I looked at this job today...................

Alan (California Radiant) Forbes

a Trane Vapor system...............beautiful. The contactor had removed the old terra cotta flue.  His question is: Can this boiler be vented with an interior B-vent flue along with the water heater which is next to the boiler?

Steamhead

Probably

but a couple other things come into play....



First of all, an atmospheric conversion burner in that type of boiler is probably sending a LOT of heat up the chimney, unless the boiler has proper baffles in its flueways.



Second, the breech on that type of boiler was sized for coal firing, which means it's way too big for gas firing. So a B-vent matching the breech will probably be way too big for the actual BTU input of the burner. Not sure if local Code authorities would let you reduce the B-vent size that much.



I would check with the B-vent manufacturer and the local Code authorities before proceeding. A new boiler might be the best way to go here.



Why was the terra-cotta liner removed?

Alan (California Radiant) Forbes

Frank

The entire chimney has been removed because they are remodeling the kitchen, directly above the mechanical room. A 5,000 square foot house in a tony neighborhood has no room for a boiler flue in the kitchen.



I don't remember what the breech size was, but I will check to see how breech size relates to boiler input. Inspectors here frown on flues smaller than breech.



I don't know about coal, but there is evidence of oil (capped off 1/2" steel lines out of the slab).

Steamhead

"A 5,000 square foot house

in a tony neighborhood has no room for a boiler flue in the kitchen"



Right....................



What you have there is a boiler that could burn any fuel- coal, oil or gas. Given the age of that system it was almost certainly coal-fired originally, then converted to oil, then gas. But the large flueways needed for coal firing reduced its efficiency on oil or gas, unless proper baffles were installed- and most times they weren't, since fuel suppliers obviously don't care about efficiency, only their fuel sales.



Today we don't need to be able to burn coal, and the boiler's design compromises that enabled coal firing are going to really get in your way here. I think it's time to replace it.

ChrisJ

Rott

I have to be honest, my neighbor has the same boiler which is oil fired.  After seeing as many pictures of these as I have, if it were mine I'd keep it.



Why?  Because they don't appear to rott out like the new ones.  Of course as steamhead mentioned I would want the baffels installed.  I would also insist that all safteys such as the pressure valve and LWCO are up to date.





I'm not a pro, just a homeowner and I'll be honest 2 years ago I knew absolutely nothing about steam.

Alan (California Radiant) Forbes

Draft

Frank: Are you concerned that the boiler won't have proper draft with a flue that is too large? I would have been interested to see how much draft there was with the old flue, but it's history now.



I don't know if the owner is open to a new boiler at this time. He just purchased the house and is spending a lot of money for a major remodel. My guess is that we have to work with the existing boiler.



The boiler looks in pretty good shape for something almost 100 years old. I operated the LWCO and got a good flush of clean water. The near-boiler piping is fine, but there is no Hartford Loop. Wet returns are minimal since there are no radiators in the basement.

Alan (California Radiant) Forbes

Draft

Frank: Are you concerned that the boiler won't have proper draft with a flue that is too large? I would have been interested to see how much draft there was with the old flue, but it's history now.



I don't know if the owner is open to a new boiler at this time. He just purchased the house and is spending a lot of money for a major remodel. My guess is that we have to work with the existing boiler.



The boiler looks in pretty good shape for something almost 100 years old. I operated the LWCO and got a good flush of clean water. The near-boiler piping is fine, but there is no Hartford Loop. Wet returns are minimal since there are no radiators in the basement.

Steamhead

A number of things could happen

If the stack temperature is very high, it would make plenty of draft, but might shorten the life of the B-vent. You'd need to talk to the B-vent maker to find out how much heat their stuff can handle.



If the stack temp is too low, you might not get the draft you need. This can also happen in a flue that's too big for the BTU load and doesn't warm up quickly, or one that is run outside the building and might not warm up at all. Any of these scenarios might also involve condensation in the flue, which again may shorten its life.



If you have George "Firedragon" Lanthier's oil burner books, he covers this in great detail.



They never should have torn down the chimney without knowing for sure what would work as a replacement.

ChrisJ

And

I just realized my response in no way answered your question, Im sorry.