FHB Logo Facebook LinkedIn Email Pinterest Twitter X Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In

Discussion Forum

Discussion Forum

Can somebody help me? Moisture in A/C?

1110d | Posted in Energy, Heating & Insulation on June 29, 2005 09:31am

With this humid weather we have been wanting to use our A/C.  The problem is that the system really isn’t getting cold.  Cool but not cold.  The guy that did our furnance last year reinstalled the condenser unit that we had from a previous installation.  The problem is that the unit sat outside for a while disconnected.  Apparently this allowed a bunch of water to enter the system which is causing the pressures to spike.  The installer is saying the compresser will have all this water in it’s oil which he’ll never be able to remove all of it.  He’s recommending we replace the condensing unit.  I was hoping there was somebody on the board that would know enough about these systems to help me make a informed decision.  Is there any way we can get this moisture out of the unit or is it really toast?  Why can’t we just replace the oil?  Why can’t just the compresser be replaced and evac the lines/evaporator/condenser?

 

Certified boat fetish.

Reply

Replies

  1. User avater
    constantin | Jun 29, 2005 11:47pm | #1

    Time to turn to HVAC-Talk. Post your question there, they're tons of AC installers over there.

    It's a shame that your condenser was allowed to sit open to atmosphere for a while. Indeed, a lot of todays oils used as lubricants in them are hydroscopic and your only hope may be to flush as much of the system with nitrogen as you can and to follow-up with over-sized filter-driers.

    Whether that works out in your favor financially is a whole other question. Installers aren't cheap and so a new condenser may not cost that much more than the maintenance to make the old one limp along.

    If you need a new condenser, make sure that a heat gain calculation is performed (i.e. right size the AC system), that the ductwork is right-sized also (i.e. Manual D compliant), and that the lineset linking the condenser and evaporator is swapped. Ideally, you'd also swap out the evaporator as anything that contaminated the condenser probably contaminated that as well.

  2. TRice | Jun 30, 2005 05:13pm | #2

    First, I would recommend that you find a competent service person. The one that told that they could never get all of the water out of the system does not, in my opinion, fit that description. Request or demand that they be NATE certified.

    A few things need to be done to make this system work the way it is designed to work.

    First is that refrigerant (freon, R22) in the system needs to be removed with a recovery system. A recovery system will remove and store the existing freon/oil charge and has a filter/drier that removes entrained moisture and contaminants from the refrigerant. The system will need to be purged with nitrogen. Compressed nitrogen is extremely dry and will remove most traces of the water. A liquid line filter/drier should then be added to the discharge of the condenser coil, upstream of the service valve. If the condensing unit has an accumulator/oil separator upstream of the compressor, a suction line filter drier is not really necessary. Without an accumulator, I would add a suction line filter/drier as well. Then a very good (28-29" Hg) vacuum should pulled on the system. Recharge and adjust to acheive the proper superheat (or subcooling with a TXV) at the conditions at the time. Run it untill the house is at the desired temperature and then perform a final check/adjustment to the charge.

    Unless your AC unit is 10 years old or older, replacement is not warranted. The service required will cost you several hundred $$, at least, but a new AC could easily run a couple $$K. If you do decide, after having a reputable service company estimate what the service will cost you, that a new unit is in order, I would still not go back to "the guy that did our furnance last year".

    1. User avater
      BillHartmann | Jun 30, 2005 06:23pm | #3

      Ah!I had to check the profiles. There are two different Timbo's, not one Timbo wiht split personality.I was confused when I saw the first post from "you".

  3. DanH | Jun 30, 2005 08:40pm | #4

    You probably want to get your terminology right. The evaporator coil is the one that goes inside the furnace, and the condensing coil goes outside with the compressor.

    Whatever bozo left either unit unsealed is at fault here. The system should have been properly evacuated, the freon recycled, and the tubing ends sealed, whether things were going to be stored inside or outside.

    It's certainly worth a try having the system re-evacuated, the dryer replaced, and fresh freon put in. The oil in question sits in the compressor, and replacing it implies replacing the entire outdoor unit, which is to say essentially the entire AC.

    1. junkhound | Jun 30, 2005 10:02pm | #5

      Good advice with one additional comment.

      Check if your compressor is a reciprocating or scroll compressor (a scroll will be higher than it is wide by a factor of 2 or so).  If a scroll, they use a synthetic polyol ester oil that does not like to release water molecules even at 200 micron vacuums. (I can't recall the chemical ring details of why so hygoscopic or retentive of H2O, read it once but getting old).  A mineral oil compressor can be dried with a 500 micron vacuum fairly easily, with the synthetic you will have to heat all the lines and compressor to 70-80C to get the water out even under vacuum according to what I've read.

      Would not hurt to even put 2 dryers on the line when you try the fixes like Dan and Timbo (II) said, they are only about $15 each.

