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Old 08-10-2009, 11:39 AM   #1
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Overall HVAC system SEER when components are mismatched


What determines it?

This is for a "live-with-it" or "replace/upgrade" decision.


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Old 08-10-2009, 02:00 PM   #2
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Overall HVAC system SEER when components are mismatched


I am not sure I understand your exactly so I'll go with what i think it means.

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Old 08-10-2009, 03:45 PM   #3
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Overall HVAC system SEER when components are mismatched


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I am not sure I understand your exactly so I'll go with what i think it means.
Well, how 'bout. . .

14 SEER evap. coil,
8 SEER condensing unit.

System SEER is a combination of the compressor, the refrigerant, and the evaporator coil.?
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Old 08-10-2009, 03:50 PM   #4
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Overall HVAC system SEER when components are mismatched


With a TXV, maybe your getting 8, or 8.5

To know for sure. You would have to test it.

It has always been a common misconception. That a larger coil automatically, got higher efficiency.

Using a new indoor coil, on an older outdoor unit, is ok.
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Old 08-10-2009, 05:33 PM   #5
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Overall HVAC system SEER when components are mismatched


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With a TXV, maybe your getting 8, or 8.5
So the lowest SEER limits the overall system SEER to that of the lowest SEER component?

Like a weak link in a chain?

Does it matter which of the two units has the lower SEER?

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Old 08-10-2009, 06:12 PM   #6
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Overall HVAC system SEER when components are mismatched


Yep.

A 10 SEER indoor coil with a 13 SEER condenser, can bring the SEER down to less then 10.
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Old 08-10-2009, 07:56 PM   #7
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Overall HVAC system SEER when components are mismatched


Thanks.

I guess the decision is to put wear and tear on a system and pay more per kwh when it could be doing better if you replaced only half of it.
It's not quite the same as the payback calc. for an entire [inefficient] system upgrade.
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Old 08-11-2009, 09:14 PM   #8
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Overall HVAC system SEER when components are mismatched


On average a unit looses 1 seer point every 3 years. So if your 8 SEER unit is 12 years old then it is a 5 SEER and no matter what Air Handler you put with it a unit is only as good as it's weakest part.

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Old 08-11-2009, 09:27 PM   #9
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Overall HVAC system SEER when components are mismatched


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On average a unit looses 1 seer point every 3 years. So if your 8 SEER unit is 12 years old then it is a 5 SEER and no matter what Air Handler you put with it a unit is only as good as it's weakest part.
Thanks, I'll add this to my file on decision making about repair/replace HVAC stuff. A lot of people on a lot of forums are asking about HVAC equipment replacement strategies.
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Old 08-11-2009, 10:02 PM   #10
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Overall HVAC system SEER when components are mismatched


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On average a unit looses 1 seer point every 3 years. So if your 8 SEER unit is 12 years old then it is a 5 SEER and no matter what Air Handler you put with it a unit is only as good as it's weakest part.

Where ae you getting this info from? It sure ain't true for scroll or rotary comps.
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Old 08-12-2009, 05:33 AM   #11
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Overall HVAC system SEER when components are mismatched


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On average a unit looses 1 seer point every 3 years. So if your 8 SEER unit is 12 years old then it is a 5 SEER and no matter what Air Handler you put with it a unit is only as good as it's weakest part.
Another untrue myth.

If that were true. Then the 30+ year old 6 SEER GE's, would be at a SEER of -4.

And when people replaced their 15 year old A/C's that were 10 SEER when new, a new 13 SEER A/C would lower their electric bill would decrease by 60% plus.

You can't measure SEER in the field.

But you can make up or repeat myths about how much SEER a unit loses in a year.
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Old 08-12-2009, 07:42 PM   #12
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Overall HVAC system SEER when components are mismatched


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You can't measure SEER in the field.
Can you measure BTUs of cooling in the field? With that and kwh consumed I'd think you can come up with COP.

BTW, can any install be fixed or improved by adding one or more dampers and one or more variable speed booster duct fans? Balancing all that would be another story.
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Old 08-12-2009, 07:59 PM   #13
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Overall HVAC system SEER when components are mismatched


Capacity, and KW can be measured.
But, the measurement is only good, for the conditions at the time of the measurement.

Although COP is applied to many things. Its of little to no value in cooling.
Since EER would mean more.

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