Reducing Noise from Zibro P122 Portable Air Conditioner: Closed Circuit Conversion

Gentlemen,

A few days ago I finished converting a portable air conditioner Zibro P122.

All the unit I moved to the balcony and to the outlet I connected a pipe, which entered through the window into the center of the cooled room (cool air intake), and the second purchased pipe connected to the evaporator (outlet of hot air from the room to the evaporator).

This created a closed circuit - the inlet pipe brings the cool air inside, and the outlet pipe discharges into the air conditioner through the evaporator of increasingly cooler air from the cooled room, so that the efficiency of the installation remains constant, regardless of weather conditions on the balcony.

The whole thing was additionally insulated at the connections with insulation tape, and everything would be fine, if not the noise of the unit at night - about 55 db. Opposite me is a hostel and so far no neighbors complain, so I assume that the noise that reaches them directly is about 35-40db.

Interestingly, I set the cooling set temperature at 19 degrees, and although according to the weather information outside the temperature reaches 18-19 degrees, the compressor is still able to turn on half the night ;/. (Could it be the fault of the temperature sensor located at the evaporator?)

In order to reduce the problem I bought 3m 32mm acoustic mat and wrapped it all over the unit, but the noise is still quite significant ;/. To eliminate vibration I put the unit on 1m of the same mat.

Do any of you have any ideas on how to dampen this type of device? Do you have to disassemble it from the housing and cover the wall, to which the compressor adheres, with acoustic foam directly?

Greetings

One picture is worth a thousand words ....
Seeing your solutions "in person" will make it easier to advise.

Foxtrott wrote:

One picture is worth a thousand words ....
Seeing your solutions "in person" will make it easier to advise something.

Nothing sensible to advise. The noise will be. The added pipes can act as resonators. Besides, the size of the exchangers is small and requires large air flows. In addition, there is the lack of rigidity of the plastic housing carrying the vibration of the heavily loaded compressor.
This "design", as with the rest of all mobile air conditioners, is rubbing the butt with glass...
Let's have a typical split. Ew. So-called Backpack where the condenser with the fan is exposed to the outside, but then the noise of the compressor stays in the room.

This is how it looks live.

The outlet pipe is connected to a basin made of 32mm insulation. Despite the lack of tightness, the draught on the side of the pipe is really strong and there is no drop in performance even in 27-degree heat, to which the entire unit is exposed.

Checking the interior of the air conditioner I noticed that the only insulation of the compressor is a sponge 10x10 cm, located right next to the compressor. So is there a point in disassembling the housing and "wrap" the inner wall of this 32mm mat?

The fact that the pipes can resonate I did not think. Probably more the former because of its permanent attachment to the cold air intake rigidly. Or maybe if I attached the pipe to some rubber gasket and only such a structure glued to the outlet resonance would be less?

Unfortunately, the room is rented, and the owner does not agree to install a split ("in my time I slept here without problems!". it's just a pity that this ignoramus didn't notice that the African heat starts in our country as early as April, and no one has seen snow in winter for half a decade).

Anachronis wrote:

The fact that the pipes can resonate I had not thought of.

Not so much the pipes themselves as the air in them. It acts as a "sound tube."
With these photos you didn't show off.
What is that black insulating mat. Is it foamed rubber
Why do you wrap the air conditioner with it? After all, it must have air inlets and outlets, and it is with them and the vibrating housing that the noise comes out.
It would be better to glue this sponge (pieces) to the housing in the places of the greatest vibration amplitude that can be felt by hand.
However, I see it in black. It would be necessary to make a zuoenie new rigid enclosure and mute it from the inside.

This foam is something like this exactly: http://allegro.pl/mata-wygluszajaca-bez-kleju-pianka-kauczukowa-32mm-i5920335038.html


The plan was to soundproof the chassis from the outside.

I'm just wondering if building an additional chassis, soundproofing it and putting on the first one would help something. Making such a mini-room damped for the whole unit

You make a good combination, but it is worth insulating those pipes that enter and leave the room. The setting at 19 degrees is unrealistic to achieve for such a device. I myself once did soembi the biggest gain is less noise in the room.

Insulate? But with what? It would have to be something flexible.

And what do you think about making a "box" of mdf, covering it with this 32mm rubber mat and putting such a box over the entire air conditioner + making a hole for the outlet of hot air?

Does it make sense?

Look for a thermoflex. You can make such an enclosure but it must have an inlet and outlet for air circulation for the condenser.

I found, but with thermAflex and these are pipe laggings.

The only question is whether I should use these laggings to dampen the unit, or to reduce the loss of cold air?

Today I discovered that after a few hours of operation, the evaporator is covered with authentic frost and the cooling performance decreases significantly. I do not really know what to do about it.

You see probably the evaporator fan does not have enough compression to push the right airflow. You would have to increase the diameter of the pipes. Or you are running out of gas from the unit .... but this can be ruled out by testing to see if this also happens with the default setting as the factory wanted.

With the company's setting frost does not overlap.

Hm, I am unable to find an air conditioning pipe of larger diameter anywhere, so it is rather out. Unless it is a matter of just widening the opening on the evaporator side.

You have too little airflow through the heat exchanger (too little cold pickup) - and this is due to the low fan compression and the use of pipes.

And will enclosing the pipe supplying warm air to the exchanger with a plastic collar so that it encompasses the entire evaporator, similar to the pipe bringing cold air into the room in this case help?

An additional fan on this pipe will help.

In the sense that I have to attach the fan to the end of the pipe right next to the evaporator? Does it need to be connected to electricity, or will it drive itself by "cug" from the side of the room?

If you have a tight connection, it can be anywhere on both pipes, and if leaky, it is best on the supply pipe. A ducted fan fitted to the pipe. Of course, it requires electricity.

Well, but the issue of frosting is secondary. The most important issue for me at the moment is the problem of damping.

Would making a box from mdf board and covering it with this 32mm insulation rubber , and then putting on the air conditioner give a reasonable level of damping? Or maybe it would still be covered with mineral wool?

No one will answer you - it is possible that it will give, but maybe not? It's this kind of dilemma. Theoretically you have a better chance of soundproofing than increasing noise.

At the weekend I will build a protective shed.

Do you think it is better to surround it with mineral wool from the inside, or from the outside?

I also came up with the idea to pour dry ice around the exchanger at night. It should last all night, and in fan mode the air conditioner would then take the cooling from the dry ice, giving a stable 18-19 degrees at the outlet, right?

Moderated By gulson:

3.1.11. Do not post messages that contribute nothing to the discussion. They are misleading, dangerous or do not solve the user's problem.

.

Go get medical treatment, or you and, for example, your family will die.
And apply dry ice to your head, but in the open, not indoors.
The horror.

Manager, as if you did not notice I am not an expert in the field of air conditioning, that's why I ask questions to people with more experience.

I expect constructive advice/criticism, not such personal excursions, so if you could in your graciousness give them to yourself, I will be grateful.

Anachronis wrote:

I still came up with the idea of pouring dry ice around the exchanger at night.

Read again what you are proposing, if not to yourself then to someone else?
CO2 is not poisonous, but if it displaces, thanks to the fan oxygen, it will be a tragedy.
There was even one episode of CSI Las Vegas about a couple suffocating on a bed from CO2 from dry ice.

Well, and thanks for the factual answer, now I understand.