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Hi guys! This doesn't have anything to do with computing, but since the TR collective has know-how on pretty much any issue apart from world peace, I figured I'd throw this in here.

Roughly a year ago, I had three Daikin air conditioning units installed in my bedrooms. The installation was done quite professionally by a very experienced technician, but the units are exhibiting a behavior that's leaving him stumped: bubbling noise.

The noise comes from the top right of the interior unit, and it sounds exactly like a boiling pot of water (muffled). This only happens when the unit is set to heat up the room, and more specifically, when the temperature difference between the outside and inside is around ~10ºC or less. In other words, if it's pretty cold outside, I will set the AC temperature higher to compensate and there will be no noise.

The noise is not constant, but very frequent—sometimes it will bubble for 20 minute to half an hour, by which time I've already shut the thing down. Another potential data point: when the bubbling is at its worst, the AC unit will stop heating for a bit. This may just be the result of the room temperature reaching its target, but the blast of not-very-hot air makes me suspect these problems are related.

I searched around the internet and we speculated that the indoor unit may have been pulling air from the outside via the drainage pipes. The technician came around to kink the pipes as to turn them into impromptu p-traps, but to no avail. He contacted Daikin support, which was very "helpful," saying that the outdoor unit should be installed 3 meters below the indoor one ( )

So, any ideas?

Sounds like you need to use the auto mechanic's stethoscope -- i.e., take a piece of wood (a section of broom handle works great) and press the end against various components while holding the handle near your ear, and figure out which one is actually producing the noise.

Since this behavior only occurs during the heat cycle with temperatures well below freezing, is it possible the condenser simply isn't working properly due to inefficiency? I know in the US, it is common to install whole-house heat pump systems with either a gas heat cycle that takes over below 3C (for climates with sustained cold periods), or to install a large electric heater inside the outdoor exchanger to feed heat into the coils below that same range (for climates with brief cold snaps).

HVAC Tech here...

First glance at the issue I'd suspect it's low on refrigerant (as in they didn't put enough charge into the system/small leak at a brazed joint). If there is a sight glass on the liquid line by the compressor unit outside it should be clear, as in no bubbles in it. If there is bubbles in the sight glass while it's running, it's low on charge. You need a solid column of liquid for an AC system to function properly.

If it was installed on a hotter day, it could have been charged for the warmer temperature and as the ambient temperature dropped, the static pressure of the charge (relative to the atmosphere) dropped. (You can look up the pressure temperature chart online.. as I'd suspect it's R-410a .. a fairly common refrigerant on newer units these days to see what I mean)
Especially when in heat mode, it will manifest more because you are basically running an AC system backwards on a cold day.

The noise you are hearing is from those vapor bubble inside the expansion valve. (Think garden hose through a spray nozzle partly open when there is air in the hose)

Hmmm

Not really familiar with these units as I have not seen them in Canada. I know AC units typically do not like being run below 15C, and heat pumps can be fussy as well, and combo units even more so.

The newer type refrigerants usually have oil additives for the compressor, depending on the temperature the refrigerant may be a liquid when it gets to the compressor, and you don't want that. It could also just be a poor design/manufacture defect, or even normal depending on conditions.

I don't really listen to my AC unit since it's outside my home, and also it only gets about 1 week of use up here in northern ontario lol

Can't really find a nice pic like my thermodynamics texts but
https://upload.wikimedia.org/wikipedia/ ... tionTS.png
Heat pump is similar, thing is when the delta T between outside and inside get close these things just don't really work well or efficient.
Most of these things can be represented by the Carnot cycle.
https://en.wikipedia.org/wiki/Carnot_cycle
http://hyperphysics.phy-astr.gsu.edu/hb ... arnot.html
The carnot cycle in theory is the best efficiency possibly and it's only around 40% IIRC. People around here typically heat with gas and cool with an AC unit.

Good luck though, as long as it has a good warranty, I wouldn't be too concerned about it. (ya basically what the tradesman said above me usually an AC heat pump combo unit has an extra valve (backflow or reversing or something) the refrigerant passing through certain valves can make specific noises, and don't ask me what, I am not an HVAC tech

morphine wrote:

...the AC unit will stop heating for a bit.

I can't really help much, except to add that (in the US at least) when folks say "AC", they're generally only referring to cooling units. If you're talking about something heating-releated, you may confuse some.


Edit: Apparently I was unaware of heat pump units. Interesting.

The Egg wrote:

I can't really help much, except to add that (in the US at least) when folks say "AC", they're generally only referring to cooling units. If you're talking about something heating-releated, you may confuse some.

Oh. Sorry

For the record, I'm talking about something like this (not that exact model): http://www.daikinac.com/content/residen ... 19-series/

morphine wrote:

The Egg wrote:

I can't really help much, except to add that (in the US at least) when folks say "AC", they're generally only referring to cooling units. If you're talking about something heating-releated, you may confuse some.

Oh. Sorry

For the record, I'm talking about something like this (not that exact model): http://www.daikinac.com/content/residen ... 19-series/

I think those are usually known as a "mini-split" or a "ductless mini-split." In North American parlance, "AC" is a one-way unit that operates only a cooling cycle for the interior exchanger, while a "heat pump" has a reversing valve and can run either a heating or cooling cycle to the interior exchanger.

