The case of why the hydronic boiler failed

RayWohlfarth

In this Friday's case, we were called to building with a single hydronic boiler. When we arrived, the boiler jacket showed sooting and discoloration. The gas valves showed water damage. The boiler room did not flood,I will let you know the answer Friday I am off to Boiler2024 in Denver.

WMno57

Gas valve water damage due to either uncontrolled humidity or too frequent wet mopping of floor.

I have a leaky unheated pole barn with a concrete floor. Whenever the weather has a rapid temperature and humidity rise, the humidity condenses on all the cold surfaces in my pole barn.

Ray's second image:

WMno57

upon further image review

Continual dripping of PRV creates puddle on floor. Puddle evaporates, then condenses on valve train.

Mustangman

Terminating a relief discharge directly over the gas valve will cause the gas valve corrosion. You can see the stain on the boiler jacket directly under the relief.

The sooting is not so easy to diagnose. For that much soot build up, I would be tearing the boiler down and throughly clean it. I also would be looking at the condition of the chimney and checking the draft. The boiler has a build in draft diverter. I would also take a look at where the boiler gets its combustion air. A lack of primary and secondary air will cause sooting too. Another thing to look at is gas pressure. All the regulators being exposed to water is not a good condition but shouldn't cause the regulators to get out of spec but anything is possible.

Sometimes the homeowner inadvertantly causes the problem. I ran into a job similar to your situation on a light commercial boiler. The room was very small so my first thought was not enough combustion air available in the small room. I saw cardboard stuffed between the bar joist and found it was covering an outdoor air louver … yep, no combustion air. The owner was trying to seal his building up before winter. Opps!!

A wise older guy once told me.. when troubleshooting, first 2 things needed are " An open mind and a bright flash light." Good advice.

Steve

ratio

Discharge from the PRV is the primary cause of gas valve failure to close or possibly slow to open, resulting in rollout. Hard to tell why the PRV was opening, but over pressure due to various failures, or a lack of maintenance, are possibilities.

Sylvain

question : why did the pressure relief valve opened (regularly?)? overfiring

first stage valve and one, two or three of second stage valves failing open? dirt in the gas train?

The dirt leg seems very short.

Why is there a black thing wrapped around the pipe before the cock valve?

retiredguy

#1, A flooded expansion tank or bad bladder in the expansion tank causing the relief valve to relieve on a call for heat. (See the water mark on the floor). #2, a bad or leaking backflow preventer. #3, The PRV leaking through providing too much system pressure. (Again causing the relief valve to lift). #4, not enough or partially blocked make-up air vent. Possibly, a combination of any of the above. All of the devices that would dump water onto the floor would raise the room's humidity and corrode the aluminum valves. It is time for a good service company, like yours, Ray, to make the necessary repairs and up dates.

EdTheHeaterMan

Waterlogged expansion tank. You experienced folks can follow the chain of events from there

Some ideas to consider:

• Steam and air (with oxygen for combustion in it) can not occupy the same space.
• Boiler pressure increases since there is no room for expansion in the tank
• Boiler pressure increases above the relief valve discharge pressure
• Some of the discharge from the Relief Valve is steam and will get drawn into the combustion chamber of the atmospheric burners
• The side of the gas flame where the steam is greater than the air for combustion will burn rich and cause sooting
• The other side of the burner compartment will still burn properly because that is getting air from the room that is not overcome by steam
• Some of the water vapor from the relief valve discharge, will form condensation that forms on the gas train parts. Over time that will cause that noticeable corrosion on the gas train.
• The entity in charge of maintenance is not doing their job, or does not know that it is their job to perform timely inspections of the boiler room.

Am I overthinking this?

I'm. still going with overloaded expansion tank as the initial cause of the problem, the chain of events is all speculation.

JUGHNE

1/4" vent tubing from regs is plugged?

Mad Dog_2

Very high humidity in room from ongoing leak. Not good for internal sections either..premature rust. Mad Dog

mattmia2

Bad/waterlogged expansion tank, continual fresh water from the relief valve blowing off for years, water in the regulator vent making it fire improperly for the soot, fresh water rotted out the boiler.

mattmia2

Or corrosion inside the valve keeping it from opening all the way. I'm thinking not enough gas to fire the furthest burner fully because of some water related issue with the gas train.

RayWohlfarth

Sorry for the delay Im still in Denver for Boiler 2024 and get messed up it’s the time change I believe the cause of the problem was a flooded expansion tank which we found at the site. I think it caused the relief valve to open but the relief valve doesn’t open fully unless the pressure gets too high. Usually the valve just weeps and doesn’t open fully The sooting was caused by two small leaks in the sections. I believe the leaks were caused by the constant makeup water to the system due to the RV opening. Here is the link

https://www.youtube.com/watch?v=561mpzkScc0

PC7060

Good case @RayWohlfarth.

Did the insurance pay out?

Seems like they would deny due to lack of regular period maintenance

RayWohlfarth

They did pay I was surprised