Multiple loud bangine noises when heat is called for

[forumpersona]

I live in a 2 story/3 zone (one for the basement) 2700 sq.ft. home in CT. We moved in 2 years ago. During the 1st winter we saw that there was some banging in the pipes when heat was called for. Usually one loud bang followed by the baseboard fins pinging.

We had some work done to the house where the main water supply needed to be shut off and pipes drained. Since then, the pipes bang a lot worse. We're talking about multiple bangs more like 5-15 of them in rapid succession as heat is called for. These bangs are all in our bedroom which is the room furthest away from the boiler.

We just had the boiler serviced and everything was ok. We mentioned the banging and the possibility of air in the system to the technician and we were pointed at some automatic vent valve that is supposed to auto-vent the air but I am not convinced. Too much of a coincidence that after we drained and refilled we got so much extra banging.

It is now interfering with our sleep because as it got colder, the heat cycles on and off many times per night. Amy suggestions?

Thx

 

[Dana]

A bit more information about the boiler and system would be useful.

This is a bit like asking to diagnose the source noises being made by a car, without specifying even the fuel type or size of the engine, etc., or even the manufacturer.

Loud bangs during initial calls for heat are common in steam heating systems, as the front of super-hot steam encounters droplets of water in the supply pipe, but it sounds as if yours is pumped hot water?

In pumped hydronic systems if the pipes are in contact with wood framing members it can cause ticks & bangs, creaks & squeaks as the length dimensions of the pipe change with the sudden change in pipe temperature, but they're not usually loud bangs. This can often be fixed by judicious placement of less-grippy pipe hangers.

A malfunctioning boiler that needs (but isn't successfully) pre-purging of the burner prior to ignition or is having ignition problems can set off micro-explosions in the exhaust venting as it starts, but that might be either ruled out or become a prime suspect, depending on the boiler type, make/model.

Draining the potable water supplies would not affect the operation of the heating system, which is isolated from the potable lines. Unless you drained the heating system as well (which would not be necessary for working on the potable plumbing), that bit of information is a red-herring. The heating system keeps the same water all the time, pumping it around in loops, and does not need (or want) a constant supply of fresh water. It also operates at a lower pressure than the potable water supply.

 

[Sponsor]

 

[forumpersona]

A bit more information about the boiler and system would be useful.

This is a bit like asking to diagnose the source noises being made by a car, without specifying even the fuel type or size of the engine, etc., or even the manufacturer.

Loud bangs during initial calls for heat are common in steam heating systems, as the front of super-hot steam encounters droplets of water in the supply pipe, but it sounds as if yours is pumped hot water?

In pumped hydronic systems if the pipes are in contact with wood framing members it can cause ticks & bangs, creaks & squeaks as the length dimensions of the pipe change with the sudden change in pipe temperature, but they're not usually loud bangs. This can often be fixed by judicious placement of less-grippy pipe hangers.

A malfunctioning boiler that needs (but isn't successfully) pre-purging of the burner prior to ignition or is having ignition problems can set off micro-explosions in the exhaust venting as it starts, but that might be either ruled out or become a prime suspect, depending on the boiler type, make/model.

Draining the potable water supplies would not affect the operation of the heating system, which is isolated from the potable lines. Unless you drained the heating system as well (which would not be necessary for working on the potable plumbing), that bit of information is a red-herring. The heating system keeps the same water all the time, pumping it around in loops, and does not need (or want) a constant supply of fresh water. It also operates at a lower pressure than the potable water supply.

Thanks, it is an oil system, hot water. I am not sure what the workers did when they drained the system. I saw them using the drain in picture called 'waterfeed.jpg'. I also attached pictures of the system.

 

[forumpersona]

Thanks, it is an oil system, hot water. I am not sure what the workers did when they drained the system. I saw them using the drain in picture called 'waterfeed.jpg'. I also attached pictures of the system.

Here's a pic of the gauge on the boiler when it was producing heat, it clicked off a few seconds after I took the pic. The system seemed to cycle on @ 170 and off at 190. To address your framing point, the copper pipes are going through the floor and the holes are not spacious. The wood is practically touching the copper. I think that's why the system used to bang once or twice in the past. My problem is that the once/twice has become 5-15 bangs.

