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Posted by Andy Energy on May 7, 2008, 9:34 am
> wrote:
>
>
>
>
>
> > My mom's 22 year old 4 Ton 10-seer Carrier A/C condenser is shot. =A0Her=
> > furnace is relatively new.
>
> > She wants to replace the old unt with a new Puron Carrier 4 ton condense=
r.
>
> > One HVAC company is saying that they do not install new evaporator coils=
> > because it is unnecessary, and the efficiency will be around 12 or 13 if=
the
> > old coils are used with a 15 seer unit. =A0They say they have never had =
a
> > problem with leaving the old evaporator coils in.
>
> > Another HVAC company is saying that it is important to install new coils=
> > because the efficency won't be good, and also the unit will be under mor=
e
> > stress with the old coils and will likely only last for 4 years.
>
> > Which of the two is correct?
>
> > Thanks,
>
> > J.
>
> Even if it did work the seer increase you get from a new coil will
> make a major difference in your electric bill, and that you want. Have
> you checked how much you will save. do so, charts might be at Carrier.
> But one more point in upgrading you may not need 4 ton, but maybe 3
> ton,[ im just guessing here] did anybody do a load calculation or
> point that out to you. You have 10 seer, probably its 9 seer by now,
> its an energy hog, 15 seer is a big saver in electric costs. If it
> didnt run nearly constantly on the hottest days, you might have been
> oversized before. You need a load calculation in writing.- Hide quoted tex=
t -
>
> - Show quoted text -
A heat load such as manual J is critical to be sure the correct size
unit is installed. One of the items in a J is a blower door test.
This can be critical as one can guess at the ACH (Air Changes per
Hour) but I do not know anyone that can get this GUESS correct every
time. Test do not GUESS. Another test that is critical is the duct
leakage. I=92d say 1 of 20 homes we test have duct leakage high enough
our equipment cannot test it. Things such as building cavities used
for ducts, a common practice in many areas of the country during
certain years. So that 15 SEER can be compromised and a larger unit
will be needed. Tight ducts can be more important than a high
efficiency unit.
Be sure dampers are installed in all ducts to balance the unit.
Andy
Think Whole House Performance, it=92s the right thing to do=85
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