65W circa 1977 boiler with a newer
model. The boiler had a tankless heater which is deactivated and was originally oil fired later converted to gas.
I can't believe that the effeciency is of 60% because of the oil chamber and
the flue size. I would like some of good quality like a Burnham or Weil Mclain with about 85% effiency.
Can I repipe the system using M copper instead of the iron with 50/50 solder or do I need 95/5.
My local dealer recommended a Crown Boiler?Cabo2. But $2400 seem a little pricey.
Can I get rid of the flow controls? I have 2 circulator pumps.
Thanks for your help.

boiler

An oil, or coal, conversion to gas is always less efficient because of the larger flue passages. We used to install baffle material to force the gases to slow down and stay in closer contact to the heating surfaces. Only an on site inspection could tell which, if any, devices are not needed.

There is something to be said about a cast iron boiler with straightforward commonly available controls. There is also a market for more sophisitcated boilers that can achieve higher efficiencies. Some of the newer boilers can exceed 94%. Weil-Mccain makes their Ultra line that is close to that. One neat thing about this type is that it has a modulating burner - mild day, you can run the burner at a low setting (which actually increases the efficiency even more) and decrease the on/off cycles which wear thing too.

The tradeoff is more expensive and more complicated vs simpler and less efficient.

Look at Viessmann, too. They are German(?) but have a factory in Rhode Island.

cpeters said:

I'm thinking about replacing my Burnham 65W circa 1977 boiler with a newer
model. The boiler had a tankless heater which is deactivated and was originally oil fired later converted to gas.
I can't believe that the effeciency is of 60% because of the oil chamber and
the flue size. I would like some of good quality like a Burnham or Weil Mclain with about 85% effiency.
Can I repipe the system using M copper instead of the iron with 50/50 solder or do I need 95/5.
My local dealer recommended a Crown Boiler?Cabo2. But $2400 seem a little pricey.
Can I get rid of the flow controls? I have 2 circulator pumps.
Thanks for your help.

Click to expand...

Needless to say I never did the job. 10 years ago. How time goes by. Now I narrowed down my selection to either a Weil McClain CGA-5 or CGA-6.
The house is 2615 x 45 (region factor) =117,675 btu.

That's still ~3x oversized of the likely load... A fuel-use against heating degree-day calculation would prove it.

Who publishes these odd ball "region factor" rules of thumb with the ridiculous oversizing factors, anyway? This is truly gonzo levels of oversizing.

It may not make huge efficiency difference to be 3x oversized with a hot air furnace (but it'll be less comfortable), but with non-modulating hydronic boilers the efficiency consequences are large. Even in Anchorage AK, using a 40 BTU/ft rule of thumb typically oversizes by more than 100%. (That a 2x+ oversizing factor). That means most homes in Anchorage have heat loads of 20BTU/ft or less. Since you are using an even larger 45BTU/ft rule of thumb in NJ where the outside design temps are 15-25F warmer than the -9F design temp for Anchorage how well do you think you'll do? It's truly nuts.

Try 15 BTU/ft as the raw guesstimate if you don't want to do the fuel-use math, then bump it by 25% if you're anxious about being cold at some point during the next ice age. You won't don't need more than 50,000 BTU/hr of boiler output for most houses that size even at -10F, let alone +5F or +10F or whatever your local design temp happens to be.

A Burnham ES23 (59,000 BTU/hr of DOE output, about $1800 at internet pricing) would surely cover it with gobs of margin, and is internally plumbed to manage the cooler water returns from your 258' of baseboard.

W-M CGa-3, or Cabo-2 CWD060 with a boiler-bypass branch to protect the boiler from condensing.

Better yet, try the cheapest 50-60K condensing boiler you can find that has stainless steel heat exchanger. Either that or find a dumber than a box'o' rocks stainless steel condensing hot water heater with a 76KBTU/hr burner. It's 2x oversized for your load, but with enough thermal mass that it probably won't short cycle unless you over-pump the sucker.