Burnham Boiler Overheating 260F

jldaddy

I have a cast iron gas fired Burnham boiler with one Taco 007 circulator pump and 3 Taco zone valves. Boiler was installed in 1990. Never had an issue until two weekends ago when I got woken up to pipes banging and water alarm going off. Boiler relief valve was shooting out steam. I turned the boiler off and called a plumber. He changed the aqua stat and the expansion tank. Boiler had issues heating up the house after these repairs, plumber came back and bled the air out of the system. Boiler ran for about a week, heating the main and second floor with no issues, basement would not heat up and reach setpoint. This morning, i woke up to the same loud banging noise and water alarm, boiler was reading 260F and 22 PSI. I immediately turned off the boiler. What can be wrong??

pecmsg

Cant tell from this side of a computer.

Id find a more qualified contractor, the safety should have shut it down long before 260°F. I wouldn't run it until then!

Jamie Hall

The aquastat should be turning the boiler off. Either it isn't working properly -- which could be as simple as not being properly seated in its well to its being defective -- or there is a wiring problem of some kind.

Or, rarely, there could be a problem in the burner control. That's not common, but it does happen.

What happens if you turn the boiler back on after fining it overheated (which, I agree, is sort of scary, eh?)? If you turn it back on within a minute or two, does it just fire right back up and threaten to do the same thing again? (there's a reason for asking: it makes troubleshooting easier if it does!)

Is the aquastat wired directly to the burner control? No relays or fancy boxes in the way? If so, and the burner does turn right back on, let us know and we can post a troubleshooting procedure which will localise the problem.

jldaddy

I bled out the system, lots of air, possibly from relief valve going. After bleeding I started the boiler back up, it fired after a 2 minute delay (normal). However what I heard as the boiler fired up was the sound of water starting to boil within the cast iron section. This was only about a minute after the boiler fired, so it didn't meet setpoint yet. I turned it off for now. Pressure gauge was at 20 PSI and the temperature gauge was 80F. Any suggestions?

EdTheHeaterMan

What about a runaway gas valve? VERY RARE but it happens.

Once you turn off all the power it may close. Then it will operate normally until it gets stuck open again a few days/weeks later.

Ask the repairman about the possibility of a runaway gas valve. He should cycle the valve off and on many many times to see if he can recreate the problem.

If you don't get the problem resolved, the next time you have the condition, turn off the gas and leave the electricity on. This way the gas control valve will be in the failed condition when the mechanic arrives. "Open with no power to it"

Just a thought. if you end up not replacing the valve on this upcoming visit.

jldaddy

The gas valve was replaced about 4 years ago. I will check if it failed. My concern is the noise I hear once the boiler fires up, after about 2 minutes you start to hear what appears to be water boiling, never heard that before.

EdTheHeaterMan

You lost some water from the relief valve, there may be air in the system. If the closed system is really tight and there are no automatic air vents (or if you do and they're blocked) your closed system may be in a vacuum which makes the water boil at a lower temperature. (that is not likely) Or there may be air in the system that is allowing the water to stay in the boiler without circulating, the water near the flame may boil before the water near the limit control gets to the temperature when it should shut down.

One odd thing did happen to me once (Probably not your situation)
I came across a 4 zone system with 4 circulators on the supply side of the boiler. They were piped so close together that it was difficult to get the electric box cover om, so the installer rotated the motor on the housing. One day the circulator failed and I replaced the part but did not realize the pump was rotated. It ended up in the wrong direction because the electric box matched the other ones with the pump that way. The system ran ok for a year or so until the son returned from college.

Now the son's room was on that zone and every once in a while the boiler would make crazy noises and boiling sounds. Not all the time, just once in a while. This went on for 2 years but it never happened when I was there until one day I was finishing up a maintenance visit and only the son's room zone was calling for heat. What a racket the boiler made. The zone was very small and the boiler water was heating up quickly but the cooler water returning from the reversed circulator was keeping the high limit from reading the true boiler water temperature.

This would not have been an issue if they never invented Internal Flo Check pumps, but there you have it. The circulator pump would operate backward. How dangerous was that? After that learning experience, I always check the direction of flow on valves, pumps, filters, and other devices to be sure it is properly installed, Things don't always appear as they seem.

I guess what I'm saying is that the obvious is not always the right answer. Thermostats that don't read the proper temperature are not necessarily defective if the appliance they are connected to is not working properly. Your repair tech will need to look deeper into the problem.


...maybe you can get him this hat if he does not have one already

jldaddy

Figured out the problem. Circulator pump failed which was only 3 years old. The aqua stat is located on the supply header, not at the boiler itself. So what I believe was happening is that the boiler was firing on, since no water was circulating, the aqua stat did not sense that the boiler was at or near setpoint. This eventually caused the boiler to overheat and the relief valve to open. The third plumber finally figured this all out. Supply and return piping near the boiler was getting hot, however when we felt the piping right at the basement finned tube, it was cold. Once he took of the pump, he confirmed it wasn't rotating. Put new pump in, everything warmed up immediately. Now we hear a humming noise from the pump and you can feel the water circulating throughout the loop.

neilc

shouldn't there still be another safety / aquastat in the boiler to prevent this?