       

      Dan, Timbo (II) - query on same subject but a little different - have a 7.5 ton old evap (old Carrier brand copper lines) that is open with no leaks, but have no idea of its history.  Have a 4T scroll on the shelf to do a DIY GSHP using the Carrier part as indoor coil (condensor in HP application).  Query is how to clean it - plan on flushing with ferric chloride solution to get rid of oxides, then water flush, followed by 200 micron vacuum overnight or until it will hold/show better than 500 micron vacuum for a day. Ever tried this, any other ideas???

      1. TRice | Jul 01, 2005 04:51pm | #7

        JH,

        There are some commercial cleaners available, their intended use is for changing a system from R22 to R410a, when line set replacement is not feasible, but, I don't carry them in my shop and don't recall the details of the product. Your coil is copper tubes, with aluminum fins (right?) so the ferric chloride should remove minor copper oxides. Maybe some chemists out there have a better idea. I am no chemist (just an engineer). Pressure test the coil after you have flushed all of the cleaners out with N2 if you have the capability. I have never tried what you are going to do, so you may want to check so more sources (ask the oldest guy at the local Johnstone Suppy).

    2. TRice | Jul 01, 2005 04:37pm | #6

      Dan,

      I made no mention of the evaporator coil in my post and I am quite clear on the terminology and the technology. You, it seems, may not be.

      The fact is, it is a common practice to pump down a condensing uint before disconnecting it for what ever reason. This done by running the system for at least 15 minutes and the closing the liquid line service valve. Allow the compressor to pump all (or most) the refrigerant into the condenser coil and then close the suction service valve. Unless the service valves are shot, no further closure is necessary except maybe to tape over the cut tubes to prevent the intrusion of debris. The unit can then be stored inside or outside.

      IF a system were left completely open, then the PROPER evacuation of the system WILL remove all oil and moisture or leave so liitle behind to be insignificant. This is assuming that the system is an R22 system and that the vacuum is in the 500 micron or better range. If I work restoring such a system to service, I would purge with nitrogen to assure there remained no debris, blockages or moisture.

      Should the compresser need replacement due to improper storage and subsequent damage, that is an easy enough repair and by no means would require "replacing the entire outdoor unit, which is to say essentially the entire AC". A replacement compressor is still a fraction of the cost of an entire condensing unit, and a small fraction of a new system.

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Video Shorts

Categories

  • Business
  • Code Questions
  • Construction Techniques
  • Energy, Heating & Insulation
  • General Discussion
  • Help/Work Wanted
  • Photo Gallery
  • Reader Classified
  • Tools for Home Building

Discussion Forum

Recent Posts and Replies

  • |
  • |
  • |
  • |
  • |
  • |
View More Create Post

Up Next

Video Shorts

Featured Story

FHB Podcast Segment: Patching Drywall Near a Shower

Learn how to patch drywall above a fiberglass shower without totally redoing everything.

Featured Video

How to Install Exterior Window Trim

Learn how to measure, cut, and build window casing made of cellular PVC, solid wood, poly-ash boards, or any common molding material. Plus, get tips for a clean and solid installation.

Related Stories

  • A Summer Retreat Preserved in the Catskill Mountains
  • Fine Homebuilding Issue #332 Online Highlights
  • The Trump Administration Wants to Eliminate the Energy Star Program
  • Podcast Episode 685: Patching Drywall, Adding Air Barriers, and Rotted Walls

Highlights

Fine Homebuilding All Access
Fine Homebuilding Podcast
Tool Tech
Plus, get an extra 20% off with code GIFT20

"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Fine Homebuilding Magazine

  • Issue 331 - June 2025
    • A More Resilient Roof
    • Tool Test: You Need a Drywall Sander
    • Ducted vs. Ductless Heat Pumps
  • Issue 330 - April/May 2025
    • Deck Details for Durability
    • FAQs on HPWHs
    • 10 Tips for a Long-Lasting Paint Job
  • Issue 329 - Feb/Mar 2025
    • Smart Foundation for a Small Addition
    • A Kominka Comes West
    • Making Small Kitchens Work
  • Issue 328 - Dec/Jan 2024
    • How a Pro Replaces Columns
    • Passive House 3.0
    • Tool Test: Compact Line Lasers
  • Issue 327 - November 2024
    • Repairing Damaged Walls and Ceilings
    • Plumbing Protection
    • Talking Shop

Fine Home Building

Newsletter Sign-up

  • Fine Homebuilding

    Home building tips, offers, and expert advice in your inbox.

  • Green Building Advisor

    Building science and energy efficiency advice, plus special offers, in your inbox.

  • Old House Journal

    Repair, renovation, and restoration tips, plus special offers, in your inbox.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters

Follow

  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X
  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences
  • About
  • Contact
  • Advertise
  • Careers
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2025 Active Interest Media. All rights reserved.

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Project Guides
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Online Learning

  • Courses
  • Project Guides
  • Reader Projects
  • Podcast

More

  • FHB Ambassadors
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • X
  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 70%

Subscribe

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in