65 degree rule question

Originally Posted By: sgilligan
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Most houses I will inspect around now (spring), systems will be set on heat mode. Since I am only to run the cycle it is in, and the temp. is 70 degrees, what to do?


Originally Posted By: lwilliams
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Good question Shawn,


I inspect in an area that has many air conditioners and I am wondering the same question. When I attended a HVAC seminar in Spokane last month the instructor gave the impression you could safely test a/c’s this time of year. But if it hasn’t been used all winter and you fire it up for the first time of the season, is there any issues there? I hope someone in the HVAC industry that frequents this site will comment because HVAC is one area I am not comfortable with and could really use some help with. Any HVAC guys out there?


Originally Posted By: roconnor
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Quote:
2.5. Cooling

I. The inspector shall inspect:
A. The central cooling equipment using normal operating controls.

II. The inspector is not required to:
A. Determine the uniformity, temperature, flow, balance, distribution, size, capacity, BTU, or supply adequacy of the cooling system.
B. Inspect window units, through-wall units, or electronic air filters.
C. Operate equipment or systems if exterior temperature is below 60 degrees Fahrenheit or when other circumstances are not conducive to safe operation or may damage the equipment.
D. Inspect or determine thermostat calibration, heat anticipation or automatic setbacks or clocks.
E. Examine electrical current, coolant fluids or gasses, or coolant leakage.


IMHO, if it's above 60 degrees and the system doesn't come right on opperating the temperature controls, evaluation by a professional should be recommended.

Hope that helps ... ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: lwilliams
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Thanks for the note Robert, I can’t tell you how many times I have read that passage in the SOP but somehow when I am standing in front of the a/c unit in the middle of an inspection those words not seem to adequately answer the clients question “does the a/c work?” I always think the a/c unit is more delicate than it really is. It would be really helpful to have an a/c tech standing at the unit with me to point out the idiosyncrasies of a/c’s. I think I will do just that, I think it would be money well spent to pay an a/c tech to teach me, hands on, the finer details of the unit! What a concept! For all you newbies, you may want to consider doing this yourself, it will pay for your peace of mind and confidence. icon_idea.gif


Originally Posted By: Vince Santos
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Great post!


I was wondering the same thing myself as it is that time of year for us in SE Michigan to start clicking on the AC.



Desire is half of life, indifference is half of death.


–Kahlil Gibran

Originally Posted By: dbowers
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. DO YOU FEEL LUCKY TODAY???


This is a simplistic explanation of the why we have the 60-65 rule.

When naive customers ask in January if the A/C works I explain this to them and move on. If they insist - only had it happen twice in 20 + years - I tell them to check with the owner first and if they want to do it themselves - go for it. The last time it happened the buyer trashed the compressor and the seller almost beat him senseless then sued him.


Originally Posted By: Ryan Jackson
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What is the 65 degree rule?



Ryan Jackson, Salt Lake City

Originally Posted By: Lew Lewis
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Shawn,


Back to the original question. Why do you only run the heat or A/C system in the mode it is currently in? Why can't you change the thermostat from A/C to heat on a hot day?


Originally Posted By: sgilligan
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As a rule, you are not supposed to run a heating cycle over 60 degrees and a cooling cycle under 60 degrees. It is my understanding it may be too taxing and risky for an inspector to run the cycles above or below 60 degrees.


Originally Posted By: rsummers
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OK I Know that I’m no the only one with a HVAC back ground but let me give you some advise. If its not above 65 degrees out side and the temp in the house is to low What are you trying to determine. With out attaching a set of gages throwing a sling around how can you be sure if it is working correctly you cant. I check the split I only check the humidity level if the split sucks and I always refer to a pro if things aren’t going the way I think they should.


Originally Posted By: jpeck
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Dan B. gave the best post and best explanation.


Being 60 degrees or 65 degrees outside when you test it is not what the issue is.

Dan said "Bottom line if the outside temperature has not been above 60-65 degrees for 24 hours prior to the inspection ... "

That is the bottom line. Not what temperature it is when you check it, but what has the temperature been for the past 12-24 hours.

Some units, such as heat pumps (and the commercial units Dan referred to) have heaters to keep the oil in the compressor warm and ready for running. Many residential units for cooling only do not have that heater. Thus, the oil in the compressor is to cold, not liquid enough (like you car engine on those -10 degree days, if you don't have a block heater, your oil is like sludge - well not quite, but that gets the idea across - maybe more like molasses).

It takes about 12-24 hours of above 60-65 degrees to allow the oil to come to a good enough consistency to where the compressor can be safely operated. I've heard 12 hours at 60 degrees and been told that the 24 hours at 65 degrees is the safety factor. Go with the safety factor. 24 hours at 65 degrees.

Thus, the answer to "What is the 65 degree rule?" is that the 65 degree rule is that you do not operate the compressor unless it has been at least 65 degrees for at least the last 24 hours.


--
Jerry Peck
South Florida

Originally Posted By: Lew Lewis
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Shawn,


Who says you are not supposed to operate a heating system over 60 degrees?

FWIW The A/C(with no sump heater) in my house gets operated frequently when it is 50-60 degrees. First thing in the morning, my wife turns on the A/C so she doesn't overheat when using a hair dryer(makes perfect sense, to her). No problem with the condenser yet.


Originally Posted By: kluce
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I tell people that the 65 degree rule is for insurance reasons. No way is it the inspectors responsibility if the unit goes bad if operating above 65 degrees.


