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Not testing the AC in winter is poor service to your client.  XML
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scotbaker
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Joined: 07/01/2014 10:28 AM EDT
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What, if any, differences are there to testing an all-in-one or package hvac unit? I inspect a lot of rooftop package units.
Cameron Anderson
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jeff32@satx.rr.com wrote:Let me address a few things...

That was a lot of information, but it struck me that in the time it took to write all that, you could have written out a detailed explanation as to how one wraps and tests AC in the winter. And everyone would benefit.

--------

This discussion is always the same; One group mostly from southern states claiming they test AC in winter using a special method and another group claiming the risk of damage isn't worth it. Well come on, you winter testers, pony up explain the method in detail. Include each step and under what conditions and controls the testing is performed. Acceptable temperatures during the test, temperatures in the previous 24-48 hours which need to be present, any special equipment needed, length of the actual operation of the AC, etc., etc.

The vague replies this topic produces on the side of winter testing do not produce confidence, they make the special method sound made up. I for one will not yet, with my client standing there, wrap my coat or a ratty old piece of cardboard around the condenser unit. I can't imagine anything that would strip my client of trust in their inspector faster than that.

Either it can be done safely under certain conditions or it can't. Don't tell us to call every manufacturer if you already have. Share the info, sharpen everyone.

Rant ended.

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Nathan
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Joined: 06/17/2014 09:32 PM EDT
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Cameron Anderson wrote:
jeff32@satx.rr.com wrote:Let me address a few things...

That was a lot of information, but it struck me that in the time it took to write all that, you could have written out a detailed explanation as to how one wraps and tests AC in the winter. And everyone would benefit.

--------

This discussion is always the same; One group mostly from southern states claiming they test AC in winter using a special method and another group claiming the risk of damage isn't worth it. Well come on, you winter testers, pony up explain the method in detail. Include each step and under what conditions and controls the testing is performed. Acceptable temperatures during the test, temperatures in the previous 24-48 hours which need to be present, any special equipment needed, length of the actual operation of the AC, etc., etc.

The vague replies this topic produces on the side of winter testing do not produce confidence, they make the special method sound made up. I for one will not yet, with my client standing there, wrap my coat or a ratty old piece of cardboard around the condenser unit. I can't imagine anything that would strip my client of trust in their inspector faster than that.

Either it can be done safely under certain conditions or it can't. Don't tell us to call every manufacturer if you already have. Share the info, sharpen everyone.

Rant ended.


It's a good rant. I have a guy in upstate New York testing down to 10 F.

I'll see if anyone wants to do an instructional video on it. Great topic.

Nobody I know is using cardboard by the way

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scotbaker
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So what would be the lowest temp anyone would would test with absolutely no second thoughts to prepping the unit? Not the standard 62-65 or else this topic would have ended. 60? 55? 50? 45? 40?
Nathan
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scotbaker wrote:So what would be the lowest temp anyone would would test with absolutely no second thoughts to prepping the unit? Not the standard 62-65 or else this topic would have ended. 60? 55? 50? 45? 40?


I don't understand the question. Are you asking what the lowest temp would be with no wrap on the A/C? That would be 60 Degrees for me.

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scotbaker
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Nathan wrote:
scotbaker wrote:So what would be the lowest temp anyone would would test with absolutely no second thoughts to prepping the unit? Not the standard 62-65 or else this topic would have ended. 60? 55? 50? 45? 40?


I don't understand the question. Are you asking what the lowest temp would be with no wrap on the A/C? That would be 60 Degrees for me.


Exactly sir
jeff32@satx.rr.com
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Cameron if you read through there i did tell you somewhat how i do it.

Ill break a few things down for you though just to make it easy.

1st i dont check below freezing or if temps are not above freezing for a couple of reasons (i go to 35 degrees only) The main reason is just because of moisture possibly creating ice in contractors etc i want it above freezing for a few hours.

2nd I said cardboard because i found a piece of cardboard laying next to a unit before and just used that.

3rd I will lay my jacket over one side or so or a place my tool box over the top of the unit that restricts the air from leaving the unit and basically does the same thing.


