Temperature Splits

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21

Originally Posted By: Blaine Wiley
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Kevin,


Isn't one of the problems with Puron that because it is a "blend" of gasses that when adding to the system the gas can be incorrectly mixed? One of my friends who owns a Carrier/Bryant/Trane HVAC company told me of this about 3 or 4 years ago.

22

Originally Posted By: kluce
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It goes in as a liquid. Never heard of that problem but its been a while since I’ve gotten any information on it.

23

Originally Posted By: kluce
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I read an advertisement a while back saying Comfortmaker is now using Puron for 14 SEER or higher. Can’t go by the test of time, but Comfortmaker is thinking it’s fine on the higher SEER units. 10 or 12 SEER standard AC units are used here most of the time. I noticed heat pumps were used about 10-15 years ago. I was told there was a rebate from the electric company and it turned out cheaper to install. Most that I run into are never used or wired just for AC. Electric is not cheap around here.


The only thing I question about Puron is the higher Pressures. Not saying there is something wrong with that. It be nice to have the pressures the same or lower as R22 (Chlorodiflouromethane). OOO, I like using those big words. :wink: I'm suprised that I still remember those big words.

24

Originally Posted By: kluce
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Rolland,


As far as I know, weighing is the only way to properly charge a unit in the cold winter. It's just not done around here.

Just curious, what is the average temp during January around you?

25

Originally Posted By: rsummers
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Kevin the temp around at night if its clear low 30s and in the day upper 40s lower 50s. We should be getting warmer spring is coming cant belive its already Feb 1. Summer temps 95 in the day 70s at night on avg.

26

Originally Posted By: Blaine Wiley
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I would hate to have a high side hose break on a Puron system while checking it. With those pressures it could be nasty.


I thought Carrier was only using Puron on their 14 & up seer models???

27

Originally Posted By: kluce
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That’s how it was when I was installing them. My father-in-law has a 12 SEER unit with Puron. Around here, It’s only the 10 SEER units that still has R-22.


I came across a unit during the summer. I'm not sure what SEER this would be. It was a carrier AC unit. Had a expansion valve with it. The condenser had a dual compressor with a two speed condensing fan. When it started, the fan was on low speed and from what the client told me, only one piston moved. When the AC went into high speed, the condensing fan went into high, and the compressor piston started rotating the other way which moved both pistons. I must say that when the AC unit was in low speed, I was as close as 3 feet to the unit to know it was on. Has anyone else ran into this type of unit?

Does anyone know why Carrier or others use puron only for certain SEER units? I would think they would use it for all units.

When it comes to Puron, Maytag air conditioner has a relief valve in the condensing unit for the Puron. I was told this by an installer that Puron is flammable. If something goes wrong, then the relief valve will let it loose outside. I did see a picture of a unit with this relief valve but not sure how this could happen. Over charging, dirty coil???? Does anyone know anything more about this?

28

Originally Posted By: poffenberger
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puron is a brand, as, cresent is to wrench, or kleenex is to tissue


r-410a ,it is a blend and should be added as a liquid. not that that matters


as far as splits go if your getting a 14degree split something is wrong, unless your from the old school that thinks a a\c unit should run for 4 hours straight…and or maybe an owner of a company that was from the school of undersizing… which also can cause a humidity problem…point being,watch those who say 14 is ok… for the may have undersized thousands of units. In closing, two conditions, which is better…


cold and clammy[humid]… or cool and clammy[humid].just a thought…

29

Originally Posted By: kluce
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R410A=Puron. Is there another name for R410A? Puron was the only thing out there at the time and I’ve never heard of anything else.


Old School! ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif) When I first started as a HVAC, I was going to HVAC school at the same time. The first day of work, I was tought by an old timer that the gauges weren't needed to charge AC units. "Put your hand on the suction line until it gets cold to the touch." Old School was a lot easier back then. I missed cutting the AC lines and having the unit tore out in 15 minutes. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

30

Originally Posted By: johlstrom
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I have a background in HVAC like many others. I used to teach a A/C troubleshooting course and have always taught 15-20 degrees across the evaporator coil. As a HI, i dont hook up my guages though. The 15-20 degrees is a rule of thumb. If you take the temps at the return grille and a supply register, allow for heat transfer throught the duct work. There are many problems if the temps are way off from filters, fan speed, refrigerant levels etc. That is why we recommend service, for someone else to find the actual problem. As far as heating, In most units, there is a temp differential number on the inside name plate. The biggest thing I do in the winter with the A/C is check the condition of the coils. You can tell if they are dirty, they will need service.

