Hi,
Well, we’ve just started running the AC this season, the first real chance since the furnance and air handler was moved in a remodel. ‘problem is that the coils freeze up after a few hours. No air flow through the vents, unless I turn the compressor off; after a few minutes I then hear the little sump pump running and air starts to flow.
Other symptoms: The unit doesn’t seem to cool that well, so the compressor run continually. However, the air out of the vents feels pretty cold. If I go out to the compressor, the air blowing out the top doesn’t seem particularly warm.
I heard once that freezing coils can be caused by too little refrigerant, is that the case? Also, since we added square footage, is the current compressor too small? OTOH, we also went from single-pane aluminum windows to double-pane Low-E Argon units.
I remember the HVAC guy who first installed the AC said that he put in a big coil unit in case we added square feet later on, but couldn’t install a big compressor at the time in becuase it wouldn’t operate efficiently.
‘just trying to gather some info here so I can talk to the HVAC guy. I’ll probably call the guy that did the orginal install, as everything worked fine when he was done. The HVAC guy the remodel GC hired just seemed to want to spend the minimum amount of time, and I got the impression that the GC thought that AC was unimportant and kinda a waste in this part of the country (OR).
Replies
Remodel..., moved air handler and a/c unit.
Freezing of the A-coil is an indication of low freon charge, or a reduced, restricted return air flow. The low charge could have occurred when the unit was moved, either from a leak caused by the move, or improper recharging if the line sets were added to or opened. The only way to really tell is to put a set a gauges on the system. Another possibility is a kinked refrigerant line that is causing a restriction. A good HVAC tech can trouble shoot most of those in an hour or so.
A dirty air filter can also cause the A- coil to freeze up, or even a dirty A-coil itself can be the cause of freezing. Reduced air flow across the coil means less than optimal heat exchange is happening.
A visual inspection of the filter, return air area of the air handler and of the A-coil will tell you if that is your problem.
Lots of other questions need to be asked and answered b/f anyone can even guess at weather your unit is under sized or not.
Dave
What Dave said.
If the unit is undersized it won't be able to keep up on a hot day, but that won't cause freeze-up.
Low refrigerant is typical cause of frozen coil, especially suspect if unit opened. Fix before it all leaks out, or face higher bill.
Re size, most houses I have seen have far more available A/C capacity than they need, but due to design, or installation, a lot gets wasted. Get things tight, heat vented out of attic, radiant barrier, well sealed duct work including all boots grilles etc, and you may be surprised how much capacity you really have. Paul
Thanks. Yes, the lines were cut and then re-attached. I don't think the people doing the work spent much time doing it either: not like at first installation, where they seemed to spend alot of time getting moisture out, checking for leaks, etc.
Got our orignal HVAC guy out to check things out ... it was indeed low on refrigerant. Things had gotten bad enough that no condensation was produced - it just froze up directly. Things are fixed now and recharged; all ready for the hot weather to return.
Keep in mind that the refrigerant was probably low because it had leaked out, since the bozos who moved things probably at least knew how to read a pressure gauge. If it loses pressure again be sure to insist that the leak be found before recharging (and send the bozos the bill).
Barry, thanks for the update. If it becomes low again, have it pressure tested with nitrogen to find the leak. A little too much or too little refrigerant can make a big difference.
See the FHB article on page 88 of new issue. It confirms what I have found; very few complete HVAC systems are installed correctly from A to Z. There are usually a dozen things I can find wrong in most installations, and the homeowner pays the utility
bills.We could greatly lower our dependency on mid-east oil by giving all USA homes a good check-up in the energy department.
Hope you didn't get burned... PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
Dan, Paul,
Thanks. I wonder about the "bozo factor", too; maybe he just marginally charged it when he moved it, or he left a leak. In any case I have alot of confidence in the orginal installer (things worked fine for years after it had been installed), and plan to use him from now on. I'll keep an eye on how it's performing over the next few months.
Haven't seen the new issue yet but I'll be sure to check it out. There really hasn't been nearly enough HVAC articles in FHB; glad to hear about this one.
The remodel was a big sucess during the heating season w.r.t. energy reduction. Added about 800 sq. ft., but the old house had 3.5" insulation in walls and ceiling, and drafty single-pane aluminum windows. The house now has R-20 walls, R-38 ceiling, and Marvin double-pane low-E argon-filled windows. Heating bills were amazingly lower.