 

[Dana]

First, if that gauge is correct the system is seriously over-pressured for a 1-3 story house. Most boilers are outfitted with pressure relief valves (PRV) set to open at 30psi. While 50psi relief valves are available, it's not standard, and would only be appropriate for a boiler heating a high-rise. Y0ur gauge is reading over 50psi- it should be reading half that or less, even when running. The maximum operating pressure specified for most cast-iron boilers is 50psi. It's likely that the PRV on your system is a 50psi unit and it's possible that it's spitting water on every burn cycle, but no WAY should you be running anywhere near that high. In the picture looks like it's riding over 40psi.

When the system is cold/tepid between calls for heat it should be about 12psi, not more. If the system has a lot of water volume (big old fashioned radiators) it might run as high as 25psi when the boiler is at it's high temp. For fin-tube baseboard it shouldn't even hit 20psi. The water expansion volume is SUPPOSED to be moderated by the expansion tank to limit the pressure, but if the expansion tank has failed or wasn't properly pre-charged, it could be hitting the stops. Yours looks like a pretty big one, which makes me think you have a high volume system. They may have installed a 50psi PRV in order to be able to run at pressures above 30psi, (which would not be a problem), but if you're blowing past 50psi you need to do something about it, since it is stretching the bolts that hold the boiler plates together.

Whether this is the direct cause of the banging noise or not remains to be seen, but this is serious and it MUST be corrected, and soon. It's possible that when the techs re-filled the system after draining it they over-filled it &/or didn't set up the pre-charge on the expansion tank correctly, or it's possible that the fill valves for the system are constantly seeping, overfilling, but you can't just let it go or the boiler itself will start leaking (at which point it's basically toast.)

If you want to do a bit of DIY diagnosis & correction, observe what the pressure is when the burner has been off for over an hour. If it's still over 20psi, (carefully, without scalding your self) bleed the system down to 15psi or so, then turn up a thermostat and see how the system behaves, and where the pressure ends up when the boiler hits 190F. It looks like there is a convenient hose-attachment valve above the circulation pump in your boiler picture. A 5 gallon bucket would likely be more than sufficient capacity for bringing the system pressure down to 15psi.

 

[Dana]

BTW: It's also unlikely that the boiler needs to run at 190F to be able to heat the house. It looks like your domestic hot water is being served by an indirect tank operated as a zone off the heating system. Adjusting the high-limit down and adjusting the differential between the high/low to the maximum (as long as the low-limit stays above 140F, to avoid corrosive exhaust condensation) will save on oil use by lowering the average boiler temp, which lowers the standby loss to the basement. The recovery from deep setbacks would be slightly slower, but in most cases the original radiation is adequate for getting the heat into house even with 150F water. Going lower temp on the radiators also has comfort benefits, with more stable room temps, less temperature overshoot, etc.

Also note, a leak in the heat exchanger in the indirect hot water tank could also slowly over-fill your heating system, which is something else to figure out if other diagnostic efforts fail.

 

[forumpersona]

BTW: It's also unlikely that the boiler needs to run at 190F to be able to heat the house. It looks like your domestic hot water is being served by an indirect tank operated as a zone off the heating system. Adjusting the high-limit down and adjusting the differential between the high/low to the maximum (as long as the low-limit stays above 140F, to avoid corrosive exhaust condensation) will save on oil use by lowering the average boiler temp, which lowers the standby loss to the basement. The recovery from deep setbacks would be slightly slower, but in most cases the original radiation is adequate for getting the heat into house even with 150F water. Going lower temp on the radiators also has comfort benefits, with more stable room temps, less temperature overshoot, etc.

Also note, a leak in the heat exchanger in the indirect hot water tank could also slowly over-fill your heating system, which is something else to figure out if other diagnostic efforts fail.

The psi is slightly less than 20. You are looking at the feet H2O number on the outside of the scale. The inside of the scale is right around 20. I noticed that it stays at that pressure all the time. The temps seem to be going from the 170 mark (when the boiler starts) to 1/3 of the way between 170 and 220 (around the 88 mark on the celsius scale which translates to 189 fafhrenheit).

 

[Dana]

Oops! Sorry for the over-reaction on that quick misread- mea culpa! I'm happy that it's running only ~20psi @ 190F, a totally normal system condition.

Did they actually drain the heating system (and if so, why?) , or did they just bleed down the pressure a bit into a bucket?

