Heat Pump

Specific Inspection Topics Inspecting HVAC Systems
21

That’s why there’s a reversing valve. The latent heat is not inside. I’ll admit that it probably is not as efficient as gas (but then I don’t think any electrical appliance is as efficient as its gas counterpart).

The only time I can see a heat pump not working well is when it’s the exact same temperature inside and outside because then there’s no differential to work with.

The greater the differential between the inside and outside, the better the heat pump will work, but it doesn’t matter whether the heat or cold is inside or outside, as long as the reversing valve works.

20 inside, 40 outside gives you 20 degrees from which to pull heat or cold
20 inside, 80 outside gives you 60 degrees from which to pull heat or cold

And reversed also works well as long as the reversing valve works.

22

Oh, I wasn’t done for the day.

Sometimes, though, one just has to say, “Ya know what. I haven’t been to the beach in three days” and then go do something about it, especially when Ms Margarita and Dr Cuervo have already deserted you and taken off. :smiley:

23

I’ve never had a complaint, not even a nuisance one, about heating and cooling because the Client or the Client’s Realtor or the seller or the seller’s Realtor always confirms at the time of the inspection that the heating and cooling systems were working.

I believe that I learned that inspection protocol at HomeTeam training.

24

Try to look at it this way Russel. A heat pump works in winter by actually raising the temperature of the freon at the outside unit (extracts heat from the outside air, even though it’s “cold” out).

For outside temperatures around 30°F to 40°F, the freon going to the outside unit is probably around 15°F to 20°F and needs to be raised to about 25°F to 30°F in order to be effective (which means the outside temp needs to be above that in order to get that rise).

For significantly lower outside temperatures a typical heat pump just can’t provide effective heating because it cant raise the temperature of the freon enough … and then the supplementary toaster wires kick in and your meter starts to spin. Not good for the wallet … :wink:

I understand that deep geothermal heat pumps work better at lower outdoor temperatures, but those are pretty expensive and less common systems.

P.S. I have not have an issue either, but the idea I liked was making it so cold/hot that it really sticks in their minds that the cooling/heating system was indeed working. A lot of things are pointed out on an inspection and memories are short, but that seems like it would stick out in their memory down the road.

25

That’s the whole purpose, to make it stick in their minds. And the more people complaining about how hot it is or how cold it is, the better. The jury will like all those witnesses.

And around here, the heating and cooling system is probably the most expensive appliance that we inspect, especially when labor is included to install the furnaces up in the attic, where I find at least half of them. So anything I can do to burn into their memories (pun intended) the fact that the heating and cooling system worked at the time of the inspection will benefit me.

I did have one Client several years ago call me. After I answered the phone, the first words of hers were “My air conditioning isn’t working.” But before I could respond in any way whatsoever, she continued, “I remember it was working at the inspection because you froze us out of there. I’m calling to ask for your help in getting my insurance company to pay for it.” And I did. And her insurance company did, although it took a letter of mine to the State of California Insurance Commissioner before they agreed to pay for it. But that’s the type of service I will provide to my Clients after the home inspection. I often tell them that there are two big disadvantages to hiring me (picture look of shock on Client’s face):

1 - They have to put up with me forever and ever. I just might drop by at any time to see how they are doing in their new home. And I do.

2 - The can call me at any time down the road for anything that they even remotely think that I might be able to help them with.

(Picture look of shock changing to pleasant smile.)

26

Freon is not used here in San Diego, so that might be the difference between your heat pump and our heat pumps.

27

R2, What do you use there for a refrigerant?

Good morning guys!
It’s early and I was up late and I’m working on my first cup of coffee. I’m not getting the questions/issue for some reason (my voice recognition software won’t recognize my voice either, so aliens probably abducted me during the night!).

These are the questions I see here:

A heat pump is not efficient. My question to answer is why.
You are all adding good pieces of information , but let me put it all together.

A heat pump absorbs heat from one location and displaces it elsewhere. In order for the equipment to absorb this heat there must be a temperature differential. We look for a 30° temperature differential between the refrigerated coil (which is the outdoor coil in the wintertime) and the outdoor air. As the outdoor air goes down, so will the refrigerant pressure and temperature. This 30° split generally remains intact.

The problem with efficiency arises when btu’s are less in the outdoor air. If you think of heat as a substance to be absorbed or collected, this may make more sense. If there is less BTU in the outdoor air, there is less to be moved to the indoors.