As a heating/cooling tech, I ran many units under 60 degrees that didn't have a heater around the compressor. This is when I worked for a heating company. It was done and I never had to go back because of problems. A lot of times in Wisconsin, the temp in the spring can be 50 degrees in the morning and 70's by noon. The owner wanted to make the money with the clean and checks before hot weather came in and people were calling for no cooling.

I'm not disagreeing with anyone above, but if you do run the unit under that 12 to 24 hour period, the odds are everything will be fine. This is from past experience.

I just wrote this just incase somebody that doesn't really know what they are doing started up the unit and realizing later that it hasn't been 60 degrees for over 12 hours. No reason to worry about it too much.


Originally Posted By: Blaine Wiley
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I had an HVAC guy that used to go with me on some inspections in VA, and he ran A/C units as long as the temp was above freezing. Never had a problem. Here in FL it’s unusual for the temp to be below 55 for very long and most days are 70 or more, so I check them all year.


Originally Posted By: cbottger
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I observed an statement that was describing the purpose of a crankcase heater on a A/C - refrigeration system compressor as its purpose is to make the oil in the compressor ready to run. That is a rather broad statement for a short moment I thought perhaps Diesel Engines were being discussed.


The reason that a crankcase heater is installed around the bottom of a compressor or embedded within the compressor as most of the newer ones are is simply to keep the oil in the compressor warmer than the freon in the system so the liquid freon will not accumulate in the compressor which it does if the crankheater is not present. This is called liquid migration and is not desirable. Freon will ALWAYS migrate to the coldest area of the system in the off cycle. When the outside ambient is colder than the inside of the residence(60 degree rule) liquid freon will accumulate in the compressor and if it is started under these conditions the possibility exists for the liquid freon to wash the oil from the compressor and damage the compressor valves in the process and if you survived not damaging the compressor valves you still would have to be concerned does the compressor still have enough oil in its sump to prevent damage until the oil has time to make the trip to the A-coil and back to the compressor I liked Dan's Statement DO YOU FEEL LUCKY.

As a hvac mechanic I have operated thousands of units below 60 degrees and have never blown a set of valves in a compressor except one time on a commercial unit I left the discharge valve closed and did blow the valve plate reeds and gaskets out of the head. AS A HI I DO NOT RECOMMEND operating a unit below 60 degrees ambient outside unless you do feel lucky

If you are ever placed in a situation that is questionable to run the unit or not there is a way to somewhat protect yourself against damaging the compressor and that is to pull the 220 volt disconnect at the unit and then activate the thermostat to the cooling mode as this will make the contactor for the compressor but not start the unit. Then go back outside and position your self by the disconnect box and bring the unit on with the disconnect you will be able to determine if the unit is pumping oil and liquid freon by the sound of the unit and if it is turn the unit back off at the disconnect. The best rule for inexperienced HI's with A/C units is the 60 degree rule Bottom Line. Unless you want to purchase a unit for your client.


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

Originally Posted By: tray
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I inspect homes in the Chicago area, where the temps this time of the year can be 60 degrees one day and 85 degrees the next. As a service to my client’s I will inform them that if the outside air temp is below 65 degrees I will not test the operation of the A/C unit, but at this time of the year I will have the client make an appointment with me to return to the property, if everyone is in agreement, and I will inspect what needs to be inspected at that time. This proves to be a great service to my client’s and real estate agents that I serve. Don’t risk having a pushy client make you do something YOU know is not right!


Originally Posted By: dbowers
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Back when I was a Factory Rep for a HVAC Manufacturer, I’ve seen Technicians and have done it myself - start and run an HVAC unit when the o/S temp was 45 - 50 degrees. We were in the Trade, we had a big truck at the curb, and we had access to the parts we would need if we screwed something up (so it was relatively cheap to fix if we blew it).


I'd guess that 95% of all HI's don't fit that description. Therefore why be stupid and do something like turning an HVAC on just to make a few Brownie Points with the Realtor or Client.

I don't walk roofs in lightning storms or when its raining - If the electrical disconnect is off, it stays turned off - I don't feel that lucky.

We've got industry standards - use them.

As far as the same day operation of heat & cooling. If its 65 degrees O/S I would normally run both my gas fired furnace and later my HVAC - or vice versa. If it was 95 degrees O/S, and the house had a Boiler and separate HVAC unit, I personally would probably not fire the boiler.

The furnace and A/C are both 28 years old and so dirty as to be almost clogged. Its 88 degrees O/S. The A/C is running when you arrive but cooling with only a 10 degrees TD. You hold off on running the furnace until the end so as to not make everyone uncomfortable. It works but is "NASTY". You tell everyone both units work but need cleaning, servicing and a full check-up - you also tell them the OLDER units are at or near the end of their useful lifespans, with replacement emminent. YOU LEAVE!!

That night you get a call from the Realtor telling you that shortly after you left the A/C quit and would not come back on and cool. The sellers are angry and have called Uncle Charlies Service Co. He tells them the HI must have done something to damage the unit and they need a new one.
By the time you get hold of themn tomorrow to explain the compressor has just kicked out on its internal overload - and to get out a garden hose to run over the compressor and get it to reset - Uncle Charlie has already put in the new unit. WHO DO YOU THINK THEY WANT TO PAY FOR THIS??

Some of this is not ground in stone rules as much as common sense.

Dan Bowers, CRI


Originally Posted By: cbottger
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Dan:


You sound like my kind of person some common sense applied in your thinking, Not just spouting code.


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