cook/server line problem

[UmmScott]

Asking for input with 2 issues I'm really scratching my head on with this remote setup here..

I've posted about this before, the restaurant is tired of fiddling with this setup and wants it fixed...but of course "we're spending too much money..blah blah blah"

So... Randell custom cook line with many drawer base units with raised cold rails. They are all Remoted to one single condensing unit. A BZT025M6C. There's 1 liquid line and 2 suction lines. All the rails are on one line and the boxes go through the 2nd suction line to an EPR valve set at 53psi to keep the box evaps at roughly 20F because the main SST is -10F (24-21psi) at the condensing unit for the cold rails.

Problem #1. All 4 of their cold rails are keeping the product in the low 40's. What I found was the temp controls cycle the damn things off so early. I think the original control was an HDCNT9901 or something like that.
Its cut in at 20F and out at 15F. That seemed way way too warm for my liking especially for a cold rail. I ordered an HDCNT100 control which cuts in at 2F and out at -5F.:"
I applied that to one rail and that seemed to help alot, on time was much much longer and off time was much shorter...but...

I'm still having the same issue, the air temp under the pans only gets to the low 30's and to 29 at the lowest. Randell says should be 20 to 23F. All TXVs for rails have 10F superheat running on the 23psi suction at the condensing unit.
What can I do here? any ideas?

2nd issue...talked about before...
1 drawer unit on the line won't temp right. What happens with this particular box is as soon as the stat energizes the LLSV, the evap gets really really cold really really fast, down to like almost 0F in 30 seconds.
So....this makes my A12700 cut out really early, the off cycle is long...and box temp never really gets there.
Its weird...sometimes it temps fine, sometimes it freezes up, I'm really scratching my head on this one.

I have a "hunch" that this box may be accidentally piped in with the cold rails running 21psi instead of on the circuit with the EPR valve running 53psi.
How can I confirm this without splitting the line apart (NOT happening LOL) There's no way to trace the lineset, it comes up in 5 different spots underground of all places.
It can't be a bad TXV could it? its the whole coil that gets cold and frosty but I could be wrong.

Sorry I know this is alot of info to process, but I'm just trying to come up with ideas, mainly with this one box. The rails...ehh...may just take the temp controls out and have them use the on/off switches only
Thanks for any input

[Blake79]

Airflow moving in the right direction? A 12 700 constant cut in is 37 degrees I believe. Is the bulb sensing coil temp or air? I have had issues before when bulb inserted inside coil and unit shutting down prematurely with longer off cycles like you state. Try mounting bulb in discharge air stream to see if cycle time and box temp change.

[VanMan812]

As for issue #1 that could be down to operator error. Might be leaving gaps in the pans or filling it with product that's not below 40 deg. Etc etc. If it were me I might jump the stat out and let her rip to see if it's actually capable of getting down to 20deg. If it can and it does so on a reasonable time then I'd look at changing the location of the bulb or type of stat. I'm not totally against the on/off switch idea. If it were a 24/7 type of place I'd say no but as long as they **** them off at night then I may at least give it a try.

Issue #2... is the TXV properly sized? I like using a coil sense stat on drawer coolers but in your case maybe an air sense would be better. You'd probably have to play with the bulb location a few times to find the sweet spot. If you can't separate the line and confirm/fix your suspicion then this may be your best option.

[icemeister]

I have a "hunch" that this box may be accidentally piped in with the cold rails running 21psi instead of on the circuit with the EPR valve running 53psi.

I would raise the EPR setting way up and note which evaps stop working.

[UmmScott]

I would raise the EPR setting way up and note which evaps stop working.

My god...


Genius

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[VanMan812]

My god...


Genius

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Hahahahaha I know right!


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[UmmScott]

Ok..so lets say in theory...

In theory i find out that it is indeed piped in wrong..ie, in the cold rail circuit and not on the epr like its supposed to be...
Install epr for that box...hell no, no room period so thats not an option.

What could i do?
Ke2Therm?
Air sensing stat with clock?
Any other ideas?

Now...if it is piped correctly and is 100% on the Epr circuit then i have another problem and will go further


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[BDOLIN]

Ok..so lets say in theory...



What could i do?
Ke2Therm?
Air sensing stat with clock?
Any other ideas?

