Eric Mele explores a medium-temp supermarket rack that uses glycol, a secondary fluid used to help with heat transfer in chiller systems. Although we show glycol in this video, some racks may use CO2 as a secondary fluid instead.
On the chiller side of a rack, the piping goes to the pump station and out to the store below. Chillers are actually quite similar to hydronic systems, as they have pumps and pump controllers. You can expect to see some spare glycol, electronic valves, and heat exchangers in the rack room on a glycol system. Heat transfer occurs in heat exchangers, where heat gets rejected from the refrigerant and moves to the glycol.
These racks may also put discharge heat into the glycol. That heat can then be supplied to the reheat coil in the air conditioner or used for warm fluid defrost.
When the rack puts discharge heat into the reheat circuit, it pumps the glycol using a circulating constant-volume pump, which helps the glycol go through the heating loop for the reheat coil. In the case of this rack, the lines go out of the rack at the bottom. Those lines run underneath the roofline and come back up into the A/C system across the rooftop. As with some other reheat coils, this system has a three-way valve to modulate the glycol flow through the coil.
The rack may have another heat exchanger for warm fluid defrost. The discharge gas can warm up some of the return glycol coming back from the A/C reheat coil. That discharge gas can also go down to evaporators or cases that need defrosting.
On the other side of the rack, we have the piping that allows the glycol to go down to the cases. There is also a three-way valve on the discharge line, which allows us to use discharge gas to heat water for use in the store. (These pipes have been labeled as "water heat reclaim." They lead to heat recovery tanks specifically for hot water.)
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On the chiller side of a rack, the piping goes to the pump station and out to the store below. Chillers are actually quite similar to hydronic systems, as they have pumps and pump controllers. You can expect to see some spare glycol, electronic valves, and heat exchangers in the rack room on a glycol system. Heat transfer occurs in heat exchangers, where heat gets rejected from the refrigerant and moves to the glycol.
These racks may also put discharge heat into the glycol. That heat can then be supplied to the reheat coil in the air conditioner or used for warm fluid defrost.
When the rack puts discharge heat into the reheat circuit, it pumps the glycol using a circulating constant-volume pump, which helps the glycol go through the heating loop for the reheat coil. In the case of this rack, the lines go out of the rack at the bottom. Those lines run underneath the roofline and come back up into the A/C system across the rooftop. As with some other reheat coils, this system has a three-way valve to modulate the glycol flow through the coil.
The rack may have another heat exchanger for warm fluid defrost. The discharge gas can warm up some of the return glycol coming back from the A/C reheat coil. That discharge gas can also go down to evaporators or cases that need defrosting.
On the other side of the rack, we have the piping that allows the glycol to go down to the cases. There is also a three-way valve on the discharge line, which allows us to use discharge gas to heat water for use in the store. (These pipes have been labeled as "water heat reclaim." They lead to heat recovery tanks specifically for hot water.)
Read all the tech tips, take the quizzes, and find our handy calculators at https://www.hvacrschool.com/.
Learn more about the 2022 HVACR Training Symposium at https://hvacrschool.com/symposium/.
Secondary fluids, so we can use glycol and other fluids to do the work of heat transfer. In this case this is the chiller end of a glycol rack and it's going over to the pump station and down to the store. So that's just essentially a big chiller over there, a big heat exchanger, the typical stuff you'd, see on a hydronic system, pumps, pump controller, all that good stuff. Sorry, it's kind of hard to see in these rooms.
Everything is not great to stand back and film from far away, but there you go. You got some pumps, a couple drives all the controls for that pumping station and that's all the medium temperature stuff. It's got a glycol solution there. You can see what the freeze point supposedly is, if you believe the sharpie got, some extra glycol there's another view of the heat exchangers.
So if we look down here, we got a couple: electronic valves feeding them as i walk right past. So if you look on the discharge side too, we're also putting the discharge heat into the glycol and using that for the reheat coil in the air conditioner. So you can see all the piping associated with that it's hard to get a good look like, i said we're so up close, but there there's a discharge gas going in and this side is the glycol going through the pump. So there's our little circulating pump for our glycol heating loop for the reheat coil.
All the stuff you'd expect to see that's just a little constant volume pump and those pipes are going down there and out to the air conditioner so walking out onto the roof, and i love making these videos for you guys so much that i'm getting rained on To do it, we're walking past the normal condenser there and over to. I believe this is a main i see at this store, so they have this unit for the sales floor and they have a few other small ones. Yeah, that's how this store was. This is a dike in mcquay opening it up.
There's our lions coming back in up there run, you know, underneath the roof line and back through the bottom of the unit. So we're going to open this section up now getting my my trusty pry bar out fighting the static pressure of the unit. There's the reheat coil the standard, evaporator coils to the right and in this section, is where your three-way valve is to modulate the flow through that coil. So you got a belimo actuator on the back.
Okay, here's another heat exchanger on the rack, and this is for the warm fluid defrost, because we also throw discharge gas in the in the glycol solution for defrost there again in that mess of piping. We use that little brace plate heat exchanger and discharge gas to warm up some of the return glycol the glycol coming back and we can send that down to the cases that need it when defrost needs to occur. If you walk down the other end of the rack, you can see where that's going to get pulled off the return glycol so the warmest glycol and then it's coming back there and it's got its own pipe to go down to the cases and one day we'll Get the valves that make that happen now, i'm throwing this in here, because it's relevant so there's a three-way valve back there on the discharge line and we can also use the discharge gas to heat up water for hot water in the store. So we're looking at some of those three-way valves there, this one over here is coming up and over and over and down. Eventually, you can see their water heat reclaim to our heat recovery, tanks for our hot water, also in the future, we'll cover using co2 as a secondary. It doesn't have to be just glycol, but that's a story for another day, thanks for watching our video, if you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click the Notifications bell to be notified when new videos come out. Hvac school is far more than a youtube channel. You can find out more by going to hvacr, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more.
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Looking forward to the co2 vid also 👍🏻👍🏻