Heat Pump

I did a early morning inspection today at 7:30 AM. The townhouse had a heat pump installed. The outside temperature was 79 when I tested the system. The cooling side worked well. I got a 15 degree split. The heating side I got less than a 5 degree split. Based on other items I saw no service disconnect, unit unstable and out of level, fins dirty, no secondary drain pan drain plumbed I reccomended further evaluation and repairs. Any ideas on what could cause the problem. It was my understanding on a heat pump if one side worked it was almost a given the other side would as well. Ideas??

Did you trip the head pressure switch?

Were you testing heat in Aux Heat setting or Heat?

If you are running the Heat Pump heat long enough to take temp splits (which tell you NOTHING, by the way) at 80 degrees, your running it too long.

There may be outdoor t-stats that keep the electric heaters off till it gets real cold out. Not common though.

I would not run a heat pump in heat (emergency or Aux heat is OK) during the summer unless you know what you are doing.

Switch not tripped. Was running it in normal heat mode.

Enlighten me why temp splits tell me nothing?

What’s a split? Anything to do with cheerleaders?

I know David will be along to further explain his comment. But the gist is that if you are taking dry bulb temps you can’t really get the true pre and post evap coil temps. He has mentioned that a chart is used in conjuction with humidity and temperature to figure it correctly.

Also the temps taken at return and supply registers will be skewed due to heat loss/gain occurring in the ducts, loose ducts, holes, location, etc. These all would have a negative impact. Depending on how you write your report, you may suggest the system is not operating correctly when in fact, it is one or more of the other factors that is the real culprit.

I will disagree somewhat with what he says, it will tell you something, just not very much. I use it to check that air is being cooled/heated and not much else. If it is going in at x degrees and coming out at something less/more then the system is cooling or heating the air. That is how I write it in my report and leave it at that.

I have come across a few houses where the temp difference was only 2-3 degrees. Along with other factors, I used that as a basis to have the systems, including the ducts, fully evaluated/repaired as necessary.

Temp splits are those workers from staffing agencies that share duties, one works in the morning and one works in the afternoons.:stuck_out_tongue:

Do you no longer check temps? I completely understand that the best way to due it would be cut holes and actually check at the coils. That being a little out of the scope I have resorted to checking the closest duct and behind the filter. I understand all about heat loss/gain from point a to point b and that the splits that I check (and most of the inspectors I personally know check) are a little off, but to say they mean nothing is off as well. Example. 95 degree summer day, 2 degree split, I would say it is safe to saw based on the split something is wrong correct? How would you suggest checking for the functionality of the unit? I not going to cut holes in the duct work, stick gauges on the system etc.

Here’s how I do it.

If the heating system is running, then I’ll turn it off and then turn the cooling system on. I continue doing my inspection until someone comes and says, “Can we turn the air conditioning off? It’s really cold in here.”

If the cooling system is running, then I’ll turn it off and then turn the heating system on. I continue doing my inspection until someone comes and says, “Can we turning the heating off? It’s really hot in here.”

Now on the off chance that everyone moves outside, I’ll help them:

Me: “How come y’all moved outside?”
Them: “It’s hot in there” or “It’s cold in there.”
Me: “Oh. Well at least we know the heating system works” or “Oh. Well at least we know the cooling system works.”

Now can you see them calling me six months down the road:

Them: “My heater’s not working” or “My air conditioning’s not working.”

I can’t.
But if they do:

Me: "Remember the day of the inspection when you complained about it being too hot [or too cold]? Well, it was working then, so I suggest you get a heating and cooling guy out there to see why it’s not working now.


Heat pumps use the existing heat available and transfer it. They are not efficient at certain temperatures.

Well they also use the existing cooling available and transfer it. I’ve never had a heat pump that is in working order not be efficient at any temperature.

If it is hot outside, then one is using the heat pump in the cooling mode, so one has heat in one place (outside) and cold in another place (inside).

