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Thread: SUCTION FILTER
10-07-2011, 11:16 PM #1Regular Guest
- Join Date
- Jul 2006
On an straight AC system, is there a hard fact that I can read about removing\not having a suction line filter installed? We have a Carrier split AC system with a suction line filter installed. It was not installed for a compressor burnout, it was installed when the system was new. I say it is not common practice to leave it in. (there is a filter installed in the liquid line) Another tech and I are debating. He states "leave it in, it doesnt hurt a thing." I think it needs removed, but I have no proof.
If this second question is to detailed for this open forum section, please do not answer...... What is the DP across the SL filter that determines it needs removed? That would give me amunition in this light hearted debate. A clue, there is no temp differential between input and out. So far, I'm losing
10-08-2011, 06:05 AM #2
10-08-2011, 06:44 AM #3
I agree with JP Smith, 2 psid replace the filter.
To answer your first question, I'm going to ask a question.
Is the suction line filter that is installed a replaceable core suction line filter?
If it is, just remove the core, leave the shell in place.
If it is not a replaceable core, then I agree with you, if the pressure drop greater than 2 psid replace the suction line filter. Because the suction line filter was cleaning the system.
AllenUA Local 602
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10-08-2011, 10:46 AM #4
Why do you want to spend your time and the customers money on something that is not causing a problem? Suction line driers are there to catch crap and acid. If there is no pressure drop leave it in. It is extra protection for the compressor.Challenge yourself, take the CM test --- Certificate Member since 2004 ---Join RSES ---the HVAC/R training authority ---www.rses.org
10-08-2011, 11:03 AM #5Professional Member
- Join Date
- Jul 2010
I dont see a problem with it! Like Paul Bee said it's extra protection.
If it's not causing a problem then leave it.
10-08-2011, 11:50 AM #6
The problem is: How much extra $$ does your customer want to spend on electricity?
The 2 psi drop is a good rule of thumb for A/C systems. Not so good for refrigeration systems.
An R-22 system designed to operate -25F (10 psi) experiencing a 2 psi drop in the suction line will require the compressors to operate at -29F (8 psi) in order to achieve the design temperature at the evaporator. The compressor's operating at a 2 psi lower suction pressure in this application results in a capacity loss of approximately 15%.
Not as bad for R-404A...it's only an approximate 8% capacity loss.
The lower the suction pressure, the higher the capacity loss is.
The design of the suction filter-drier results in a much higher natural pressure drop than a suction filter. When the contaminated system has been cleaned up, the suction filter-drier should be removed and replaced with the suction filter.
Now, for any given customer the practicality must be weighed against the best practice. On a small system it's likely that your customer doesn't want you coming back the next day to remove a suction filter-drier. In these applications it's important to use the correctly sized filter-driers (liquid and suction) to clean up a contaminated system...particularly on the suction side. Rather than selecting them based on cost or line size, they should be selected based on capacity.
A properly sized suction filter-drier, along with an oversized liquid filter-drier (most manufacturer's recommendation for cleaning up a system after a hermetic motor burn) in small systems with minimal piping runs will be sufficient to remove the contaminants, and not cause excessive pressure drop problems should the filter-driers not be replaced after installation. Still a good idea to check the pressure drop after a day's operation.
On larger applications where replaceable shells are used, it's much easier to remove the spent suction filter-drier and replace it with a suction filter. Given the size of the equipment that would require a suction shell, it would probably be easier to justify to the owner doing the need for a follow up call to do so.