Air Conditioning - Noise In The Gas Pipeline (Like Running Water)

I have just had installed a 12000btu carrier Split Unit. The distance between the indoor and outdoor units is about 22 meters (70 yard). The cooling is fine but when turned on a hissing sound is very noticeable from the pipes as though you have running water.

It is very annoying specially that the majority of the pipeline runs indoors.

The technician says this is normal due to the length of the pipeline.

Is this true or could it be due to another factor e.g. gas/oil in the system?

Appreciate your feedback

The liquid line ( small line) may be undersized. Thats a very long run! Thats almost 3/4 of a football field!:eek: Was there no closer place for the outdoor unit? I will go ahead and assume there wasnt. The size of the liquid line is critical for this length of run. I believe its either the line is too small or it is undercharged.

Your assumption is correct in not having a closer place to install the outdoor unit. Its definitely a long run costing a bundle in copper!

The return pressure was reading at close to 60 psi. At some point the gauge was vibrating +/- 2 psi but then the technician did something to stop this vibration. It didn't make a noticeable difference on the sound.

I am worried that due to the long run of pipes there might be some air pockets in the system (I am not sure if that would cause such a noise)? The technician says that he compensated for this by adding more refrigerant to the system.

I will check the pipe size and post back hopefully it will shed more light on the problem.

Shouldn't be a problem with air if the technician ran a good vacuum prior to start-up. The noise you are hearing is probably due to flash gas in the liquid line. This means the liquid line is metering refrigerant instead of just carrying refrigerant indicating it is undercharged or the line is too small.

This is actually a very long run for this size unit! Give me some details if you can about the size space you are cooling and outdoor conditions. What is temp outside, is it humid? Are there outside walls or windows to the space being cooled?

I suspect the contractor is doing the very best under the circumstances but make sure you are satisfied in every way before you give him the thumbs up.

22 meters should be 70 feet, not 70 yards, isn't it ?

22 meters should be 70 feet, not 70 yards, isn't it ?

clocert: You are absolutely correct ... my error ... I should have caught on that when Motown_HVAC compared it to a football court.

I am still waiting for the pipe size, but I believe it is the standard size that comes with the unit he just welded several rolls together.

I have 2 12000btu units cooling an area of 24 m2 which is about 24 sq yards (I believe this time my units are correct :) The room does have a couple of windows.

The outside temperature could reach a high of 105F during August. Humidity reaches over 80%.

The lines are probably properly sized, maybe still a little short of refrigerant.