Bought House - Air Conditioning Woes


Hello,
We bought a house a while back, and part of the deal was to fix the air conditioning unit (heat pump), on the advice of our home inspector.
The outside unit was replaced, and it is physically quite a bit larger than the previous heat pump. (I couldn't find any performance information on the stickers, just part numbers, and I plan to look that up tomorrow.)
Fast forward to now: Spring has arrived (Northern Kentucky), and the house is in the low to mid-80's inside with the air conditioner on.
I've been doing some homework, and think I understand the components better now (compared to when we bought the house.)
I took the panel off of the air handler unit (located in our basement), in order to have a look at the evaporator coil. The coil has rust on the copper tubing, and it looks like the fins are dirty on the inside (it is hard to get a good look though.)
Notably, the air blows considerably harder through our vents with the panel off of the air handler - I assume that this is a sign that the evaporator coil is "dirty"?
I also wonder if there might be a refrigerant leak, as the big copper intake tube does not feel very cold at all.
Having said that, I have one important question, as this pertains to whether the people who installed the new heat pump did their job right:
1. Everything I've read in the last couple of days says that you should replace the evaporator coil unit at the same time you replace the outdoor condenser / heat pump. The installers did NOT do this - they just replaced the heat pump. SHOULD they have replaced the evaporator coil? Is there a strong enough reason to do this that I would be justified in demanding that they replace it now?
2. I've also read that it is important that the evaporator coil must be carefully matched in size to the condenser / heat pump. Unfortunately, neither of my units have any performance information on them, but I do have the model numbers, and so I will try to find that information out soon. But, I can tell you that the new heat pump is considerably larger (physically, at least) than the old one. Assuming that the new one is (significantly?) larger (in capacity) than the old one, and that the existing evaporator coil was in fact matched to the old, smaller, heat pump - does this also justify me in demanding that they (the installers) replace the evaporator coil with a new (matched) unit?
When we bought the house, I didn't understand how the whole heating/cooling system really worked. They said they would replace the heat pump, as the old one was making strange sounds. However, it would seem to be a bit negligent to blindly hook up a larger heat pump to an old (rusted & dirty) evaporator coil. If this is the case, I'm also concerned that this may affect the life of the new heat pump (being mismatched.)
Anyway, I would appreciate any comments on this, particularly on what the installers _should_ have done (if different), as well as any suggestions on what to do next.
Thanks for any help!
Mike
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Mike Mills wrote:

You have a lot of good questions, but I don't think too many good answers can be given on line. The physical size of a unit does not mean much. It may be a larger capacity or not it may be a more efficient unit or not. It is not always a good (practical money considered) idea to replace both parts at the same time or not. While in general I would suggest that the word Heat Pump in includes both the interior and exterior units, it could be argued otherwise.
I suggest you need to have a competent HVAC man or woman take a good look at what you have, do the numbers and determine where you now are and if and what you might need to do to get where you should be. It sounds a lot like someone did a short cut already. There is no way of doing the job right without looking at the whole including air flow duct and fan sizing etc.
--
Joseph Meehan

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On Mon, 26 Mar 2007 01:21:49 -0400, Mike Mills

Always give the original installers the first shot at fixing their install. It is usually free and you get to learn whether you want to continue doing business with them.
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Mike Mills wrote:

    Just curious, how long ago is a "While back?" I don't know about heat pumps, but I don't believe a typical AC unit can be "Properly" charged and checked unless the the temperature is over 70 degrees. Before I get flamed, I realize there is a capacity to which such units should be charged, but it is only an approximation if I am correct.
    From what you have stated, I would immediately contact those responsible for the installation of the new heat pump. It sounds like you got short changed. If the evaporator coil is clogged, that is NOT an acceptable installation in my book.
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wrote:

I've sold several homes in my life and every single one of them had a big 'AS IS' on the face of the contract.
There was also a clause with bold print that said 'BUYER PAYS FOR ALL INSPECTIONS AND REPAIRS'.
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That's one way to do it, but not the only way. It's possible to argue about things that "ought to have been done" in the normal course of operating and maintaining the house.
For example: we bought a house a year and some ago. We paid for a home inspector and made the purchase conditional on dealing with any problems he found. He found two broken windows, and the seller agreed to fix them. There were two gas fires, but one had the gas supply turned off so the inspector couldn't inspect it (it's against his policy to turn on stuff that's been turned off). The seller agreed to have both fires turned on and serviced by a local dealer's service department. There was a huge welded structure that used to be a "breakfast nook" lying under the rear deck, and the seller agreed to get rid of it before closing.
On the other hand, the inspector also pointed out that the hot water heater and roof would need replacing nearly immediately. We tried to get the seller to give us some credit against the anticipated cost, but they argued that since the water heater and roof didn't appear to be leaking yet, they didn't need immediate replacement. So we bought with those in the condition they were in, knowing we'd need to replace them soon.
    Dave
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I think I'm going to report you to the Society for Prevention of Cruelty to Parenthases.
As to your questions. yes, it sounds like the evaporator coil is dirty. The air flow difference with the cover off is a signifigant test.
The performance is hidden in the model number, most have the BTU rating as part of their model number.
Depending how long ago was the home sale and the other work done, you may be out of warranty. But you'll have to try to find out.
The large line is the return line. The small line supplies the refrigerant to the evaporator. And, yes, the large line should get cold. Definitely should get cold if the air flow through the evaporator is reduced.
Different units have different physical size for the same BTU rating.
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Christopher A. Young
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On Mar 28, 6:40 am, "Stormin Mormon" <cayoung61-

With the cover off, the air is still flowing through the same evaporator, dirty or not. What it's not flowing through is the return air duct. It's much harder to pull air through return ducts, than it is to pull air from the wide open air handler with the door off. That's why air flow increases and it's normal.

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you cant really get an accurate freon charge if the evap coil is clogged.clean it and go from there.
http://www.minibite.com/america/malone.htm
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