If it is cold outside, then one is using the heat pump in the heating mode, so one has heat in one place (inside) and cold in another place (outside).

In both cases, there is heat and cold, which is what’s needed for them work and which is why they work so well in our high desert and mountainous areas where it is 120° during the day and 20° at night.

Brian, it’s your turn to get into a war of words with R² and explain how a heat pump will not efficiently heat a dwelling when it’s 20° outside and that is when the Aux/Emerg Heat is used to turn on the electric strip heaters or even a gas-fired furnace.

Virtually all of the aux/emerg heat connections out here have been disconnected after the energy crisis of 2000-2001, so they’re not working. The heat pumps, however, seem to do quite well when I’m out in Julian testing them, heat or cold.

Excellent! We should all be so lucky. My experience has been that a heat pump, at least here in the South, begins to lose the capability to efficiently heat somewhere around 28° - 30°. I’m sure wet-bulb temps have a lot to do with it and that balance point value may very well be much lower for your area, I wouldn’t know.

Bottom line, If you want heat, you need FIRE.

Now back to testing.

I went to IV Tech for continuing ed a couple months ago. The teacher there told us and showed us how to inspect the heating and cooling system. Along with the visual and running the equipment part of the inspection. Take your thermometer and place it on the suction line just outside the furnace housing. The temp. of the line should be 48 to 52 degrees. If the temp. is above 52 then the unit is low on freon and needs service.

Michael stole this somewhere, and have found it does not work very well with my wife :wink: . But I still get a laugh from it.

" I can explain it to you, but, I can’t understand for you.":stuck_out_tongue:

I just find that absolutely astonishing.

I don’t know of any home that is comfortable at 28° or so, so it just seems to me that a heater otta be able to heat up the place to something a little more comfortable. And, indeed, the heaters I have been inspecting out in the mountains and the snow have been able to do that.

Ms Margarita and Dr Cuervo sometimes have to help me understand. They’re at the beach right now, which is where I am heading in about 30 minutes.

Electric Heat pumps do not work well where it gets cold, not enough latent heat outside to pump back inside.

I’m jealous RR done for today maybe I’ll jump in the pool because today it’s HOT.

Luckily my temps splits on my AC are good and my range fan is not sucking all the cool air outside.:stuck_out_tongue: :wink:

I will tend to the rest of the posts later. I just got in (8:56) and I need food to think.

I just tested a unit that had a 59 degree suction line at the condensing unit.
The refrigerant pressures were 82/255# psig. What does that tell you?
New construction Inspection.

No room for any more refrigerant here!!!
Shot that to hell with the last inspection!
Tell your teacher to go back to school!

If you want to know why, I’ll post it later when I figure it out on the psychrometric chart when I do the report. You’ll have to stay up late though.

I have a lot more electrical issues I have to figure out before I deal with the HVAC.


That IS my point Andrew. I am glad to see someone out there is listening! Good post!


That is the usual assumption for a home inspection, although running it in cooling mode wouldn’t tell you anything about the auxiliary heat. But you really shouldn’t operate a heat pump in heating mode with an outside temp above about 65°F, and the system may have disabled/locked-out the heating mode (or maybe there was a problem or you smoked the system/compressor … :shock: ) as the temp rise/split does seem very low … although I agree with David/Andrew that temp rise/split doesn’t tell you much in heating mode.

At the risk of over simplifying, a typical heat pump is essentially a AC system with some modifications to enable it to run backwards. They are not very good at heating in colder areas, which is why you get a much lower heat split than a furnace and why you need supplementary heat in colder areas … usually electric heat strips (“toaster wires”). Here in the northeast that type of system would spin your electric meter to effectively heat a house (which may put you in the poor house with the local cost of electricity … lol).

I like that approach … probably kills the complaint even before you get a chance to say “Well let me get the report out, and see what it says” … :idea:

JMO & 2-nickels … :wink: [/FONT]