I have seen other posts on the subject but am wondering what everyone usually says about Heat pump compressors and air handlers that are not the same brand (or even the same year of mfg., for that matter). Given that there has eben so much consolidation in the industry, it is possible that company “A”, which purchased “B” and “C” could have published charts of acceptable compatibility among their family groups. For sure, the average HI is not going to know that information, if it exists. The easy thng to do is to refer it, but that makes you look uninformed, if the vendor then says it is ok.
Mismatched Manufacturers is not recommended but may not be wrong. The indoor unit has a coil number. it must be compatible with outdoor unit. This information is available at ahridirectory.org. I do this all the time for Energy Audits and HERS Ratings. But it would seem to be beyond SOP for a Home Inspection. Would you note different manufacturers and recommend assessment by a licensed HVAC contractor?
I always mention it, especially when the dates on the units are different. We are seeing a lot of newer 13+ SEER rated condensers and older 10-12 SEER rated air handlers in the same homes. While they might function, the energy rating will suck. Both units should be replaced at the same time. It gives the client something to bargain for possibly.
I use to own a hearting and cooling company. There are very few manufactures of heating and cooling equipment but each manufacture will have several different brands. The brands of the same manufacturer will all basically be the same on the inside.
I agree that checking the compatibility is beyond the SOP, but that it probably should be montioned, especially if manufacturing dates are more than about a year apart; but given that a lot of home sales are forclosures these days and are being sold “as-is”, I’m not sure it will help the buyer much. Generally they will not spend the money to make it right.
And it voids all warranties (if they are young enough to have one).
Something I’ve noticed this year more than ever is sellers advertising New AC Units and then discover only the outside condenser unit was replaced and still have an older (original) evaporator coil. I’ve seen this at least a half dozen times this spring.
My standard report format is to list the manufacturer of the HVAC components and the age of each. The client will be able to see if they are mismatched if they bother to read the report. But otherwise, I don’t mention it.
That’s the way I currently report as well. However, I doubt most clients would grasp the significance of mismatched brands / dates, so I usually explain that in general and leave it at that if that situation arises.
Help me understand the significance of mismatched brands. I have been going with a hvac friend of mine, when I can, for the last 6 months to learn more about hvac. Many times we replace just one component and they are a different brand. He gets the system info to the distributor and they match the component and he usually has several options on manufacturers. Don’t understand why it would matter as long as it matches the system.
As someone mentioned in an earlier post, mismatched brands may not be incorrect if both pieces have been approved for use together by the manufacturers. HVAC technicians have resources for that info, but HIs generally do not. If pieces are improperly matched, they may not operate properly and may have poor energy performance. So the delimina for a HI is whether what they are seeing is properly matched or just the result of sloppy work or an effort to get a system back in operation cheaply. This is especially likely when the manufacturing dates are many years apart.
I note that the age of the mis matched units, mention that they may not be as efficient as matched units.
On the other hand, a mismatched system could possibly be more efficient. It’s just that nobody knows because it hasn’t been tested and is not listed in the book.
Naturally, any manufacture wouldn’t approve of using a competitor’s equipment and loosing sales.
Years ago an “A” coil would outlast three condensing units but not anymore.
This is from NACHI continuing ed (energy auditing).
Thanks David, good info. Need to find the time to get to the new energy auditing course. Sounds like it has good information I could use.
1/2 way through.
Worth the time!
Generally speaking, here in AZ mis matched units are an Old Air Handler and a Newer Condensing Unit… There is no way that they will be as efficient Matched Newer Units…
Some things do not need to be tested… 
Mismatching systems can seriously affect system performance and efficiency. One also has to be careful even with equipment with one manufacturer. One coil may work perfectly in cooling only mode but could cause high head pressures when in heating mode if a heat pump.
Here are two pdf files I have three more. One from Carrier, Bristol compressors, and ARI but they exceed the 250 byte files size for upload.
It may always be a good idea to explain that in most cases HVAC equipment mismatch is Ok but there can be compatibility issues that are best confirmed.
It may always be a good idea to keep your mouth shut in cases like this!
Confirmed?
I guess you’re one of those “call it out because I don’t know what I’m talking about” guys?