View Full Version : Mismatched indoor/outdoor coil
04-13-2006, 04:12 AM
I recently inspected a townhome whereby the outdoor air condenser had since been replaced with a Carrier. However, the Hvac contractor left the older/original 'York' indoor evaporator coil in place. First of all, since most if not all SEER ratings today are predicated upon installing the manufacturer's evaporator coil designed for use with the outdoor air condenser unit, I would imagine that the home owner is not going to attain the efficiency rating that the Carrier system was designed for. This noted, are there by chance any other adverse ramifications that may develop over time given this type of installation or does this only affect the SEER rating? Thank you ahead of time.
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04-13-2006, 06:12 AM
You normally have to overcharge the higher SEER outdoor unit in order to move enough refrigerant through the older coil so I would expect that to have an effect on compressor life too.
k c iceman
04-13-2006, 06:54 AM
Something that you didn't mention was the nominal efficiency rating of the new condenser and how old the "old" coil was. If the new condenser is a 10 SEER there might not be much of an adverse affect on the system operation. You still won't know exactly what the efficiency will be. But if the new condenser is higher than a 10 I would agree with BaldLoonie. Even with the new systems and matching coils you can have a wide range of effiencies. For instance I recently sold a system using a condenser with a nominal rating of 15. The homeowner is keeping their existing furnace so I was limited to certain width and heighth constraints. using the mfg's. data I could get anywhere between 13 an 15.5 SEER.
I use to own a 13 seer Rheem Heat pump matched with a 1983 airhandler with a seer rating of about 6 or 8. Had a ton of problem every heating season, constant repair, high electric bill, and it finally killed the compressor
04-13-2006, 12:12 PM
The most important issue as I see it is to verify that the condensing unit is SMALLER than the evaporator. It's not uncommon to match a larger evaporator with a smaller condenser. You'll get slightly more capacity from the condensing unit and slightly higher efficiencies since you have more evaporator surface for heat transfer.
If the condensing unit is larger than the evaporator you run the risk of freezing up the evaporator since the condensing unit has more capacity than the evaporator.
SEERS, EERS, and COPS being what they are - a comparision similar to your "government estimated mileage" when you're buying a new car don't mean a whole lot unless you're replacing the entire system and want to compare apples to apples. In most cases whatever you do in replacing old equipment with new will be more efficient so who cares what the SEER is.
04-14-2006, 01:11 AM
Thanks all for the replies.
> Something that you didn't mention was the nominal efficiency rating of the new condenser and how old the "old" coil was
The current 2.5 ton Carrier air condenser is around 4 years old and has a 10 SEER rating. This particular a/c unit replaces what's believed to be a former York air condenser (given original/existing York indoor evaporator coil) installed at time of original construction or in 1990.
> If the condensing unit is larger than the evaporator you run the risk of freezing up the evaporator since the condensing unit has more capacity than the evaporator.
Valid point. Unfortunately, not something easily determined as the tag was partially ripped off/missing from the outside of the evaporator coil. Understand that I am an independent building inspector/consultant, so major tear down was not an option. Also, it was too cold (well below 65 degree outdoor ambient air) to run the system to perform a full evaluation of the cooling system at this time.
> . In most cases whatever you do in replacing old equipment with new will be more efficient so who cares what the SEER is.
True, but only when installing a matched system or this statement contradicts your previous one.
Thanks again for all of your replies. It's most appreciated.
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