Ok this is what i do, i walk in and turn the heater on/up to at least 75 degrees before i touch anything else, it takes a while to warm a cold house. I prefer i get it up closer to 80 but sometime people start chocking at that temp lol. I go around doing my inspection over the next couple of hours to give the home time to warm up, i take my large tool box and lay it over the top of the condensing unit restricting the air flow out of the unit. I then turn the a/c on and let it run for a few minutes to warm up (check the line for heat at the compressor). Once the unit is warmed up i remove the restriction (tool box) and wait until the system balances in cold temps about 15 minutes. I take my temperature drop and return the system back to its original setting.

Now its been stated that taking the temps at lower ambient temperatures wont work because the The unit will absorb the cold from the outside and return it into the home and your point is what here?? The condensing unit compressor generates heat to dissipate and is pulling the hot air out of the home so we have heat at the condenser. The other thing is say its 7 degrees and i check a system, on another day its 104 and a check the system, under your idea if my ambient were not always the same i would not be able to get a a proper drop which is just not the case. Remember we a 6 degree difference for a temp drop, certainly on the 104 day it may be slightly different than the 70 but it will still be in my range for a proper drop if the system is operating properly.

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jeff32@satx.rr.com
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Drewlevy

Yes the HVAC system is designed to remove moisture, hence the name air conditioner, the system conditions the air. This formula was invented by carrier who was a mechanical engineer (if my memory serves me right) who developed the formula to pull the moisture out of the air by cooling the air temps to the dew point and removing through the condensate drain system to the exterior. This formula was so far advanced that it has stood for a 100 yrs and will never change.

The moisture is a different animal when you think of HVAC and it effects the temperature drop more than the heat its self. Dry air heats and cools fast moist air is slow to respond, i find that most people do not run the HVAC system long enough on humid days to properly get a temperature drop and with newer equipment having an expansion valve rather than an orifice tub it takes long for the metering device to balance out and get you to a proper temp drop, On humid days the unit will have to run for a good while to drop the moisture in the home to a good level to allow for proper cooling of the system. Sub cool and super heat is the terms used for these processes in the HVAC world to measure the flow of the freon and the boiling temps, etc, etc, expansion valves will open and close more often and allow a free flow of refrigerant until it balances (based on temp and humidity). Come summer time on humid days you will need to run the system approximately 30 minutes to an hour to allow the system to drop the humidity and allow the air to be more easily cooled. To many people run the system for 10-15 minutes and take the drop.

If any of you ever get the chance there are some great 1-2 day sit down classes on HVAC, some of it will go over your head unless you are also in HVAC but you will grasp a huge amount of it. If you ever get a chance to go to one of Mr potters classes it will be the best money you will ever spend on an HVAC class http://hvacrconcepts.com/

Also please remember the info i give you is my businesses practices and may not be right for everyone, im not telling you you need to or must do what i do or your doing a poor job. I have merely commented on the original post response saying you cannot check the a/c, you can but you dont have to and you can refer your clients back to the manufacturers laymen terms. If you are not comfortable with extensive a/c knowledge that may be the best way for you just dont tell them you cant inspect tell them you wont inspect it and pint them to the manufacturers verbiage on the laymen terms of not running it. If you get hauled into court on an a/c that you put you could not test and they haul in an engineer from say carrier and he says oh no you can test it it will be hard to defend.

Thanks for all the responses on these posts, this is all part of the learning process and each and everyone of you will have great input on topics that help educate us all.

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Dan Hagman
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You sure he meant a coil leak requires a whole system replacement? A leak in a system that is a blend refrigerant requires a total new virgin charge, you can't just add some refrigerant to a blend, you have to recover it all and start over Repair the leak, pull it in a vacuum and charge it back up with all new refrigerant.
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Mike Raines
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Peter, not related to the question, but do you have family in Detroit? ha, 'not related' no pun intended.

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Cameron Anderson
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jeff32@satx.rr.com wrote:Cameron if you read through there i did tell you somewhat how i do it.

Ill break a few things down for you though just to make it easy...

