pressure problems continued

[ozbound]

Hi

Still having problems but running a littlte better!

From the start,
Cold room size 32m x 20.4m x 4m to run at plus 6 degs.
Kit sized on 113kw duty.
using 4 x Copeland eazycool OMQ 110 3 phase 23700w 15hp each and 8 x searle DSR 116-4 13700w each.

R404A

Have only installed one system at presant and this is where the problems begin. First installed the wrong valves TES2 (your fault my mistake kind of thing) then valves were cross ref with sporland SSE 04C matched with Danfoss TES 5 with No 1 orifice (4 ton) but i am having nothing but trouble with pressure. At each evap the suction pressure fluctuates between 3-4bar slight frosting to the coil from tev/dis then not much happens to the rest of the coil temp wise. (2 x evaps off one condenser).approx 6 degs from tev to suction. while out at the condenser the suction fluctuates from 4-2.5 bar and the head pressure ranges from 19 - 21.5 bar. Sight glass is not full and flashes.
If anyone could help would be great as i'm stressed with it at the moment:confused:
Or could anyone tell me if the valve is correct

All the best Ozbound

[nike123]

Hi

Sight glass is not full and flashes.
If anyone could help would be great as i'm stressed with it at the moment:confused:


What is subcooling at TXV inlet? Or, what is subcooling at condenser outlet and, if any, is that enough to cover pressure drop from condenser to TXV?
Do you know difference between normal flash gas in sight glass for R404A and half full sight glass?

[ozbound]

What is subcooling at TXV inlet?The liquid line 37c at txv out let 4c suction at evap 10c. what is subcooling at condenser outlet ? i is that enough to cover pressure drop from condenser to TXV?
Do you know difference between normal flash gas in sight glass for R404A and half full sight glass?

Just started out worked for the same person for years. pipe A to pipe B. Needed a change. So got this Spect by Company used for years.

[mad fridgie]

So if i got this right, you have a room that should have 4 system running to satisfy the load, but you only have one running. You are trying to pull the room down and balance the system?
Forget it! Install the other gear, bring the room down, then set your system up for stability.

[ozbound]

So if i got this right, you have a room that should have 4 system running to satisfy the load, but you only have one running. You are trying to pull the room down and balance the system?
Forget it! Install the other gear, bring the room down, then set your system up for stability.


no i'm not trying just to use one unit to cool the whole room, the room still has the old kit in it and as and then they will be shut down. So the room is running around 8-9c. Extra duty on new coolers to bring down to 6c.

Even at this room temp i should be able to balance the units and have a better running pressures.

Suction at CU 3.5 bar Liquid at CU 22 bar, with 4 bar at evap.:( Temp out of TEV ranges as the flash gas passes 12c down to 5c suction at pipe between 10-14c :mad:

[AndyHX]

How is the head pressure controlled?
I am not quite sure if you managed to get the correct txv , could you clarify that point.
cheers Andy

[nike123]

Oscillating pressures could be from many reasons. Here are some:
-To big expansion valve = not your case. I think your is properly matched or slightly small and that could not produce oscillation.
-Faulty TXV
-Bulb placement
-Equalization line placement
-Head pressure control - You have Alco FSP 150, maybe he is cause of problem
-Not enough refrigerant - little bubbles in sight glass mean nothing, dense stream of bubbles are lack of refrigerant (no subcooling).
-Interaction between evaporators
-Air flow fluctuations or intermittent recirculation
etc..

Turn off fan speed control and see if that stabilize pressures, than see if it is enough subcooling before TXV. Check that bulb and equalization lines are placed per instalation instructions. Isolate bulb. Check that distributor is vertical.
Do you have any other control element in your instalation?

[icecube51]

Maybe if we would get some info on the design like tubing lenght and diam. What is the calculated refrigload and what is the present load. Who or what is regulating the unit, or steps of compressors. What is the oilregulation in this concept, each compressor separated or in cascade. So many missing links, so many things to think about.

Ice

[Peter_1]

Making a simple drawing should clarify a lot.
I even don't understand your setup.

[ozbound]

HI
MAIN PIPE RUN 30M 1 5/8 SUCTION 7/8 LIQUID, BRANCH OFF 1 1/8 SUCTION 5/8 LIQUID.
liquid temp at TEV 44c out off TEV 8 -11 c. Suction temp15c 3.4 bar Room temp 13c. Air on to condenser 25c
Single copeland comp Discharge 87c.
Went for short of gas opption filled reciever but sight glass still bubbled.

[mad fridgie]

HI
MAIN PIPE RUN 30M 1 5/8 SUCTION 7/8 LIQUID, BRANCH OFF 1 1/8 SUCTION 5/8 LIQUID.
liquid temp at TEV 44c out off TEV 8 -11 c. Suction temp15c 3.4 bar Room temp 13c. Air on to condenser 25c
Single copeland comp Discharge 87c.
Went for short of gas opption filled reciever but sight glass still bubbled.
You are working on at least 19TD on your condensor or you are overcharged. You need to sub cool your liquid at the reciever outlet. You do not have sub cooling in the reciever, you have a pressure drop in your liquid line prior to the sight glass. This is made worse due to glide of the refrigerant. Fix this problem and the rest will be sorted.

[ozbound]

You are working on at least 19TD on your condensor or you are overcharged. You need to sub cool your liquid at the reciever outlet. You do not have sub cooling in the reciever, you have a pressure drop in your liquid line prior to the sight glass. This is made worse due to glide of the refrigerant. Fix this problem and the rest will be sorted.

Cheers what would be the best way for me to sub cool the liquid. Do not think i'm over charged as i'm 3kg of calculated amount(19kg) and the reciever is not full not even when pumped down. No level in sight glass. Multible bubbles in liquid line sight when running.
Have spoke to person who sized the whole system been told to change to No2 orrifice see if that works if not then change the gas, may have non condensibles in it.

At a total loss with it.

[ozbound]

Have changed orrifice's to No2. Head runs at 23 bar suction at 3 bar. Can make no dif when adjust the valve unless close it fully. Valve open or nearly closed. TEV out let 6-10c Suction 15c.

[coolstuf]

Hi,

Relax and go back to basics, don't talk about pressures, talk about temp.
What is your evap temp, you want +4 C deg room temp, your evap temp should be at least -6 C or bit lower. Then check superheat, between 4 to 6 K, if more , why (bulb placement, short of gas etc etc). Measure subcooling, do you have at least some. What is your condensing temp, is it roughly air on + 15 deg. Just a thought, had a liquid line running across a hot black tarmac roof once, when sun was out, poof, no more capacity, all that flashgas messed everything up. Good luck and keep it simple:)

[Peter_1]

Hi,

Relax and go back to basics, don't talk about pressures, talk about temp.
What is your evap temp, you want +4 C deg room temp, your evap temp should be at least -6 C or bit lower. Then check superheat, between 4 to 6 K, if more , why (bulb placement, short of gas etc etc). Measure subcooling, do you have at least some. What is your condensing temp, is it roughly air on + 15 deg. Just a thought, had a liquid line running across a hot black tarmac roof once, when sun was out, poof, no more capacity, all that flashgas messed everything up. Good luck and keep it simple:)

This is a post we should copy and paste each time someone has a question which goes back to a basic problem. It has almost everything in it to diagnose a system. Very good post coolstuf.