Air Conditioner Freezing Up

[RP]

Every word of CB's post was spot on. You can never adjust the charge correctly on this system after the condenser airflow has been increased over its engineered value, unless you make a few other modifications. One of those is the piston size, just in case you don't remember that post that I spoke to you about. With the old piston and higher condenser airflow the system is mismatched. The subcool will run too high and the superheat will never correspond to the superheat chart over the range of ambient temps that the unit runs under. Moreover the system will be easier to freeze up, i.e. it will do so at a higher ambient than it did before. Even when you change the piston out, the indoor air volume will now be a tad too low since by increasing the condenser airflow the capacity of the unit will be a tad greater than before. Now don't get me wrong, the system will work, but it will never work as it was engineered to work. Put a TXV on the evap coil and you have yourself a blanket fix to all of these potential problems.

Now there's the issue of the under-loaded condenser fan motor and premature failure due to overheating. This can be fixed by selective capacitor sizing as a hack fix, but it isn't supported by the motor manufactures unless you have the trip-saver, but I'm not even going to go into any of this with you since you already have enough to digest for one night :)

hvacrmedic

hvacrmedic

[Stretch]

Turtle,

If the OP replaced an 825 RPM motor with a 1075 RPM motor, the condensor air flow would go up quite a bit. Check your fan laws. This would lower the head pressure which could also lower the suction pressure enough to start freezing the indoor coil. Especially if he has a clogged or restrictive air filter and marginal refrigerant charge. However the outdoor fan amps would also go up quite a bit and most likely burn the new motor out.

Cleaning the outdoor coil with a marginal refrigerant charge and a very dirty outdoor coil would have a similiar effect. I have seen it a number of times

Most likely the two problems are unrelated and just a coincidence that they happened around the same time.

Stretch

[Stretch]

What kind of filter did you put in? Some of the washable filters and most of the pleated filters are very restrctive to air flow. They can cause the indoor coul to freeze on a system with marginal performance.

Stretch

[CBHVAC]

Terry, as a true, licenced, trained, and educated HVAC professional with a grasp of the English that I use daily, and a grasp of how a charge issue can be created and indeed, seems to be the case here, by a fan with too high of a speed that has created a false ambient for the current temps, and COULD have been corrected without replacing the fan....well, after 40 years (you state you started working in HVAC at 6...wow...all those child labor laws your father should have been fined for) you should know what was being stated.

Thank you again for proving to those of us that have a clue (lets see, you are still, after 40 years, a one man, Pinto wagon band right?) that you are indeed, nothing but a sweet talking salesman, that has no idea why the units he installs work, but damned if they dont.

[RP]

Let's just put it all into one list :)

Potential causes of evaporator coil freezing:

1) Insufficient indoor air flow, which can be caused by any obstruction to airflow whatsoever. ( I Once found that the homeowners dog liked to lie next to the intake grill, when I wasn't there of course, blocking about 75% of the airflow. Finally caught the bastard on the third trip out. Excessive dog hair on the air filter had me suspicious already:)

2) Low refrigerant charge

3) Wrong refrigerant

4) Metering device underfeeding, caused by either a restriction, metering device failure, or wrong metering device size.

5) Refrigerant restriction in the refrigerant circuit.

6) Oversized compressor

7) Excessive condenser temperature drop, caused by excessively low ambient temp, precipitation, water spray, oversized condenser fan motor, condenser fan motor RPM too high, blade pitch to high, wrong blade, wrong capacitor, voltage too high.

8) Undersized evap coil

9) Air bypassing evap coil

10) Restriction in evap coil tubing.

11) Indoor temp and or RH too low

12) Non-condensables in system

13) Indoor blower undersized

14) Indoor blower wheel dirty

15) Indoor blower running backward

16) 17) 18) ??? (add any causes that I missed here)

hvacrmedic

[Edwin Pawlowski]

Oversized fan motor? That will not have any effect if it is turning the same rpm. The speed of roation is going to change the air flow, bt if a 3/4 hp motor turns at 1140 rpm and a 1.5 hp motor turns at 1140 rpm, the cfm of air moved by the fan will be the same.