31

Originally Posted By: cbottger
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I am going to stir the mix and make some statements that are going to be contrary to popular belief and even published in a lot of HVAC manuals.


The temperature split or Delta T is the difference between supply and return air temperature. The most used theory is 14 to roughly 20 degrees.


I try to use common sense with this theory and I am basing this on many years of trouble shooting A/C units. I use 10 degrees Delta T as the cut off point in determining if the unit is performing as intended. The units that I refer to as builder units(cheep) with small condenser areas. Most of these type units only have the capability of producing 10 degrees Delta T and are performing as intended. The high efficiency units with the large condenser areas will perform 14 and above Delta T. As to using gages on A/C units even though I am qualified I do not install them as it is a waste of my valuable time as a HI. I follow the standards of practice as any other inspector should and operate the unit from the thermostat.


The two most common reasons for the suction line to frost is a lack of freon in the system and a lack of air flow across the furnace A-coil. I do not remove the front cover on the A-coil as this is not considered a normal access panel. What I do observe from the access panel is the amount of dirt and lint accumilated on the fan blower wheel and the return air chamber this will usually determine If the filters have been properly changed in the past and if the A-coil is blocked with a blanket of lint. This can all be determined with a simply visual inspection. Restrictions in the freon lines are are not all that common and yes they do happen, most of the time they will not be detected visually. The most common place that a restriction occurs is at the refrigerant dryers and the expansion valve inlet screen or the cap tubes. The high side dryer/filter if restricted will be very similar to closing a valve in the line as the system will try to pump down. If the high side filter is partially restricted you would be able to feel a temperature difference between the inlet and outlet of the filter as the outlet would feel cooler than the inlet. There was some comment on the blending of puron freon. Puron is a blend of different types of freon but it is blended at the factory and comes in a cylinder ready to charge as any other freon does. Just for general knowledge it is not recommended by any compressor MFG that liquid freon be added to the suction side of a compressor as they are designed to pump vapor not liquid. There is not a HVAC person that is alive that can say they have never dumped liquid freon into the suction of a compressor they will get in a hurry and it will be done but highly not recommended. That is the reason that HI’s are not suppose to operate A/C units when the outside ambient is below 60 degrees. Liquid freon migrates to the coldest area of the closed system so when its below 60 degrees the compressor is setting full of liquid and if you was to start the unit you would hear the valves in the compressor make noise as they are designed to pump vapor. There are many units designed to operate in very cold outside ambient but not many residential type units. JC this has been HVAC 101 sorry about that I get long winded.

–
Don’t argue with an idiot someone watching may not be able to tell the difference.

32

Originally Posted By: jpeck
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I’ll stir the mix even more.


When even take TD readings?

The TD will tell you absolutely NOTHING *UNLESS* the coil is clean, the filter is clean, there are no restrictions in the air to and through the coil, including the supply duct downstream, and there is no leakage from the cabinet upstream of the coil.

That means, unless you find everything clean and sealed, taking TD readings is meaningless.

Now if all is well, a TD may give the a/c tech clues on where to start trouble shooting the system, but, how many air handlers do we find which are clean, have clean filters, and are properly sealed, not leaking air? Not many, if any. That means that before you measure the TD, look at the air handler unit. If it is not one of the 'all is well' ones, don't bother taking a TD, it will only give a false reading. The system, based on you observations, are screaming out for service and repair by a qualified and licensed a/c service contractor. Taking a TD will not tell you anything reliable, and if you take one, the agent may try to use it to shoot down your other findings.

HI: The filter was clogged, the coil was clogged, the TD was -18 degrees.

Agent: TD was -18 degrees? Why that is right where it should be, there is nothing wrong with that system.

