Refrigeration Rack Overview w/ Sped up Oil Change

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Bryan Orr gives a refrigeration rack overview, and he joins the Kalos team to do an oil change on a grocery store rack (sped up). The rack in this video was once a 502 rack and has acidic oil, so the customer has requested an oil replacement.

The refrigeration circuit of a rack has the same main parts as an HVAC refrigeration circuit, but there are a few extra parts. These racks have a liquid receiver on the liquid line; the liquid line feeds into the receiver from the top via a ball valve and resumes out of the bottom. The receiver holds extra liquid refrigerant. (You can see if you’re overfilling the receiver by checking a dial indicator or the display.) Then, the liquid line continues into the pressure differential valve and into the filter drier. This rack has a sight glass after the drier to ensure that we have a full column of liquid refrigerant before that refrigerant goes to the liquid header. The compressors on this rack have fans mounted to them, which assist with cooling the compressors.

Refrigeration rack systems often have hot gas defrost, which sends hot discharge gas backward through the suction line and the coils to melt ice off the coil. As the hot gas moves through the coil, it will lose heat and eventually condense back to a liquid. The liquid will go through the distributor tubes and come out just before the metering device and go through the liquid return line. A check valve allows that liquid refrigerant to merge back into the main liquid line past the differential valve.

The compressors are all indoors on refrigeration racks. So, the discharge line runs out of the rack room to the outdoor condenser. Then, the liquid line runs from the outdoor condenser back to the receiver inside the rack room. The outdoor condensers do the same thing as they do in HVAC units; they turn gas into liquid via desuperheating, changing state, and subcooling.

As with HVAC units, signs of oil are important leak indicators on refrigeration racks. The suction lines and suction header (which the suction lines feed into) should all be free of oil. Bryan also likes to check that the fans are all running as they should.

The compressors all individually discharge into individual discharge lines that tie into a single discharge header; the discharge gas comes together at the header and goes back to the condensing unit in a single line. Racks also have suction and liquid core driers, which have replaceable cores (which may have activated carbon in them). The core drier screens can become restricted, which can cause flashing to occur in the sight glass; these can be cleaned quite easily with electrical contact cleaner.

We are using alkylbenzene (AB) oil for the oil change, which is better for oil return than mineral oil. We’re also replacing the cores with high-acid driers because the system has tested positive for acid. After some time, we’ll replace the cores and do another acid test. Whenever we install a new drier, we pull a vacuum on it to make sure there is no air in the line; otherwise, you could end up with non-condensables, high head pressure, and high humidity.

The oil separator takes the discharge gas and separates the oil from the refrigerant. Oil separates from the refrigerant through velocity changes or screens, and it drains out of the bottom while the discharge gas continues through the circuit. The oil then runs back to the reservoir. From there, the reservoir would send oil to the oil filter and then to the compressor oil level controllers.

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Comments

Charles Johnson says:

I like this. Seems like so few rack guys do videos or podcasts and now that I'm doing markets I wish there was more of them to listen to. Keep it up!

Vital Ral says:

I thought hvac techs don't go near a rack unit.

6Diego1Diego9 says:

Do you get a lot of girls as an HVAC technician?

Nestor Martinez says:

Those suction line are not insulated 😳

J W says:

Thinking of moving from restaurant ref after 17 years to supermarket work.

John D says:

Were I work they send hvac guys out to work on racks and expect them to know how all this works and do it in an hour. I see you have several guys. My company would send one guy out and expect it be done in half the time it should take. And they wonder why equipment fails.

Aremin Foxxtrot says:

This looks like a Publix.

John Tyszka says:

An HH drier is used for wax removal after a burnout. If you are trying to remove acid from a system, the standard 4864 drier is the correct drier to use. This has been a misconception in the industry for years. Check Sporlan or Alco’s specs on their cores. They will tell you the same thing.

Scott kasper says:

What’s the core depressor tool called?

Jimmy P says:

Been doing hvacr for 20 years and starting to move into supermarket… great videos brotha I really appreciate them and they def help!! 🤘🤘🇺🇸🇺🇸

Jedidiah Lawton says:

Where was the torque spanner?

Chad says:

I have hot discharge gas too.

Dave Whelan says:

Can't believe that rack has CDS valves. Must have been a retrofit. My guess is if the oil is acidic and breaking down the system is probably running high super heat or high head. A system running properly doesn't need an oil change unless your changing the refrigerant.

Johnny SaltyAirCrabCake says:

OMG Hill Dual Mates…. .. They still chug along as they have maintenance done…. energy users and leaking monsters.. from our end

Anthony says:

Good old publix.. looks like a 400 series store

HVAC Rider says:

Thanks for the video, a good tech always admit there mistake .. well done.

Neilvester Victor says:

i want to learn supermarket refrigeration its interesting the methods you use are u base in florida i work on chill water systems looking to come to the states to study looks like it might be florida

Cen Cal Industrial & market guy says:

Great rack video. Best I’ve seen yet. Please keep em coming 👍🏽

Quang Nguyen says:

So i would like to come and have some hand on training on service and installation of this rack system. Please tell me how and what the cost.

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