I have two cars with the same transmission and differential. The new one is 205 hp, the old one is 170 hp, but at 70 mph, they both turn at 2,000 rpm. Accelleration and top speed may differ, but the speed at 2000 rpm is still the same.

[Tony Hwang]

Hi, At what rpm is the Hp rating? And torque? And the weight and shape of the car?...... Tony

[RP]

Well that's called wishful thinking on your part. A typical indoor blower for instance, has three or four speed taps. All of these will cause the motor to run at near 1200RPM under no load. Low speed is only lower because it has lower torque and thus more slippage. The same applies to a 1075 RPM condenser fan motor. If you oversize sufficiently you can approach and RPM of 1200, which I think you'll agree is much faster than 1075.

hvacrmedic

[TURTLE]

This is Turtle

You just spoke the most Hog Shit that i've ever heard in my lift. Boy Howdee do we get some Rookies of the year on this group. Here below i will make a statement which you will be ask to reply to.

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If you have a correctly charged hvac system and it running good with no problems. Then you come along and change the condenser fan motor to a faster speed/ more house power / more air across it . I say you can not freeze the evaperator coil up by increasing the speed of the condenser motor or the air across the condenser coil.

Then you say you can do it.

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Watch out Rookie of the year for this question will eat you up if you don't try to talk your way out of it. You should not be telling Hog wash like this and expect people to believe it.

TURTLE

[RP]

You're digging it deeper Turtle. "If the system is marginal already" as Stretch noted, meaning that it was under conditions such that it was

*close* to freezing already, then it will go ahead and freeze if you increase condenser airflow. You aren't reading what Steve is writing. I wonder how many times you've had callbacks on units that you serviced. Just washing the condenser coil can sometimes be more than sufficient to cause freezing, in particular "when it was marginally close to freezing before you got there".

hvacrmedic

[TURTLE]

Snipe add on's

This is Turtle.

They don't have no fan laws that would speak about too much air across the coil as small as going from a 825 rpm motor to a 1075 rpm motor. It would move more air but it would play very little difference in the head or the suction pressure as to what you say trouble or freeze up the evaperator coil.

Also in my life i have changed bunches -- 825 Lennox cond. fan motors over to 1075 and just change the blade or increase the h.P. and leave the blade.

Stretch, Someone has been bullshitting you by saying changing the speed of the air going though the condenser will in some way make the evaperator coil freeze up if it is correctly charged. In the real world it don't happen. In the Salesmanship world it maybe true.

TURTLE

[RP]

So you've hacked up a bunch of peoples systems. That's nice. Did you at least consult the fan laws when you only increased HP and left the blade? You might be surprised at how much higher in HP you have to go to keep running amps down to the nameplate rating of the new motor.

That isn't what he said Turtle.

hvacrmedic

[TURTLE]

This is Turtle.

Your speaking of other thing low of freon, and 50 other thing that could be going wrong and then you make the statement as fact that if you increase the condenser fan speed it will cause the evaperator coil to freeze up. Then Stretch repeats your words again by saying just increasing the speed of the condenser air to the condenser , it will make the evaperator coil freeze up.

All the words your speaking about is other things causing the problem and then say make the increase of air to the condenser coil will cause the evaperator to freeze up. It's not going to happen in your life time.

TURTLE

[RP]

Seems the problem here is that you don't know what *marginal* means. Suggest you look it up before continuing. Here, I'll do it for you:

marginal (mär´je-nel) adjective

1. Of, relating to, located at, or constituting a margin, a border, or an edge: the marginal strip of beach; a marginal issue that had no bearing on the election results.
2. Being adjacent geographically: states marginal to Canada.
3. Written or printed in the margin of a book: marginal notes.
4. Barely within a lower standard or limit of quality: marginal writing ability; eked out a marginal existence.

Excerpted from The American Heritage® Dictionary of the English Language, Third Edition © 1996 by Houghton Mifflin Company. Electronic version licensed from INSO Corporation; further reproduction and distribution in accordance with the Copyright Law of the United States. All rights reserved.

