Why exactly?
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I am already in the repeat mode. If I haven’t explained to your satisfaction, then the threshold for your satisfaction is beyond my abilities.
Can not, or should not? 
Don’t forget the power of construction adhesive.
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I see pictures like that and I realize how much I love living in San Diego. Me and winter don’t get along very well.
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Sorry, I’m just waiting for you to deliver data, rather than opinions…
You know, why and when combustion gas goes through the sublimation or deposition process as it moves through the flue.
Never mind, I was just trying to understand your thought process. Was confusing to readers.
Dave, I know you know a lot about HVAC. You gave me some valuable insights into inspecting heat pumps which I rarely see. But your comments on this topic have me scratching my head.
Where do you see an extreme? Surely, not 23F. I reviewed my comments here and no where did I say that the combustion gas temp is wrong. In fact, I said that the flue temps are what they are. Sizing and designing the flue correctly so that the flue gases stay warm enough to evacuate most of the moisture in the gases is what I claim is important. Here is a photo of a flue on an 80% furnace (with water heater tie-in) where excessive condensation dissolved the flue on a five year-old system.
Then your next sentence in that post is…
You seem to say that there is a problem in the original post, but then say ice has nothing to do with it. What design flaws do you see? Would the ice still be there if there were no design flaws? Maybe we disagree about what is excessive condensation. I think when the condensate becomes free flowing that is bad. I claim that it can (and often does) “eat” a hole in the flue which can leak combustion gases into a house. My conclusion is that since 23F is a common winter temp, then if free flowing condensate is occurring at that temp, then there is a high likelihood of damage occurring to the furnace flue in an 80% furnace.
BTW, here is a photo of those “white marks” that you mentioned earlier.
I don’t like to see that either, because in my opinion, that is an indicator of excessive condensation.
And finally, since your comments have confused me, maybe we are somehow talking past each other. You have made comments and even posted a photo of the damage from excessive condensation where a galvanized flue was used on a 90% furnace. So, why wouldn’t similar excessive condensation be a concern on an 80% furnace? Isn’t free flowing condensate excessive? Do we really disagree that a gas-fired furnace should be able to evacuate the combustion gases sufficiently that the humidity suspended in the gases does not condense enough to free flow condensate back down the flue at a mere 23F?
@dandersen I did not mean to imply that I would vent a condensing furnace this way.
I meant to leave the impression that Murphy’s Law applies: if it can be done wrong, it will be done wrong, and it’s up to the HI to catch it.
What an arrogant worthless response and frankly not one that I expected from you. Luckily, for all home inspectors they don’t have to misspell psychrometrics to understand that excessive uncontrolled condensation in a gas furnace is bad.
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Last year a new boiler was installed. There seems to be some knocking going on. The first remedy was to add piping. A year later, there is still knocking. The tech determined that water wasn’t getting through therefore he opened the valve. Now there is condensation resulting in an ice formation on the roof. I am waiting to be told what the next step is.
Really not much information here. I would be in contact with the HVAC company.
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The HVAC company that installed my boiler sent an email stating that “during the cold weather like we were experiencing it is normal for ice to build up like you are seeing” Additionally, they explained that the warmer weather will make the ice disappear (I think we all know that warm temps melt ice however that has no bearing on the cause of sudden ice build up or the functioning of the newly installed boiler.
On the last service call, the technician noted that he added H20 and set autofill to 15psi. I had the furnace thermostat turned down to 65 at the time of service. The outside temperature was around 7 Fahrenheit. When he was finished, I turned up the heat. The next day I saw the stalagmite on my roof. The stalagmite did not seem to grow during the next few day before the above freezing temperatures settled in.
My question to the group is: Do you think this was a one time occurrence resulting from the adding of water into the boiler or is this a problem with the new boiler in general. The old boiler/vent never did this.
Why would adding water to the boiler make water vapor out of the flue? The ice you see is from combustion gas. The water added was for the circulating loop throughout the house.
How often is it 7F there?
The ice comes from the moisture of the fuel you are burning. Like your car exhaust steam when you first start up on a cold day. The water is not coming from the radiator, it’s from the fuel you are burning.
This ice is from condensation occurring from the rain cap. When it drips down to the roof, it would freeze immediately at 7F, would you not agree?