EBEBRATT-Ed

@jldaddy

@neilc is correct.
For safety reasons you must have a high limit control that is inserted in the boiler water.

The next time the pump or something else fails you could have the same issue........overheating.....I don't think you want to replace the boiler before it's time.

You can only overheat a boiler so many times before it is likely to fail

Jamie Hall

and silly me -- I just assumed that the boiler aquastat was the one we were talking about!

pecmsg

jldaddy said:

Figured out the problem. Circulator pump failed which was only 3 years old. The aqua stat is located on the supply header, not at the boiler itself. So what I believe was happening is that the boiler was firing on, since no water was circulating, the aqua stat did not sense that the boiler was at or near setpoint. This eventually caused the boiler to overheat and the relief valve to open. The third plumber finally figured this all out. Supply and return piping near the boiler was getting hot, however when we felt the piping right at the basement finned tube, it was cold. Once he took of the pump, he confirmed it wasn't rotating. Put new pump in, everything warmed up immediately. Now we hear a humming noise from the pump and you can feel the water circulating throughout the loop.

What model do you have that "Doesn't" have a H T Safety on the boiler?

jldaddy

The Boiler is a Burnham Model P-206-WNI. I don't believe it has a built in HT Safety within the boiler. It was manufactured in 1987, I plan on replacing it this spring. Its 33 years old, got my moneys worth out of this boiler.

neilc

why don't you post a picture of all the boxes on the boiler,
and a shot of what's under the front cover,
the high limit has to be there somewhere

pecmsg

jldaddy said:

The Boiler is a Burnham Model P-206-WNI. I don't believe it has a built in HT Safety within the boiler. It was manufactured in 1987, I plan on replacing it this spring. Its 33 years old, got my moneys worth out of this boiler.

that should have a High Limit on the cast iron!

jldaddy

These are the photos of my boiler. The only aqua stat I have is on the supply header (see photo). Problem with its location is it doesn't read the true temperature of the boiler (internal) and if there is no flow (bad pump) it will take a long time before the aqua stat reads the boiler temp. In my case, I was hitting 240-260F and the relief valve was opening up since the pump failed. I don't see anywhere else where a high limit is installed at the boiler.

pecmsg

Ill bet that aqua stat is in the wrong location if not just a BAD location! Any other plug's in the block?

EdTheHeaterMan

That was the factory location back in the day. Later on, Burnham realized their mistake and turned the block around so the supply tapping was in the front left side of the boiler and added a limit as shown in the middle diagram


I have serviced many of them and for the most part, the aquastat well is far enough in, to read the boiler temperature. Perhaps the original installer replaced the factory-installed short nipple from the boiler supply to the reducing tee that accommodated the aquastat well adaptor. Who knows why the installer might do that? I wan s not there when it was installed, Were You?

neilc

from the picture, one would think that it should work there,
but, as it's field installed, one could question the correctness of its wiring.
can you lift the cover and shoot a picture inside?

EBEBRATT-Ed

Picture of the supply piping is not clear enough but that aqaustat will not control properly unless the pump is running as you have already found out.

That aquastat isn't close to being in the boiler water.

I would not run it as is

EdTheHeaterMan

neilc said:

from the picture, one would think that it should work there,
but, as it's field installed, one could question the correctness of its wiring.
can you lift the cover and shoot a picture inside?

The factory installed the aquastat there, but they used a smaller nipple. As I said, I have no idea why the original installer changed it. Could be that it leaked and the longer nipple was the only one he had at the time. But, I was not there to know for sure, Were you?

neilc

EdTheHeaterMan said:

Were you?

nope, I was not

3rdGenPlumb_heat

EdTheHeaterMan said:

What about a runaway gas valve? VERY RARE but it happens. Once you turn off all the power it may close. Then it will operate normally until it gets stuck open again a few days/weeks later. Ask the repairman about the possibility of a runaway gas valve. He should cycle the valve off and on many many times to see if he can recreate the problem. If you don't get the problem resolved, the next time you have the condition, turn off the gas and leave the electricity on. This way the gas control valve will be in the failed condition when the mechanic arrives. "Open with no power to it" Just a thought. if you end up not replacing the valve on this upcoming visit.

I wanna take a moment to appreciate this post, I’m third generation heating contractor who learned from my father that did this for 50 years before retiring. Both me and him were completely stumped working on a 1970 burnham boiler that was overheating to the point of making steam. Turned out to be a runaway gas valve, something my father has never seen in his years in this buisness. Appreciate your wealth of knowledge Ed