I did some real MacGyver **** here tonight

[Jim K]

And none of my family can appreciate it. I spent the latter half of my day putting the new brains into my boiler. I was expecting it to be plug & play, but it wound up involving re-wiring the entire unit and cutting holes in the chassis for the new harnesses.



And....it was still not firing. Clearly the bad board was not the only issue. These boilers sometimes have to be "choked" by putting your hand over the air intake if they haven't been run for a while. Helps suck the propane into the burner. I discovered I could keep it running if I constricted the air intake. Starting poking around the gas valve and discovered that the venturi is worn out for some reason. The gas valve uses a venturi to create negative pressure to keep the valve open, so if the airflow stops for any reason the valve shuts before the computer even senses a problem.



The venturi eroded enough that it broke in two pieces and disrupted the airflow. After noodling on it for a while, I collected a Sprite can, some aluminum foil tape, and some scissors, and rebuilt the missing portion of the venturi. I was not convinced it was going to work, so I didn't take a picture, for which I'm really kicking myself now. It works prefectly. Boiler fired right up and we have hot water again.

So if you hear of a house explosion in central IL tonight, you'll know why. I'm debating whether to leave the thing on overnight, but it seems completely happy. I'll order a new venturi (which of course only comes as part of the gas valve assembly for $350), but at least I won't have to pay overnight shipping again.

Looking around on the internet, I don't find any discussion of these venturis failing like this. It's very sooty, in spite of being a long way from the burner. The actual combustion chamber is on the other side of the blower fan. Hard to believe it's backfiring that hard often enough to erode the venturi, but that's the only explanation I can come up with. Is there soot in propane? Odd that the blower is NOT sooty or eroded.

Knowing what I know now about the company that installed it, I doubt they ever adjusted it. I have the flame looking good in the window, but once I get it buttoned back up with a new gas valve, thinking I may call an HVAC guy who actually owns a combustion analyzer to get it dialed in correctly.

Anyway, I tried explaining to my family what I went through to get them hot water, but they have no idea what I'm talking about. Oh well.

 

[catmandu]

You, sir, are awesome. Your family appreciates you, even if they do not tell you. Someday they will change your diaper, and you will remind them of this boiler escapade. Ending the reminder with "So, there!"

 

[SoonerAviator]

Anyway for the flame to "rollout" into the venturi? I wouldn't think it would be possible on that side of the valve, but I'm sure stranger things have happened.

 

[Racerx]

Tell them you're a mechanical savant that gave them hot water when "the guy" couldn't....and you can just as easily turn the heat off mid shower. Just because. Then say your thirsty. First one to bring you a beer definitely gets a hot shower

 

[aterry1067]

Good on ya' for the quick fix, but I'd want to seriously find out why there is evidence of dirty burning that far back. When it lights off, is it a subtle light, or a big whomping WHOOSH sound? What do the burners look like?

 

[Dave Theisen]

Are we not going to discuss the train tracks?

 

[AV8R_87]

I'll order a new venturi (which of course only comes as part of the gas valve assembly for $350), but at least I won't have to pay overnight shipping again.

See if someone made a 3D model for ut and 3D print it. Actually, it looks simple enough to design and 3D print.

Is that soot on it, or just plastic dust? I'm thinking the airflow made it vibrate and flex to failure?

Also, MacGyver got lazy

 

[AV8R_87]

Are we not going to discuss the train tracks?

That would derail the thread.

 

[aterry1067]

That would derail the thread.

With a malfunctioning boiler, this thread has already jumped the tracks.

 

[Jim K]

Good on ya' for the quick fix, but I'd want to seriously find out why there is evidence of dirty burning that far back. When it lights off, is it a subtle light, or a big whomping WHOOSH sound? What do the burners look like?

Nope... nice & quiet. I can't find any fault with the thing. When I "choke" it, I get a little whomp and can feel it push air back a bit. As I said, it's a long way from the burner to the venturi:



And of course it shuts the gas off long before the fan. It'll be interesting to see what the aluminum can piece looks like after a couple days of running, because i know what it looked like going in. That venturi has seen a decade and 10s of thousands of cycles. The one pictured above actually is one my dad had replaced ten years ago with the exact same failure mode. He kept it, of course

See if someone made a 3D model for ut and 3D print it. Actually, it looks simple enough to design and 3D print.

Is that soot on it, or just plastic dust? I'm thinking the airflow made it vibrate and flex to failure?

Also, MacGyver got lazy
View attachment 137846

Printing one was my first thought. It's more complicated than it looks, as there's a gas passage on the back side. There's also the fact that it don't know what a new one looks like. My repair was based on my intimate knowledge of Bournoulli's Principle . I wish I had a scanner.

Never thought about plastic dust. Where it failed isn't actually touching anything though. Maybe it needs an air filter

 

[aterry1067]

Keep us updated.

The fact that the Venturi is so far away from the burner and still seeing a flame front is the concerning part. But…. It’s been flying that way for years, so it should be ok.
Check it out in a day or two and see what you find.