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I do agree, I do believe that this is a problem. How do I get my HVAC to seriously address the “symptoms “ of poor installation? Whenever the furnace turns on there is knocking in the pipes. I feel like I am in a bowling alley listening to a 1 pin spare being picked up. Thank you for your response.
Tell them to get the air out…
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As I understand what you said, you are talking about two different and isolated systems within your boiler:
What you describe appears to be the distribution component of your boiler, the fluid that runs through the tubes to the heating elements in each room of your house. Unless there is a leak inside the heat exchanger, none of this fluid goes up the flue. Knocking on the pipes is from air in the distribution system. That should not be present. A bleed valve should be present in your distribution system to remove that air.
This condensation is from exhaust gasses of combustion. This is the combustion gas exhaust system. It has nothing to do with the fluid in your heat distribution system. Recognize that large amounts of H2O are present in combustion exhaust gasses. Turning up the heat results in more exhaust gasses moving up your flue. If the flue is not warm, then water condenses as it moves up the flue. Maybe your boiler is short cycling, the result being the flue does not heat up enough to reduce condensation. Maybe it is exposed to excessive cold air, thus your flue is cold, resulting in condensation. Or as already said, maybe there is a leak in your heat exchanger.
Your boiler picture shows what appears to be an atmosphere vented boiler using an electric vent damper. I don’t see a draft hood on that flue configuration. Without researching manufacturer installation instructions and not knowing the details of that electric vent damper, a draft hood may or may not be required in your flue configuration.
I did not catch the fuel you use.
Oil requires a specific flue temperature to be maintained.
Gas has more water in it than Oil.
But you’re talking about a 7F day? Is this the normal regional design temperature for this equipment?
We do not design equipment to the worst case weather scenario.
Why did they have to add water?
The boiler has an automatic fill system. There is no need to add, unless there is another problem we don’t know about.
Maybe find another technician.
Thank you for your response David……I do feel like I am in a David and Goliath situation due to my limited knowledge of HVAC.
Regarding:
- __I did not catch the fuel you use.__My Boiler is a Burnham Series 3 Low Press Boiler and it uses gas.
- But you’re talking about a 7F day? Is this the normal regional design temperature for this equipment____? I live in Minnesota and extreme temperatures are quite common during our winter season. We just went from a stretch of -20F windchill to 40F this week. The 40F is the odd temperature for January. Our normal overnight is about 8F.
- Why did they have to add water?
The boiler has an automatic fill system. There is no need to add, unless there is another problem we don’t know about. According to the technician’s note, he added water by opening a valve and then made an adjustment to the autofill setting. He told me that the reason for the hot pipes was because sufficient water wasn’t coming through. Maybe the original installer did not have the valve properly opened? Or maybe the autofill wasn’t turned on?
I just checked my pipes and currently they are warm to the touch as they should be. Previously the pipes were very hot, in my opinion far too hot.
Since the adjustment I am not getting the big bangs that sounded like a sonic boom overhead.
Although I still hear my furnace turning on with clicks and hollow knocks here and there. I don’t mind the noises as long as my furnace is operating safely. I think the formation of the stalagmite may have been a one time thing. It is hard for me to be certain. This morning, the temperature is 28F. There is no ice formation. I am guessing that the stalagmite was a result of the previous state of the boiler prior to the technicians adjustment.
I am disappointed that my new furnace is giving me more concern that the really old boiler I had. Since being installed last year I have had a technician out four times.
#1 something to do with the pilot light and a switch (the installer was embarrassed because he had forgotten to do something very simple).
#2 try to figure out why it is knocking, ( after looking at my furnace, technician reassigned the fix to the original installer)
#3 the original installer then added piping to the system, he said that combustion was building because there wasn’t enough (space)?
#4 added water, opened valve and adjusted auto setting.
I think maybe it is fixed now? The technician told me that the furnace has safety features built into it and that it would turn off before any catastrophic event would occur. Oh yeah and I was told “the warm temperatures would melt the ice” lol.
Once again, thank you David.
Dayna Gulley
Wow Michael, thank you for that information.
I will re- read again.
About 9 years ago I had a water heater installed during a time where I was going through a difficult divorce.
The installer told me that my flu wasn’t to code and left.
I didn’t know what to do, so I ignored it and went on and fought my divorce battle.
So, when I bought my new boiler I also bought a new water heater to make sure that all issues were resolved.
They built a whole new system.
Is the problem on the roof or down in the furnace room?
Thank you so much,
Dayna
I agree with that, thank you.