There is rarely a reason to run the boiler that hot, but it seems to be an unusually high differential swing. Running from 170-220F is a 50F differential- most aquastat controls don't let you set it that high.

Have you tried having someone turn up the thermostat while you were in the basement to observe the boiler operation? You may be able to isolate where the noise is coming from. If the burner is mis-firing on ignition and making small explosions in the vent piping and flue it is potentially dangerous (especially if it's getting worse), so it would be good to rule that out ASAP.

 

[forumpersona]

Oops! Sorry for the over-reaction on that quick misread- mea culpa! I'm happy that it's running only ~20psi @ 190F, a totally normal system condition.

Did they actually drain the heating system (and if so, why?) , or did they just bleed down the pressure a bit into a bucket?

There is rarely a reason to run the boiler that hot, but it seems to be an unusually high differential swing. Running from 170-220F is a 50F differential- most aquastat controls don't let you set it that high.

Have you tried having someone turn up the thermostat while you were in the basement to observe the boiler operation? You may be able to isolate where the noise is coming from. If the burner is mis-firing on ignition and making small explosions in the vent piping and flue it is potentially dangerous (especially if it's getting worse), so it would be good to rule that out ASAP.

Dana, thx, it does not reach 220. It think it starts at 170 and stops at around 190. I have been in the boiler room while the boiler starts. It's completely quiet. The noises are purely in the pipes in the upstairs bedroom. The colder it is outside, the louder the noise of the pipes. I've read about using outdoor reset to keep the pipes from cooling off too much. Perhaps that could be the fix but it bothers me that it got so much louder after they had turned off the water. I don't know exactly what they did. It was a bath remodel so they had the water off for a while.

 

[Dana]

Unless they moved the radiators/baseboards in the bath they shouldn't have had to drain the heating system, so I'll assume that's why they did it.

A 20F differential swing 10F either side of 180F is pretty common, but the actual need for 180F water is pretty rare. With the model number you can probably find the installation & operation manuals online, which would show you where/how to set the high/low limits & or differential.

If it were air in the system the vents would have purged most of it by now, but if there is a bleeder valve on the radiator/baseboard in the bedroom you could bleed it and see if there's any air there, and whether that improves the noise symptoms. The best location for a system vent is at the highest elevation of the system, since bubbles collect more quickly there, but on pumped systems they can still work in a number of locations, such as the one on top of the cast-iron air-scoop whatzit that the expansion tank is hanging on.

 

[Tom Sawyer]

Tridicator gaugs are notoriously inaccurate. Pretty good chance that the boiler is running hot and making steam which causes the banging in the pipes. The pinging is a sign at the baseboard element slides are not properly aligned within the baseboard or that some of the piping holes are slightly undersized and the pipes are fibbing on them but, more probably it's the fins themselves. Lower the high limit temperature about ten degrees and see if the banging stops. If not, try another ten degrees.

 

[Dana]

The sizzle & bang to be flash-boiling was a possibility I too was considering, except for the statement:

"I have been in the boiler room while the boiler starts. It's completely quiet. The noises are purely in the pipes in the upstairs bedroom."

It's possible that this observation isn't correct, and it's worth verifying, but for now that would rule out boiler kettling as the issue, which would be more apparent in the boiler room than somewhere out on the zone. If the system pressure is 5psi when it starts up, that would contribute to a flash-boil situation, but if the system was already at temp and running 12psi+ you wouldn't get flash-boil until the temp rose to something ridiculously high, over 230F. Gauges could be 30-40F far off, but the aquastats? Probably not. This may take more careful system observation & notes to rule that out.

 

[forumpersona]

The sizzle & bang to be flash-boiling was a possibility I too was considering, except for the statement:

"I have been in the boiler room while the boiler starts. It's completely quiet. The noises are purely in the pipes in the upstairs bedroom."

It's possible that this observation isn't correct, and it's worth verifying, but for now that would rule out boiler kettling as the issue, which would be more apparent in the boiler room than somewhere out on the zone. If the system pressure is 5psi when it starts up, that would contribute to a flash-boil situation, but if the system was already at temp and running 12psi+ you wouldn't get flash-boil until the temp rose to something ridiculously high, over 230F. Gauges could be 30-40F far off, but the aquastats? Probably not. This may take more careful system observation & notes to rule that out.

