Originally Posted by
clmssun
First post here. I have already learned a lot from reading other posts. Thank you all for your advice.
\ I live in Phoenix, Arizona.
I am looking to replace/upgrade two Carrier CKC-350 HVAC units.
The house was built in 2004, and the HVAC is original.
My upstairs unit is sized at 3.5T and my downstairs unit is sized at 3T.
Until a refrigerant leak became evident last year (2018), we were content with these Carriers for our summer cooling.
Internet search says original SEER of these Carriers is 10 SEER;
I had a home energy audit done in December 2017 which stated the two Carriers were 7 SEER.
The home energy audit gave us helpful advice about duct sealing, air sealing, attic insulation,
and shade screens for windows; we have not installed any improvements yet.
For 16 SEER, both contractors quoted 3T downstairs and 3.5T upstairs like my original/present system.
Neither contractor did a Manual J Load calculation before issuing me formal quotes.
Upon questioning the second contractor about this, he stated that he would do the Manual J Calculation
when I am prepared to finalize the sales contract. (I have not contacted the first contractor about Manual J Load.)
I have never gotten a Manual J Load for my house:
not from home inspection,
not from home energy audit,
not from AC tuneups/repairs,
not from new AC quotes (as of yet).
We would like to pursue energy efficiency, so, at the surface,
high SEER is very appealing.
But I gather that SEER is like MPG: calculated from a standard formula for a "standard" condition.
Living in Phoenix, I have seen our 2.5% Design Temperatures are approximately 107F DB and 71F DB;
we cool our house to between 78F to 80F.
How do those outdoor design temperatures and preferred interior temperatures impact my "real world" SEER?
I am gathering that if I did perform the energy-efficiency improvements to my house
(air sealing, duct sealing, more attic insulation, shade screens on S,W,E windows),
that my Manual J Load would decrease.
If so, that means I am being quoted (for high SEER units) for oversized (4T vs 3,5T) HVAC units for my upstairs.
That will adversely affect my "real world" efficiency, yes?
I read on here that having a coil rated at a higher capacity than the condenser is wise/typical for Phoenix,
and the second contractor did that.
Thank you very much for any advice and clarification about "real-world" SEER
for Phoenix, Arizona,
as well as EER, Manual J Load,
and the true energy-saving benefits of multi-stage or variable cooling or other household energy-saving improvements.
================================================== =================================
I was quoted the following specifications for four Lennox systems:
XC16 Brochure: Up to 17.20 SEER
Multi-Stage -- Quote: SEER 16,16, EER 12,12
XC21 == Brochure: Up to 21 SEER
Two-stage -- Quote: SEER 18,19, EER 14,14