Whooshing/ Decompressing Sound On Boiler

AnthVale

Everything seems to be working fine until my boiler reaches its target temperature and turns itself off. Once off I hear this wooshing sound or what sounds like something's decompressing in the boiler which stops I'm about 10-15 seconds.

The entire system has been purged/flushed thoroughly.

I was told the unit was relatively new within the past couple of years. I have this unit here with a Hydrostat:

https://uticaboilers.com/product/three-pass-high-efficiency-oil-boiler-trifire-trb/

EdTheHeaterMan

So you have a flame in the firebox and at some point the limit control opens the circuit to the burner because the temperature at the aquastat reaches the cut off temperature. Since the burner is no longer making any noise, you hear the boiling water inside the boiler. This would be the water closest to the crown sheet of the boiler. The part of the boiler closest to the flame just above the combustion chamber.

I might suggest that the noise was already there and you could not hear it over the burner noise.

What is the high limit temperature set to?

What is the boiler temperature on the gauge?

How close is the Aquastat sensor well to the crown sheet?

How close is the temperature gauge to the crown sheet?

AnthVale

@EdTheHeaterMan

Yesterday I ran it for a few hours and the Hydrostats target temperature climbed throughout those three hours from 145 degrees to 180 before I ended up shutting it down. This seems to be normal behavior as it learns how much heat the house needs. The noise was making me nervous in between cycles of the burner firing so I turned it off and have not turned it on since.

High temp was set to 193 but I've lowered it to 182.

Not sure about sensor. There is a wire running off to the right that eventually enters into the top under the lid. I put photo below.

The temperature I'm not sure I do not have unit running. After running it for three hours the whooshing noise made me nervous so I shut it down. I don't believe it got over 180 on either the gauge or Hydrostat LED.

I was thinking that the noise could have been there last winter when I was nowhere near as sensitive to different noises as I am now that I'm doing the work on the system.

Like you mentioned in the other post, I may just get a professional over here to go through the system. Handle some of the things I can't DIY.

But, it is really cold in my house so I was hoping to get it running at least, safely.

Thanks again

EdTheHeaterMan

Not exactly sure of the whooshing noise you are speaking of. If it is what I have described above, that is nothing to be alarmed about. I like to think if it as the noise that might happen when you pour a bottle of coca-cola over a glass of ice. All the carbon dioxide molecules are being released from the liquid as those bubbles bound around the glass and the foam eventually settles in the glass.

That can be described as violent interaction of the carbon dioxide with the change in pressure. Or it can be described as a soft fizzz. It depends on weather you shook the bottle of Coke before you opened it.

Im guessing that noise is normal as long as you can describe it as a soft fizz that dissipates within 30 seconds or less, and not a violent interaction that rocks the basement and the pipes and lasts for 15 minutes. You can also reduce that whooshing by lowering the high limit temperature to 165°F. See if that helps

EdTheHeaterMan

One thing does come to mind about your control, the sensor, and the location. If the sensor is not places as far into the well adaptor (Brass hole at the top of the center picture) indicated by the red arrow. Then you may be getting a false reading. But I don't believe that is the case. Check that the sensor at the end of the wire is as far into that well adaptor as possible. A pencil eraser is the best tool for that. But be sure the pencil is long enough to push in 6 to 7 inches. See illustration on the right for a detail on that.

AnthVale

Thanks @EdTheHeaterMan

I was hearing the noise after the initial cycle. It firesd, reached the hydrostats initial target temperature which was 145° and it turned off (needed to reach 135 in order to kick back on) and then I heard that noise. But, now that you mentioned the Coca-Cola it does sort of sound like that. It's not shaking anything haha. It's not very loud and lasts maybe 15 seconds.

I going to fire it up again a little later tonight and let it run and see how it goes.

I Will try and see how far the sensor is down into the well as well.

Thanks again

EdTheHeaterMan

Just as long as it doesn't sound like Dr. Pepper, you should be fine!

Think of it like this. you have a 2500°F flame on one side of the metal in the boiler, and you have water that will not go above 245° (at 12 PSI boiler pressure). that metal has a lot of heat to get rid of fast when the flame is burning. Look at a pot of boiling water on the stove. (I bet it will never boil when you watch it). Those bubbles on the bottom of the pan don't go away instantly, the minute the flame is turned off. But they eventually go away. And you boil water in your kitchen just fine without reporting the alarming results on any cooking forum???