The second part of this is that the temperature difference between inside the house and outside the house becomes greater as the outside temperature falls. The heat transfer rate is Q=UADelta T. As the temperature difference between indoors and outside increases, heat/BTU passes through the house wall/roof at a greater rate(one multiplier per degree Fahrenheit). To maintain a constant indoor temperature, this amount of loss must be made up by the HVAC equipment. As there is less available BTU in the outdoor air, its not possible to absorb a sufficient amount to maintain the indoor air temperature. Thus, auxiliary heat is installed.

Another efficiency issue which may not be realized is that the power consumption used to run the equipment in the wintertime is dramatically reduced as the BTU availability in the outside air falls. Also, All electrical power utilized to run the compressor is change from electrical to mechanical energy thus producing heat which is absorbed by the refrigerant and sent back into the house. So, actually the system is quite efficient in using electrical power (it’s just not sufficient to keep you “comfortable”). In the summer, the unit may draw 45 amps. In the winter it may draw 6 amps. So, even though it runs continuously, it takes less to operate.

Heat pumps are very efficient when operating in temperate temperatures, such as the spring and fall where there is sufficient heat in the outdoor air and conditioning of the indoor air is required for comfort. This is where you save money. These savings must be averaged and is absorbed by the entire heating season’s use, and depending on where you live may become drastically reduced. In essence, you are operating a straight electric furnace in the deep winter.

Comparing natural gas and electric is not an option for many people who use heat pumps. The reason they use heat pumps is that natural gas supply is not available. Their only option is through electric appliances and the heat pump is much more efficient on a yearly basis than straight electric heat.

Another subject:
As you know, I damn the use of temperature split calculations. Let me amend my position for clarification. I test and use temperature splits all the time. However, I do not report equipment deficiencies based upon these temperature splits. When you test a branch electrical circuit, you turn on the switch and see if the light comes on. If it does not come on, some of you check the light fixture for a blown out light bulb with your ticker. Based upon the presence of electrical power at the light fixture you determine whether the circuit is operating as intended (in spite of the blown out light bulb). Taking temperature splits is like turning on the light switch. If it’s there (or the light comes on) then the equipment is apparently functioning(but not necessarily correctly). However, the lack of a temperature split indicates that the unit may not be functioning or running and requires further investigation by yourself to determine if in fact it’s trying to operate or it is not operating for some other reason (a circuit breaker is turned off, a head pressure control is tripped, there is an electrical mechanical problem). Using the temperature split as a “diagnostic” of equipment “efficiency” is the issue. It cannot and should not be done. There are too many other factors that can not be evaluated through such a simple diagnostic inspection to warrant further investigation and expense to the homeowner.
Though you have been taught this in school, the use of this procedure should be limited to a system check procedure , not a diagnostic of operation/capacity.

28

I’m not done! But, that post was getting verbose! :slight_smile:

Another issue I would like to discuss with you is:
there is a time when HVAC equipment becomes “inefficient”.
This may be encountered while conducting your inspection in the off-season (testing the air-conditioner in the winter).

What happens when you run the air-conditioner in the wintertime?
The air-conditioner puts out extremely cold air.
The air-conditioner has a very low temperature split.
The evaporator coil will freeze up because the refrigerant gets so cold.

Answer; the air-conditioner will have a very low temperature split.

If you operate the air-conditioner when the outdoor air temperature is low, without modifying the equipment to operate at low ambient temperatures the equipment functions differently but appropriately. As you know, there is some sort of metering device which regulates the refrigerant through the evaporator or cold coil. In order for this metering device to function properly there must be a sufficient pressure differential across the metering device. When you operate the air-conditioner when it’s cold outside, the refrigerant comes extremely sub-cooled and as temperature falls, so does the pressure. This starves the metering device and the evaporator coil does not receive sufficient refrigerant to cool, thus a narrow temperature split.

Another thought on pressure differential; is the event of the reversing valve not functioning when testing in the off-season. Again, temperature differential is critical for the operation of this device. If the indoor and outdoor air temperatures do not have a sufficient differential (as Russel posted), or if it has a reverse differential, which may be present when you’re testing in the opposite season/mode, the HVAC equipment may not produce sufficient pressure differential to operate the reversing valve. The reason the valve sticks is because it partially switches position half opening all ports allowing the compressor to short cycle the refrigerant from the discharge to the suction line. When this occurs, it is difficult for the compressor to generate sufficient pressure differential to finish sliding the valve back into either mode. Eventually, the valve will begin operating again if the temperature differential increases (which may be the result of the electric heaters operating and causing a sufficient temperature differential).

For those interested in the operation of the reversing valve; there is a low-voltage solenoid that controls the pressure with a small piston on the pilot tube (small tube from one side of the valve to the other). This releases pressure on one side and directs positive pressure to the opposite side of the large piston in the reversing valve. If there is approximately a 40# pressure differential, the large piston will slide over to the other side.