--
Jerry Peck
South Florida

33

Originally Posted By: kluce
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Temp drop does tell you that something is wrong but is very vague on what the problem is. Is it a dirty A coil? Is the blower set at the wrong speed when it was installed? Or is there a major problem with the outside unit itself?


I think looking for Major Defects is one big reason why were are there. After checking the furnace and filter, I open the cover on the outside A.C. unit to check the wiring and check to see if a hard start capacitor is being used. I check the outside coil and put my gauges on. I check to see what the pressures are compared to the temp. If freon is really low on the section and head pressure gauges, that lets me know that there is a possible Major Defect at the outside unit. I find a few home owners have a company come out and charge the unit for the season never fixing the leak. If they have a 20 year old unit, replacement might be recommended.

If I report that the air conditioner is not operating properly and further evaluation is needed by a heating company, this might not give my clients a good indication of how bad the problem could be. Putting gauges on also lets you know if the valves are going bad which normally requires replacement. In short, if you are experienced enough to understand pressures and what they can indicate, then it can be very valuable during the home inspection.

I don't think it's a waste of time when I have a better idea of what I'm telling my clients and they have a better understanding of the possible severity of the problem.

Just my two cents. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

34

Originally Posted By: cbottger
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Jerry:


Isn’t this a great country or not we can disagree with each other without being placed in front of a firing squad. icon_smile.gif


No Delta T is not meaningless to me I check it on every unit I inspect.
Granted in a perfect world the unit should be clean,filters,A-coil and soforth. As to your stating about air loss on the supply side of the system the A-coil does not give a flip about how much air is lost from the system down stream all it is concerned with is the return air temperature from the home to the inlet of the coil and can it reduce that temperature 10 to 20 degrees depending on the type of unit or in other folks views 14 to 20 degrees. Yes we do not want air loss into a unconditioned space and I check this very closely simply stated if you are loosing to much air to an unconditioned space the unit is going to have to perform for a much long time period before the thermostat can satisfied and this is indicated on the customers electric bill. A clogged A-coil gives the very same symptom as a system low on freon. Frosted suction line, which is very visible even to HI's. A dirty return filter in my opinion is a normal maintenance item and does not appear on my list of repairs. If I even suspect that the A-coil is stopped up this does appear on the repair list to have a HVAC company further investigate. I determine this by the amount of dirt in the furnace blower wheel which is readily viewable.
If I enter a home and the inside temperature is 90 degrees( I was born at night but not last night) I turn on the A/C immediately and with 90 degree return air temperature the unit will probably only be discharging 70 to 75 degree supply temperature but as the return temperature decreases so does the supply temperature thus the unit is performing as intended even with a dirty filter. I would have to agree with your Realtor if a unit is producing 18 degrees delta T and has sufficient air being discharged into the home to reduce the temperature to the thermostat setting and cycle off within a reasonable time 10 to 15 minutes per cycle with a outside ambient of say 85 degrees.
Jerry its been great disagreeing with you lets do it again.

Gotta Luv this country. ![icon_smile.gif](upload://b6iczyK1ETUUqRUc4PAkX83GF2O.gif)

--
Don't argue with an idiot someone watching may not be able to tell the difference.

35

Originally Posted By: cbottger
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Kevin:


It is absolutely great that you place gages on the A/C unit if you desire to do that. Everything that you stated you could discover such as low freon, bad valves in the compressor also effects the delta T. If the valves are bad such as the discharge valve leaking back into the suction valve your discharge pressure will be low and the suction pressure will be high thus giving a delt T of squat. If the unit is low on freon the discharge pressure will be low and the suction pressure will be low the suction line will usually be frosted and the Delta T will be squat. My personal choice is to use delta T not the gages. There are no gray areas the unit is either performing as intended or it is not. And I will tell you why I do not use gages as a HI the first time that you put gages on a unit and then start to take them back off and low and behold the valve stem on the high side is stuck in the depressed mode and here we are dumping all of the freon out of the system or you have to donate your gages to the buyer as a permanent fixture. Yes I have had valve stem cores stick on me more times than I can remember but as a HVAC mechanic I had a tool to remove and replace this valve stem with out taking the freon out of the system. Just hope you don't have to donate your gages to some home buyer as he will probably not no how to use them. ![icon_smile.gif](upload://b6iczyK1ETUUqRUc4PAkX83GF2O.gif)

--
Don't argue with an idiot someone watching may not be able to tell the difference.

36

Originally Posted By: jpeck
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kluce wrote:
Temp drop does tell you that something is wrong but is very vague on what the problem is. Is it a dirty A coil? Is the blower set at the wrong speed when it was installed? Or is there a major problem with the outside unit itself?


Kevin,

The TD did not tell you anything is wrong, in fact, it may make you think things are right.

If you take a TD and do not look at the unit (that is the only way the TD will tell you anything), you could get a false good reading.

If you look at the unit, the TD did not tell you something was wrong, you visually saw something was wrong (dirty coil, blocked filter, whatever), but the TD did not tell you that, you saw it.

Kevin, you could have a TD of -20 degrees, excellent, right?

Not with a dirty coil, clogged return air filter, blockage in supply duct after coil, etc. (anything which will slow the air down and allow more heat to transfer from the air to the refrigerant. TD of 120 degrees = good? No. MAY=good, but does not =good. The other conditions need to be known, in which case you don't need to check the TD.

Charley, the coil does care how much air is lost before the coil and how much air is blocked after the coil. Without the right amount of air flowing over the coil, there will not be the proper heat transfer. Too much air at too great of a speed means the TD will be lower, and, vice versa, too little air at too little of a speed with produce a TD which is higher. You could have the fan set too high (too much air at too high of a speed) and a clogged coil (too little air at too slow of a speed) and (provided the coil is not clogged too much) they could equalize out, making a TD reading within the expected range. Thus, taking the TD told you nothing, other than giving you a false sense that it was 'okay'.

--
Jerry Peck
South Florida
37

Originally Posted By: cbottger
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Jerry: here we are again.


I never stated that I relied solely on delta T but yes I routinely take the pulse (temperature) of every unit. We all can understand that water freezes at 32 degrees. And we also know that R-22 at 50 PSIG equals 32 degrees and if we restrict the air flow across the coil for any reason be it fan speed or dirty coil the freon pressure will drop in the system to 50 psig and less. Thus that condensate running down the evaporator is going to solidify real fast. The problem with A-coils most true shaped A-coils are not visible without first removing the panel of the A-Coil box and on top of that there is usually an inside panel across the coil itself that acts as a deflector to ensure the air flow is across the coil and not around it. Most of these coil are not viewable unless the coil is actually partially pulled out of the box. Slant coils are totally different and are very viewable with just the front panel of the box removed. I must state that in all of my years as a A/C mechanic I have never observed a blocked A-coil with a perfect Delta T. The standards of practice in Okla states that Hi's are only allowed to remove panels on fixed equipment that would be considered as panels for routine maintenance by the home owner. Thus eliminating the A-coil box. If I miss anything on a home Inspection it will not be the furnace or A/C unit.

--
Don't argue with an idiot someone watching may not be able to tell the difference.

38

Originally Posted By: kmcmahon
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When I want to get into the home heating diagnostic business, I’ll have to give this thread another look. I think what you guys are talking about goes waaaay above and beyond what’s expected of an HI.

–
Wisconsin Home Inspection, ABC Home Inspection LLC


Search the directory for a Wisconsin Home Inspector
39

Originally Posted By: kluce
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Kevin,


It still falls under the category "Inspection". ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

I find really low freon pressures at least a couple of time each summer. A couple of times, I found the leak due to oil at a fitting. I didn't have to look to hard. ![icon_eek.gif](upload://yuxgmvDDEGIQPAyP9sRnK0D0CCY.gif)

40

Originally Posted By: jpeck
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cbottger wrote:
Jerry: here we are again.

I never stated that I relied solely on delta T


Didn't say you did. You need to read my posts more carefully. I am explaining TO ALL why taking TDs is not necessary and why they cannot rely on the TD reading to make a determination of a systems condition.

'Taking TD readings and using them to tell you if the system is working or is not working is unreliable.'

Let's start with that statement.

Do you agree with that statement, as I stated it, without modifying it by putting other conditions on it. Yes, or no.

--
Jerry Peck
South Florida