Questions about AC work to be done on 7/25 (Contractor analysis)

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Old 07-24-12, 02:53 PM
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Questions about AC work to be done on 7/25 (Contractor analysis)

Unfortunately I never know how to explain problems without including too many details but...

I've recently bought an older home (ok, it's been a year). My experience with having to maintain and deal with AC problems is new as I always had the landlord deal with it. So I want to know if some of the feedback I'm getting based on the data points I have...makes sense.

Summary Background:

We moved in at the end of last summer so I'm not sure we ever stress tested the AC but I don't remember it having issues cooling so I assume it worked well. I live in a part of LA that can have summers with 100+ days with MANY days in the 90s.

I don't know the service history of the unit, but it was installed/built in 2002. Compressor is outside on the ground with a line fed into the attic (through outside wall) and down into the furnace/blower closet in the center of the house...seems pretty ordinary.

Suddenly a week or so ago I noticed that I had the air on ALL night (ok 5 hours straight which for us is a lot as we're poor right now) and the temp only went down 2 degress (84 to 82).

I walked around and also noticed that not only was the air not coming out much from the vents but that the temp was barely above the ambient room temp.

Someone at work told me to check my air filter. Never knew I had one It's an after-market 5" thick 20x25 one so I changed it and felt a ton of air coming through so thought "It's fixed!"

Not so much.

The air flow was great (this was to be coincidental and had nothing to do with the filter). But the temp was still low. Some people at work suggested it might just need refrigerant as that is a common issue. Hey, sounds good to me. Out comes a tech from a company I found on Angies List.

The guy has been very good at answering all my questions in detail so I have no reason to doubt him but I'm cynical and inquisitive.

He connected his gauges to the outside compressor unit and said our unit is missing about 4 pounds of refrigerant (it takes close to 10 I think).

Before leaving he checked the supply and return vents and mentioned there should be a 15 to 20 degree difference and according to him there was. Problem now solved, $270 later.

That night I tested it out and it worked well enough but it was a cooler night so I only kept it on for 1.5 hours or so and the temp went from like 81 to 78 or 77 and I shut it off.

The next night I did the same as it was warmer and again it stayed on for almost 3 hours and barely moved 1 to 2 degrees. I again noticed really low airflow so I pulled out the filter thinking maybe something was wrong. It looked fine.

After 30 minutes I tried again and the airflow was back to normal.

I now realize it has to do with the evaporative coils freezing because it's clear we have a pretty good sized leak. As it in 48 hours or less and it basically lost what we put in.

On to my questions:

1) Since he had no history of service, he'd have had no reason to suspect a large leak (meaning this might be the first time in 10 years it's been serviced so losing 4 pounds in 10 years isn't horrible); I guess he could have suggested I spend $400 for leak detection first but then I'd also need to pay to refil ALL the refigerant so it would all-around be more. But should he have strongly suggested I do a leak detection in the absence of unit behavior or history?

2a) He won't be charging me for the leak detection testing given our wasting the $270 (and we'll have to pay to refill all of it now). He said while the leak can be anywhere or caused by anything (we had asbestos duct insurlation replaced before we took ownership but have no clue what they really did) but 90% of the time he said it's within or near the evaporative coils. Is this true? Why? He said he'd fix the leak if he can but if it's in a bad part of the coils, then you usually need to replace the coils and it can be 2k+

2b) Is there anything that suddenly would cause a leak like this (i.e. not minor one)?

3) Is there an easy way for me to check what the "pressure" is in the system or how many pounds of refrigerant is in the system? Can I do it with something I can purchse beside all those gauges he had?

4) My wife said he friend had someone service their unit in a condo they own and that he "checked" for leaks before filling more refrigerant. From what I've learned since, isn't that impossible without draining the system of refrigerant, filling it with nitrogen, etc. etc. In other words was he just BSing her or?

Sorry for such a long post but hopefully someone else learns a thing or two.

Thanks!
 
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Old 07-24-12, 03:31 PM
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If you lose 4 pounds of freon in a few days it must be a large leak. It could be in the evap coil or it could be at the outoor unit. Usually evap leaks are small so unless you can hear a hissing sound coming from the evap coil when the system is off the. The leak is probably outside. Although if the blower motor shuts off it would also cause it to ice over. Id say check the outdoor unit for dark stains or oily spots. You shouldnt have to put nitrogen to find a leak just the freon in the systrm is enough.
 
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Old 07-24-12, 03:43 PM
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they can "pump down" the refrigerant into your outside unit if it has valves on it.that way you don't lose the refrigerant that you have and they can run nitrogen thru the lines and find leak
 
 

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