Mike Mills wrote:
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

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

Dia 's Muire duit