Steam Pressure & Leaks
Our ancient boiler finally bit the dust, so we hired Keyspan / National Grid to replace it with a Burnham IN6 gas-fired steam boiler, for our one-pipe steam heating system. We have a four-story townhouse. The original system & the radiators seemed to work fine without any troubles until now. For reference we used Size…
Our ancient boiler finally bit the dust, so we hired Keyspan / National Grid to replace it with a Burnham IN6 gas-fired steam boiler, for our one-pipe steam heating system. We have a four-story townhouse.
The original system & the radiators seemed to work fine without any troubles until now. For reference we used Size No 4’s air valves on the 1st floor, increasing to Size D on the top floor.
Three of our radiators have sprung leaks since the new boiler has been installed. They hiss & whistle and water burbles from the air valves, and now water is also leaking from the pipe-to-radiator connection as well.
So the installer reduced the pressure from 5 psi to 3 psi, but this hasn’t stopped the hissing and leaks. They said the radiators were not in their scope of work, and suggested that I should hire another plumber to correct the problem.
The manufacturer literature for Burnham cites numbers like 0.5 psi to 2 psi, so the 3 psi to 5 psi range that Keyspan used seems high. Could this be forcing steam out of the radiator pipes in unexpected ways? Am I even comparing correct numbers?
I am going to try replacing the air valves with new ones, but I need to know why the radiators might be leaking. Before I call in another plumber, any suggestions what may be going on?
“Pressuretrols have two different functions when working with Heat Timers. One is they signal to the control that the system is full of steam and cycle timing begins.
The other is they temporarily cut off power to the burner circuit in the presence of rising pressure in a redundant high-limit configuration.
Either function is kind of sucky. There are better ways to signal a Heat Timer.”
I should have mentioned that our Heat Timer has a sensor on the return, which triggers the cycle start (at 164 degrees). So I guess in our case, the pressuretrol is just serving as a high-limit? For whatever reason, it is set to 6 psi (with a -2 differential) so I don’t imagine its doing a lot of limiting.
Does lowering the pressure limits usually require a round of adjustments to the heat timer? Changes to radiator steam vents?
good info eman, thanks. just wanted to add: emphasis on “should”…and if the homeowner doesn’t know anything, there’s no way to know the “professional” is not really professional.
This is why it’s good that you post the detailed info….
The “boiler guys” left my pressure at the highest setting and I still have no oil filter…things I ‘shouldn’t’ have to worry about, but here I am. I’m sure there are tons more mistakes on my setup if I only knew…
the steam header is an oversized pipe that the boiler feeds into…in an ancient installation boilers fed into maybe a 2 inch line…later plumbers understood that feeding steam into a big 4 inch pipe allowed you to get rid of most of the water that is generated during the process of turning steam into water.. if the distance between the line on the sight glass where the water is supposed to be in the boiler when it is making steam is not 22 inches below the header, water will be forced up ahead of the steam , and you will will hear a sloshing sound , accompanied by leaking steam vents…etc…these are concerns that should be addressed by a heating professional, not a homeowner
WoW! This sure is a technical thread! Thanks!
eman1234
re:
“if the old steam header …is not high enough over the water line to allow for dry steam on the makeup, you are doomed to have knocking and condensate problems”
Is the ‘header’ the outgoing hot steam pipe that runs horizontally away from the boiler, and the ‘water line’ the return condensate?
Could you please explain in more detail what this means, and why the same configuration of pipes would now collect condensate, when previously with the old boiler it would drain correctly?
Since the new boiler install, i do notice there is definitely a sloshing sound in pipes now, and I saw that the leaky condensate from one of the failed radiators had rust and black specks in it too. I thought for sure that Santa was going to leave coal in my stocking, but it seems to have come out of the radiator water instead. : (
if you signal the heat timer for the “heat met” with a sensor at the furthest point from the boiler in the heating system you would have a lot better control than a simple “pressure met” as a signal…the latter gives you no idea what is going on outside the boiler room…admittedly the “pressure met” is really cheap to set up,but it makes no sense in the actual heating of a building
That pressure rule applies for big boilers, too.
The Empire State Building runs on 3psi. Any plumber worth his salt knows that by now.
Pressuretrols have two different functions when working with Heat Timers. One is they signal to the control that the system is full of steam and cycle timing begins.
The other is they temporarily cut off power to the burner circuit in the presence of rising pressure in a redundant high-limit configuration.
Either function is kind of sucky. There are better ways to signal a Heat Timer.
A flush port is at the lowest part of the return line generally at the nearest or farthest points from the boiler. A flush port above the water line would be no help.
Does the <1.5psi guideline for boiler pressure apply to larger boilers as well (eg, for a 25 unit apartment building)?
Also, how does the pressuretrol work in conjuntion with a Heat Timer? If the pressuretrol is working properly, will the boiler be cycling on/off during the heating phase of the heat timer cycle?
Last, where would a flush port generally be found? In the return piping near the boiler? Or some location above the boiler water line?
Thanks as always for info.
i hope that they at least used a float type low water cutoff instead of a probe type low water cutoff