Steamhead

The water may be moving too fast through the boiler. Here's one I ran into many years ago- note that we replaced that old boiler some years ago:

https://www.heatinghelp.com/systems-help-center/adjusting-the-flow-rate-for-an-old-gravity-hot-water-system/

AnthVale

Thanks @Steamhead and @EdTheHeaterMan there is a corroded looking globe valve in my crawl space... I wonder if that has anything to do with it.

For now, i may wait until spring if it's safe to operate as is.

Things ive noticed after running for half a day now:

1: Boiler temperature gauge is always about 10° off from the hydrostat LED gauge. I've checked sensor well, it's as deep as it can go. My guess is the hydrostat is correct and the gauge might be a little off not sure.

2: Once boiler is on for a couple hours and pressure begins to raise in the system, I begin to hear a very faint ring or whistle. Hard to hear but it exists. Pressure seems to stabilize at around 20 to 24 PSI (on boiler gauge...gauge directly after feed regulator topss iff at around ,15-17psi). 20-24psi seems high to me. So, this morning I let water out a bit to see if that ringing will stop.

Cold pressure is at 12 psi directly after the pressure reducing valve. But, the gauge on the boiler always says something higher normally by a couple degrees.

So, adjusted feed regulator and let water out. Does the cold PSI need to be 12 or can it start at 10:00 with expectations of water heating up?

3: Along with the Coca-Cola fizz (which you can hear in this video a bit) there's this crackling sound once it stops firing. Originally I chalked this up as cold boiler components shifting around/settling since I haven't run this in months. But, not sure if this is kettling or how serious/if I can run this this winter and address this in spring.

Heres a video of it shutting off and fizzing then crackling:

https://drive.google.com/file/d/1bU8qPRHHT887VqQ-EKahayNpqlpoa_ll/view?usp=drivesdk

delcrossv

All i hear is the clicking from the heat exchanger cooling off (normal)

Edit: listened closer and heard the fizz.

Dunno. That's a new one. Sounds like water on a frying pan.

SuperTech

I'd open that boiler up and get a good look at the chamber and sections. That's typically a good boiler but I had one last winter that was leaking water into the chamber and caused a huge chunk of carbon to form in the chamber between the burner head and cast iron. Boiler was only two years old and it was wild to see. I hope you don't have something like that happening.

mattmia2

It sounds like a piece of thins sheet metal cooling down and moving as it contracts but i suppose it could be water flash boiling on the surface of the inside of the hx. When was the last time the burner was serviced, the flame could be impinging on the casting somewhere and causing a hot spot.

EdTheHeaterMan

The noise I heard was normal…. You are overthinking this!!!

You can purchase 3 new gauges from the same manufacturer in the same supply house and open the box, place them on a pipe with 3 tee fittings and find that all three will have a different pressure reading and temperature reading, from the same water. These gauges are not used for "Rocket Surgery". They are to give the professional a guide to what is happening in the boiler. We are not using Laboratory Grade instruments here.

Finally the temperature in a boiler can vary as much as 100°F or more depending on where you take that temperature. If you measure next to the Crown Sheet, it can be as high as 240° at 12 PSI, at the return inlet you can have 60°F return water coming back from the radiators, and the water leaving the boiler at the supply opening will be at 180°F and the burner will still be operating. If the circulator pump is off as a result of DHW demand on a tankless coil, that could be a normal temperature range in your boiler. Since your boiler does not have a tankless coil, then your boiler temperature variations from one place to another may never get that extreme. Just know that some boilers operate under those conditions and last for 40+ years…. 

You are overthinking this.

delcrossv

https://forum.heatinghelp.com/discussion/comment/1814293#Comment_1814293

That would account for the clicking, not the sizzle. A look see would be worthwhile IMO.

EdTheHeaterMan

I would thing that the 240°F near the wet side of the heat exchanger closest to the flame would account for the sizzle. Have you ever looked at a pot of water just before it boils. there are lots of air bubbles (may be dissolved air bubbles separating or it could be bubbles of steam getting ready to be released form the bottom of that pot. The fact is that they are there and the sizzle is coming from those bubbles forming and then re-condensing or re-dissolving back into the water that is further away from that "Hottest Place" and finding a relatively cooler 210° place to not be a bubble anymore. The ticking is metal changing shape that may not even be on the water side of the HX.

My "minds eye" works in mysterious ways. And I never even used LSD 🤣