Heat pump good or bad ?

Inspecting a Philco 2.5 ton 8 year old heat pump today (inside unit was original 1990), the outside temp. was 50 degrees. I usually check the temperature differential between the return and supply when testing the unit. I need to get a 20 degree differential temperature to call it acceptable. This unit failed the test, I recommended servicing . I only had a 10 degree differential. My question is what does everyone else do ?

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what was the suction line temp?

Needs service no doubt , did you test the back up heat also separately

I check/operate it just like a homeowner would living there…

I don’t check the suction line temp. and if I were going to what equipment would I use and what temp range would I need ?

yes, auxiliary heat came on after bumping temp. up by 2 degrees

You would have to a attach a bulb to the suction line , most will not do that i was just curious Personally i use my finger . How ever at the outside temp and what your showing would indicate a problem . I would not relay on a laser to take temperatures use a bulb thermometer .

I recommend that you stop doing what you’re doing immediately.

#1 it’s a heat pump.

#2 you’re using the wrong equipment to test.

#3 your using the wrong technique to evaluate the situation.

I’m not going to get into this because I would have to write a novel about the number of variables that need to be considered to evaluate air temperature of the heat pump heating system. Most of which you would not understand.

If you’re going to do anything, as Wayne indicated you need to be looking at the suction refrigeration line temperature (better yet the compressor discharge line temperature).

You need to know the refrigerant in the system.

Next you need to determine the BTUs per pound of air outdoors. This is the energy available to be absorbed by the HVAC system. If it’s not there, you cannot absorb it. If it’s not there to absorb, you can’t collect it and discharge it into the house.

This is not an electric heater or a gas heater or an oil heater where you can determine the heating capacity of the fuel being utilized.

A lot of HI’s just do too much, go way over SOP’s, all to try to impress. Evaluate, document, recommend, move on…

Well hell yes we should all try to impress our clients its what were paid to do. SOP as stated a million times on this forum its minimum standards.

Do more charge more but you can not do more if you don’t know more

Geez that was a mouth full

  1. It looks to me as if you have more problems than your temps. Looking at one of your round supply type ceiling register your taking a temp with the damper closed.

  2. looking at the electrical furnace I am wondering if it is a down flow or a upflow furnace. I see a floor register in your pic indicating that the system is a down flow with the blower discharging across the A-coil. If its a upflow the blower would be drawing thru the A-coil.

  3. Lets assume its a downflow furnace which makes it improperly installed you are not allowed to have wood as a supply air plenum, Wood and moist supply air in the cooling mode creates mold on the wood thus its distributed through out the home every time the blower activates.

  4. You stated the indoor unit was original 1990 and the outside unit was 8 years old. Another big concern for me was the A-coil changed out to match the 2008 HP or is the coil original also. The original outside unit may not have been a HP and if it was not the indoor coil would not have matched the outdoor unit.

You could have a real mess on your hands that just operating the system from the thermostat won’t answer;-)

A question I have is; will the subcooling calculations be the same on the heat pump mode as the cooling mode? I’ve found literature on the A/C side and calculations but I have not seen anyone state that the calculations would be the same in the heat pump mode. Also keep in mind I don’t have a license to hook up to the refrigerant system so I’m doing this just by temperature measurements.

Also in order to do the calculation I need access to the coil; today I had an inspection where I couldn’t get into the system to take the coil temperature.

Can you take just the gas line temperature and liquid line temperature at the exterior coil and get an accurate result? I’m assuming there is enough air flow at the coil. If so what temperature differentials do you look for between the two lines? I am aware that it is different for different refrigerants. I’m looking at the subcooling target stated on the equipment label to verify the system is working properly.

If you need the calculations/equations I’m trying to use let me know; but I’m basically trying to to subcooling/superheat the non-invasive way without gauges.

Someone get technical on me, if you can. I thirst for this kind of knowledge.

Different refrigerants have different pressures that corresponds to different temp and unless you have a chart that tells what temp corresponds to a given pressure for a given refrigerant your just wasting your time.

I used to work on laboratory systems that were cascade in nature they used R-12 as the cooling medium for the systems condenser, the evaporator was required to be at least -40 F to test the viscosity of motor oil. To obtain these low temps required a blend of refrigerants that required manual blending of instrument grade propane and R502 and the propane had to be weight in actually to the fraction of a Ounce.

Not to avoid your question there are just to many variables without the use of gauges. Refrigerants are all about pressure temp relationship

How did you decide on a 20° differential?

Oh c’mon Dave, you are being way to nice.:wink:

I used to do this until I wised up after you, Charlie and others set me straight.
Inspectors, clients, agents need to know the difference between a generalist (me the inspector) and the specialist (someone like you that will do all the necessary steps to ensure the equipment is running safely, properly and efficiently).

I always appreciate the response, but let me ask it this way. If you actually hook up to a system will the subcooling/superheat be the same in the heat pump mode as it would in cooling mode? So if your hooked up to the system in the heat pump mode would your gauges read the same as if it is in cooling?

Depends on where your taking the superheat temp at but basically your answer is no because you have different condensing mediums temps in the two modes