29

Foxe (my apologies for calling you Peter earlier),
Yes I do check the temps but only to show that cooled/heated air is coming out of the supply registers.

Your example was just what I was referring to when I said I have come across houses with very little temp differential. I just don’t use it as the sole reason to determine operation or to make an evaluation/repair recommendation. David’s analogy is dead on perfect. It is an indicator that something MAY be amiss.

I will take your example and change it up a little. What would you report if the outside temp was 90F, return air is at 70F and supply air is 65F? That is well below the ranges suggested for appropriate temp differentials. Is there a need to have someone come and check that system? I personally would hesitate to make that recommendation. Could they have recently had 40lbs of Freon added, yep. But since I don’t hook up gauges, I won’t ever know that.

The only place I have seen temp differentials mentioned is in HI books. I think it was a notion that was put forth years ago that has morphed into fact. But like the tonnage/square feet rule of thumb it isn’t really a proven method. Even the range of the differential changes. I have seen 14F-20F, 15F-22F, 16F-20F, and 16F-22F, heck I think I remember seeing 18F-22F, so which is correct?

30

Oh God! don’t take me there! :slight_smile:

31

What a great thread.

Please keep up the debate.

32

Chlorodifluoromethane.

Freon was banned for production and consumption in the United States as of January 1, 1996.

33

David & Robert, if Russel is serious with this quote ,and I don’t see any smilies, then all the explanations will not convince him otherwise. You have to remember, Russel also has a vehicle with a/c that works without the engine running as well. No one was ever able to successfully convince him otherwise.
http://physchem.ox.ac.uk/MSDS/CH/chlorodifluoromethane.html

34

RRay is technically correct.

Freon is a brand of refrigerant and has nothing to do with the chemical composition of the gas.

Freon is commonly referred to as the R-12 (dichlorodifluoromethane) which has been replaced in new equipment, but still in use.
It can not be manufactured or imported into the US, but the reclaimed existing R-12 is still being used.

35

E. I. du Pont de Nemours & Company holds the patent on Freon. When the ban on Freon was passed, to be effective January 1, 1996, many manufacturers of Freon replacement refrigerants tried to abscond with the Freon name. DuPont put an end to that practice real quickly. I was living in Houston at the time. My company, Just Your Type, was doing word processing for the legal department at DuPont, and I found the various cases to be vastly interesting.

The most common refrigerant in use in America today, post-ban of January 1, 1996, is R-22. The “Freon 22” name from Michael’s posted link was used in the earliest days of R-22; it’s the name that DuPont put an end to. I actually had never seen that name used since my work at DuPont back in the late '80s and early '90s.

36

So that is what lead to the use of the word Puron?

37

Puron is another DuPont registered trade name designed to replace R22. The refrigerant is blended from two other refrigerants, R32 and R125, and does not deplete the ozone as R22 supposedly does. Most equipment manufactured since 1996 uses Puron.

R12 was a highly toxic and atmosphere-damaging form of Freon used in some househould appliances and most older automobiles. Older refrigerators used R500 and other blends of Freon. The different types of Freon were used to compensate for differences in manufacturing various products.

38

What’s with this? Are you a non-believer?

Let’s stir up some more crap!

Have any of you aimed your infrared thermometer skyward?

The boiling point of R- 12 refrigerant is -29.8 degrees C.

The vapor density of R-12 is 4.2 times greater than air. Which means it doesn’t float.

I placed a question to the EPA (now I am a believer in recycling refrigerant from the day before reclaim machines were available. I built a reclaim machine for the school I was working at and one for myself and the EPA certified and grandfathered my machines which remained in service three years after refrigerant venting became illegal) as to how a refrigerant gas, heavier than air and has a condensing temperature at about 0°F can get to the 03 layer of the atmosphere without condensing and falling back to the earth as a liquid. The answer: wind!

Isn’t it interesting that the DuPont patent expired about the same time they did away with R-12?

Puron (developed by DuPont) came out with a replacement for R-22 which is known to become unstable in the upper atmosphere and breaks down by infrared radiation.

What part of the refrigerant damages the ozone layer?
Chlorine.
My swimming pool has probably damaged more of the ozone layer than all the refrigerant gases I allowed to escape as an HVAC man!

Just something else to think about! :slight_smile:

39

My personal favotite was Freon 113 , can you say vapor degreaser.

40

Ahh yes…I think I cleaned a few thousand circuit boards with that stuff at TI and Compaq in the 70’s & 80’s. Maybe that explains a few things…:slight_smile: