more complicated than chinese arithmatic

[guilbertj2006]

I'm looking to understand better South Florida Supermarket (Publix) Heat Reclaim. There are valves in the drop leg, of course, but we don't have the low ambient issues. I see the water tanks run 120F on 90-95F OAT. Are the water tanks supposed to only de-superheat the refrigerant? or do they saturate the refrigerant, too; and is there liquid/vapor feeding back into the condenser. Also, what other, alternately, heat sinks are there for Publix Heat Reclaim. Any link on their protocol, how the system is set up, or just firsthand information, would be helpful. Thankyou in advance.

[jpsmith1cm]

Moved to Refrigeration and Ice making.

[jpsmith1cm]

The theory is that those tanks are desuperheaters.

They typically don't absorb enough heat to start to get into phase change of the refrigerant.

[guilbertj2006]

The theory is that those tanks are desuperheaters.

They typically don't absorb enough heat to start to get into phase change of the refrigerant.

Yes, thank you for your reply. And I've read some of your other posts on supermarket rack systems, and found them clear and helpful.
Here's my understanding so far, with a follow-up question: the valve in the drop leg diverts hot gas to a water htr much smaller than the normal heat sink, the condenser, so the H2O can be heated to a higher sensible temperature. The cap loss due to higher compression ratio is more than paid for by the COP of the hot water. The de-superheated ref. saturates in the condenser. Okay? But is there, or have you heard also of, another Heat Reclaim heat sink in Publix stores, coming off the HG dsch line of the multi-plex rack? (I'm reaching) possibly for air re-expansion for reduction of relative (not actual) humidity? Thank you for your explanations.

[jpsmith1cm]

Yes, thank you for your reply. And I've read some of your other posts on supermarket rack systems, and found them clear and helpful.
Here's my understanding so far, with a follow-up question: the valve in the drop leg diverts hot gas to a water htr much smaller than the normal heat sink, the condenser, so the H2O can be heated to a higher sensible temperature. The cap loss due to higher compression ratio is more than paid for by the COP of the hot water. The de-superheated ref. saturates in the condenser. Okay? But is there, or have you heard also of, another Heat Reclaim heat sink in Publix stores, coming off the HG dsch line of the multi-plex rack? (I'm reaching) possibly for air re-expansion for reduction of relative (not actual) humidity? Thank you for your explanations.

What is your position?

I see a few things in this post that make me doubt your familiarity with the equipment.

Using hot gas to reheat the airstream for dehumidification isn't uncommon.

I'm not familiar with Publix stores specifically, so I can't speak to them.

Typically you don't see an increased compression ratio with systems like this, so that isn't really a factor.

[guilbertj2006]

What is your position?

I see a few things in this post that make me doubt your familiarity with the equipment.

Using hot gas to reheat the airstream for dehumidification isn't uncommon.

I'm not familiar with Publix stores specifically, so I can't speak to them.

Typically you don't see an increased compression ratio with systems like this, so that isn't really a factor.

My position is repair and maintenance on the racks and 35 - 50 ton ACs, a step up in scale from residential, and walk-ins. That's why I'm posting. The aim is for a 15-20F condenser approach on the racks. But heat reclaim has to be higher. The valve throttles, so there isn't much effect on compression ratio, I gather. The 35-50 ton McQuay ACs have there own heat reclaim coil in the supply, or a loop is piped from the racks to the AC supply, or, more than likely, all of the above? depending on what store and blueprints. Fort Lauderdale does have split condensers, but no where near the outdoor ambient changes north. The material I've found so far has focused on solving problems for lower ambients. So I'm asking the pros that knows to shorten the curve, so hold those bloodhounds.

[jpsmith1cm]

My position is repair and maintenance on the racks and 35 - 50 ton ACs, a step up in scale from residential, and walk-ins. That's why I'm posting. The aim is for a 15-20F condenser approach on the racks. But heat reclaim has to be higher. The valve throttles, so there isn't much effect on compression ratio, I gather. The 35-50 ton McQuay ACs have there own heat reclaim coil in the supply, or a loop is piped from the racks to the AC supply, or, more than likely, all of the above? depending on what store and blueprints. Fort Lauderdale does have split condensers, but no where near the outdoor ambient changes north. The material I've found so far has focused on solving problems for lower ambients. So I'm asking the pros that knows to shorten the curve, so hold those bloodhounds.

Why does the approach for heat reclaim have to be higher?

Some rack controllers do have a feature to bump the head pressure up a bit to squeeze a little more heat, but the majority don't and it really isn't necessary.

Depending on the piping configuration, your discharge gas will feed into a hot water reclaim tank or an air reclaim tank. Some larger racks will run both but that isn't common.

What valve are you referring to that throttles in regards to heat reclaim? Not a common setup at all.

[Blackmira]

Are you having problemos or just looking for theory?For dehumidification the three way valve is setup to energize once heat setpoint(71) is reached.

[icemeister]

Heat reclaim water heating is almost always a desuperheating process. Regardless of what discharge pressure the rack systems are running at, there's usually more than enough heat available from just the superheated discharge gas to satisfy the water heating loads in a supermarket....ie, no condensing required. Even if the discharge pressure floats down to 70ºF SCT, the discharge superheat will still be high enough to give you 110ºF water.

The total heat of rejection (THR) of a typical market is around 1,500,000 Btuh, of which roughly 15% of that is in the form of superheated refrigerant gas. That's nearly twice the Btu rating of a standard 120 gallon commercial gas water heater.

[guilbertj2006]

Heat reclaim water heating is almost always a desuperheating process. Regardless of what discharge pressure the rack systems are running at, there's usually more than enough heat available from just the superheated discharge gas to satisfy the water heating loads in a supermarket....ie, no condensing required. Even if the discharge pressure floats down to 70ºF SCT, the discharge superheat will still be high enough to give you 110ºF water.

The total heat of rejection (THR) of a typical market is around 1,500,000 Btuh, of which roughly 15% of that is in the form of superheated refrigerant gas. That's nearly twice the Btu rating of a standard 120 gallon commercial gas water heater.

Thank you for helping out, with clear, concrete knowledge. The compressor's superheated discharge vapor is higher in sensible temperature than the gas' saturation p/t. The refrigerant has to de-superheat, and drop in sensible temperature, before it can saturate: might as well make use of it by reclaiming it in water heaters. Got it. I didn't think that the sensible temperature of the water in the tank can rise above the sensible temperature of the superheated gas. Please correct me if I don't have that right.

[jpsmith1cm]

Thank you for helping out, with clear, concrete knowledge. The compressor's superheated discharge vapor is higher in sensible temperature than the gas' saturation p/t. The refrigerant has to de-superheat, and drop in sensible temperature, before it can saturate: might as well make use of it by reclaiming it in water heaters. Got it. I didn't think that the sensible temperature of the water in the tank can rise above the sensible temperature of the superheated gas. Please correct me if I don't have that right.

It can't.

Take a temperature reading on a discharge line. They're typically above 200 degrees F and I don't think I've ever seen one under 175

[guilbertj2006]

Are you having problemos or just looking for theory?For dehumidification the three way valve is setup to energize once heat setpoint(71) is reached.

The dispatcher, she asked for receiver liquid-levels on the racks both with and without Heat Reclaim. The dispatcher likes to give scolding lectures, too, so since all I've seen in the stores is hot water reclaim off the racks, I'll just keep an eye peeled on the blueprints HVAC/Refrigeration mechanical plans pages, whenever I'm not performing my normal duties of 'covering all the bases' (and selling popcorn in the stands). But any insight you have is always welcome.

[guilbertj2006]

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