Heat Pump Identification

Can anyone tell me any unique features that would help identify the exterior unit as a heat pump? I seem to have a hard time with this. Help


A heat pump has some unique components you should normally be able to easily see and identify when you inspect the outside unit. Ive attached a photo of one such component (a 4 way valve). Another is a suction line accumulator which I do not have a photo of or at least not readily available. I will go thru some of my photos to see if I have one or more. A standard air conditioner will not have either of these two components. It will normally have a compressor (either a reciprocating type or a scroll compressor) The 4 way valve is usually very easy to see and is a dead give away it is a heat pump. You are going to run across some strange units on occasion but over time you should become more familiar with the various types, their configurations and other items that will cue you as to what type of system you are dealing with. You will one day undoubtedly come across a geothermal heat pump and none of what I am discribing will apply.

Lets try again…

Tried twice to load some photos but it just will not cooperate. Hard to describe what you need to be looking for. May try something else later. Sorry bout that.


Look for tags on the exterior of the unit (I know, it sounds obvious). Many, maybe most of the HVAC Manuf’s. will identify the unit as a Heat Pump. Depending on areas of the country, HP units are pretty much a given design, but other areas almost never see a Heat Pump system.
If that doesn’t work for you, look down inside the unit, usually from the top through the louvered/top discharge grill. It’s a little tricky, but you should see a black cannister looking component, that’s the compressor, used for cooling (A/C) operation. To convert that same basic unit design to a Heat Pump the Manuf. adds a couple of other components next to the compressor. Look for a another black (thinner) cannister (Accumulator) and/or a Brass/copper looking valve mounted on the upperside of the Compressor (reversing-valve). Once you have seen one, you won’t forget.

Good Luck

Charles -

Take the easy way out to start with. Look at the I/S thermostat to see if it says “Heat Pump” or has an EMERGENCY Heat switch on it.

Then look outside at the unit Name Plate or Data Tag for the words “Heat Pump”. Then look down into the O/S coil case to see if it has a reversing valve or NOT. If you don’t know what one looks like go back to the school you took your HI Training at and look at the A/C condensors again.

Last but not least stop by an A/C Distributors Parts House and look at the units and look at a reversing valve.

I saw my first heat pump t’stat last week that did not have an Emerg Heat switch on it. That function was programmed via the touch screen and was not readily visible or obvious. Until I got a copy of the t’stat operating instructions I was thinking the wrong t’stat had been installed.

If you have never observed a reversing valve perhaps this description will help. The valve normally is approximately the size of two broom handles in diameter roughly 8 inches in length and will have at least two 3/4 or 7/8 inch diameter copper lines coming out of the side and one of the same size on the opposite side they can lay horzionally or vertical and do not resemble any other item in a A/C system. The valve is most usually visible thru the safety shield for the condenser fan motor and on the other hand some times it is not easy to see at all.

Thanks for all the input, we don’t see too may heat pumps up north, I eventually figure it out, just trying to simplify it.

Thanks again,

To All

Just one caveat to nomenclature plates on existing older units. Now, this is unusual, and I’m not sure why I checked inside the unit.

A couple of weeks ago on a H/I, I noted that the HVAC system was a Heat Pump and that recent repairs were evident. Closer inspection confirmed that the Compressor had been replaced recently, but not all the parts were reinstalled. The reversing valve and accumulator had been cut out, making the designed Heat Pump a Cooling only A/C unit. Heat was now being provided by the designed Aux. Strip Heater, and at a less that 100% designed heating capacity needed for the home.

I have never seen this done before, and I can only guess why the repairs (HA) were done this way ($$), but obviously I’m glad I looked further. I can only imagine what this would have cost me, down the road, when my Client calls me for an explanation.


Some heat pumps are dual fuel. When you see a gas line going to the airhandler don’t assume it is gas heat only. It can be a heat pump with the gas section wired to the emergency or aux heat thermostat mode. The gas comes on if the temperature in the house is around 3 degrees less than the setpoint (same as electric strips). The electric strips will not be installed in a dual fuel unit.

Some newer heat pump thermostats have the capability of “locking out” the automatic emergency heat based on what the homeowner programs for outside temperature. The optional exterior temperature sensor is easy to see on the outside unit. When “locked out” the electric strips will still come on during the defrost cycle but can also be disabled in the setup mode.

That would have been my recommendation.

I’ve never found a heat pump that did not have an emergency heat switch on it. However, I have found standard FAUs with brand new thermostats that were for heat pumps, so sometimes the thermostat can fool you.

I am reminded of an occasion when I did a home inspection for a neighbor’s daughter when she went out on her own and bought her first home. The home had a heat pump thermostat installed on a standard AC unit. Verify in at least two ways or locations you are in fact inspecting what you think you are.

Now that is a waste of $$$$$!

Just for information purposes, all heat pump thermostats are not created equal!

If you find a newly replaced thermostat on an older unit, I would be sure to test all functions of the thermostat.

To answer the initial question of this thread, I recommend that you look inside the outdoor HVAC unit of an air-conditioning unit and compare it to what you see inside of a known heat pump. There are a lot of extra parts in there! The extra piping and reversing valve is the most obvious as it is normally located above the compressor.