Burnham Series 2 leaking??

[Carl5061]

I have a Burnham series 2 boiler for my forced hot water heating system. I recently had an addition added to my house and the plumber added another zone for the bedroom. After all the contractors left, I noticed water pooling in the low end of the basement. I traced it back to the boiler, which had several leaks. There was a leaking pump gasket, leaking valve stem and a leaking spigot. I fixed them all. But to day I found another pool of water. I can't find where this water is coming from, but because of the pitch of my floor, I know it is coming from the boiler. My questions are: Any ideas where to look for a leak? If there is an internal leak, can it be fixed? If not, what is the best boiler for quick replacement?

The name plate shows 1983, manufacture date? Has this boiler out lived its life? I find that hard to believe because I have a two family that has a steam boiler that is probably original with the house. I believe my buddy the plumber called it a "snowman".

[jadnashua]

It's really hard to tell from afar where a leak may be!

FWIW, yes, the boiler might last a lot longer, but then again, it could be shot. Depends somwhat on how it was setup and run. Also, it's likely that a boiler that old is radically oversized. AN oversized boiler is usually very inefficient. The local utility company probably has a rebate program to replace it with something much more efficient. Whatever you do, if you go this route, do NOT just replace it with something the same size, as something maybe 1/3 the size or maybe even less would be enough, and save both a lot on the installation cost (bigger boilers cost more), and in efficiency, and in comfort. Idealy, a boiler runs constantly with just enough output to keep you warm as the start/stop cycles tend to waste lots of energy and create a lot more wear and tear on the parts.

Do you have an autofill valve? Is it open? Is the pressure stable (it probably should be if the autofill is open, but that masks leaks)? Is this a tank with an embedded water heater coil? If so, it could be potable water that is leaking, not boiler water.

[Dana]

A boiler pushing 30 years old is definitely a candidate for outright replacement, even if it ISN'T leaking.

And just 'cuz there are tens of thousands of pre-1950 steam boiler still in operation (@ 50% AFUE or less) doesn't mean a hot-water boiler that started out on day 1 with 78% DOE efficiency is worth fixing. Unless it's perfectly "right sized" for the design day heat load it's likely not running at more than 65-70% AFUE, but with a right-sized mid efficiency boiler you can hit 84-87%, and with a right-sized modulating condensing boiler it's likely you can hit the mid-90s. Odds are it was 2x+ oversized on day 1, and if the place has been improved at all since 1983 in terms of storm windows, air sealing, additional insulation, etc it's probably more than 3x oversized and running under 65% AFUE.

Getting rid of the ancient asbestos-dripping "snowman" steam beastie before it becomes a liability is worth it too, but probably more money than replacing your Burnham.

A reasonable lifecycle on cast iron hydronic boiler is 20-25 years- it doesn't owe you a thing (and conversely). Yes, I've seen 1950s vintage hydronic boilers still plugging away too, but at sub-60% as-used efficiency. If the leak is between the heat exchanger plates or has a cracked heat exchanger plate it may be fixable, but it wouldn't be worth the money. If it's leaking at either the input or output fitting it may be fixable for reasonable money, but it's still worth assessing the bigger picture.

If you can nurse it through the rest of the heating season, installing a new one (even another cast iron beast) before November is probably still the right choice, but take the opportunity to at least right-size the replacement, eh? I'm not in this biz, but I know from first-hand experience that most of the hydronic boilers in my zip code are 3x or more oversized for the actual loads, and running at truly crappy efficiency relative to their AFUE rating. The "best boiler" for the replacement will vary depending on the actual heat loads, type and amount of radiation, and the relative amount of local support for that manufacturer.

As a sanity check on sizing, what are the input & output BTU numbers on the nameplate (usually found inside the front hatch on Burnhams), and what are the exact billing dates and fuel use of your last gas bill (for correlating heating degree-days to fuel use, by which we can quickly calculate an upper bound on the heat load at the outside design temperature for Watertown)?

[Carl5061]

I believe the leak is coming from the boiler. But it doesn't leak all the time. It seems the leak is only at night, (when the boiler is the coldest?). Any ideas?

There is city water connected which is opened with a back flow preventer. This is actually something that has changed since the home addition. I closed the city fill line because the back flow preventer leaked. Since it has been replaced and the plumber did his stuff, I have water showing up. Again, we are not talking about a big leak, but enough to make me concerned. I'd just like to find where exactly the water is coming from so maybe I can fix it until the season is over and then tackle this in the summer.

[Dana]

The fact that the leaks only became apparent after the plumbers had been hacking on the system is curious. Did they set the system pressure correctly? (It should be 12-15psi, not more, tweakable a the auto-fill valve) Is the expansion tank properly sized for the now higher system volume, and properly charged? It's concievable that the expansion tank it toast or undersized, and where as without the backflow preventer the system might have been limited the system pressure the city water pressure is (which is probably over the rated pressure for the boiler, but still less than the pressures it might see otherwise.)

Assuming all is in order on that front, if it's only leaking when cold it's conceivable that it could be the plates separating slightly from the contraction of the iron when cold. The plates are held together with through-bolts which can stretch over time and temperature cycling. You MAY be able to tighten them to fix a leaking plate seam if the threads aren't frozen but after 29 years of service it's also possible that one or more bolts could have rusted up to to the point where it can't be tightened and need replacement, which in most cases would require some disassembly. You can probably find the manual for this beast online (or the manual of it's immediate successors online, which may be similar enough.)

The series 2 model numbers I'm familiar with are P20x , where X= the number of heat exchanger plates- what is your exact model number?

The basic internal assembly looks like this:



Note the through-bolt on the flanges of the end sections. They don't give torque-specs, and there are more than just that one bolt holding the thing together.

See: http://residentialparts.usboiler.net/gas/series2-2h.php#1

You may be able to inspect the bottom of the section seams from below with a mirror by pulling the panel and getting a "burner-eye's view". If a section has been leaking for awhile it could be apparent. There is also a sheet metal section under the burners which might appear wet in the AM when the boiler is coldest (at least before the first burn of the day) if it's been leaking at the plate seams.