The system is around 19-20 psi all the time. I spoke to a local plumber and he suggested I set the LO. I did that, set it to 130. The high is at 180. I also increased the High Diff to 20 (from 10). Now, the boiler goes on less frequently. The banging has decreased dramatically both in frequency and intensity (loudness) but it still happens and when it happens I get 30-40 in a row. It's possible that some of the requests for heat coincide with the boiler being at the high of 180 while the majority may come in when the temps are between LO and HI and just the circulator provide the heat. My wife is complaining that the house feels cooler although the thermostats in the house read the same temps as before. It could be placebo. I am thinking of lowering the HI to 160 and keeping the LO at 130 as a test.

 

[Tom Sawyer]

Yep, do that. She's making steam.

 

[Dana]

If so, it's very odd that it's not audible in the boiler room, only in the second floor zone. It's usually dead-obvious standing next to the boiler when it's flashing or kettling.

When it's in the sizzle-pop-bang mode the heat transfer efficiency from the fire side to the water is dramatically reduced- it's an efficiency problem too, not just an annoyance. This will sometimes happen if the flow through the boiler is too low- how old is the pump? If its old enough to vote and the symptom persists even after you lower the HI temp, it's probably worth replacing- either the whole pump, or just the impeller cartridge, assuming it's that type of pump. (Most of the green Taco pumps have replaceable impeller cartridges) .

Most houses with systems set up for 180F water can still be heated with 150F (or even 140F). Since this weekend is going to hit temps below the 99% outside design temps in most of CT, set the HI to 150F with a 20F differential and see if it keeps up.

If it does keep up, leave it there, then test to see if it short cycles on zone calls. (Ignore short cycling on the basement zone.) To test short cycling, turn up the T-stat on the zone with the least amount of radiation by several degrees, and turn the T-stat on the other zone way down (or off), then go to the boiler room and time the burns. If it's getting 5 minutes + per burn and fewer than 10 burns/hour it'll be close to hitting it's AFUE numbers. If it's getting 10minute burns or higher it'll surely make the numbers. At 3 minutes or less you'll have to bump it up 10F and see how much it improves. If you can't get more than 3 minutes out of it you may have to install a heat purging boiler controller that runs it over a wider differential.

By lowering the operating temp of the boiler you lower the standby & distribution losses, which improves the fuel economy numbers. The boiler room may no longer be the warmest room in the house, but that would be a GOOD thing (especially if it's in an uninsulated basement.)

 

[forumpersona]

I just set it to LO 135 HI 165 and Diff of 20. Let's see how it does tonight. I will adjust accordingly. Dana, I have to read your email a few times to digest the procedure you're describing

 

[Dana]

Set it lower than 165F- that's not a big enough bump. Start at 150F w 20F delta and a 130F LO. Then bump it up 5F at a time if the radiation doesn't keep up or the boiler has ridiculously short burn cycles (on any zone other than the basement, which will probably short-cycle no matter what.)

Odds are better than even that it WILL be able to keep up with a 150F high-limit, if history is any guide. From the pictures it looks like the burner is plumbed with natural gas, right?

If it's an oil burner, better to set the LO limit at 140F, and set the HI to 155F with a 15F delta, to prevent corrosive condensation.

 

[forumpersona]

Set it lower than 165F- that's not a big enough bump. Start at 150F w 20F delta and a 130F LO. Then bump it up 5F at a time if the radiation doesn't keep up or the boiler has ridiculously short burn cycles (on any zone other than the basement, which will probably short-cycle no matter what.)

Odds are better than even that it WILL be able to keep up with a 150F high-limit, if history is any guide. From the pictures it looks like the burner is plumbed with natural gas, right?

If it's an oil burner, better to set the LO limit at 140F, and set the HI to 155F with a 15F delta, to prevent corrosive condensation.

It's oil.

 

[Dana]

Don't set the LO below 140F then, no matter how you set up the rest. (If it were gas 130F would be fine.)

A 20F (or higher) differential will give you longer, more efficient burns, than a 15F diff at 155F/140F, so try it at 160F/140F for awhile and see how it does.

 

[forumpersona]

Good news, with the HI set to 160 and LO at 140 with a Diff at 15 the house stayed warm and the noises really diminished although the outside temps were around zero last night. The boiler did run every 10 minutes or so for 2 minutes at a time though.