Thank you, that's the kind of info this discussion needs. I especially appreciate you noting the temp limit at which you stop doing the test.

There are still a couple questions which have not been dealt with but are important.
1. What is it about this method which guarantees oil will not have migrated out of the compressor or refrigerant will not be in a liquid state in the compressor during start up? or...
2. Do you see the above as an actual risk or not a concern at all? If so, do you perform the test with these risks in place–or what about your method eliminates them?
3. Where do you control the unit from during start up? The interior thermostat or the exterior disconnect?
4. Where does this method come from? Is it a manufacturer's method of an HVAC trade secret?
5. Is it universal among different brands and refrigerants?
6. Is your limit of 35°F part of the method or just personal choice? Can this work at lower temps per the source from where you learned this method?

I'm asking these of anyone who uses a method similar or identical to the one above. Let's keep the info going.

This message was edited 1 time. Last update was at 12/15/2014 06:24 PM EST

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jeff32@satx.rr.com
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1-2, gravity. The weight of the oil with a condensing unit below the evaporator keeps the oils in the compressor. Also this is no different than a cold start on an engine, any oil that has migrated will come back around. Also with a properly installed system the refrigerant should not be in a liquid state in the compressor. Now keep in mind I do not run roof top systems.

3, I controll it from the thermostat. I run the heater to bring the heat load in the home, I then cover the condensing unit to restrict airflow. I then turn the unit on and let it build up heat in the high pressure line. I then remove restriction and tack the drop after it runs a bit.

4,If you talk the HVAC engineers they will tell you this, I have spoke to carriers engineers several times on this and this is how they told us to check them.

5, everyone I have talked to has said yes, I have not talked to every manufacture but they all work the same.

6, I use 35 because it gives me a buffer above freezing, the reason I worry about freezing temps is because if there is any moisture preasant the starter contact could have ice and may not close properly damaging the contacts, etc, etc on the freezing/ice.

Let me ask some of you here, do you think restaurants or convienant stores shut there walk ins off when the temperature drops below 60??? If a store is closed and the cooler door is kept closed over night the walk in cooling deck won't kick on most of the night. Now it gets down to freezing and the store opens the next day, now the unit has to come on in a cold state. Do you think everyone's system is damaged when it kicks on???

If you have a proper inverted loop the freon does not really return to the compressor as a liquid.

This message was edited 1 time. Last update was at 12/16/2014 10:21 PM EST


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jtroth
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jeff32@satx.rr.com wrote:Actually per many of the HVAC MANUFACTURERS YOU CAN TEST THE SYSTEM. PER CARRIER YOU CAN RESTRICT AIR FLOW TO THE UNIT UNTILL COMPRESSOR BUILDS HEAT. SOME OTHER MANUFACTURERS TELL YOU TO RUN INSIDE TEMPS UP AND RESTRICT AIRFLOW OF CONDENSOR.

I personally test units down to around 35 degrees, below that I dont. With a little time and knowledge you can safely test units, with this said this is a business decision on my end and I respect those that decide not too. One last thing I do not test the unit unless temps have been above freezing for several hours. There are several reasons why I do what I do but is way to long to post here, if you are testing units at low temps and low inside temps and are not restricting air flow you are asking for problems, please talk to the manufacturers engineers and learn the proper way to test in low temps.



Do you have a link to an hvac manufacturer stating how to test it? I would to show that to some hvac guys

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Turn the unit on FAN ONLY operation and bring that free cold air in and cool those Thanksgiving guests down. Most thermostat settings don't go below 60degrees anyway. If its below 60 outside then bring that cool air in. do a good visual of the components and sniff for possible Freon leaks. Give what info you can give. Let the homeowner know the risks of damaging the compressor by sucking liquid coolant into the compressor. As a buyer I would ask my attorney for a contract revision to have the seller pay for repairs if the unit doesn't work come summer.
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One of the joys of Florida living is heat pumps used for both heating and cooling. Since every component of the system is operating in either heat or cooling mode, with the exception of the reversing valve, it is beyond rare to have a problem after the inspection.

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