[CBHVAC]

Go on Terry, try to dig out of this one, but its obvious that in this case, you are clueless, and I suspect in this case, its more for your desire to attempt a discredit, instead of simply saying you dont understand what is being discussed.

How about you go on, since you are on a roll, and start with your male sexual statements next...other than bullshitting someone that simply likes sweet talk from you about a problem you cant fully diagnose over the net, you sweet talk em and fail to mention the little things that you would if you were there.

I never said, CORRECTLY CHARGED. I doubt seriously you know what correctly charged is.

I DO hope that when you change out a fan motor, you check superheat/subcool after, since you dont know how long the motors been on a downward spiral, or how its perfomance was PRIOR to the failure, and if another tech was there trying to correct the problem.

Because it can.

Hey Terry...why dont you go back, read the OPs statement, and you tell US oh great one...what would really cause it not to freeze PRIOR to the fan replacement.

The only Rookie here is you, obviously. You exist to flame anyone that does not agree with you.

Flame on, and while you are at it, learn a new language: English.

[CBHVAC]

Name the 50. Name them.

I want to learn from a master...name the 50 things that can cause it...there are not 50..dont go and bullshit the readers here.

Not when you dont have a clue, or learn....or get called back after you rape a customer.

[TURTLE]

This is Turtle.

Earth to Richard , been there and done that. I use to have a chart for the units you wanted to convert. yes Pecker Wood , I went to Lennox and got the required cu. ft. per minute for all their stuff and keep a blade for each unit as to 2 and 5 ton condenser blades. There is 6 blades that would cover most any of the brands and just keep them on the truck. In the last 5 or 10 years the number of blade have changed so much that you have to get the right blade for the job. there was very few Trane around and lennox was the only 825 rpm motors needing to change out this away. Then when everybody stated the 850 rpm motors I stopped doing that. In my area a Lennox Wholesale cost of a 850 rpm motor [1960's & 70's ] was more than What i got for the whole job if it was a 1075 rpm motor. After the Lennox Union Strike we had to go to other companys to sell equipment and Lennox cut our dealer ship because they would not ship equipment for 8 months and expected use to shut down our business till the strick was over. We went back to Rheem / Ruud/ dunn & Bush / singer / others which got them to killing us for parts because we did not wait out the strick and stay loyle to Lennox.

In 1970 Lennox wanted $141.00 wholesale for 1/3 house power 850 rpm condenser fan motor We changed out 1076 condenser fan motor for $125.00 total cost.

TURTLE

[TURTLE]

This is Turtle.

Just put it on Furly Hot Speed !

TURTLE

[TURTLE]

This is Turtle.

I have to dig no where here. Your have to answer the question about the increase of the air to the condenser only will cause the evaperator to freeze up. That is Plain and simple BULLSHIT. If you can't answer correctly , please don't try to answer question here with BULLSHIT.

Nowe call you on some bullshit is not called flame or discrediting at all but i want you to explan this Bullshit to me. If you say some bullshit , be prepaired to explain it.

TURTLE

[RP]

Ok, you've covered your ass on one of the two statements that you made. How about the other statement that you left the old blade and just upsized the motor when going from 825 to 1075RPM? Sure you can adjust the charge, but like I said, the system is now mismatched, not to mention the fact that the OEM blade wasn't necessarily designed to withstand that kind of added stress. I'll tell you now that I've converted a couple of 825s to 1075, but I didn't leave the original blade on them. You're correct about the pricing, not an issue these days, but it was at one time. Just keep in mind that those units that you left with excessive condenser airflow never worked right after you left. Hell yes they *worked*, but that isn't exactly sufficient. If you cost them $100 dollars extra on their light bill over the life of the unit then you didn't do them any favors by using the cheaper motor, and you didn't do yourself any favors either because you made less on that job than you were supposed to. It isn't your fault they had an 825RPM motor that was out of stock or 3 weeks out.

hvacrmedic