Now...if it is piped correctly and is 100% on the Epr circuit then i have another problem and will go further


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I like this idea:angel

[BALloyd]

Issue 1....you positive there is no air infiltration?

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[UmmScott]

Issue 1....you positive there is no air infiltration?

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Pretty positive, their drawers are in ok shape.

Beings they seal decent for now.

They even have a low boy under the grill thats missing the dividing piece that seals between the bottom of the top drawer and the top of the bottom drawer. They say its been like that for a while. And this one doesnt have any freeze up or temp problems

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[UmmScott]

I will confirm the issues with the box and how its piped monday...

As for the rail...what are other things i can check?
They are only open 11am till 10pm. So ive thought and thought and thought some more about just getting rid of the temp controls...because thats the problem, they cycle off so soon.

The control i put in that closes at 5F and opens at -5F, the customer said its working much better on that particular rail but another rail has an etc1111111000000000000 on it set to cut in at 5F and out at -10.
The original controls were an HDCNT9904 i think and they close at 20 and open at 15 at the midsetting. That seemed too warm for my liking so i chose the other control

All rails frost evenly and completely along the back and sides but the air temp under them is in the low 30s.

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[VanMan812]

We service a local chain that has maybe 50 stores in the tri-state area. They have similar systems to this and they use a low pressure control to cycle the rails. I personally don't like it but it works. It's touchy and sometimes needs adjusted seasonally. It could be an option for you. Something to consider at least.

[UmmScott]

We service a local chain that has maybe 50 stores in the tri-state area. They have similar systems to this and they use a low pressure control to cycle the rails. I personally don't like it but it works. It's touchy and sometimes needs adjusted seasonally. It could be an option for you. Something to consider at least.

Its a remoted line with many cold rails.
Pressure control wont work here

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[VanMan812]

Its a remoted line with many cold rails.
Pressure control wont work here

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The stores I'm referring to have 3 cold rails and 3 drawer coolers running off of 1 remoted condensing unit. The rails have their own LPC as do the drawers. It might not work for you but it's possible.

[BALloyd]

Stupid question but they keep all the pans in the rail all the time right?

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[COOLJIM]

randall have a range of cabinet,s , base and rail on 1 circuit , low back pressure compressor, 1 txv is low temp. 1 is refrigerator range. they are looking for 25psi freezer 37psi refrigerator, when they both run suction is around 50 psi if memory serves me.
they can be difficult to trouble shoot .

[UmmScott]

To top it all off, theres ZERO pressure taps anywhere on the line...not one effing tap.

Its making me irritated cuz im a determined person and when i cant figure something out right away it bugs me until i do

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[UmmScott]

If this was a walk in setup like a rack it would be much much much easier to work on..

Checking superheat is near impossible on the drawer units. Gotta disassemble the whole thing to access the evap and now you dont have doors lol. Better find some cardboard i suppose

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[trippintl0]

If this was a walk in setup like a rack it would be much much much easier to work on..

Checking superheat is near impossible on the drawer units. Gotta disassemble the whole thing to access the evap and now you dont have doors lol. Better find some cardboard i suppose

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Yeah that sucks, it's ridiculous bc as soon as you pull drawers and racks box is at 60 deg and all opportunity for testing is out the window.

I would consider a Dixell type controller mounted in control area. So you get box control based on air temps, but the advantage of a guaranteed defrost with termination based on coil temp. Regular air Stat + defrost will work but much higher probability of a freezeup.

The randell low boys tend to run colder evap temps mainly due to drawer racks blocking 98% of airflow out of Mullion evaps. It's a poor design I think. Even on self contained I've seen them running 5-10° SST and instantly cycling. I tried to use an Etc sensing coil temp with like a 5° cutout 37 cutin. Still didn't work well. Took to long for coil to thaw during off cycle. I never fixed it. I'm thinking the dixell, sensing air temp in box somewhere (NOT in direct return air stream of coil, sense airflow on that box essentially short cycles against rail), coil.sensor, defrost interval 1hr (yes as in 24 defrosts a day) with 40deg termination max duration 20 min might be the best bandaid for a poor airflow.

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[trippintl0]

Regarding cold rails, all you can do is let it run more. Control temps with an ETC strapped by txv bulb, cycle somewhere around -15 cutout 0 cut in.

Again the generously sized condensing unit is prob causing premature cycle during low load situations.

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