Suction Line Muffler..........

[airflo]

Hello,

I have been told by the powers that be to install a suction line muffler on a air conditioner to prevent a hummimg sound that the unit generates (The customer said they can hear humming in the house).

Now i have been given this suction line muffler and it has a 3/4 joint either side and is roughly 3inch round.

My question is can i mount it horizontally or must it be vertically?

Also it seems as if it doesn't have a direction of flow on it so i'm assuming it can be mounted either way?

Do you think this will stop the humming?

Cheers,
airflo

[NoNickName]

I think that the pipes have been fixed to some concrete slab or beam, and now the compressor vibrations are carried over to the building. Just remove the fixing or use some soft insulation material between the pipes and brackets. Also some insulation shall be applied to the air conditioner, under or around it (depending whether it is wall-mounted, ceiling-mounted or window ac).
The muffler only helps for noise, not for vibrations.

[US Iceman]

The only time I have ever seen a suction muffler is on very, very large reciprocating gas compressors. I have never heard of one being used on refrigeration compressors and wonder how someone came to that conclusion.

NoNickName is correct;

The muffler only helps for noise, not for vibrations.

Mufflers are typically used on the discharge side as that is where most of the energy is in the gas.

[coolhibby1875]

as iceman says mufflers are always fitted to discharge pipes i would doubt very much that fitting it to the suction would reduce the noise

[GXMPLX]

Hello,
I have been told by the powers that be to install a suction line muffler on a air conditioner to prevent a hummimg sound that the unit generates (The customer said they can hear humming in the house).

Now i have been given this suction line muffler and it has a 3/4 joint either side and is roughly 3inch round.
My question is can i mount it horizontally or must it be vertically?

I think they can go either horizontal or vertical but what I think is irrelevant you must follow manufacturer's instructions.

If you install it vertical the refrigerant flow MUST go down.

If you install it horizontal it should have a higher slope than the suction line because the refrigerant velocity will be lower in the muffler. If this is important or not depends on velocity, and suction line lenght.

Also it seems as if it doesn't have a direction of flow on it so i'm assuming it can be mounted either way?

This is usually correct but check if it is symmetrical at both ends sometimes they have a metal protection at the entrance and not at exit.

Again you should hear the manufacturer's opinion on this.

Do you think this will stop the humming?
Cheers,
airflo

I don't think so but this depends on what is causing the humming. You got several posts on possibilities.

So powers also does his rounds there too, I see!

[GXMPLX]

as iceman says mufflers are always fitted to discharge pipes i would doubt very much that fitting it to the suction would reduce the noise

Yes they are. Reciprocating compressors produce sound waves at discharge and also at suction ... but I would rather solve these with a suction accumulator not a muffler.

Sometimes a couple of pipe turns act like a muffler bot at discharge and suction.

And by the wah I forgot in my previous post that airfo should check the pressure drop too!

[US Iceman]

If you install it vertical the refrigerant flow MUST go down.

If you install it horizontal it should have a higher slope than the suction line because the refrigerant velocity will be lower in the muffler. If this is important or not depends on velocity, and suction line lenght.

And... you might need to recognize the problems associated with oil return. It would depend on how the baffles are oriented in the muffler to allow for oil return. So... there would have to be TOP location marked on the muffler.

An accumulator could work also, but I would hate to try to design the choke tube and separation capabilities to work together.

[GXMPLX]

And... you might need to recognize the problems associated with oil return.

Who me? ... I do, I do, I swear I do!

It would depend on how the baffles are oriented in the muffler to allow for oil return. So... there would have to be TOP location marked on the muffler.

I don't see why if it is symmetrical.

An accumulator could work also, but I would hate to try to design the choke tube and separation capabilities to work together.

choke tube? ... What choke tube?

[US Iceman]

The baffles in a muffler could be seen as the baffles in a DX chiller. It is sometimes necassary to rotate the baffles (during design) to achieve specific results.

In the case of the muffler if the baffles (if that is what is used) are oriented in the wrong position they could trap oil and prevent it from returning to the compressor.

Eventually that would take care of the noise problem though.

A choke tube is used in some muffler designs to change the acoustic signature of the gas flow.

[GXMPLX]

Ok I thought it related to the suction accumulator, but again ... it must be my english!

[Peter_1]

For smaller units, we sometimes let expand the discharge in a much bigger size of tube and then go further in the original tube.
So a 1/2 in 1 feet 1 5/8 and then 1/2 again.
We then have a more smoother flow of th discharge gases without or less pulsations of the pistons.
This really helps.

