Author Topic: calibrated orifice DFS2A  (Read 9129 times)

Offline patvac

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calibrated orifice DFS2A
« on: May 24, 2009, 10:18:51 PM »
Hi, i own an international comfort products AC system (duct free systems)

The evaporator his always freezing. I tough the calibrated orifice might be clog (chunk of welding). I need your help to know exactly where it should be located.



thank you

Offline Repair-man

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Re: calibrated orifice
« Reply #1 on: May 25, 2009, 05:57:58 AM »
Any orifice deisgned to meter the refrigerant will be found at the intake of the evaporator coil. Freezing up is a sign of undercharging or poor airflow. Your inference regarding chunks of material from brazing does not pan out unless you are a very sloppy welder and is doubtful to be a factor. Only by doing a pressure check at the condensing unit can you determine the refrigerant status.

Is this one of those skinny fan/coil units that mounts in a room with the condenser outside?

A restriction or an undercharge will show up during a proper pressure check from the outside unit. Do a pressure check before you present any more questions and provide your result, please.
« Last Edit: May 25, 2009, 06:42:11 AM by Repair-man »
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Offline patvac

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Re: calibrated orifice
« Reply #2 on: May 25, 2009, 12:22:32 PM »
Hi, The unit is the type with the evaporator inside and the compressor outside ( not a thermo pump). The unit has been install 2 years ago, It never work properly. The unit has been check for leak, refregirant quantity and pressure twice. Everything was ok according to the 2 compagny that pass by. My knowledge are limited to HVAC for CARS. But from what i think the flow seems to be restricted. The line were supposed to be scew with union but the guy weld them. The pressure line is very small about 1/4 some im thinking may be it create a restriction or that a chunk may have circulated in the system and block the unit. Ice create rapidly on the evaporator and eventualy all you see is ice.

Offline jumptrout51

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Re: calibrated orifice
« Reply #3 on: May 25, 2009, 01:32:11 PM »
What high side low side pressure do you read?
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Offline patvac

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Re: calibrated orifice
« Reply #4 on: May 25, 2009, 01:57:25 PM »
i will buy
my self a set of gauge and i will post results tomorrow

Offline Icehouse

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Re: calibrated orifice
« Reply #5 on: May 26, 2009, 08:02:07 AM »
The proper method of determining if the unit is properly charged.  :)

Superheat (for units with fixed metering device): Compute the superheat by determining saturated suction temperature from Temperature Pressure Chart. Subtract from actual suction line temperature six inches before compressor. The manufacturers recommended superheat is usually listed in the installation instructions on the units rating plate.
If it is not listed use 15 degrees of superheat as a default.
NATE, NCCER, PHCC,HVAC Certified Instructor
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Offline JWWebster

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Re: calibrated orifice
« Reply #6 on: May 26, 2009, 06:56:45 PM »
If you suspect a high head pressure you could always measure the amp draw with a clamp on meter. You can charge a unit with an amprobe. Just look up the nominclature tag and add the combined amp draw of the fan and the compressor. Then see what the actual amp draw is. if it is over then you probably have a blockage.
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Offline patvac

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Re: calibrated orifice
« Reply #7 on: May 27, 2009, 11:52:31 AM »
Today is not perfect day but here we go

Inside temperature 68.9 degrees F
Inside 48% humidity


Outside 65degrees F
59 % humidity

After 1 hour
Outside 60.7 degrees F
69% humidity

 Unit off (static pressure) 63 pi
These readings are done at 10 minutes intervals

28 psi 105 psi
29      112
32      115

Readings after 45 minutes
18 psi 100 psi
15 minutes later
13psi    100psi

The evaporator his starting to freeze ice is building in the fins
and the outside fitting where the gauge are attaching are covert with snow

i can add pictures if you want( but i will need you guys to explain me how to do it.

Thank you


Offline Icehouse

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Re: calibrated orifice
« Reply #8 on: May 27, 2009, 02:08:38 PM »
 :) This system will not operate correctly because the "outdoor temperature" is nearly the same as the "indoor temperature".
The unit is so efficient that too much refrigerant is condensing in the condenser. Remember that this is a critical charged unit, therefore the condenser,evaporator,suction line and liquid line will contain the proper amount of refrigerant. If at anytime there is an unbalanced condition, the system will fail to operate in the prescribed manner. The condenser has too much refrigerant due to the low ambient therefore starving the evaporator thus resulting in lower pressure which results in lower temperature (frost accumulation).
To remedy this situation, block off the condenser allowing the head pressure to build up to a corresponding pressure of a 95*F day. You will then notice the suction pressure will also rise and now is the time to check the superheat.
NATE, NCCER, PHCC,HVAC Certified Instructor
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Offline JWWebster

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Re: calibrated orifice
« Reply #9 on: May 27, 2009, 10:17:10 PM »
Excellent
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Offline Icehouse

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Re: calibrated orifice
« Reply #10 on: May 28, 2009, 09:42:43 AM »
 :) Sorry I get long winded.
NATE, NCCER, PHCC,HVAC Certified Instructor
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Offline Icehouse

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Re: calibrated orifice
« Reply #11 on: June 01, 2009, 03:22:13 PM »
pat, I see you also went on "Romans" site. There you said it happens on hot days also.
Here is a little more for you to digest.

Diagnosing A Restricted Feed Device
To diagnose the problem, it is easy as 1,2,3.
1. Shut the blower section off
2. Start the compressor
3. View the evaporator coil and be sure that there is a "full frost" pattern from the enterance of the evaporator to the exit.

If there is a restriction, part of the evaporator coil will be free of frost.
NATE, NCCER, PHCC,HVAC Certified Instructor
Member RSES, US Army Refrigeration Specialist(Retired), Former Refrigeration Teacher NYC Board of Ed.
a tragedy has happen to me : http://web.me.com/zenzoidman/Bobice/

Offline JWWebster

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Re: calibrated orifice
« Reply #12 on: June 01, 2009, 10:30:08 PM »
OK so far we have learned how to diagnose a restriction now onwards toward a solution? Now what must we do to be saved?
« Last Edit: June 01, 2009, 10:32:30 PM by JWWebster »
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Offline Icehouse

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Re: calibrated orifice
« Reply #13 on: June 02, 2009, 09:32:51 AM »
Give the correct information, those pressures are way off for R22.  ;)
NATE, NCCER, PHCC,HVAC Certified Instructor
Member RSES, US Army Refrigeration Specialist(Retired), Former Refrigeration Teacher NYC Board of Ed.
a tragedy has happen to me : http://web.me.com/zenzoidman/Bobice/

Offline Icehouse

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Re: calibrated orifice
« Reply #14 on: June 02, 2009, 10:27:05 AM »
Read the following:  :)
NATE, NCCER, PHCC,HVAC Certified Instructor
Member RSES, US Army Refrigeration Specialist(Retired), Former Refrigeration Teacher NYC Board of Ed.
a tragedy has happen to me : http://web.me.com/zenzoidman/Bobice/