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Thread: Confusion
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22-01-2008, 06:42 PM #1
Confusion
Hi
A cold store with two refrigeration systems:10 and 15 tons . When they are running together the thermometer established at -20C.When the 15 tons runs alone the thermometer established at -22C. Help will highly appreciated .
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22-01-2008, 07:11 PM #2
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22-01-2008, 09:03 PM #3
Re: Confusion
Hi afak,
Are the refrigeration systems independent of each other, or connected together?
Is the defrost performed by hot gas or electric?If all else fails, ask for help.
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22-01-2008, 09:18 PM #4
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Re: Confusion
How their condenser's are placed? Does their airflow is affecting each other?
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22-01-2008, 10:47 PM #5
Re: Confusion
what is the control method and where is it's sensor?
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23-01-2008, 07:45 AM #6
Re: Confusion
All of the above and 2 more You don't say why you need to run the 2nd (10 ton) system?
Is it to supliment the other due to incresed Chamber/s load?
Also you don't say wether the 10 ton plant is capable of reaching -22c on it's own?
Grizzly
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23-01-2008, 02:44 PM #7
Re: Confusion
Could you please describe the system more precisely as stated above. This will help to detect the problem. Also please state what is the required temperature.
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23-01-2008, 05:58 PM #8
Re: Confusion
yusuf amur:the systems are independent.
Hi US Iceman:with electric defrost.
nike 123:there is no affection between condensers.
bill1983:they share the same thermostat installed at the middle intake side of the two evaporators.
samarjit sen: probably -27 . The system is with air cooled condenser.R22.
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23-01-2008, 07:51 PM #9
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Re: Confusion
Does both systems cools? It looks like 10 ton system adding some heat. Maybe you should check that defrost heaters are not ON on one of systems if it is electrical defrost. Or, it could be, that you measured second temperature when one of the system performed defrost.
Does the goods in cold store are not loaded during measurements?
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23-01-2008, 10:59 PM #10
Re: Confusion
if there is only one thermostat why does one system cut out first or am i mis interpreting your question
how long ago did the problem start what has changed or been replaced on the system recently?
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23-01-2008, 11:32 PM #11
Re: Confusion
If you have a 2 stage stat and the lead compressor is the 10 ton and the lag is the 15 ton the and both are running then at some point (22*C) the 15 ton may shut down first and only the 10 ton is running = 20*C
On a 2 stage stat the lag compressor starts last and turns off first. This doesn't seem like a serious problem but more like a control adjustment problem
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24-01-2008, 06:01 AM #12
Re: Confusion
Hi Afak, will you please operate the units independently and check the temperatures being attained. Please check the defrost system and its timing. I am sure from what you have stated, it is a minor adjustments that are required. Shall await your reply.
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24-01-2008, 06:50 PM #13
Re: Confusion
Grizzly:when the load is frozen chicken the 10tons stand by;for ice cream in summer they need them work together to reach about -27
nike123:the temp checked after established load,closed doors, defrost system works properly.
bill 1983:the thermostat controls the two systems.
wambat:the systems work independently but sharing the same thermostat.
Hi Samarjit San:I will check that.
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25-01-2008, 05:17 PM #14
Re: Confusion
Hi to All
checking the system to day I found:
1.the characteristic of the overload that protect the fans was changed making the contacter of the fans continuously on and off ,but the pressure did not reach the cut out limit of the hi pressure protection.
2. unqualified technician widely opened the TEV and add more refrigerant.
3.change the overload,readjust the TEV ,dismiss the additional charge the system now works properly.
4.but we still need explanation.Last edited by afak; 25-01-2008 at 05:19 PM. Reason: grammer
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25-01-2008, 10:27 PM #15
Re: Confusion
hi afak try this
1. fans cycling on overload when near operating temp is causing compressor to cycle on low pressure
2. previous tech(s) thought that due to low pressure system was short of refrigerant after adjusting tev
3. original problem and created problems rectified
4. 1 system cycling on lp creating false duty on working system lag system only operating down to set temp for stage1? what is anticycle time, lp, defrost setting are fans cycling causing heat load near thermometer sensor?
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26-01-2008, 04:59 PM #16
Re: Confusion
Hi bill1983:the two systems are independent,one thermostat control the two systems. Indeed it seems the former serviceman farly misunderstood the original problem so added more refrigerant and opened the TEV.The question is it possible that this wrong proceeder cause that the 10tons system work at higher evaporating temp that made the difference wide enough between the two evaporators that made the 10tons system to act negatively;i.e the 10tons evaporater were relatively "warmer" enough than the 15tons evaporator that caused the the thermometer read slightly higher degree when the 10tons enter work?