[GXMPLX]

... but related, I just re-learned-membered that Scroll compressors might need a suction muffler too if you don't install a U bend at it's suction, you can see here:

http://www.ecopeland.com/literature/...ef_Small_0.pdf

sorry that was low temp, but here:
http://www.ecopeland.com/literature/..._C060209_1.pdf

or elsewhere it seems they use, like me, lot´s of copy and paste!

[airflo]

the muffler is actually hollow and has no baffles............

[airflo]

the compressor is a copeland scroll 3 phase

[GXMPLX]

Don’t worry, US_Iceman would look for inclined buffers that never were in symmetrical mufflers, a suction accumulator is a good muffler just because it has more volume than the pipe it is installed in.

A good design though should try to prevent waves bouncing off the walls, but it’ll work anyway.

You may install it considering slope but anyway not vertical if the refrigerant flow is up, this would produce an oil trap.

As you learned Scrolls might need it if it doesn’t have a “U” bend.

By the way the “U”bend has another function the muffler does not, it reduces stress on the pipes with the compressor starts and stops. This also transmits noise through the pipes and won’t be solved by the muffler.

You can feel this if you hold the pipes when the compressor starts and stops.

Muffler may help, but tell the powers that it might not solve the problem so you won’t get canned nor whacked after, like me.

[US Iceman]

A good design though should try to prevent waves bouncing off the walls, but it’ll work anyway.

A good design would throw the gas frequencies out of phase so that they cancel one another, based on what I have read...

[GXMPLX]

A good design would throw the gas frequencies out of phase so that they cancel one another, based on what I have read...

Absolutely right! But the one airflow has is a Reactive Silencer while you want an Active Silencer System with microphone and loudspeaker. It would not solve pipe transmitted sound anyway.

I made a mistake and you didn’t even blink!

Airflo I know you know this but just for future reader’s reference, the muffler should not be mounted where the refrigerant flow slopes upward. Not vertical nor inclined. It must be on a downward slope and I have to whack myself.

[US Iceman]

I made a mistake and you didn’t even blink!

I've had a long day, so consider yourself lucky.

[airflo]

hmmmm ok one of them i installed was installed vertically where there is downward flow..........the other 2 were installed inside the unit just before the flare connection.

WHoops........hope i don't get a callback

[airflo]

post to make up 15 posts so i can post a picture

[airflo]

4 more to go

[airflo]

3 more to go

[airflo]

nearly there 2 more to go

[airflo]

1 more blank post then i can show you the photos of the mufflers i installed

[airflo]

[airflo]

[airflo]

so any opinions will the one mounted below the flare connection do anything? if not why?

The second photo should be ok huh?

[GXMPLX]

hmmmm ok one of them i installed was installed vertically where there is downward flow..........the other 2 were installed inside the unit just before the flare connection.

WHoops........hope i don't get a callback

I wouldn't have thought of the 15 post limit trick!

You see I always complain about absolute remarks that are out of context or without the corresponding IF clauses and I do the same.

I didn't know the size of the muffler and if it becomes an oil trap or not depends a lot on temperature (viscosity), velocity of the refrigerant, how the oil is mixed with the refrigerant (foaming, in droplets, annular flow, etc.) Amount of oil in the system too because if you fill with oil an oil trap it will stop being a trap.

Of course the size of the muffler affects too and these are pretty small, less problem with oil trap, not very efficient as silencers.

Yes there could be a problem with the flared one but if it has worked it needs another condition to trap oil and cause a failure. For example low refrigerant flow if you set the LP switch too low or loss of charge or low ambient temperatures and the oil-refrigerant is not forming a mist (insulating it would help).

The point is if you install it with the flow going down it will never work as an oil trap. Installing it in other positions COULD be a problem.

The muffler looks really small compared to the size of the compressor and I'd worry more on it not being efficient as silencer and less on oil trapping.

Stop buying these mufflers and install a U bend or better a loop in the compressor suction!

[airflo]

Thanks for your comment...........
I must add that the muffler is insulated, just not in the photo's so all you guys can see it.

I spoke with the customer and he said that the humming noise he was hearing from inside the house has now gone since installing the muffler..........

[GXMPLX]

Thanks for your comment...........
I must add that the muffler is insulated, just not in the photo's so all you guys can see it.

I spoke with the customer and he said that the humming noise he was hearing from inside the house has now gone since installing the muffler..........

Great! You see seldom the powers are right! ... and scrolls need a muffler.