Help! Mayday! Calling all engineers, scientists, HVAC experts. For over a year in my new apartment I've had an abnormal, cyclical thunderous thud (see video below) in the area of my HVAC unit. We've determined it's not my unit as it happens even when it's off. Subsided in winter, worse again now in summer, so much so I can't sleep through it, getting if I'm lucky 6, but usually 3 or 4 hours a night, hardly sleeping with the sound and the anticipation of the 12-minute cycle of banging.

I'm on the 5th of 7 floors, but the apt above has a different configuration so my unit is the last in the line. There are no ducts, only risers. The sound is like thunder and vibrates the entire wall and ceiling but definitely comes from the area of the unit. And it's a fairly new building, (c) 2009. My building can't figure it out, they've opened up the ceilings in my BR and LR near where the unit is. They've switched out HVAC units around me. They've investigated the mechanicals on the roof. They've played with the water pressure - all to no avail. In the meantime I'm in torment, with no option (financially or otherwise) to move at the moment. Any help / ideas appreciated. It's been physical and mental torture.

My grandmother refered to such unexplained noise as "hants"moveing around at night. Grandpaw said it was a just nest of coons. I didn't like either explaination so refused to spend the night over there.

This probably won't help either: Guessing doesn't fix anything and apartment life where you call on site maintenance dept. to solve complex problems rarely ends in anything you want.

What needs to be done: The noise HAS to be 'investigated' when it is making the noise. In other words if the noise happens at 3am that's when you get people "physically looking at it".

Good luck getting your apartment paying for that one. It's probably more common for people to move somewhere else to resolve issues like this.

Perhaps an expansion/contraction banging? Is there anything else in this "HVAC area" like a boiler or water heater? Perhaps there is a loud damper on a make up air intake?

Thanks Vith. Nothing near, no. The roof is two floors up, and they've been checking dampers, water pressure. Each apartment has their own individual Omega unit for heat and a/c. and everything else is in the basement - I'm on the fifth floor.

Any other piping that runs through the area? It could be a water hammer also. Shouldn't happen at specific intervals though. Maybe it isnt a specific interval, perhaps it is whenever people in the other units use water and it just happens often. Water hammer is common with toilets when they get full and stop fast.

If the HVAC isnt running, there is no way we can guess what the noise is without being there to see what else it could be. That noise could be anything, but usually wouldnt happen at normal intervals.

Thanks again Vith. Last year when this happened someone suggested water hammer as well. But yes, when it cycles, it's like clockwork, every 12 minutes. Then there's been other periods when it's absolutely silent. It's maddening. Also seems to happen mostly during the summer. happened a bit intermittently in the winter, stopped totally in March, and then came back with a vengeance end of May. They've got HVAC people looking at it but I'm amazed they can't find it. New building, 2009, they've pulled blueprints, it only happens in my apartment. HVAC people coming in next week to hear the sound.

If I had to guess I think I would look at the water pumps to the facility. The every 12 minute thing seems to dictate it is something that is 'timed to run'.

Water pumps within a facility are used to maintain water pressure and distribute it to where it's needed. They also may have a loop that cycles hot water and maintains hot water availability. Typically this is done in large buildings so the wait time for hot water to reach certain destinations isn't too long of a wait.

Why this noise disappeared in March is a tough one. This is merely a guess.

It also could be the timing of an irrigation system for the grounds of the facility. 12 Minutes for each zone, when the zone shuts off makes a water hammer sound. Only to be followed 12 minutes later when that zone shuts off and a new zone opens...

Disappeared in March because "they weren't running the sprinklers to the facility."

Those are my guesses.

Thank you so much Austin Air Companies. I will bring this to their attention. No irrigation systems here though.

I should add to this bang/thud doesn't happen all day all the time, but it happens especially in the mornings, sometimes into late morning or noon, sometimes at night -- obviously can't tell when I'm not here during the weekdays. But it's not constant. But it's been pretty much constant overnight and in the mornings since before Memorial Day. And no sound at all for over a 2- hour period last Saturday. It's baffling.

Sounds like a perfect reason to break your lease and find a new place.

It's not that simple. sktn77a I love the apt, it's otherwise the quietest, cleanest place I've ever lived in. I have a garden on a sun-splashed balcony that I love - I'll never find that again here in NYC. And the cost to move in Manhattan is prohibitive - at least 5K to even think about it - and I've moved twice in the past year after selling my apt. I am absolutely stuck. I don't want to leave - I just want the thing found and fixed. It's not normal, nobody else hears it - there's got to be a physical cause and a resolution. Hoping, anyway. Thank you!

"nobody else hears it - there's got to be a physical cause and a resolution." That nobody else hears it is frightening. Sounding more and more like Granny's hants as it unfolds.

klem1 That's to say, nobody else hears it in other apartments, but it definitely has been heard in my apt. The video I attached shows it, in my first post. My hard-of-hearing Mom visited and heard it and recorded the 12-minute cycling as well. The super and management have heard it. Unfortunately there's not much humor to be found in this.

Are laundry facilities inside the apartment or in a main area some where within the complex. Where are these located in relation to your apartment?

It might be water hammer of a single washing machine or maybe when it goes to spin cycle it's out of balance or something making the noise?

merely cheap guesses. My crystal balls say nothing.

Austin AC, we all have individual W/D - mine is not near HVAC unit. Doubtful that it would be W/D given that the noise often happens at the wee hours in the morning, and at other times I've recorded it for hours in the 12-minute cycle, nonstop. This weekend it's been intermittent, yesterday in the loud banging 12-minute cycle for hours in the morning, silent all evening (atypical, lately); this Sunday morning a bang 4 or 5 times between 3 and 6am (as opposed to the nonstop cycle I've heard before). It's so impossible to predict. I appreciate the guessing! Better than nothing.

