Author Topic: Replacing low pressure control on refrigeration system  (Read 6245 times)

Offline harry

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I have a refrigeration unit that I have to replace the low pressure control.After calling a friend of mine who has the recovery unit I have used before and finding out it is at a brother-in-laws, about 80 miles away, on vacation for the next two weeks. Reading a previous post someone suggested sucking freon out of system with a jug in a bucket of ice water. Will this work? The compressor has service valves on both side so can valve off the rest of system. I need to recover all freon in compressor and replace it as it is a measured charge after the sight glass is clear[ has a receiver tank and flood valve]so it would be nice to not have to evacuate the entire system and start over. Will the ice water recovery work or should I find another recovery system? It is a R-22 system. Thanks

Russell HTLH 401 H22

Offline jumptrout51

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Re: Replacing low pressure control on refrigeration system
« Reply #1 on: May 29, 2009, 07:45:51 PM »
It is about 90% effective.
Take a Kid fishing.

Offline Icehouse

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Re: Replacing low pressure control on refrigeration system
« Reply #2 on: May 29, 2009, 08:26:32 PM »
When replacing a low side component, preform a high side pump down.
HIGH SIDE PUMP DOWN

1. Turn power off.

2. Install gauge manifold as such. High side on Liquid Line Service Valve (King Valve) located on receiver.

3. Install Low Side on Suction Service Valve.

4. Place a jumper across control leads.

5. Crack both suction service and liquid service valves off of back seat position.

6. Turn Power Back on.

7. Slowly front seat liquid line service valve while observing low side gauge. Do not let it go below 2 psig.

8. When low side gauge reads 2 psig, turn off power and front seat suction service valve quickly.

You have now isolated the system charge in the receiver and can now remove the low pressure control with out the loss of refrigerant, nor the need for a recovery machine.

9. Replace the low pressure control and replace the drier. (Anytime you open a system, replace the drier).

10. With the power off, gently reverse the procedure.

Now you are done.
« Last Edit: June 10, 2009, 12:44:31 PM by Icehouse »
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Offline JWWebster

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Re: Replacing low pressure control on refrigeration system
« Reply #3 on: May 29, 2009, 08:40:13 PM »
If using the bucket and ice method just watch the low side gauge. When it is close to zero you have done it. You may now proceed to change the switch.
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Offline Icehouse

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Re: Replacing low pressure control on refrigeration system
« Reply #4 on: May 29, 2009, 08:51:44 PM »
If using the bucket and ice method just watch the low side gauge. When it is close to zero you have done it. You may now proceed to change the switch.
If he follows what I have outlined, there is no need for an "ice bath". Been using the method over forty years, but then again I don't know that much.   ;)
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: Replacing low pressure control on refrigeration system
« Reply #5 on: May 29, 2009, 09:29:30 PM »
Let me get this straight. While the unit is running, I shut off the high side valve. I let the compressor capture the freon, I watch my guage to zero pressure or near it, and then I close the low side valve,and shut down the outside unit?
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About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.
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Offline Icehouse

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Re: Replacing low pressure control on refrigeration system
« Reply #6 on: May 30, 2009, 06:24:42 AM »
JW, he is replacing the control on a "Refrigeration Unit", that's why the mention of receiver and sight glass. No not in the compressor, rather the receiver although you can apply this to A/C as well isolating the charge in the condenser.  :)
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: Replacing low pressure control on refrigeration system
« Reply #7 on: May 30, 2009, 06:26:30 AM »
JW, he is replacing the control on a "Refrigeration Unit", that's why the mention of receiver and sight glass. No not in the compressor, rather the receiver although you can apply this to A/C as well isolating the charge in the condenser. Also not closing the high side, rather the "liquid line service valve". :)
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: Replacing low pressure control on refrigeration system
« Reply #8 on: May 30, 2009, 09:01:38 AM »
See attached.  :)
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: Replacing low pressure control on refrigeration system
« Reply #9 on: May 30, 2009, 05:26:24 PM »
Whichever method you use you want minimize the loss of freon into the atmosphere. Since the unit is an R22 unit you allowed a small amount of freon loss. A pound or less I believe it is.
May the hinges of our friendship
        never grow rusty.

About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.
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