testing AC in winter?

[gkay]

Originally Posted by eholliday

Robert you give a perfect example, often times in my area the overnight temp could be below 60 and easily be in the 70-80 during the day. Steven I agree that a minimum temp is needed during installation. Now to Gordons post what if you decided not to test the unit because the outside temp ws 72 degrees, after closing the buyer finds the compressor is locked. What facts will you base the 75 degree min. temp on.
I would like for someone to post something from the manf. stating do not test below a certain temp.

Yeah that was probably worded poorly. I do run them at 60 F and greater but I don't evaluate the refrigerant charge per say in conditions less than 75 F. I only observe that the unit(s) responded satisfactory to operating controls. Such as compressors and associated fans and what I consider reasonable operating temperatures given the conditions.
Any reference to system charge or unsatisfactory cooling should be evaluated by an HVAC contractor under ideal conditions (because that is when the problem will be noticed not at 60F) as per manufacturer’s specs.
These operating characteristics are typically on the interior of the electric panel
and that’s where you will find the limitations to operating as per manufacturer.
I have never had any problems, my clients are reasonable and understand the limitations if explained properly.
Your best tools are touch, listen, look before you bring out any real tools. I have also observed many problems using this approach. You can hear a seized compressor trying to start or hear that it is not running or other abnormal sounds.
You can see frost or iced coils and compressors, you can see lack of condensation and you can feel temperature differences by hand if you know where.
Let the a/c run for 2 - 3 hours (under proper conditions) while you are there and you will also get a good idea if it is working within reason.

[gkay]

Originally Posted by rwashington

An HVAC tech. told me that that the oil in the condensing unit cannot circulate properly when the outside temp is below 60 degrees.

Refrigerant will migrate to the coldest part of an a/c, the outside section. Oil in the crankcase of the compressor will absorb the refrigerant as a liquid. When you start the compressor you reduce the pressure in the crankcase. When you reduce the pressure on liquid refrigerant it boils or evaporates. The rapid evaporation of refrigerant in the oil upon a cold start up will remove much of the oil from the cmpressor and it runs without the oil until it is returned. Oil circulates continuously in the entire refrigerant circuit not just the condensor.

[David A. Andersen]

Well ****! I learned something never posted here before!

Where is Ben?

[Andrew W. Hinz]

Originally Posted by eholliday

Robert you give a perfect example, often times in my area the overnight temp could be below 60 and easily be in the 70-80 during the day. Steven I agree that a minimum temp is needed during installation. Now to Gordons post what if you decided not to test the unit because the outside temp ws 72 degrees, after closing the buyer finds the compressor is locked. What facts will you base the 75 degree min. temp on.
I would like for someone to post something from the manf. stating do not test below a certain temp.

Eldon, This is not a limitation set by manufacturer's (to the best of my knowledge) But most inspecting standards state that the inspector is not required to test the AC unit below a certain temp. Our state standards, here it TX, state that the inspector should not operate when temps are below 60. I believe the NACHI standard states "below 65." Following the standard limits liability. However, if there were a magic way to test them at lower temps, I'd like to know the method.

[rmaday]

Originally Posted by dandersen

Well ****! I learned something never posted here before!

Where is Ben?

http://www.nachi.org/hvaccourse.htm

Section 20. About 2/3 of the way down.

[Eldon E. Holliday, Jr.]

Sorry Andrew, from your first post I did not realize we were discussing SoP, only if you could test the unit below a certain temp. We are now on the second page of this thread and still waiting for someone to post limitation set by manf.

[Bruce A. King]

Several clients have been hvac techs, I remember one of them turning on the A/C unit (not a heat pump) in cold weather for about a minute or two. I was outside and right next to the unit when it came on, he came around the corner and said "I just wanted to see if it would run".

[Chuck Lambert]

Originally Posted by eholliday

We are now on the second page of this thread and still waiting for someone to post limitation set by manf.

See page 3 of manual (page 4 of the PDF)

http://www.chasroberts.com/Manuals/C...nace-Final.pdf

Chuck

[Eldon E. Holliday, Jr.]

Thanks Chuck, I've seen this questions numerous times on several different m/b and this is the first time someone produced anything in writing.

[Jeffrey R. Jonas]

Interesting tidbit...

I just replaced the thermostat for a friend. Before I began to explain to her how to use it (her old one was the old mercury type) I happend to glance at the operating instructions...

Read the Caution after section 1.3...

I don't recall seeing this stated in the Tstat manual before.

[Merwin T. Scruggs]

enough said - I learned something - I had always been told not a good idea and not standard of practice but now we have manufacturer's proof

[David A. Andersen]

Well **** I wrote it down!

It is in writing.

Mein Kampf was written! so what is the damn point?

Just keep following the mindless!

I attempt to explain the issue and all I get is grief because of a lack of willingness to learn something out of the ordinary.

Yeah, those home inspection schools have it all wrapped up!

[David A. Andersen]

Originally Posted by eholliday

Thanks Chuck, I've seen this questions numerous times on several different m/b and this is the first time someone produced anything in writing.

see the above post.

Go ahead and do it. you'll do it anyway.

It's 27° here today and I ran five air-conditioners! Sue me!

[Dan Bowers, CMI]

Many commercial units run year round BUT they have special controls to help them do this. Like in a restaurant or building with a lot of heat load.

You hear that in cold climates many car owners have ENGINE BLOCK HEATERS or similar that keep the oil in the engine warm. Makes starting easier. A/C compressors can have similar issues.

When started up COLD the oil in the refrigerant will be sluggish and can travel through the system as such and damage the compressor or valves.

Most new units have crankcase heaters that IF energized help keep the compressor warm in cold weather. BUT how do you know its on and working. In actuality if its ON and working for the previous 24 hours, I could probably briefly start an A/C and run it down to maybe 45 degrees.

I wouldn't get much of a heat load BUT I know it runs. HOWEVER as a home inspector doing a VISUAL home inspection, I know it came on BUT don't know much else - Especially NOT enough to give it a GREEN light and say it works properly AND is good to go.

Therefore as a PRUDENT, intelligent and professional home inspector, when the temperature is down at 55, 50 or below / I simply state the obvious:

Every couple of years we see some idiot COWBOY home inspector think he's being a big boy and operating the units at 40-50 degrees. Sooner or later the A/C shoots craps AND other inspectors OR HVAC service techs are more than willing to tell the owner its BECAUSE the doofus home inspector turned it on in COLD weather.

Then GUESS who gets to pay for a NEW A/C unit?

[rmaday]

Originally Posted by dandersen

Just keep following the mindless!

I attempt to explain the issue and all I get is grief because of a lack of willingness to learn something out of the ordinary.

Yeah, those home inspection schools have it all wrapped up!

David, generally you do explain HVAC issues well, however, if you think your getting grief in this thread, it may because IMO, you haven't explained anything...

Your previous two posts in this thread...

Originally Posted by dandersen

Besides Tim, we all live in the tropics in comparison to many!

For those that do "turn on", what/how do you evaluate the test?

Originally Posted by dandersen

Yes there is.

Are you EPA certified to handle ozone depleting agents?

You need to access the refrigerant circuits on the equipment to do this.

If you routinely run HVAC units in winter, is there anything special you do? Or do you you just set the t-stat to cool and run it?

What do you think an inspector without an extensive HVAC background should do re: AC compressors in winter?