So, I'm back to dealing with this. I eventually had the tech come around and remove and replace the gas in the unit, and even though it's generally quieter, the main problem still remains. I have, however, narrowed it to the following situation: it only apparently happens when the unit doesn't have to do much work, and only on its "silent" setting. It also gurgles a little when firing it up but it's barely noticeable.

This problem only crops up on chilly-but-not-cold days. Here's a few scenarios where it triggers:

1) I make it heat the room. Eventually the room will become warm and I'll hear the unit "loading" gas again and gurgling starts.
2) I make it heat the room. If I eventually find it's a getting a little too hot, I'll dial it down. A minute or so after that, "loading" sound and gurgling starts.
3) I make it heat the room, just a tiny bit. Eventually the gurgling starts.

I'm really pissed with all this, and I've spent days searching the web for ideas but other than "coolant leak" (which has been double-checked), or "too much coolant", there isn't any info on this particular issue. And it's a real shame, because these units are next to inaudible in normal operation.

It's the lack of difference between the room temp and the outside temp. Your units expect to see a sharp difference between the two. Any A/C or heat pump that is working with equal temps inside and out will do this because it cycles between dumping the waste heat outside and inside. The system simply can't change the temperature of the working fluid as it expects to do and it boils in unexpected places, hence the noise.

In generally heat pumps can only turn down so far (say 4:1 or 5:1) from their maximum heating or cooling position, the situation you describe is one where the units might be trying to only output 5-10% of their capacity (mild weather, trying to do minimal heat). I hate to say it, but because of that this may be expected behavior. One way to mask it might be to allow a larger temperature difference before heating (instead of starting at 69 DegF when you want to maintain 70 DegF, don't let it kick on till 68 DegF). That would put more load on the system and might reduce the amount of gurgling you get. Unfortunately most thermostats won't let you select the internal deadband. Maybe one of the new fancy Nest thermostats or similar would allow that?

Another thing to make sure of is that you have at least a few degrees between your heating and your cooling setpoints. If it is trying to maintain exactly 70 DegF and automatically cycles between heating and cooling modes it could cause issues too. The energy codes now require 5 DegF between heating and cooling so I assume your thermostat will "enforce" that but ???

Well, here's the thing, we're still talking a 10-15ºC difference between the outside and inside, easy. Just a little while ago it was about 13ºC outside according to the Goog, and I had the unit set to 26ºC, until it eventually started bubbling.

And for the record, these aren't thermostat-controlled. There's a remote control where you set the mode (heating, cooling, just the fan, or dehumidifier), and the air temperature for that mode. Here's an example. What annoys me is that I've never ever seen (well, heard) one of these systems behave like this.

Air conditioners often improve efficiency by using a slinger to throw water in the pan over the evaporator. The water normally comes from dripping off the cold condenser which wouldn't be likely with a split unit. If you care about noise more than efficiency you can adjust the overflow tube so the pan empties more.

A heat pump is simply an air conditioner that can be reversed to air condition the outdoors, the waste heat being diverted inside instead.

A relative is dealing with one of these units at the moment in Japan. The damn thing keeps making pinging and popping and dripping noises. For a unit that is only 18 months old not very impressive! The temperature over there is a good 10-12 degrees hotter outside this time of year, so no heating going on! Any thoughts? The Japanese service guy is stumped,

Bubbling sound is usually due to leak (Low refrigerant) , before sealing the leak, vacuuming the cooper pipes (this is important) is required. I had a similar problem with my AC cooling unit (Indoor unit) and it would make a lot of bubbling and blasting, a lot of tech guys looked into it and finally one of the tech guy, removed all the gas, sealed the leak and did the vacuum process for 1 hour. After the vacuum process the AC worked without any issues.


EDIT: Oops, by mistake didn't see i was assisting in necroing the thread. My bad.

That's fine, it's not like the problem went away magically.

I agree with Captain Ned. Does the gurgling occur when the insulated line from the outside unit becomes bares as it enters the inside unit?

I assume you meant "where." It's hard to tell where the exact noise is, but I can tell it's inside the house, not outside. The outside piping goes inside through the wall at about chest height and run upwards until they meet the indoor unit in its right side. The noise comes from somewhere in that rightmost part where the pipes go into the inside unit.

A while back I had the tech replace the gas and it helped with the problem somewhat but didn't fixed. I don't think he ran the vacuum procedure that Jigar described, though.

morphine wrote:

A while back I had the tech replace the gas and it helped with the problem somewhat but didn't fixed. I don't think he ran the vacuum procedure that Jigar described, though.

Did the tech only add refrigerant to the system? That's sometimes a cheap fix for a system that has only partially depressurized from a slow leak, but otherwise the system has to be brought under vaccuum to remove of any foreign gasses, moisture, etc. and then fully recharged.

Hrm, I'll keep that in mind the next time I have maintenance done on these, thanks!

morphine wrote:

A while back I had the tech replace the gas and it helped with the problem somewhat but didn't fixed. I don't think he ran the vacuum procedure that Jigar described, though.

Probably not. I have the same issue in my minivan. Got depressurized somehow (not really sure how though) so I got one of those kits from Auto Zone to re-fill it. Now it sounds like water running everywhere I drive. It's been like that for around two years, so I'm guessing it's not leaking. The depressurization remains a mystery.

derfunkenstein wrote:

It's been like that for around two years, so I'm guessing it's not leaking. The depressurization remains a mystery.

Those vehicle AC-charge kits virtually always contain sealants to plug small leaks, so that might be the explanation.

It could also just honestly be a mystery too, though hahaa