Rust in five year old boiler

bruce_21

I went to check out a no heat call and found all this rust in the chamber. What is doing this? I've seen plenty of boilers that won't go from soot, but this is the cast iron rusting away and the unit is only five years old.

L'town Radiant_2

Low return water temps?

Maybe low return water temperature, 140 deg or less, causing condensattion and therefore a rusted section assembly.

Steamhead

Not on a steam boiler

you can see the bottom sight glass valve in the pic.



What's causing that? Is the basement really humid?

bruce_21

it has outside combustion air

The boiler has outside air piped to the burner. I'm going back by there tomorrow to see what's going on at the air intake outside.

bruce_21

more pics

Well its pretty wet in the basement, water seem to be coming through the door to the steps, but I don't think that much matters since there is outside air for combustion, it could be damp too, I don't know, check the pic of the outside air inlet. Question is what to do about the situation? Should I worry about this rust or not? seems it might eat the whole boiler in time, and maybe not that long a time.

Edward A. (Ed) Carey_3

Rust in Boiler

Bruce,

Is this your first service of this boiler, or is it your previous install?



Since it is steam, I do not believe that low return water temp is issue.   

I also will presume that you have checked the casting thoroughly, and have eliminated a gasket leak between the sections. If not, make sure you check that out first. Based on the photos, and the uniformity of the corrosion, I doubt it is a leak, but don't assume anything, otherwise ASSUME becomes **** U ME. 



If you have a gas HWH in the same chimney I also presume you do not operate this boiler for DHW in summer. Does the boiler go to cold start, or do you maintain minimum low temp in summer?



With boilers that are off in the summer you usually find a mucky mess of moist soot in the boiler. However, if the boiler is running with an exceptionally clean flame, (which is a good thing), then there is no soot to get moist. You will just have the moisture which will cause corrosion.  



Actually, there is another thread about a very similar issue, however it is not about rust in the boiler, it is about very moist soot found during end of summer cleanings with a cold start boiler. Remember, if the boiler is sooty, that soot is unburned oil, that will essentially lubricate the casting and prevent the rust for forming as you have. If there is no soot in the boiler, then the moisture directly contacts the uncoated cast iron. However the root cause of the problem would essentially be similar.     



A suggestion. Clean the boiler thoroughly now. Restart it and let it run now. Be sure to adjust to a 0 smoke to prevent soot from forming so the casting condition is the same as you found it. Keep the temps on the T stat up so you are sure this boiler runs daily, preferably several times a day. Come back and check it in a few weeks. If no rust, it is obviously not an internal leak. If there is no rust now it is likely to be an off cycle temp issue in the summer.



I assure you that the HO will not care to hear this, however your solution to the problem would be to install an aquastat and maintain low temp in the boiler over the summer. In the long run, It will be much better for both the boiler and the chimney.



Please keep us posted



Thanks,

Ed Carey

bruce_21

Could a major steam leak be the cause?

I went back and cleaned the boiler and started it up, after it started making steam I found a big leak near the end of one of the steam mains. The whole basement was like it had a fog machine in it. The house had been occupied last winter by a single woman who was not there all the time and may have never gone into the basement. The boiler would not have fired after the end of April. There was a wasp nest covering part of the outside air inlet screen, so the little regulator on the outside air kit was likely a little bit open at least, allowing the steam to be sucked into the firing chamber. There is some rust also on the inside of the breeching and at the top of the water heater where it vents to the draft diverter.



So now we'll repair the steam piping which, given that the leak is in a 2 foot crawl space will not be a lot of fun, then I can get to your suggestions for further troubleshooting. Thank you very much for your help. Yes I did install this unit about five years ago and it has performed well until now.



One side note to this situation is that the HO has a service contract with an oil company who shall remain nameless. Their tech came in August and "serviced" the unit and left their tag showing a nozzle and filter were changed. The tech could not have looked inside or test fired the boiler because he would have found what I did when the HO called me thinking that the new tenant just couldn't find the right switch to turn the unit on.

Edward A. (Ed) Carey_3

Follow up

Bruce,

 

First of all I really want to commend you for your detailed and analytical approach to finding the actual origin & cause of the problem.  That is the sign of a true professional.



You said "Yes I did install the unit about five years ago and it has performed well until now".  Did you personally perform annual service on the boiler after the install and therefore have a definitive time as to when you can say that the condition definitely did not exist? If so, then obviously something has occurred or changed since that time.  



If you do not, and your comment was based on the absence of a homeowner complaint, then also based on the obvious non thorough service that the oil company has been doing, the problem may have been there and just not noticed and/or addressed by others.  



If you do have a definitive baseline when the problem definitely did not exist, then that steam leak causing a very moist environment in the basement combined with a partially blocked OA intake could be the combination of events to cause or contribute to just such a problem.  



That partial blockage of the OA hood will cause the relief damper on the OA intake pipe to be pulled open to ingest basement air for combustion. That basement air and the entire basement environment would have been abnormally moist.



After the burner shuts off and the flame is out, that moisture caused by the released steam would be drawn in though the relief damper on the OA intake pipe and through the boiler by the natural chimney draft. 



Once the boiler cools, the moisture would condense on the surfaces in the combustion chamber and in the flu passages. This condition surely could be a cause, or at least be a contributing factor to the problem.



Additionally, that steam leak during the heating season would have made the basement environment exceptionally and abnormally moist. Usually the basement would be much dryer in the winter, and cool & moist in the summer.



During the off season, the elevated moisture level in the basement combined with inactivity of the boiler, could be the icing on the cake.



Please let us know what else you find on this one.



Keep up the good work



Regards

 

Ed Carey