What type of AC system does the building have?

Are they individual ducted forced air system? OR Is the building cooled by a chiller?

If it's a chiller there's only one gigantic condenser usually water cooled. Sometimes the chiller condenser is on the ground with a large fence around it. Other times it's on the roof.

If it's individual ducted forced air then each apartment would have it's own condenser sometimes on the ground, sometimes on the roof.

There is a cooling tower on the roof (which actually "went out" yesterday for the whole building - and it's been silent ever since -- hmm -- and since repaired, and still silent in my apt), and individual ductless units (risers, no ducts) in each apartment with forced air - Omega, they're called. Hope this answers your question. Here's a link to the unit that's in each apartment: Omega

the link you provided is no good...

ok, suspicion is now back on the HVAC system. I would suspect most likely a pump or some other valve near where you hear the noise. It is something that is timed to operate. The reason you hear the noise (an no one else) maybe due to the proximity of which your apartment is to this pump or valve.

Given the age of the building (2009)... has the noise always occurred since you lived in this apartment? Has there ever been a time for the period of a year or longer that the noise was never heard.

You claim you heard this noise for over a year. When did you move into the apartment?

Chillers operate with brine solutions that run thru them, the brine is forced to flow thru the system via large pumps. Think of a large slurpee machine... but you don't actually see the slurpee mix, just large pipes with pumps.

If you have only lived in this apartment for just over a year. The problem has likely always been. Which isn't good news for you.

The hammering of a pump turning on or shutting off due to possibly poor piping design of the chiller installer in an apartment complex? Realize this is a guess, but if this is what it is, it would explain why they haven't fixed it and why they probably won't fix it either.

Thank you Austin again! I moved in March of last year, the noise started around the summer, and stopped after September, some banging a bit over winter, totally stopped in March, and started again in Memorial Day (right around the time A/C was being used again here in NYC). Previous tenants never reported anything.

However, this weekend, the A/C in the building totally went out, emergency work was done, a pump on the roof was replaced, and NO SOUND SINCE THEN. I'm hoping this is the problem - I've told them before that my sounds indicate a systemic problem. But it has stopped before (last August for 2 weeks and come back with a vengeance ). But this is very suspicious and I'm hoping that just by luck the problem has been fixed.

The building management did look over last year and this year, could not find the problem in this relatively new (2009) building, switched out many HVAC units, had people searching on the roof, playing with dampers etc. Only time now will tell. Thank you!

Unfortunately sound is back. After silence since Sunday morning, banging occurred last night 3am-4am and some this morning. So dismayed. They didn't replace a pump but apparently fixed a valve on Sunday. But banging is back. So sad. After a year of this I don't have much hope at this point. HVAC team coming tomorrow to my apt.

It has to be some HVAC zone near your apartment that is getting hammer effect due to timing of either a valve closing or a pump that starts and stops on a 12 min cycle.

It could be poor chiller piping design.

I only think this 'poor piping design' because it sounds like the sound has always existed for you since you moved in except for a few months here and there. Was the apartment rented before? Try to find out who it was, track them down and ask them if they moved because of the noise. That would probably help you realize your situation much faster from what it sounds like you've already been thru with the maintenance dept. of the facility.

Are all the other apartments around yours occupied? Get some more people on your side that might be hearing the noise.

Thanks Austin - the previous renters as far as I know they did not move because of this. I asked and the building said they nor anyone else has complained of such banging, and I've asked my neighbors. They've cut holes in the ceiling, been on the roof, checked dampers. It's baffling - no pun intended. HVAC vendor was there yesterday, don't know the results. I so appreciate your comments! Are you in TX?

Oh I see, Houston :)

Yeah I service mostly Katy and a few surrounding areas. I don't service all of Houston only certain west side zip codes.

While I know the principles of chiller systems and how they operate, I don't work on them. I specialize in forced air, ducted central HVAC systems for the residential market.

I suppose it could be a bad valve like the one they supposedly fixed over the weekend. But given all the 'units' they've changed out since you reported it, one would think they would have found it by now rather than wasting all these resources to be no better than when they originally started.

Yes I'm learning a lot -- I didn't even know we didn't have ducts and now I've learned the difference between chiller systems and ducted - it sounds so much like a duct kind of vibration. It's actually quite a good management company and a concierge building, very responsive -- I'm sure they don't want to waste resources either, so I'm baffled as to the lack of solution.

Austin Air Companie, since you've been so helpful, I'm updating. So the banging stopped for 3 weeks with no apparent reason, and then came back. After much back and forth and work on the cooling tower and the boiler, the vendor came in and actually went up into the holes cut in my ceiling at 7am yesterday.

He felt the bang with with his hand on the piping - he's fairly certain it's banging somewhere caused by the water in the condenser piping. - as if the pipes aren't strapped down enough and are reverberating. He mentioned that from his POV there's not enough straps in general on the pipes in the building. He turned down the pump speed in the boiler (not the pressure, which is what was tinkered with before). And he mentioned the frequency driver which should automatically control water velocity according to usage in buildings - sometimes in a system the main switch doesn't work, so he manually overrode it.

So literally up until that point it was banging like clockwork every 12 minutes, and as soon as he changed the pump speed, it stopped. Haven't heard it yet, so we're hoping this is the solve. After a year plus some months. We shall see!